Page 69 - 84 human physiolofy part-1

The Nervous System

• The median pectoral nerve, C8 and T1, to the pectoralis muscle
• The medial brachial cutaneous nerve, T1
• The medial antebrachial cutaneous nerve, C8 and T1
• The median nerve, partly. The other part comes from the lateral cord. C7, C8 and T1 nerve
roots. The first branch of the median nerve is to the pronator teres muscle, then the flexor carpi
radialis, the palmaris longus and the flexor digitorum superficialis. The median nerve provides
sensation to the anterior palm, the anterior thumb, index finger and middle finger. It is the nerve
compressed in carpal tunnel syndrome.
• The ulnar nerve originates in nerve roots C7, C8 and T1. It provides sensation to the ring
and pinky fingers. It innervates the flexor carpi ulnaris muscle, the flexor digitorum profundus
muscle to the ring and pinky fingers, and the intrinsic muscles of the hand (the interosseous
muscle, the lumbrical muscles and the flexor pollicus brevis muscle). This nerve traverses a
groove on the elbow called the cubital tunnel, also known as the funny bone. Striking the nerve
at this point produces an unpleasant sensation in the ring and little fingers.

Other thoracic spinal nerves (T3-T12)

The remainder of the thoracic spinal nerves, T3 through T12, do little recombining. They form the
intercostal nerves, so named because they run between the ribs. For points of reference, the 7th
intercostal nerve terminates at the lower end of the sternum, also known as the xyphoid process. The
10th intercostal nerve terminates at the umbilicus, or the belly button.

The somatic nervous system is that part of the peripheral nervous system associated with the
voluntary control of body movements through the action of skeletal muscles, and also reception of
external stimuli. The somatic nervous system consists of afferent fibers that receive information from
external sources, and efferent fibers that are responsible for muscle contraction. The somatic system
includes the pathways from the skin and skeletal muscles to the Central Nervous System. It is also
described as involved with activities that involve consciousness.

The basic route of the efferent somatic nervous system includes a two neuron sequence. The first is
the upper motor neuron, whose cell body is located in the precentral gyrus (Brodman Area 4) of the
brain. It receives stimuli from this area to control skeletal (voluntary) muscle. The upper motor neuron
carries this stimulus down the corticospinal tract and synapses in the ventral horn of the spinal cord
with the alpha motor neuron, a lower motor neuron. The upper motor neuron releases acetylcholine
from its axon terminal knobs and these are received by nicotinic receptors on the alpha motor neuron.
The alpha motor neurons cell body sends the stimulus down its axon via the ventral root of the spinal
cord and proceeds to its neuromuscular junction of its skeletal muscle. There, it releases acetylcholine
from its axon terminal knobs to the muscles nicotinic receptors, resulting in stimulus to contract the
muscle.

The somatic system includes all the neurons connected with the muscles, sense organs and skin. It
deals with sensory information and controls the movement of the body.

The Autonomic System

The Autonomic system deals with the visceral organs, like the heart, stomach, gland, and the
intestines. It regulates systems that are unconsciously carried out to keep our body alive and well, such

Wikibooks | 69