Anatomy and Physiology of the Human Body 11 Anatomy and Physiology of the Human Body

2 The Nervous System U N I T Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

The Two Main Divisions of the Nervous System Central nervous system (CNS) Made up of the brain and spinal cord Peripheral nervous system (PNS) Made up of all the nerves that connect the CNS to every organ and area of the body Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Two Types of Peripheral Nerves 12 pairs of cranial nerves Connect the brain directly to the sensory organs (eyes, ears, tongue, nose, and skin) 31 pairs of spinal nerves that act as: Motor nerves to permit movement Sensory nerves to perceive stimuli Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Simple and Complex Reflex Actions Simple reflex actions No interpretation or decision is required; the nerve impulse travels only to the spinal cord and back Complex reflex actions The impulse is relayed through the spinal cord to the brain and the brain interprets the sensory impulse and sends it back down the spine Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Synapses A synapse is a minute space between the axon of one neuron and the dendrite of another. These impulses release chemicals called neurotransmitters that either speed up or slow down the transmission. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

The Effect of Various Substances on the Action of a Synapse Alcohol slows down reactions. Stimulants speed up reactions. Diseases can invade the body and neurotoxins from the bacteria are released that can cause contraction or paralysis of muscle groups. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

The Purpose of the Automatic Nervous System As part of the peripheral nervous system, these nerves are involuntary and unconsciously control breathing, heartbeat, and digestion. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

The Action of the Two Divisions of the Autonomic Nervous System The sympathetic nervous system begins at the base of the brain and runs down the spinal cord. These nerves extend to all vital organs and blood vessels, the eyes, and the sweat glands. (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

The Action of the Two Divisions of the Autonomic Nervous System The parasympathetic nervous system contains the vagus nerve and the pelvic nerve, which are affected by emotions. The vagus nerve extends from the brain to the upper abdominal organs. The pelvic nerve branches into the lower abdominal and pelvic organs. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

The Main Parts of the Brain and Their Functions (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

The Main Parts of the Brain and Their Functions Cerebrum Controls sensory and motor activities and is divided into lobes Frontal lobe Located behind the forehead; related to emotion and personality Occipital lobe Located at the far back of the cerebrum; related to vision (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

The Main Parts of the Brain and Their Functions Temporal lobe Located on the side of the cerebrum; associated with hearing and smell Parietal lobe Located between the frontal and occipital lobes; associated with movement in the hands, feet, and tongue as well as sensations of pain, heat, and cold (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

The Main Parts of the Brain and Their Functions Cerebellum Found beneath the cerebrum; responsible for smooth muscle movement and coordination The medulla oblongata Adjoins the spinal cord; influences the function of the heart and lungs, stomach secretions, and opening of blood vessels (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

The Main Parts of the Brain and Their Functions Pons Located just above the medulla; regulates breathing and is responsible for chewing, tasting, and the secretion of saliva Midbrain Located superior to the pons; control center for reflex movements and pupil dilation of the eyes Thalamus Located between the cerebrum and the midbrain; acts as a relay station for impulses going to and from the brain Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

The Hypothalamus Located just below the thalamus Responsible for: Controlling the autonomic nervous system Controlling blood pressure Maintaining body temperature Stimulating hormones to conserve water and maintain water balance Assisting in appetite regulation Increasing intestinal secretions and motility Playing a role in emotions such as fear & pleasure Maintaining state of wakefulness Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

The Coverings of the Brain and Spinal Cord and Their Purpose The meninges are the coverings on the brain and the spinal cord Made up of 3 layers: Pia mater: inner layer contains nerve tissue Arachnoid: middle layer made of delicate, lacelike membranes Dura mater: outer layer that protects CNS from damage from contact with bony surfaces of the skull and spine Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

