A muscle of the posterior upper arm which acts to extend the forearm. So-named because it originates from three heads.
n. a muscle with three heads of origin, particularly the triceps brachii, which is situated on the back of the upper arm and contracts to extend the forearm. It is the *antagonist of the *brachialis.
The muscle at the back of the upper arm. At the upper end of the triceps are 3 “heads”; 1 is attached to the outer edge of the scapula (shoulderblade), and the other 2 to either side of the humerus (upper-arm bone). The lower part of the triceps is attached to the olecranon process of the ulna (the bony prominence on the elbow). Contraction of the muscle straightens the arm. (See also biceps muscle.)... triceps muscle
a tendon reflex that acts at the level of the seventh cervical spinal nerve. With the elbow flexed and relaxed, the triceps tendon is struck just above the elbow, causing contraction of the triceps and extension of the elbow. This reflex is increased in upper *motor neuron lesions and absent in lower motor neuron lesions.... triceps jerk
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