Stimulus Health Dictionary

Muscular contraction of the bronchi (air passages) in the LUNGS, causing narrowing. The cause is usually a stimulus, as in BRONCHITIS and ASTHMA. The result is that the patient can inhale air into the lungs but breathing out becomes di?cult and requires muscular e?ort of the chest. Exhalation is accompanied by audible noises in the airways which can be detected with a STETHOSCOPE. Reversible obstructive airways disease can be relieved with a BRONCHODILATOR drug; if the bronchospasm cannot be relieved by drugs it is called irreversible. (See CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD).)... bronchospasm

A succession of intermittent muscular relaxations and contractions usually resulting from a sustained stretching stimulus. An example is the clonus stimulated in the calf muscle by maintaining sustained upward pressure on the sole of the foot. The condition is often a sign of disease in the brain or spinal cord.... clonus

The degree of stimulation, or electrical depolarisation, necessary to produce an action potential in a nerve-?bre (see NEURON(E); NERVE). Stimulation below this level elicits no conducted impulse, and supramaximal stimulation will elicit the same response as a threshold stimulus.... threshold

A condition in which stimulation of one of the senses (by a sound, for example) produces an additional response, such as the appearance of a colour in addition to the normal perception associated with that stimulus.... synaesthesia

The formation of a specific response to a specific stimulus.

In classical conditioning, a stimulus that consistently evokes a particular response is paired repeatedly with a second stimulus that would not normally produce the response.

Eventually, the second stimulus begins to produce the response whether the first stimulus is present or not.

In operant conditioning, attempts to modify behaviour are made through a system of rewards and/or punishments.

The theory that inappropriate behaviour patterns in some psychological disorders are learned through conditioning and can be modified by the same process underlies behavioural psychology (see behaviour therapy).... conditioning

A perception that occurs when there is no external stimulus. Auditory hallucinations (the hearing of voices) are a major symptom of schizophrenia but may also be caused by manic–depressive illness and certain brain disorders. Visual hallucinations are most often found in states of delirium brought on by a physical illness (such as pneumonia) or alcohol withdrawal (delirium tremens). Hallucinogenic drugs are another common cause of visual hallucinations. Hallucinations of smell are associated with temporal lobe epilepsy. Those of touch and taste are rare, however, and occur mainly in people with schizophrenia. People subjected to sensory deprivation or overwhelming physical stress sometimes suffer from temporary hallucinations.... hallucination

An action that occurs automatically and predictably in response to a particular stimulus, independent of the will of the individual.

In the simplest reflex, a sensory nerve cell reacts to a stimulus, such as heat or pressure, and sends a signal along its nerve fibre to the central nervous system. There, another nerve cell becomes stimulated and causes a muscle to contract or a gland to increase its secretory activity. The passage of the nerve signal.

from original sensation to final action is called a reflex arc.

Reflexes may be inborn or conditioned. Some inborn reflexes occur only in babies (see reflex, primitive). Inborn reflexes include those that control basic body functions, such as contraction of the bladder after it has filled beyond a certain point, and are managed by the autonomic nervous system. Conditioned reflexes are acquired through experience in a process called conditioning.

Several simple reflexes, such as the knee-jerk, are tested in a physical examination. Changes in the reflexes may indicate damage to the nervous system. The examination of vital reflexes controlled by the brainstem is the basis for diagnosing brain death.... reflex

Formerly known as adult respiratory distress syndrome. A form of acute respiratory failure in which a variety of di?erent disorders give rise to lung injury by what is thought to be a common pathway. The condition has a high mortality rate (about 70 per cent); it is a complex clinical problem in which a disproportionate immunological response plays a major role. (See IMMUNITY.)

The exact trigger is unknown, but it is thought that, whatever the stimulus, chemical mediators produced by cells of the immune system or elsewhere in the body spread and sustain an in?ammatory reaction. Cascade mechanisms with multiple interactions are provoked. CYTOTOXIC substances (which damage or kill cells) such as oxygen-free radicals and PROTEASE damage the alveolar capillary membranes (see ALVEOLUS). Once this happens, protein-rich ?uid leaks into the alveoli and interstitial spaces. SURFACTANT is also lost. This impairs the exchange of oxygen and carbon dioxide in the lungs and gives rise to the clinical and pathological picture of acute respiratory failure.

The typical patient with ARDS has rapidly worsening hypoxaemia (lack of oxygen in the blood), often requiring mechanical ventilation. There are all the signs of respiratory failure (see TACHYPNOEA; TACHYCARDIA; CYANOSIS), although the chest may be clear apart from a few crackles. Radiographs show bilateral, patchy, peripheral shadowing. Blood gases will show a low PaO2 (concentration of oxygen in arterial blood) and usually a high PaCO2 (concentration of carbon dioxide in arterial blood). The lungs are ‘sti?’ – they are less e?ective because of the loss of surfactant and the PULMONARY OEDEMA.

Causes The causes of ARDS may be broadly divided into the following:... acute respiratory distress syndrome (ards)

Functions that are dominated by epinephrine (the blood hormone) or norepinephrine (local sympathetic adrenergic nerve stimulus)... adrenergic

Sesame (Sesamum indicum).

Plant Part Used: Seed, seed oil.

Dominican Medicinal Uses: The seed oil is traditionally taken orally for asthma, bronchitis, common cold, flu and pneumonia, and the seed emulsion is taken orally for asthma, administered to both children and adults.

Safety: The seed and seed oil are generally regarded as safe for human consumption, and no adverse reactions have been reported in clinical studies.

Contraindications: None identified in the available literature.

Drug Interactions: None identified in the available literature.

Clinical Data: The following effects of the seed oil or seeds have been investigated in human clinical trials: antidiabetic, dry nasal mucosa treatment, enterolactone precursor, hypocholesterolemic, hypotensive, infant growth stimulus, postmenopausal support, sex hormone binding globulin increase, sleep improvement, thiobarbituric acid reacting substance decrease and Vitamin E status improvement.

Laboratory & Preclinical Data: The following biological activities have been investigated in laboratory and preclinical studies (in vitro or animal models): antitumor, antineoplasm, antihypertensive, antioxidant, hypocholesterolemic and improved Vitamin E bioavailability.

