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The C8 nerve contributes to the motor innervation of many of the muscles in the trunk and upper limb. Its primary function is the flexion of the fingers, and this is used as the clinical test for C8 integrity, in conjunction with the finger jerk reflex.
The brachial plexus is a network of nerves (nerve plexus) formed by the anterior rami of the lower four cervical nerves and first thoracic nerve (C5, C6, C7, C8, and T1).This plexus extends from the spinal cord, through the cervicoaxillary canal in the neck, over the first rib, and into the armpit, it supplies afferent and efferent nerve fibers to the chest, shoulder, arm, forearm, and hand.
externally rotate the arm C6, C7: Extend elbow and wrist (triceps and wrist extensors); pronate wrist C7, C8: Flex wrist; supply small muscles of the hand: T1–T6: Intercostals and trunk above the waist: T7–L1: Abdominal muscles L1–L4: Flex hip joint: L2, L3, L4: Adduct thigh; Extend leg at the knee (quadriceps femoris) L4, L5, S1
The test can be performed by tapping the triceps tendon [3] [note 1] with the sharp end of a reflex hammer while the forearm is hanging loose at a right angle to the arm. A sudden contraction of the triceps muscle causes extension, [note 2] and indicates a normal reflex. [4] [5]
The last four cervical spinal nerves, C5 through C8, and the first thoracic spinal nerve, T1, combine to form the brachial plexus, or plexus brachialis, a tangled array of nerves, splitting, combining and recombining, to form the nerves that subserve the upper-limb and upper back. Although the brachial plexus may appear tangled, it is highly ...
The cervical spinal nerve 7 (C7) is a spinal nerve of the cervical segment. [1] It originates from the spinal column from above the cervical vertebra 7 (C7). It runs through the interspace between the C6 and C7 vertebrae.
An action potential (or nerve impulse) is a transient alteration of the transmembrane voltage (or membrane potential) across the membrane in an excitable cell generated by the activity of voltage-gated ion channels embedded in the membrane. The best known action potentials are pulse-like waves that travel along the axons of neurons.
The posterior interosseous nerve (or dorsal interosseous nerve/deep radial nerve) is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminished in size compared to the deep branch of the radial nerve.