Structure And Functions Of The Peripheral Nervous System Biology Essay

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The two main cells in the nervous system are neurons and neuroglia. The neuron is the function unit for the nerve cell. In the neuron it has the following structure: cell body, one axon, and one or more dendrites. The cell body contains the nucleus and cytoplasm, the axon conducts impulses away from the cell body, and the dendrites do the opposite function and conducts impulse towards the cell body. The neuroglia is the support system for neurons. They protect the nervous system by digesting unwanted substances. In addition, neuroglia has three types of cells known as astrocytes, microglia, and oligodenrocytes. The cells serve as attachment, digestion of waste products and as a protective barrier of myelin that cover the cell body. Astrocytes are the only cells found in the central nervous system.

Structure and Functions of the Peripheral Nervous System

The peripheral nervous system is consisted of nerves and ganglia. The peripheral nervous system has two different nerves known as afferent and efferent. Afferent nerves carry impulse to the central nervous system and the efferent nerve carries them from the central nervous system to muscle and glands. The PNS is divide into two nervous systems; the somatic which provides voluntary control over skeletal muscles and the autonomic which provides involuntary control over smooth muscles, cardiac muscles and glandular activity. The autonomic nervous system contains sympathetic and parasympathetic nerves. Sympathetic nerves increases the heart rate and blood pressure. The parasympathetic does the opposite effect in the peripheral nervous system and relaxes the body.

Main Components of the Central Nervous System

The central nervous system is consisted of the brain and spinal cord. The meninges and the cerebrospinal fluid are the main components of the CNS. The meninges have three layers known as the dura mater, arachnoid membrane and the pia mater. The dura mater is the outermost layer and has subdural and epidural space surrounding it; it serves as support of the dura mater. The arachnoid membrane has a spider web appearance that attaches the inner layers of the meninges. This membrane has a space around it that serves as the house for the cerebrospinal fluid, which is known as the subarachnoid space. The cerebrospinal fluid protects and serves as a shock server for the brain and spinal cord. The last layer is the pia mater. This layer is bound to the surface of the brain, and spinal cord. In this layer the cerebrospinal fluid contains protein, glucose, urea, salts and some white blood cells.

Structures of the Brain

There are 13 structure of the brain. The structures have their own functions.

cerebrum- largest, uppermost portion of the brain. Controls consciousness, memory, sensation, emotions, and voluntary muscles.

gyrus- separated by grooves.

sulci- the grooves that separate the gyrus.

longitudinal fissure- divides the cerebrum.

right cerebral hemisphere- first hemisphere of the longitudinal fissure.

left cerebral hemisphere- second hemisphere of the longitudinal fissure.

cerebellum- attached to the brain stem and it maintains muscle tone and coordination of movement and balance.

diencephalon- located between cerebrum and the midbrain. Consists of the thalamus, hypothalamus, and the pineal body.

thalamus- receives all sensory stimuli except smelling ands relays them to the cerebral cortex.

hypothalamus- located beneath the thalamus and is responsible for activating, controlling, and integrating. Some example are the body temperature, sleep and appetite.

brain stem- is the region between the diencephalon and the spinal cord. It includes the midbrain, pons and the medulla oblongata.

midbrain- the upper part of the brain stem.

Pathological Conditions of the Nervous System

Alzheimer’s disease- It begins with minor memory loss and progresses to complete memory loss of mental, emotional, and physical functioning. Their is no test to identify Alzheimer’s disease (AD). Treatment for it includes the use of Cognex to improve memory up to 40%, anti-depressants and tranquilizers are often used.

anencephaly- is an absence of the brain and spinal cord at birth, a congenital disorder. This condition can be detected through ultrasonography early in pregnancy.

brain abscess- is a localized accumulation of pus located anywhere in the brain tissue due to an infectious process symptoms is a complaint of a headache. A computerized tomography (CT) scan or (EEG) electroencephalogram will verify the diagnosis and location.

carpal tunnel syndrome- punch or compression of the median nerve with in the carpal tunnel due to inflammation and swelling on tendons. Anti-inflammatory medicine, splints, physical therapy and stopping repetitive overuse is the treatment this syndrome.

cerebral concussion- is a brief interruption of brain function, usually with loss of consciousness last for few seconds. Starts with a headache, blurred vision, drowsiness, confusion, and dizziness. Treatment will be individualized observed for signs.

cerebral contusion- is a small, scattered venous hemorrhage in the brain (bruise in the brain tissue), swelling of the brain and increased intracranial pressure (ICP). Treatment is closed observation of secondary effects.

cerebral palsy- is a collective term used to describe congenital brain damage that is permanent but not progressive. Functions may range from extremely bright and normal to severe mental retardation.

cerebrovascular accident (CVA)- death of specific portion of the brain tissue. Also known as a stroke. Treatment depends on cause and effect of the stroke.

degenerative disk- is the deterioration of the interverbral disk due to constant motion and wear on the disk. Pain is the primary symptom of the spinal nerves. Treatment includes best rest, bracing the back, non-steroidal anti-flammatory drugs (NSAID’s) and surgical intervention.

epilepsy- is a syndrome of recurring episodes of excessive irregular electrical activity of the brain resulting in involuntary muscle movements called seizures. Anticonvulsant medication can reduce or control most seizure activity. Treatment is a complete neurological exam, MRI and CT scans.