The Function of Cerebrospinal Fluid Cerebrospinal fluid (CSF) acts as a watery cushion or shock absorber to provide additional protection for the CNS. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Common Diagnostic Tests Arteriography A catheter is inserted into an artery and then threaded up to the carotid artery in the neck. A dye is injected to detect aneurysms, hemorrhage, arteriosclerosis, or to check for signs of a stroke. (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Common Diagnostic Tests Glasgow coma scale Tool used to determine the level of unconsciousness Assesses eye movement, verbal response, and motor response Computerized axial tomography Series of x-rays of the layers of the brain; makes a three-dimensional picture Can identify tumors, bleeding, blood clots, disease, and edema (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Common Diagnostic Tests Electroencephalography A brain wave test that measures the brain’s electrical signals, both normal and abnormal Can detect abnormalities caused by epilepsy, tumors, strokes, head injuries, or infections (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Common Diagnostic Tests Electromyography Uses electrical stimulation passed through small needles inserted into the muscle to demonstrate the electrical activity of peripheral muscles Can diagnose disorders such as diabetic neuropathy and carpal tunnel syndrome (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Common Diagnostic Tests Lumbar puncture A spinal needle is inserted into a small space in the lower back to remove small amounts of cerebrospinal fluid Can help diagnose bleeding or infection and can measure fluid pressure in the spine Myelography After a lumbar puncture is performed, dye is instilled to outline the structures of the spinal cord to detect abnormalities of the spinal cord (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Common Diagnostic Tests Positron emission tomography Uses agents, such as glucose or hormones; agents are mixed with chemicals and injected into the blood; records images of where the material ends up in the body Can help diagnose epilepsy and Alzheimer’s disease Skull x-rays X-ray images of the bony structure of the skull to identify tumors and fractures Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Common Diseases and Disorders Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Alzheimer’s Disease Progressive, degenerative disease that attacks the brain Results in impaired memory, thinking, and behavior, as well as memory loss 8th leading cause of death in the United States Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Amyotrophic Lateral Sclerosis (Lou Gehrig’s Disease) Fatal, progressive neurological disease that causes degeneration of motor neurons in the brain and spinal cord Usually occurs between ages 40 and 70 Death occurs within 2 to 5 years of diagnosis Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Bell’s Palsy Disease that affects the 7th cranial nerve of the face It occurs spontaneously and will usually subside spontaneously within 1 to 9 weeks. Causes weakness or paralysis on one side of the face Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Cerebral Palsy Nonprogressive brain injury that occurs during fetal development, perinatally, or in early infancy; affects muscle and brain development Four forms of cerebral palsy include: Spastic (50% to 75%) Athetoid (15% to 20%) Atonic (10%) Mixed Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Encephalitis Severe brain inflammation that causes edema and nerve cell destruction Onset of fever, headache, vomiting, and stiffness in the neck and back is sudden and acute Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Epilepsy Seizure disorder that affects 1% to 2% of the population Generally associated with abnormal electrical impulses from the neurons Causes uncontrollable convulsions, loss of control of bodily functions, and unconsciousness Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Essential Tremor Most common movement disorder of the nervous system Causes involuntary shaking of the hands and head, which is made worse by action or movement Often confused with Parkinson’s disease Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Headache Often classified as vascular, muscle contractions (tension), or traction (inflammatory) Causes dull, persistent aching, and a feeling of a tight band around the head Can be caused by stress, fatigue, or environment Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Migraine Headache Headache that causes severe throbbing pain Beginning symptoms may include fatigue, visual disturbances, or sensory symptoms Triggers that may initiate migraines are chocolate, red wine, and bright lights Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Herpes Zoster Acute unilateral inflammation of the dorsal root ganglion Causes fluid-filled vesicle lesions on the skin and severe pain from the affected nerves The vesicles erupt in about 2 weeks Episodes can last from 1 to 4 weeks. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Hydrocephalus Excess accumulation of cerebrospinal fluid within the ventricles of the brain Occurs most commonly in newborns Increase in fluid compresses the brain tissue against the skull and results in brain damage Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Meningitis Inflammation of the meninges of the brain and spinal cord May be caused by a virus or bacteria If untreated, mortality is 70% to 100% if it is bacterial meningitis. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Multiple Sclerosis Demyelinating disorder of the nervous system that affects the central nervous system; usually first diagnosed between ages 20 and 40 The disease attacks the myelin sheath of the nerves and destroys patches of tissue, which are replaced by scar tissue. (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Multiple Sclerosis The scar tissue distorts or interrupts the passage of the nerve impulse. This results in paralysis, double vision, loss of balance, weakness, speech and hearing difficulties, foot dragging, numbness, and a sensation of pins and needles. