30 The Nervous System.

30 The Nervous System

Learning Outcomes (cont.)
30.1 Describe the general functions of the nervous system. 30.2 Summarize the structure of a neuron. 30.3 Explain the function of nerve impulses and the role of synapses in their transmission. 30.4 Describe the structures and functions of the central nervous system.

Learning Outcomes (cont.)
30.5 Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system. 30.6 Recognize common tests that are performed to determine neurologic disorders. 30.7 Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system.

Disorders are numerous and often difficult to diagnose and treat
Introduction Highly complex system Controls and helps to maintain balance in all other organ systems Learning Outcomes: Describe the general functions of the nervous system. Disorders are numerous and often difficult to diagnose and treat

General Functions of the Nervous System
Central Nervous System (CNS) Brain Spinal cord Peripheral Nervous System (PNS) Peripheral nerves Somatic nervous system (SNS) Autonomic nervous system (ANS) Learning Outcomes: Describe the general functions of the nervous system. The peripheral nervous system is split into two separate sections The somatic nervous system (SNS) – governs the body’s skeletal or voluntary muscles The autonomic nervous system (ANS) – in charge of the body’s automatic functions, such as the respiratory and gastrointestinal systems.

General Functions of the Nervous System (cont.)
Afferent nerves ~ sensory information Efferent nerves ~ impulses that allow for movement or action Interneurons – interpreters between afferent and efferent nerves Learning Outcomes: Describe the general functions of the nervous system. Three types of neurons carry out the actual functions of the nervous system. Afferent nerves (sensory) – responsible for detecting sensory information from the environment or from inside the body and bringing it to the CNS for interpretation. Efferent nerves (motor) – bring information or impulses from the central nervous system to the PNS to control the movement or action of a muscle or gland. Interneurons Lie between the sensory and motor nerves. Interpretive neurons within the CNS Act as go-betweens or interpreters between the afferent and efferent nerves.

Apply Your Knowledge Correct! ANSWER: Match the following:
___ Somatic nervous system A. Motor nerves ___ Autonomic nervous system B. Governs skeletal or voluntary muscles ___ Afferent nerves C. Governs respiratory and GI systems ___ Efferent nerves D. Go-betweens or interpreters ___ Interneurons E. Sensory nerves B C A E Learning Outcomes: Describe the general functions of the nervous system. D Correct!

Neuron Structure Functional cells of NS Transmit nerve impulses to
Other neurons Effectors Cannot divide Neuroglia Support cells for neurons Astrocytes Microglia Oligodendrocytes Learning Outcome: Summarize the structure of a neuron. Neurons transmit electrochemical messages called nerve impulses to other neurons and effectors (muscles or glands). An important characteristic of neurons is that they lose their ability to divide. Neuroglia Do not transmit impulses Never lose their ability to divide. The three types of neuroglia Astrocytes – star-shaped cells that anchor blood vessels to the nerve cells. Microglia – small cells that act as phagocytes, watching for and engulfing invaders. Oligodendrocytes – specialized neuroglial cells that assist in the production of the myelin sheath.

Neuron Structure (cont.)
Cell body Nucleus and organelles Generates proteins and energy Nerve fibers ~ extend from cell body Learning Outcome: Summarize the structure of a neuron.

Axons One per neuron Send nerve impulses away from the cell body Dendrites One or more per neuron Receive nerve impulses for the neuron Learning Outcome: Summarize the structure of a neuron. Nerve fibers Axon – typically long and branch profusely after they have extended far away from the cell body Dendrites – usually short and branch profusely near the cell body.

Schwann cells Wrap around axons Membranes contain myelin White matter – myelin sheath Gray matter – no myelin sheath Learning Outcome: Summarize the structure of a neuron. In the peripheral nervous system, neuroglial cells called Schwann cells wrap themselves around some axons. The Schwann cell membranes contain myelin, which is a fatty substance. Myelin insulates axons and enables axons to send nerve impulses more quickly.

GOOD JOB! Apply Your Knowledge True or False:
___ Effectors are neurons. ___ Neurons can reproduce. ___ Astrocytes anchor blood vessels to nerve cells. ___ Microglia act as phagocytes. ___ Oligodendrocytes are reproductive cells. ___ Repolarization is the return to the resting state. ANSWER: F They are the muscles or glands. F Neurons cannot reproduce. T T Learning Outcome: Summarize the structure of a neuron. They take part in myelin production. F T GOOD JOB!

