Peripheral Nervous System

Together the CNS and the PNS provide three general functions: sensory, integrative, and motor. The sensory function consists of receptors that monitor the body both externally and internally. The sensory receptors convert their information into nerve impulses, which are then transmitted via the PNS to the CNS, and the signals are integrated. They are brought together, creating sensations and helping to produce thoughts and perceptions. As a result, we make decisions and use motor functions to act on them. The PNS includes the cranial and spinal nerves as well as the ANS.

Cranial Nerves

Twelve pairs of cranial nerves come from the brain. They are named both by Roman numeral and name. The Roman numeral partially identifies the cranial nerves’ location in the brain. Refer to Table for a summary of the cranial nerves and their function.

READ:   Autonomic Nervous System

Table. Cranial Nerves

NUMBER AND NAME FUNCTION(S)
I Olfactory • Sense of smell
II Optic • Sense of sight
III Oculomotor • Movement of the eyeball• Constriction of pupil in bright light or for near vision
IV Trochlear • Movement of eyeball
V Trigeminal • Sensation in face, scalp, and teeth• Contraction of chewing muscles
VI Abducens • Movement in the eyeball
VII Facial • Sense of taste• Contraction of facial muscles

• Secretion of saliva

VIII Acoustic (vestibulocochlear) • Sense of hearing• Sense of equilibrium
IX Glossopharyngeal • Sense of taste• Sensory for cardiac, respiratory, and blood pressure reflexes

• Contraction of pharynx

• Secretion of saliva

X Vagus • Sensory in cardiac, respiratory, and blood pressure reflexes• Sensory and motor to larynx (speaking)

• Decreases heart rate

• Contraction of alimentary tube (peristalsis)

• Increases digestive secretions

XI Accessory • Contraction of neck and shoulder muscles• Motor to larynx (speaking)
XII Hypoglossal • Movement of the tongue

Spinal Nerves

Thirty-one pairs of spinal nerves branch from the spinal cord. There are 8 pairs of cervical nerves (C1–C8), 12 pairs of thoracic nerves (T1–T12), 5 pairs of lumbar nerves (L1–L5), 5 pairs of sacral nerves (S1–S5), and 1 pair of coccygeal nerves. Each set of nerves has a specialized task.

The spinal cord and spinal nerves

FIGURE. The spinal cord and spinal nerves. The distribution of spinal nerves is shown only on the left side. The nerve plexuses are labeled on the right side. A nerve plexus is a network of neurons from several segments of the spinal cord that combine to form nerves to specific parts of the body. For example, the radial and ulnar nerves to the arm emerge from the brachial plexus. (From Scanlon, VC, and Sanders, T: Essentials of Anatomy and Physiology, ed 5. FA Davis, Philadelphia, 2007, p 173, with permission.)

TRANSIENT ISCHEMIC ATTACKS ICD-9: 435.9 Description Transient ischemic attacks (TIAs) are temporary, often recurrent episodes of impaired neurological activity resulting from insufficient blood flow to a part of the brain. These “little strokes” or little brain attacks may last for seconds or hours, after which the symptoms gradually subside. TIAs share a common pathophysiology with brain attacks and may serve as a warning of an impending CVA. Ten percent of individuals who have TIAs suffer a stroke within 3 months. Etiology TIAs are caused by the temporary obstruction of cerebral arterioles by very small emboli or by ischemia of a small portion of brain tissue due to arterial narrowing in that region. These processes are usually the result of atherosclerotic disease. Signs and Symptoms The particular combination of symptoms during a TIA, like those for a CVA, depend on which portion of the brain is affected. Symptoms may include the sudden onset of muscle weakness in the arm, leg, or foot on one...
RESTLESS LEG SYNDROME ICD-9: 333.94 Description Restless leg syndrome (RLS) is a neurological disorder in which sensations in the leg create an uncontrollable urge to move the leg when at rest. Trying to relax the leg only makes it worse. The only relief is to get up and move around. This action creates poor sleep patterns and exhaustion the next day. It is believed that as many as 12 million individuals in the United States have RLS, and many more are undiagnosed. Etiology The cause is essentially unknown; however, risk factors include heredity, pregnancy, stress, and related disorders. Peripheral neuropathy and/or an iron deficiency, diabetes, and Parkinson disease can cause or worsen RLS. Signs and Symptoms Individuals describe a restless or unpleasant sensation in their legs. The terms creeping, tingling, burning, and crawling are often used to describe the feeling. The RLS begins when an individual is inactive, is relieved by moving, and worsens at night. Diagnostic Procedures RLS...
NERVOUS SYSTEM The nervous system consists of highly specialized cells designed to transmit information rapidly between various parts of the body. Topographically it can be divided into two major parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The brain and spinal cord constitute the CNS, which lies within the skull and vertebral canal, while nerves in the PNS connect the CNS with all other parts of the body. The CNS is a massive collection of nerve cells connected in an intricate and complex fashion to subserve the higher order functions of the nervous system, such as: thought, language, emotion, control of movement and the analysis of sensation. It is isolated from the rest of the body; its cardinal characteristic is that it is located wholly within the skull and vertebral canal. The PNS consists of cells that connect the CNS with the other tissues of the body. These cells are aggregated into a large number of cable-like structures called nerves, which are thr...
NERVOUS SYSTEM ANATOMY AND PHYSIOLOGY REVIEW The body’s nervous system is an elaborate, interlaced network of nerve cells of astonishing complexity and sophistication. This network includes the brain, spinal cord, and nerves. The entire system functions to regulate and coordinate body activities and bring about responses by which the body adjusts to changes in its internal and external environments. The nervous system consists of two divisions: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. It processes and stores sensory information and includes the parts of the brain governing consciousness. The PNS is composed of all other nervous tissue outside the CNS and includes 12 pairs of cranial nerves, 31 pairs of spinal nerves, all sensory nerves, and the sympathetic and parasympathetic nerves. The sympathetic and parasympathetic nerves comprise the autonomic nervous system (ANS), which regulates involuntary muscle movements and the action of glands. The P...
Learn About the Peripheral Nervous System The nervous system consists of the brain, spinal cord, and a complex network of neurons. This system is responsible for sending, receiving, and interpreting information from all parts of the body. The nervous system monitors and coordinates internal organ function and responds to changes in the external environment. This system can be divided into two parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is composed of the brain and spinal cord, which function to receive, process, and send information to the PNS. The PNS consists of cranial nerves, spinal nerves, and billions of sensory and motor neurons. The primary function of the peripheral nervous system is to serve as a pathway of communication between the CNS and the rest of the body. While CNS organs have a protective covering of bone (brain-skull, spinal cord - spinal column), the nerves of the PNS are exposed and more vulnerable to injury. Types of Cells There are two types of cells in...