n. 1. one of the conical masses that make up the medulla of the *kidney, extending inwards from a base inside the cortex towards the pelvis of the kidney. 2. one of the elongated bulging areas on the anterior surface of the *medulla oblongata in the brain, extending downwards to the spinal cord. 3. one of the divisions of the vermis of the *cerebellum in the middle lobe. 4. a protrusion of the medial wall of the vestibule of the middle ear.
a type of neuron found in the *cerebral cortex, with a pyramid-shaped cell body, a branched dendrite extending from the apex towards the brain surface, several dendrites extending horizontally from the base, and an axon running in the white matter of the hemisphere.... pyramidal cell
a collection of nerve fibres in the central nervous system that extend from the *motor cortex in the brain to the spinal cord and are responsible for initiating movement. In the medulla oblongata the fibres form a *pyramid (hence the name), within which they cross from one side of the brain to the opposite side of the spinal cord; this is called the decussation of the pyramids. Damage to the pyramidal system manifests in a specific pattern of weakness in the face, arms, and legs, abnormally brisk reflexes, and an extensor *plantar reflex (Babinski response).... pyramidal system
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