* See entry for Ajonjolí in “Part 3: Dominican Medicinal Plant Profiles” of this book for more information, including references.... ajonjolí

Like the previous, but less dangerous and more frequently caused by purely neurologic stimulus. The pain is more spasmodic and there is usually little actual blood vessel blockage.... angina, vasomotoria

A technique whereby an auditory or visual stimulus follows on from a physiological response. Thus, a subject’s ELECTROCARDIOGRAM (ECG) may be monitored, and a signal passed back to the subject indicating his or her heart rate: for example, a red light if the rate is between 50 and 60 beats a minute; a green light if it is between 60 and 70 a minute. Once the subject has learned to discriminate between these two rates, he or she can then learn to control the heart rate. How this is learned is not clear, but by utilising biofeedback some subjects can control heart rate and blood pressure, relax spastic muscles, bring migraine under control and even help constipation.... biofeedback

A distinctly slow heartbeat, which may be a normal idiosyncrasy or with causes ranging from regular strenuous exercise to abnormally slow heart stimulus to the side-effects of medication. Bradycardia is usually defined as a pulse below sixty beats a minute, or seventy in children.... bradycardia

The development of a speci?c response by an individual to a speci?c stimulus. The best-known conditioned re?ex is the one described by Ivan Pavlov, in which dogs that became accustomed to being fed when a bell was sounded salivated on hearing the bell, even if no food was given. The conditioned re?ex is an important part of behavioural theory.... conditioned reflex

Organs whose function it is to secrete into the blood or lymph, substances known as HORMONES. These play an important part in general changes to or the activities of other organs at a distance. Various diseases arise as the result of defects or excess in the internal secretions of the di?erent glands. The chief endocrine glands are:

Adrenal glands These two glands, also known as suprarenal glands, lie immediately above the kidneys. The central or medullary portion of the glands forms the secretions known as ADRENALINE (or epinephrine) and NORADRENALINE. Adrenaline acts upon structures innervated by sympathetic nerves. Brie?y, the blood vessels of the skin and of the abdominal viscera (except the intestines) are constricted, and at the same time the arteries of the muscles and the coronary arteries are dilated; systolic blood pressure rises; blood sugar increases; the metabolic rate rises; muscle fatigue is diminished. The super?cial or cortical part of the glands produces steroid-based substances such as aldosterone, cortisone, hydrocortisone, and deoxycortone acetate, for the maintenance of life. It is the absence of these substances, due to atrophy or destruction of the suprarenal cortex, that is responsible for the condition known as ADDISON’S DISEASE. (See CORTICOSTEROIDS.)

Ovaries and testicles The ovary (see OVARIES) secretes at least two hormones – known, respectively, as oestradiol (follicular hormone) and progesterone (corpus luteum hormone). Oestradiol develops (under the stimulus of the anterior pituitary lobe – see PITUITARY GLAND below, and under separate entry) each time an ovum in the ovary becomes mature, and causes extensive proliferation of the ENDOMETRIUM lining the UTERUS, a stage ending with shedding of the ovum about 14 days before the onset of MENSTRUATION. The corpus luteum, which then forms, secretes both progesterone and oestradiol. Progesterone brings about great activity of the glands in the endometrium. The uterus is now ready to receive the ovum if it is fertilised. If fertilisation does not occur, the corpus luteum degenerates, the hormones cease acting, and menstruation takes place.

The hormone secreted by the testicles (see TESTICLE) is known as TESTOSTERONE. It is responsible for the growth of the male secondary sex characteristics.

Pancreas This gland is situated in the upper part of the abdomen and, in addition to the digestive enzymes, it produces INSULIN within specialised cells (islets of Langerhans). This controls carbohydrate metabolism; faulty or absent insulin production causes DIABETES MELLITUS.

Parathyroid glands These are four minute glands lying at the side of, or behind, the thyroid (see below). They have a certain e?ect in controlling the absorption of calcium salts by the bones and other tissues. When their secretion is defective, TETANY occurs.

Pituitary gland This gland is attached to the base of the brain and rests in a hollow on the base of the skull. It is the most important of all endocrine glands and consists of two embryologically and functionally distinct lobes.

The function of the anterior lobe depends on the secretion by the HYPOTHALAMUS of certain ‘neuro-hormones’ which control the secretion of the pituitary trophic hormones. The hypothalamic centres involved in the control of speci?c pituitary hormones appear to be anatomically separate. Through the pituitary trophic hormones the activity of the thyroid, adrenal cortex and the sex glands is controlled. The anterior pituitary and the target glands are linked through a feedback control cycle. The liberation of trophic hormones is inhibited by a rising concentration of the circulating hormone of the target gland, and stimulated by a fall in its concentration. Six trophic (polypeptide) hormones are formed by the anterior pituitary. Growth hormone (GH) and prolactin are simple proteins formed in the acidophil cells. Follicle-stimulating hormone (FSH), luteinising hormone (LH) and thyroid-stimulating hormone (TSH) are glycoproteins formed in the basophil cells. Adrenocorticotrophic hormone (ACTH), although a polypeptide, is derived from basophil cells.

The posterior pituitary lobe, or neurohypophysis, is closely connected with the hypothalamus by the hypothalamic-hypophyseal tracts. It is concerned with the production or storage of OXYTOCIN and vasopressin (the antidiuretic hormone).

PITUITARY HORMONES Growth hormone, gonadotrophic hormone, adrenocorticotrophic hormone and thyrotrophic hormones can be assayed in blood or urine by radio-immunoassay techniques. Growth hormone extracted from human pituitary glands obtained at autopsy was available for clinical use until 1985, when it was withdrawn as it is believed to carry the virus responsible for CREUTZFELDT-JAKOB DISEASE (COD). However, growth hormone produced by DNA recombinant techniques is now available as somatropin. Synthetic growth hormone is used to treat de?ciency of the natural hormone in children and adults, TURNER’S SYNDROME and chronic renal insu?ciency in children.

Human pituitary gonadotrophins are readily obtained from post-menopausal urine. Commercial extracts from this source are available and are e?ective for treatment of infertility due to gonadotrophin insu?ciency.

The adrenocorticotrophic hormone is extracted from animal pituitary glands and has been available therapeutically for many years. It is used as a test of adrenal function, and, under certain circumstances, in conditions for which corticosteroid therapy is indicated (see CORTICOSTEROIDS). The pharmacologically active polypeptide of ACTH has been synthesised and is called tetracosactrin. Thyrotrophic hormone is also available but it has no therapeutic application.

HYPOTHALAMIC RELEASING HORMONES which affect the release of each of the six anterior pituitary hormones have been identi?ed. Their blood levels are only one-thousandth of those of the pituitary trophic hormones. The release of thyrotrophin, adrenocorticotrophin, growth hormone, follicle-stimulating hormone and luteinising hormone is stimulated, while release of prolactin is inhibited. The structure of the releasing hormones for TSH, FSH-LH, GH and, most recently, ACTH is known and they have all been synthesised. Thyrotrophin-releasing hormone (TRH) is used as a diagnostic test of thyroid function but it has no therapeutic application. FSH-LH-releasing hormone provides a useful diagnostic test of gonadotrophin reserve in patients with pituitary disease, and is now used in the treatment of infertility and AMENORRHOEA in patients with functional hypothalamic disturbance. As this is the most common variety of secondary amenorrhoea, the potential use is great. Most cases of congenital de?ciency of GH, FSH, LH and ACTH are due to defects in the hypothalamic production of releasing hormone and are not a primary pituitary defect, so that the therapeutic implication of this synthesised group of releasing hormones is considerable.