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Neuralgia Terms used to describe generalized nerve pain Neuralgia causes severe pain along the course of the involved nerve or nerves. Can be the result of pressure, nutrition, toxins, inflammation, or ganglial changes. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Paralysis Term used to describe temporary or permanent loss of voluntary function Spastic paralysis Caused by upper motor neurons Flaccid Caused by lower motor neurons Can be caused by trauma or by the destruction of nerve tissue Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Hemiplegia Term used to describe one-sided paralysis that results from brain damage Damage to the left side of the brain will result in right-sided paralysis. Damage to the right side of the brain will result in left-sided paralysis. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Paraplegia Term used to describe the loss of motor or sensory function in the lower extremities Usually the result of trauma Paralysis may be temporary or permanent, spastic or flaccid Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Quadriplegia Devastating permanent paralysis that affects all body systems, the arms, the legs, and all of the body below the level of the injury to the spinal cord Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Parkinson’s Disease Progressive, crippling disease that affects 1 in every 100 people over the age of 60 Parkinson’s disease affects more men than women Main symptoms are muscle rigidity and hand tremors with a masklike facial expression (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Parkinson’s Disease Symptoms progress to include a peculiar gait, drooling, progressive tremors of the hands, and the head becomes bowed Body bends forward and steps become faster and faster; often results in falling Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Reye’s Syndrome Acute childhood illness characterized by fatty infiltration of the liver and increased intracranial pressure Prognosis depends on the degree of CNS depression that results from the increased pressure This syndrome almost always follows within 1 to 3 days of an acute viral infection, such as an upper respiratory infection or chickenpox. A correlation exists with the use of aspirin in children and the flu and chickenpox. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Sciatica Term used to describe inflammation of the sciatic nerve of the leg It is usually a unilateral pain that begins gradually and runs down the back of the thighs Generally affects middle-age males Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Spinal Cord Defects These defects result from the failure of the tissues of the spinal cord to properly close during the first trimester of pregnancy Spina bifida occulta Characterized by the incomplete closure of one or more vertebra without protrusion of the spinal cord or meninges (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Spinal Cord Defects Spina bifida with meningocele Myelomeningocele A sac protrudes from the opening that contains the meninges and cerebrospinal fluid Myelomeningocele In the sac that protrudes from the opening there is the meninges, CSF, and a portion of the spinal cord (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Spinal Cord Defects Treatment and prognosis depend on the location and extent of the spinal cord defect. If CSF and meninges are involved, surgery is required to prevent further injury. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Subarachnoid Hemorrhage Term used to describe a collection of blood in the subarachnoid space usually caused be spontaneous rupture of a weakened blood vessel Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Subdural Hematoma Term used to describe a collection of blood within the subdural space This is generally a slow process in which the gradual accumulation of blood causes progressive symptoms of seizures, motor disturbances, and progressive weakness. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Tourette Syndrome Neurological disorder that is characterized by “tics,” involuntary, rapid, sudden movements that occur repeatedly Onset is usually before the age of 21. Some people may also vocalize unacceptable words or echo things just heard. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Transient Ischemic Attacks Recurring strokelike events that last from a few seconds to a few hours and then disappear after 12 to 24 hours Considered to be a warning sign of an impending stroke Characterized by double vision, slurred speech, dizziness, and falling Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Trigeminal Neuralgia Disorder of the fifth cranial nerve on one side of the face Produces episodes of excruciating pain on stimulation of a trigger zone Frequently follows exposure to heat or cold (continued) Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Trigeminal Neuralgia Episodes may last from 1 to 15 minutes and recur from several times a day to a few times a year. Occurs mostly in people over age 40 and affects more women than men Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Tumors Abnormal masses that can occur anywhere in the body, but when the tumors are malignant and located in the brain, almost all limit life from 6 months to 6 years following diagnosis Tumors are more common in men than in women. Tumors are most prevalent between ages 40 and 60 in adults and ages 2 and 12 in children. Symptoms vary with the size and location of the tumor. Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

Unit Summary Name the parts of the brain. What is the largest part of the brain? What causes multiple sclerosis? Copyright © 2008 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.