Page 68 - 84 human physiolofy part-1

Chapter 4

The 10 out of the 12 cranial nerves originate from the brainstem, and mainly control the functions
of the anatomic structures of the head with some exceptions. CN X receives visceral sensory
information from the thorax and abdomen, and CN XI is responsible for innervating the
sternocleidomastoid and trapezius muscles, neither of which is exclusively in the head.

Spinal nerves take their origins from the spinal cord. They control the functions of the rest of the
body. In humans, there are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1
coccygeal. The naming convention for spinal nerves is to name it after the vertebra immediately above
it. Thus the fourth thoracic nerve originates just below the fourth thoracic vertebra. This convention
breaks down in the cervical spine. The first spinal nerve originates above the first cervical vertebra and
is called C1. This continues down to the last cervical spinal nerve, C8. There are only 7 cervical
vertebrae and 8 cervical spinal nerves.

Lateral cord

The lateral cord gives rise to the following nerves:

• The lateral pectoral nerve, C5, C6 and C7 to the pectoralis major muscle, or musculus
pectoralis major.
• The musculocutaneous nerve which innervates the biceps muscle
• The median nerve, partly. The other part comes from the
medial cord. See below for details.

Posterior cord

The posterior cord gives rise to the following nerves:

• The upper subscapular nerve, C7 and C8, to the
subscapularis muscle, or musculus supca of the rotator cuff.
• The lower subscapular nerve, C5 and C6, to the teres major
muscle, or the musculus teres major, also of the rotator cuff.
• The thoracodorsal nerve, C6, C7 and C8, to the latissimus
dorsi muscle, or musculus latissimus dorsi.
• The axillary nerve, which supplies sensation to the shoulder
and motor to the deltoid muscle or musculus deltoideus, and the
teres minor muscle, or musculus teres minor. Diagram showing human
• The radial nerve, or nervus radialis, which innervates the dermatoms, i.e., skin regions with
triceps brachii muscle, the brachioradialis muscle, or musculus respect to the routing of their
brachioradialis,, the extensor muscles of the fingers and wrist nerve connection of their afferent
nerves through the spinal cord.
(extensor carpi radialis muscle), and the extensor and abductor
muscles of the thumb. See radial nerve injuries.

Medial cord

The medial cord gives rise to the following nerves:

68 | Human Physiology