GALACTORRHOEA is frequently due to a microadenoma (see ADENOMA) of the pituitary. DOPAMINE is the prolactin-release inhibiting hormone. Its duration of action is short so its therapeutic value is limited. However, BROMOCRIPTINE is a dopamine agonist with a more prolonged action and is e?ective treatment for galactorrhoea.

Thyroid gland The functions of the thyroid gland are controlled by the pituitary gland (see above) and the hypothalamus, situated in the brain. The thyroid, situated in the front of the neck below the LARYNX, helps to regulate the body’s METABOLISM. It comprises two lobes each side of the TRACHEA joined by an isthmus. Two types of secretory cells in the gland – follicular cells (the majority) and parafollicular cells – secrete, respectively, the iodine-containing hormones THYROXINE (T4) and TRI-IODOTHYRONINE (T3), and the hormone CALCITONIN. T3 and T4 help control metabolism and calcitonin, in conjunction with parathyroid hormone (see above), regulates the body’s calcium balance. De?ciencies in thyroid function produce HYPOTHYROIDISM and, in children, retarded development. Excess thyroid activity causes thyrotoxicosis. (See THYROID GLAND, DISEASES OF.)... endocrine glands

The rigid state of the PENIS when it responds to sexual stimulus. An erection is necessary for e?ective penetration of the VAGINA. As a result of sexual arousal, the three cylinders of erectile tissue in the penis become engorged with blood, lengthening, raising and hardening the penis. Muscles surrounding the blood vessels contract and retain the blood in the penis. Erections also occur during sleep and in young boys. Inability to have or maintain an erection is one cause of IMPOTENCE (see also SILDENAFIL CITRATE).... erection

Mental arousal that the individual may ?nd enjoyable or unpleasant. The three components are subjective, physiological and behavioural. The instinctive fear and ?ee response in animals comprises physiological reaction – raised heart rate, pallor and sweating – to an unpleasant event or stimulus. The loving relationship between mother and child is another wellrecognised emotional event. If this emotional bond is absent or inadequate, the child may suffer emotional deprivation, which can be the trigger for behavioural problems ranging from attention-craving to aggression. Emotional problems are common in human society, covering a wide spectrum of psychological disturbances. Upbringing, relationships or psychiatric illnesses such as anxiety and DEPRESSION may all contribute to the development of emotional problems (see MENTAL ILLNESS).... emotion

The protein, produced mainly in the kidney, that is the major stimulus for the production of ERYTHROCYTES, or red blood corpuscles. It is used when treating ANAEMIA dure to end-stage kidney failure and in premature newborns with anaemia. (See also BLOOD.)... erythropoietin

Extrasystole is a term applied to premature contraction of one or more of the chambers of the heart. A beat of the heart occurs sooner than it should do in the ordinary rhythm and is followed by a longer rest than usual before the next beat. In an extrasystole, the stimulus to contraction arises in a part of the heart other than the usual. Extrasystoles often give rise to an unpleasant sensation as of the heart stumbling over a beat, but their occurrence is not usually serious.... extrasystole

A behavioural response or practice that is established by the individual frequently repeating the same act. The process is called habituation, and the more a person is exposed to a particular stimulus, the less is he or she aroused by it. People may also become habituated to certain drugs, requiring more and more of a substance to produce the same e?ect – a process known as TOLERANCE.... habit

False perceptions arising without an adequate external stimulus, as opposed to illusions, which are misinterpretations of stimuli arising from an external object. Hallucinations come from ‘within’, although the affected individual may see them as coming from ‘without’. Nevertheless, they may occur at the same time as real perceptions, and may affect any sense (vision, hearing, smell, taste, touch, etc.).

Causes They may be the result of intense emotion or suggestion, sensory deprivation (for example, overwork or lack of sleep), disorders of sense organs, or disorders of the central nervous system. Although hallucinations may occur in perfectly sane people, they are more commonly an indication of a MENTAL ILLNESS. They may be deliberately induced by the use of HALLUCINOGENS.... hallucinations

Oversecretion of fluids by a gland. It may occur from irritation, infection, or allergy, as in the nasal drooling in a head cold or hay fever, or, as in gastric hypersecretion, from a functional imbalance in the chemical and neurologic stimulus of the stomach lining.... hypersecretion

The process of producing a state of mind known as hypnosis. Although recognised for hundreds of years, the precise nature of this process is still poorly understood. One modern writer has de?ned hypnosis as ‘a temporary condition of altered attention, the most striking feature of which is greatly increased suggestibility’. There is no evidence, as has been claimed, that women can be more easily hypnotised than men; in fact, children and young adults are the more easily hypnotised, with middle-aged people being more resistant.

Hypnosis is induced by various methods, but the basis of all is some rhythmic stimulus accompanied by the repetition of carefully worded suggestions. The most commonly used method is to ask the patient to ?x his or her eye on a given spot, or light, and then to keep on repeating, in a quiet and soothing voice, that the patient’s eyes will gradually become tired and that he or she will want to close them.

There are various levels of hypnosis, usually classi?ed as light, medium, and deep, and it has been estimated that 10 per cent of people cannot be hypnotised; 35 per cent can be taken into light hypnosis; 35 per cent into medium hypnosis; and 20 per cent into deep hypnosis.

Hypnosis can be used as a treatment for some psychiatric patients and in some people with psychosomatic conditions in which emotional or psychological disturbances precipitate physical disorders such as skin lesions or headaches. Hypnosis may help to relieve pain in childbirth; asthma may also respond to it. Some people may ?nd hypnosis to be of help in overcoming addictions to smoking, alcohol or gambling. The process has associated risks, and its use in treatment should be by doctors trained in the technique.... hypnotism

Short for Prostaglandin E, presumably the fifth subtype discovered, and usually separated into PGE1 and PGE2. These two, if made by the kidneys, slow sodium reabsorption; if within in the uterus, induce a stronger response to less stimulus; if made in the stomach lining inhibit gastric secretion; if secreted by macrophages, target tissues become more accessible to infiltration...and inflammation. These are the two prostaglandins whose levels are meant to be stabilized by gamma-linolenic acid (GLA) supplements. See PROSTAGLANDIN... pge

This is the triangular basement muscle of the urinary bladder. It differs in structure and nerves from the top of the bladder, the detrusor muscle, which expands as the bladder fills, and contracts during urination under parasympathetic nerve stimulus. The trigone does not expand, is under sympathetic nerve stimulus, and supplies the rigidity and sphincter support for the urethra in front and the ureters in back.... trigone

The tracing of electrical activity in the brain in response to a specific external stimulus. The procedure is similar to that for an EEG.

The technique is used to check the functioning of various sensory systems (such as sight, hearing, or touch). The information obtained can be used to reveal abnormalities caused by inflammation, pressure from a tumour, or other disorders, and to help confirm a diagnosis of multiple sclerosis.... evoked responses

An endocrine gland somewhat behind the eyes and suspended from the front of the brain. The front section, the anterior pituitary, makes and secretes a number of controlling hormones that affect the rate of oxidation; the preference for fats, sugars, or proteins for fuel; the rate of growth and repair in the bones, connective tissue, muscles, and skin; the ebb and flow of steroid hormones from both the gonads and adrenal cortices. It does this through both negative and positive feedback. The hypothalamus controls these functions, secreting its own hormones into a little portal system that feeds into the pituitary, telling the latter what and how much to do. The hypothalamus itself synthesizes the nerve hormones that are stored in the posterior pituitary, which is responsible for squirting them into the blood when the brain directs it to. These neurohormones act quickly, like adrenalin, to constrict blood vessels, limit diuresis in the kidneys, and trigger the complex responses of sexual excitation, milk let­down in nursing, and muscle stimulus in the uterus (birthing, orgasm, and menstrual contractions), prostate, and nipples.... pituitary

The large organ lying to the left of, below, and behind the stomach. This organ is partially responsible for white blood cell formation (red blood cells in childhood), and it is lined with resident macrophages that help it filter the blood, remove and recycle old and dead red blood cells, and send this all up to the liver in the portal blood. The liver, in fact, does most of the recycling of splenic hemoglobin derivatives. The spleen initiates much resistance and immunologic response, being made mostly of lymph pulp, and it stores and concentrates a large number of red blood cells. These can be injected into the bloodstream for immediate use under flight or fight stress, since the spleen is covered with capsule and vascular muscles that constrict in the presence of adrenalin or sympathetic adrenergic nerve stimulus.... spleen

A condition characterised by SPASM of muscle, usually caused by a fall in blood CALCIUM levels. This results in hyperexcitability of muscles which may go into spasm at the slightest stimulus. This is well demonstrated in two of the classical signs of the disease: Chvostek’s sign, in which the muscles of the face contract when the cheek is tapped over the facial nerve as it emerges on the cheek; and Erb’s sign, in which muscles go into spasm in response to an electrical stimulus which normally causes only a contraction of the muscle. Tetany occurs in newborn babies, especially if they are premature, and in infants; as a result of RICKETS, excessive vomiting, or certain forms of NEPHRITIS. It may also be due to lack of the active principle of the PARATHYROID glands. Overbreathing may also cause it. Treatment consists of the administration of calcium salts, and in severe cases this is done by giving calcium gluconate intravenously or intramuscularly. High doses of vitamin D are also required.... tetany

Two female reproductive organs situated below the Fallopian tubes, one on each side of the womb, comparable to testes in the male. An egg cell or ova develops inside the ovary and when mature bursts through the surface into the abdominal cavity where it is attracted into a Fallopian tube and conveyed to the womb. If fertilised, the egg attaches to the lining of the womb and develops into a foetus. Otherwise it is expelled from the womb during menstruation. In addition to producing eggs, ovaries secrete hormones essential to body function. Ovarian disorders include:– 1. Inflammation (oophoritis – usually with salpingitis).

Causes: mumps, tuberculosis, gonorrhoea or, if following childbirth or abortion, sepsis. Inflammatory adhesions may cause ovary and tube to mat together and ulcerate.

Symptoms: feverishness, pelvic pain, abdominal swelling.

Treatment. Decoction, powders, liquid extracts or tinctures.

Formula. Echinacea 2; Helonias 1; Cramp bark 1; Liquorice quarter. Dosage. Decoction: half-1 cup. Powders: one-third teaspoon. Liquid extracts: 1 teaspoon. Tinctures: 2 teaspoons. Thrice daily in water/honey.

External. Castor oil pack to abdomen.

2. Cysts. Single or multiple hollow growths containing fluids may grow large, obstruct abdominal circulation, interfere with digestion and cause shortness of breath. They are caused by excessive stimulus from the pituitary gland. A fluid-filled sac on the ovary grows in preparation for egg release but fails to rupture. The follicle continues to grow, accumulating fluid and a cyst results.

Liquid Extract Thuja: 5-10 drops, thrice daily. Of value.

Notes. Bulimia Nervosa (eating disorder) has been linked with polycystic ovary disease. (St George’s Hospital Medical School, London)

The presence of acne is a valuable clue to ovarian disorder: a treatment for acne reacts favourably on ovaries.

3. Tumour (non-malignant). May avoid detection. Usually revealed by laparoscopy or X-ray. When a tumour or cyst twists on an ovary’s ligament severe abdominal pain is followed by vomiting and shock.

Treatment. Secondary to surgery. Decoction, powders, liquid extracts, or tinctures. Combination. Cramp bark 2; Poke root 1; Thuja half. Dosage. Decoction: half-1 cup. Powders: 500mg (one-third teaspoon). Liquid extracts: 1 teaspoon. Tinctures: 1-2 teaspoons in water/honey thrice daily.

Following surgical removal of ovaries: Pulsatilla. Pre- and post-operative pain: Cramp bark BHP (1983). Black Willow. (Dr J. Christopher)

Supplements: calcium, magnesium.

Note: Increased bone loss is associated with ovarian disturbances in premenopausal women. (Canadian Study in “New England Journal of Medicine”) See: OSTEOPOROSIS.

Polycystic ovaries have an important association with heart attacks in elderly women. (Professor Howard Jacobs, Middlesex School of Medicine) ... ovaries

Altered sensation in the skin that occurs without a stimulus (see pins-and-needles).... paraesthesia

An automatic movement in response to a stimulus that is present in newborn infants but disappears during the first few months after birth. Primitive reflexes are believed to represent actions that were important in earlier stages of human evolution. They include the grasp reflex when something is placed in the hand and the rooting reflex, which enables a baby to find the nipple. The rooting reflex can be evoked by touching the baby’s cheek with the fingertip. These reflexes are tested after birth to give an indication of the condition of the nervous system.... reflex, primitive

The previous subject is obviously an endless one, but as this is the glossary of an herbal nature, let me assure you, virtually no plants have a direct steroid hormone-mimicking effect. There are a few notable exceptions with limited application, like Cimicifuga and Licorice. Plant steroids are usually called phytosterols, and, when they have any hormonal effect at all, it is usually to interfere with human hormone functions. Beta sitosterol, found in lots of food, interferes with the ability to absorb cholesterol from the diet. Corn oil and legumes are two well-endowed sources that can help lower cholesterol absorption. This is of only limited value, however, since cholesterol is readily manufactured in the body, and elevated cholesterol in the blood is often the result of internal hormone and neurologic stimulus, not the diet. Cannabis can act to interfere with androgenic hormones, and Taraxacum phytosterols can both block the synthesis of some new cholesterol by the liver and increase the excretion of cholesterol as bile acids; but other than that, plants offer little direct hormonal implication. The first method discovered for synthesizing pharmaceutical hormones used a saponin, diosgenin, and a five-step chemical degradation, to get to progesterone, and another, using stigmasterol and bacterial culturing, to get to cortisol. These were chemical procedures that have nothing to do with human synthesis of such hormones, and the plants used for the starting materials-Mexican Wild Yam, Agave, and Soy were nothing more than commercially feasible sources of compounds widely distributed in the plant kingdom. A clever biochemist could obtain testosterone from potato sterols, but no one would be likely to make the leap of faith that eating potatoes makes you manly (or less womanly), and there is no reason to presume that Wild Yam (Dioscorea) has any progesterone effects in humans. First, the method of synthesis from diosgenin to progesterone has nothing to do with human synthesis of the corpus luteum hormone; second, oral progesterone has virtually no effect since it is rapidly digested; and third, orally active synthetic progesterones such as norethindrone are test-tube born, and never saw a Wild Yam. The only “precursor” the ovaries, testes and adrenal cortices EVER need (and the ONLY one that they can use if synthesizing from scratch) is something almost NONE of us ever run out of...Low Density Cholesterol. Unless you are grimly fasting, anorectic, alcoholic, seriously ill or training for a triathlon, you only need blood to make steroid hormones from. If hormones are off, it isn’t from any lack of building materials...and any product claiming to supply “precursors” better contain lard or butter (they don’t)...or they are profoundly mistaken, or worse. The recent gaggle of “Wild Yam” creams actually do contain some Wild Yam. (Dioscorea villosa, NOT even the old plant source of diosgenin, D. mexicana...if you are going to make these mistakes, at least get the PLANT right) This is a useful and once widely used antispasmodic herb...I have had great success using it for my three separate bouts with kidney stones...until I learned to drink more water and alkalizing teas and NEVER stay in a hot tub for three hours. What these various Wild Yam creams DO contain, is Natural Progesterone. Although this is inactive orally (oral progesterone is really a synthetic relative of testosterone), it IS active when injected...or, to a lesser degree, when applied topically. This is pharmaceutical progesterone, synthesized from stigmasterol, an inexpensive (soy-bean oil) starting substance, and, although it is identical to ovarian progesterone, it is a completely manufactured pharmaceutical. Taking advantage of an FDA loophole (to them this is only a cosmetic use...they have the misguided belief that it is not bioactive topically), coupled with some rather convincing (if irregular) studies showing the anti-osteoporotic value of topical progesterone for SOME women, a dozen or so manufacturers are marketing synthetic Natural Progesterone for topical use, yet inferring that Wild Yam is what’s doing good. I am not taking issue with the use of topical progesterone. It takes advantage of the natural slow release into the bloodstream of ANY steroid hormones that have been absorbed into subcutaneous adipose tissue. It enters the blood from general circulation the same way normal extra-ovarian estradiol is released, and this is philosophically (and physiologically) preferable to oral steroids, cagily constructed to blast on through the liver before it can break them down. This causes the liver to react FIRST to the hormones, instead of, if the source is general circulation, LAST. My objection is both moral and herbal: the user may believe hormonal effects are “natural”, the Wild Yam somehow supplying “precursors” her body can use if needed, rejected if not. This implies self-empowerment, the honoring of a woman’s metabolic choice...something often lacking in medicine. This is a cheat. The creams supply a steady source of pharmaceutical hormone (no precursor here) , but they are being SOLD as if the benefits alone come from the Wild Yam extract, seemingly formulated with the intent of having Wild Yam the most abundant substance so it can be listed first in the list of constituents. I have even seen the pharmaceutical Natural Progesterone labeled as “Wild Yam Progesterone” or “Wild Yam Estrogen precursor” or, with utter fraud, “Wild Yam Hormone”. To my knowledge, the use of Mexican Yam for its saponins ceased to be important by the early 1960’s, with other processes for synthesizing steroids proving to be cheaper and more reliable. I have been unable to find ANY manufacturer of progesterone that has used the old Marker Degradation Method and/or diosgenin (from whatever Dioscorea) within the last twenty years. Just think of it as a low-tech, non invasive and non-prescription source of progesterone, applied topically and having a slow release of moderate amounts of the hormone. Read some of the reputable monographs on its use, make your choice based solely on the presence of the synthetic hormone, and use it or don’t. It has helped some women indefinitely, for others it helped various symptoms for a month or two and then stopped working, for still other women I have spoken with it caused unpleasant symptoms until they ceased its use. Since marketing a product means selling as much as possible and (understandably) presenting only the product’s positive aspects, it would be better to try and find the parameters of “use” or “don’t use” from articles, monographs, and best of all, other women who have used it. Then ask them again in a month or two and see if their personal evaluation has changed. If you have some bad uterine cramps, however, feel free to try some Wild Yam itself...it often helps. Unless there is organic disease, hormones are off is because the whole body is making the wrong choices in the hormones it does or doesn’t make. It’s a constitutional or metabolic or dietary or life-stress problem, not something akin to a lack of essential amino acids or essential fatty acids that will clear up if only you supply some mythic plant-derived “precursor”. End of tirade.... steroids, plant

The sense that enables an individual to assess the physical characteristics of objects – for example, their size, shape, temperature and texture. The sense of touch is considered here along with other senses associated with the skin and muscles. The cutaneous senses comprise:

Touch sense proper, by which we perceive a touch or stroke and estimate the size and shape of bodies with which we come into contact, but which we do not see.

Pressure sense, by which we judge the heaviness of weights laid upon the skin, or appreciate the hardness of objects by pressing against them.

Heat sense, by which we perceive that an object is warmer than the skin.

Cold sense, by which we perceive that an object touching the skin is cold.

Pain sense, by which we appreciate pricks, pinches and other painful impressions.

Muscular sensitiveness, by which the painfulness of a squeeze is perceived. It is produced probably by direct pressure upon the nerve-?bres in the muscles.

Muscular sense, by which we test the weight of an object held in the hand, or gauge the amount of energy expended on an e?ort.

Sense of locality, by which we can, without looking, tell the position and attitude of any part of the body.

Common sensation, which is a vague term used to mean composite sensations produced by several of the foregoing, like tickling, or creeping, and the vague sense of well-being or the reverse that the mind receives from internal organs. (See the entry on PAIN.)

The structure of the end-organs situated in the skin, which receive impressions from the outer world, and of the nerve-?bres which conduct these impressions to the central nervous system, have been described under NERVOUS SYSTEM. (See also SKIN.)

Touch affects the Meissner’s or touch corpuscles placed beneath the epidermis; as these di?er in closeness in di?erent parts of the skin, the delicacy of the sense of touch varies greatly. Thus the points of a pair of compasses can be felt as two on the tip of the tongue when separated by only 1 mm; on the tips of the ?ngers they must be separated to twice that distance, whilst on the arm or leg they cannot be felt as two points unless separated by over 25 mm, and on the back they must be separated by more than 50 mm. On the parts covered by hair, the nerves ending around the roots of the hairs also take up impressions of touch.

Pressure is estimated probably through the same nerve-endings and nerves that have to do with touch, but it depends upon a di?erence in the sensations of parts pressed on and those of surrounding parts. Heat-sense, cold-sense and pain-sense all depend upon di?erent nerve-endings in the skin; by using various tests, the skin may be mapped out into a mosaic of little areas where the di?erent kinds of impressions are registered. Whilst the tongue and ?nger-tips are the parts most sensitive to touch, they are comparatively insensitive to heat, and can easily bear temperatures which the cheek or elbow could not tolerate. The muscular sense depends upon the sensory organs known as muscle-spindles, which are scattered through the substance of the muscles, and the sense of locality is dependent partly upon these and partly upon the nerves which end in tendons, ligaments and joints.

Disorders of the sense of touch occur in various diseases. HYPERAESTHESIA is a condition in which there is excessive sensitiveness to any stimulus, such as touch. When this reaches the stage when a mere touch or gentle handling causes acute pain, it is known as hyperalgesia. It is found in various diseases of the SPINAL CORD immediately above the level of the disease, combined often with loss of sensation below the diseased part. It is also present in NEURALGIA, the skin of the neuralgic area becoming excessively tender to touch, heat or cold. Heightened sensibility to temperature is a common symptom of NEURITIS. ANAESTHESIA, or diminution of the sense of touch, causing often a feeling of numbness, is present in many diseases affecting the nerves of sensation or their continuations up the posterior part of the spinal cord. The condition of dissociated analgesia, in which a touch is quite well felt, although there is complete insensibility to pain, is present in the disease of the spinal cord known as SYRINGOMYELIA, and a?ords a proof that the nerve-?bres for pain and those for touch are quite separate. In tabes dorsalis (see SYPHILIS) there is sometimes loss of the sense of touch on feet or arms; but in other cases of this disease there is no loss of the sense of touch, although there is a complete loss of the sense of locality in the lower limbs, thus proving that these two senses are quite distinct. PARAESTHESIAE are abnormal sensations such as creeping, tingling, pricking or hot ?ushes.... touch

A collection of techniques, based on psychological theory, for changing abnormal behaviour or treating anxiety. The treatment relies on 2 basic ideas: that exposure to a feared experience under safe conditions will render it less threatening, and that desirable behaviour can be encouraged by using a system of rewards.

Specific behaviour therapy techniques include exposure therapy (also called desensitization), response prevention, flooding, and modelling. Exposure therapy is commonly used to treat phobic disorders such as agoraphobia, animal phobias, and flying phobias. It consists of exposing the patient in stages to the cause of the anxiety. The patient is taught to cope with anxiety symptoms by using relaxation techniques. In flooding, the patient is confronted with the anxiety-provoking stimulus all at once, but with the support of the therapist. In response prevention, the patient is prevented from carrying out an obsessional task; the technique is used in combination with other methods. In modelling, the therapist acts as a model for the patient, performing the anxiety-provoking activity first, in order that the patient may copy.... behaviour therapy

n. 1. the phenomenon in which a sense organ shows a gradually diminishing response to continuous or repetitive stimulation. The nose, for example, may become adapted to the stimulus of an odour that is continuously present so that in time it ceases to report its presence. Similarly, the adaptation of touch receptors in the skin means that the presence of clothes can be forgotten a few minutes after they have been put on. 2. a process of change to enable adjustment to a condition or environment.... adaptation

n. a specific post-traumatic syndrome after nerve injury, in which a limb remains exquisitely sensitive to any stimulus and later develops disuse *atrophy. See complex regional pain syndrome.... algodystrophy

n. pain due to a stimulus that would not normally cause pain, such as a light touch or mild changes in temperature. It occurs acutely after injury but also in many chronically painful conditions, including *peripheral neuropathy.... allodynia

A tendency to have recurrent seizures. In many people with epilepsy, the cause is unclear, although a genetic factor may be involved. In other cases, seizures may be the result of brain damage from head injury, birth trauma, brain infection (such as meningitis or encephalitis), brain tumour, stroke, drug intoxication, or a metabolic disorder.

Many people with epilepsy do not have any symptoms between seizures. Some people experience an aura shortly before. In some cases, a stimulus such as a flashing light triggers a seizure. Epileptic seizures may occur more frequently in times of illness or stress.

Epileptic seizures can be classified into two groups: generalized and partial. Generalized seizures cause loss of consciousness and may affect all areas of the brain. There are two types: grand mal and absence (petit mal) seizures. During a grand mal seizure, there may be an aura initially, then the bodybecomes stiff and consciousness is lost; breathing may be irregular or may stop briefly, then the body jerks uncontrollably. The person may be disorientated for hours afterwards and have no memory of the event. Prolonged grand mal seizures are potentially life-threatening. Absence seizures occur mainly in children. Periods of altered consciousness last for only a few seconds and there are no abnormal movements of the body. This type of seizure may occur hundreds of times daily.

Partial seizures are caused by abnormal electrical activity in a more limited area of the brain. They may be simple or complex. In simple partial seizures, consciousness is not lost and an abnormal twitching movement, tingling sensation, or hallucination of smell, vision, or taste occurs, lasting several minutes. In complex partial seizures, also known as temporal lobe epilepsy, conscious contact with the surroundings is lost. The sufferer becomes dazed and may behave oddly. Typically, the person remembers little, if any, of the event.

Diagnosis is made from examination of the nervous system and an EEG.

CT scanning or MRI of the brain and blood tests may also be carried out.

Anticonvulsant drugs usually stop or reduce the frequency of seizures.

Surgery may be considered if a single area of brain damage is causing the seizures.

Epilepsy that develops during childhood may disappear following adolescence.... epilepsy

Enlargement of one or both breasts in the male, due, in some cases, to an excess of the female sex hormone oestrogen in the blood.

Mild, temporary gynaecomastia can occur at birth as a result of maternal hormones, and it is common at puberty.

Gynaecomastia developing in later life may be due to chronic liver diseases such as cirrhosis. Hormone secreting tumours such as pituitary or testicular tumours may also be a cause.

Adult gynaecomastia, which sometimes occurs in only one breast, can also occur when synthetic hormones and some drugs, such as digoxin, spironolactone, and cimetidine, change the balance of sex hormones. Rarely, a discrete lump that develops on one breast may be due to a male breast cancer.

Investigation may involve blood tests. If cancer is suspected, a biopsy will be performed. Treatment depends on the cause. If a drug is responsible, an alternative will be prescribed if possible. If there is no underlying disease, swelling usually subsides without treatment. Cosmetic surgery may be considered in severe cases (see mammoplasty).

H2-receptor antagonists A common abbreviation for histamine2-receptor antagonists, a group of ulcer-healing drugs. (See also cimetidine; ranitidine; famotidine.) habituation The process of becoming accustomed to an experience. In general, the more a person is exposed to a stimulus, the less he or she is affected by it. People can become habituated to certain drugs and develop a reduced response to their effects (see tolerance).... gynaecomastia

n. the absence of sweating in the presence of an appropriate stimulus for sweating, such as heat. A reduction in sweating is known as hypohidrosis. Anhidrosis and hypohidrosis may accompany disease or occur as a congenital defect.... anhidrosis

(in psychology) linkage of one idea to another in a regular way according to their meaning. In free association the linkage of ideas arising in dreams or fantasy may be used to discover the underlying motives of the individual. In word association tests stimulus words are produced to which the subject has to respond as quickly as possible. See also loosening of associations.... association of ideas

adj. 1. remaining at the site of formation. A blood clot that has not been carried in the bloodstream from its point of origin is described as autochthonous. 2. originating in an organ without external stimulus, like the beating of the heart.... autochthonous

a form of *behaviour therapy that is used to reduce the occurrence of undesirable behaviour, such as sexual deviations or drug addiction. *Conditioning is used, with repeated pairing of some unpleasant stimulus with a stimulus related to the undesirable behaviour. An example is the use of *disulfiram in the treatment of alcoholism. Aversion therapy is little used nowadays. See also sensitization.... aversion therapy

n. a technique in which the heart is stopped by injecting it with a solution of salts, by hypothermia, or by an electrical stimulus. This has enabled complex cardiac surgery and transplants to be performed safely.... cardioplegia

One of the most common types of pain. A headache is only rarely a symptom of a serious underlying disorder. The pain arises from tension in the meninges, and in the blood vessels and muscles of the scalp.

Many headaches are simply a response to some adverse stimulus, such as hunger. Such headaches usually clear up quickly. Tension headaches, caused by tightening in the face, neck, and scalp muscles as a result of stress or poor posture, are also common, and may last for days or weeks. Migraine is a severe, incapacitating headache preceded or accompanied by visual and/or stomach disturbances. Cluster headaches cause intense pain behind 1 eye.

Common causes of headache include hangover and noisy or stuffy environments. Food additives may also be a cause. Some headaches are due to overuse of painkillers (see analgesic drugs). Other possible causes include sinusitis, toothache, cervical osteoarthritis, and head injury. Among the rare causes of headache are a brain tumour, hypertension, temporal arteritis, an aneurysm, and increased pressure within the skull.

Most headaches can be relieved by painkillers and rest. If a neurological cause is suspected, CT scanning or MRI may be performed.... headache

A distorted sensation based on misinterpretation of a real stimulus (for example, a pen is seen as a dagger). It is differs from a hallucination, in which a perception occurs without any stimulus.Usually, illusions are brief and can be understood when explained. They may be due to tiredness or anxiety, to drugs, or to forms of brain damage. Delirium tremens is a classic inducer of illusions. imaging techniques Techniques that produce images of structures within the body. The most commonly used and simplest techniques are X-rays (to view dense structures such as bone) and contrast X-rays, in which a medium, such as barium, that is opaque to X-rays is introduced into the body. Contrast X-ray techniques include barium X-ray examinations (used to examine the oesophagus, the stomach and the small intestine); cholecystography (used to visualize the gallbladder and common bile duct); bronchography (to view the airways connecting the windpipe to the lungs); angiography and venography (to provide images of the blood vessels); intravenous urography (to visualize the kidneys and urinary tract); and ERCP (by which the pancreatic duct and biliary system are examined).

Many X-ray imaging techniques have been superseded by newer procedures. These include ultrasound scanning, MRI (magnetic resonance imaging), PET scanning, and radionuclide scanning. However, X-rays are used in CT scanning. Some of these techniques use computers to process the raw imaging data and produce the actual image. Others can produce images without a computer, although one may be used to enhance the image. imipramine A tricyclic antidepressant drug most commonly used as a longterm treatment for depression. Possible adverse effects include excessive sweating, blurred vision, dizziness, dry mouth, constipation, nausea, and, in older men, difficulty passing urine.... illusion

Tests carried out to assess the extent of nerve damage caused by disorders of the peripheral nervous system (see neuropathy). In the test, an electrical stimulus is applied to a nerve, and the speed at which the nerve responds to the stimulus and transmits a signal is recorded.

nerve injury Damage or severance of conducting fibres within a nerve as a result of trauma, causing loss of skin sensation and muscle power. (See neuropathy for nerve damage from cause.

other than injury.)

If a peripheral nerve (a nerve outside the brain or spinal cord) is only partially severed, the cut fibres may be able to regenerate. Provided the severed ends are still aligned, new fibres can grow across the cut to rejoin the connection, restoring function. If a nerve is totally severed, the individual fibres cannot regenerate successfully and there is no recovery of function. Nerve tracts within the brain and spinal cord are structurally different from the peripheral nerves, and severed fibres in these tracts do not regenerate. For example, vision cannot be restored if the optic nerves are cut.Microsurgery can sometimes be used to stitch a severed peripheral nerve into place, but recovery is rarely complete.... nerve conduction studies

n. movement of a cell or organism in response to the stimulus of a gradient of chemical concentration.... chemotaxis

the electrical potential generated by the cochlea in response to an acoustic stimulus. It can be detected by *auditory brainstem response audiometry or *electrocochleography and is useful in the diagnosis of *auditory neuropathy spectrum disorder.... cochlear microphonic

(CLS) an inherited disease, more severe in males, that results in developmental delay and profound learning disability. It is characterized by distinctive facial anomalies, short stature, microcephaly, and *kyphoscoliosis; some patients have episodes of collapse when startled or excited (stimulus-induced drop episodes; SIDE). [G. S. Coffin (1923– ), US paediatrician; R. B. Lowry (1932– ), British geneticist]... coffin–lowry syndrome

a reflex in which the response occurs not to the sensory stimulus that normally causes it but to a separate stimulus, which has been learnt to be associated with it. In Pavlov’s classic experiments, dogs learned to associate the sound of a bell with feeding time and would salivate at the bell’s sound whether food was then presented to them or not.... conditioned reflex

Dulled, unpleasant, or otherwise altered sensations in the absence of an obvious stimulus.

Numbness and pins-and-needles are common abnormal sensations. The special senses can be impaired by damage to the relevant sensory apparatus (see vision, disorders of; smell; deafness; tinnitus). Other causes of abnormal sensation include peripheral nerve damage caused by diabetes mellitus, herpes zoster infection, or pressure from a tumour, and disruption of nerve pathways in the brain or spinal cord due to spinal injury, head injury, stroke, and multiple sclerosis.

Pressure on or damage to nerves can sometimes be relieved by surgery or by treatments for the cause.

In other cases, distressing abnormal sensation can be relieved only by cutting the relevant nerve fibres or by giving injections to block the transmission of signals.... sensation, abnormal

n. (in psychology) the state produced when a stimulus produces two opposing reactions. The basic types of conflict situation are approach–approach, in which the individual is drawn towards two attractive – but mutually incompatible – goals; approach–avoidance, where the stimulus evokes reactions both to approach and to avoid; and avoidance–avoidance, in which the avoidance reaction to one stimulus would bring the individual closer to an equally unpleasant stimulus. Conflict has been used to explain the development of neurotic disorders, and the resolution of conflict remains an important part of psychoanalysis. See also conversion.... conflict

(ECoG) n. a test to measure electrical activity produced within the *cochlea in response to a sound stimulus. It is used in the diagnosis of Ménière’s disease and other forms of sensorineural *deafness.... electrocochleography

n. 1. a state of abnormal mental excitement or irritability. 2. rapid response to a stimulus.... erethism

n. a drug that enhances the expulsion of sputum from the air passages. *Mucolytic expectorants act by decreasing the viscosity of the bronchial secretions so that they are easier to cough up. Drugs such as *ipecacuanha and ammonium chloride are claimed to be stimulant expectorants in small quantities: they irritate the lining of the stomach, which is said to provide a stimulus for the reflex production of sputum by the glands in the bronchial mucous membrane. At higher doses they produce vomiting.... expectorant

n. 1. mental or physical tiredness, following prolonged or intense activity. Muscle fatigue may be due to the waste products of metabolism accumulating in the muscles faster than they can be removed by the venous blood. Incorrect or inadequate food intake or disease may predispose a person to fatigue. 2. the inability of an organism, an organ, or a tissue to give a normal response to a stimulus until a certain recovery period has elapsed.... fatigue

n. 1. (in psychology) a simple type of learning consisting of a gradual waning response by the subject to a continuous or repeated stimulus that is not associated with *reinforcement. 2. (in pharmacology) the condition of being psychologically dependent on a drug, following repeated consumption, marked by reduced sensitivity to its effects and a craving for the drug if it is withdrawn. See also dependence.... habituation

(startle reflex) a primitive reflex seen in newborn babies in response to the stimulus of a sudden noise or movement: the baby will fling its arms and legs wide and will appear to stiffen; the arms and legs are then drawn back into flexion. The Moro reflex should disappear spontaneously by four months. Its presence beyond this age is suggestive of an underlying neurological disorder, such as cerebral palsy. [E. Moro (1874–1951), German paediatrician]... moro reflex

a reflex action of the intestine in which a physical stimulus causes the intestine to contract above and relax below the point of stimulation.... myenteric reflex

n. a form of abnormal growth that is independent of the body’s normal homeostatic growth-regulating mechanisms, continues after the initiating stimulus has been removed, and is purposeless. Neoplasia is always pathological. See cervical intraepithelial neoplasia; MENS; prostatic intraepithelial neoplasia; vulval intraepithelial neoplasia. Compare hyperplasia. —neoplastic adj.... neoplasia

n. movement of a cell or organism in response to a stimulus of light.... phototaxis

n. an abnormal change in the nature of a tissue, usually in response to an environmental factor. For instance, columnar epithelium lining the bronchi may be converted to squamous epithelium (squamous metaplasia) following exposure to cigarette smoke. Prolonged exposure to gastric acid may result in the squamous epithelium of the oesophagus being converted to glandular epithelium (glandular metaplasia). Myeloid metaplasia is the development of bone marrow elements, normally found only within the marrow cavities of the bones, in organs such as the spleen and liver. This may occur after bone marrow failure. Metaplasia is not itself a premalignant condition, but neoplasms (abnormal new growths) may arise in metaplastic tissues if the initiating stimulus is not removed. —metaplastic adj.... metaplasia

(OAE, Kemp echoes) tiny sounds that emerge from the inner ear either spontaneously (spontaneous otoacoustic emissions, SOAE) or shortly after the ear is exposed to an external sound (evoked otoacoustic emissions, EOAE). An objective test of hearing has been developed using otoacoustic emissions. The test equipment creates a small sound and then detects any response from the ear. This can be done using a click stimulus (transient otoacoustic emissions, TOAE) or two separate tones (distortion product otoacoustic emissions, DPOAE). A normal response suggests that the ear is functioning and that hearing is satisfactory. All newborn children in the UK are now screened using this technique.... otoacoustic emissions

n. the return or increase of a condition after cessation of treatment or other stimulus. Rebound headache, which may be worse than the initial headache, may occur after stopping medication, particularly if too much was taken. Similarly, rebound insomnia may occur after the cessation of sleeping pills, particularly after long-term treatment.... rebound

n. 1. (in physiology) the phenomenon whereby an increase in the strength of a stimulus or repetition of the stimulus will stimulate increasing numbers of nerve cells to respond. 2. (in audiology) the phenomenon in which a person with sensorineural deafness cannot hear quiet sounds but can perceive loud sounds just as loudly as, or even more loudly than, a person with normal hearing.... recruitment

(in neurology) the time of recovery needed for a nerve cell that has just transmitted a nerve impulse or for a muscle fibre that has just contracted. During the refractory period a normal stimulus will not bring about excitation of the cell, which is undergoing *repolarization.... refractory period

n. (in psychology) the strengthening of a conditioned reflex (see conditioning). In classical conditioning this takes place when a conditioned stimulus is presented at the same time as – or just before – the unconditioned stimulus. In operant conditioning it takes place when a pleasurable event (or reinforcer), such as a reward, follows immediately after some behaviour. The reinforcement schedule governs how often and when such behaviour is rewarded. Different schedules produce different effects on behaviour.... reinforcement

n. the way in which the body or part of the body reacts to a *stimulus. For example, a nerve impulse may produce the response of a contraction in a muscle that the nerve supplies.... response

n. (pl. saccades) a rapid movement of the eye used to shift gaze from one object to another. It can be done voluntarily or occurs as a reflex triggered by a visual stimulus in the peripheral visual field.... saccade

a collection of specialized cells (*receptors), connected to the nervous system, that is capable of responding to a particular stimulus from either outside or inside the body. Sense organs can detect light (the eyes), heat, pain, and touch (the skin), smell (the nose), and taste (the taste buds).... sense organ

n. the ability to be affected by, and respond to, changes in the surroundings (see stimulus). Sensibility is a characteristic of cells of the nervous system.... sensibility

adj. possessing the ability to respond to a *stimulus. The cells of the retina, for example, are sensitive to the stimulus of light and respond by sending nerve impulses to the brain. Other *receptors are sensitive to different specific stimuli, such as pressure or the presence of chemical substances.... sensitive

n. impairment of the ability to perceive or focus on more than one element of a complex visual stimulus at a time, resulting in inability to understand the overall meaning of a situation or scene. This may result from trauma or a stroke at the junction of the occipital and parietal lobes.... simultanagnosia