Nerve Impulse and Synapse
Cell membrane potential - polarized Depolarized – sodium ions move into the cell Action potential is created Repolarization Positive ions move out Returns to polarized state Learning Outcome: Explain the function of nerve impulses and the role of synapses in their transmission. Neuron cell membranes have a cell membrane potential which means the membrane is polarized. The inside is negatively charged and the outside is positively charged. Membrane potential is very important for the function of neurons The number of sodium and potassium ions is greater outside the membrane. As long as the neuron is at rest, it remains in this polarized state. When a neuron responds to stimuli the membrane depolarizes The amount of polarization across its membrane is changed to make the outside of the membrane less positive. This allows some of the sodium ions flow to the inside of the cell membrane. Depolarization results in an action potential (a nerve impulse) – the flow of electric current along the axon membrane. Repolarization Return to the original polarized state. Positively charged ions return to the outside of the cell membrane. Refer to CONNECT to see an animation about Nerve Impulse .

Nerve Impulse (cont.) Synaptic knob contains vesicles
Neurotransmitters Produced in vesicles Released to allow impulse transmission to post-synaptic structures Functions Learning Outcome: Explain the function of nerve impulses and the role of synapses in their transmission. An unmyelinated axon does not conduct a nerve impulse as quickly as a myelinated axon. The speed of the nerve impulse is related to the diameter of the axon. Synaptic Knob End of the axon branches. Contain small sacs called vesicles, which produce neurotransmitters. Neurotransmitters Allow impulse transmission to continue to the postsynaptic structures – the dendrites, cell bodies, and axons of other neurons. There are about 50 different neurotransmitters. Most neurons release only one type of neurotransmitter. Their functions include Causing muscles to contract or relax Causing glands to secrete products Activating neurons to or inhibiting neurons from sending nerve impulses. Synaptic space – between the axon of one neuron and the dendrite of the next.

Right! Apply Your Knowledge What is the function of neurotransmitters?
ANSWER: Neurotransmitters cause muscles to contract or relax, cause glands to secret products, activate neurons to send nerve impulses, or inhibit neurons from sending them. Learning Outcome: Explain the function of nerve impulses and the role of synapses in their transmission. Right!

Central Nervous System
Brain and spinal cord Blood-brain barrier Protects layers of the membranes of the CNS Formed by tight capillaries Learning Outcome: Describe the structures and functions of the central nervous system. Prevents certain substances from entering the tissues of the CNS (waste products and drugs). Inflammation can make this barrier more permeable.

Central Nervous System (cont.)
Meninges Dura mater Epidural space Subdural space Arachnoid mater Pia mater Subarachnoid space ~ cerebrospinal fluid (CSF) Learning Outcome: Describe the structures and functions of the central nervous system. Meninges – membranes that protect the brain and spinal cord. Dura mater The toughest and outermost layer of the meninges. Epidural space –above the dura mater. Subdural space – below the dura mater. Arachnoid mater – the middle layer, named for its spider web-like appearance. Pia mater The innermost and most delicate layer. Directly on top of the brain and spinal cord. Holds blood vessels onto the surface of these structures. Subarachnoid space Between the arachnoid mater and pia mater It contains cerebrospinal fluid (CSF), which cushions the CNS.

Spinal Cord Descends through vertebral canal 31 spinal segments:
8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal Cervical enlargement Lumbar enlargement Learning Outcome: Describe the structures and functions of the central nervous system. The spinal cord is a slender structure that is continuous with the brain and descends into the vertebral canal ending around the level of the first or second lumbar vertebra. Cervical enlargement The thickening of the spinal cord in the neck region. It contains the motor neurons that control the muscles of the arms. Lumbar enlargement Thickening of the spinal cord in the lumbar region. It contains the motor neurons that control the muscles of the legs.

Spinal Cord (cont.) Gray matter White matter Central canal
Neuron cell bodies and their dendrites Horns White matter Myelinated axons Funiculi Central canal Center of the gray matter Contains CSF Learning Outcome: Describe the structures and functions of the central nervous system. Grey matter The inner tissue Darker in color Contains the neuron cell bodies and their dendrites. Has bulges or sections called horns. White matter Outer tissue contains the myelinated axons of neurons Divided into columns (funiculi) that contain groups of axons called nerve tracts. Central canal – runs down the entire length of the spinal cord.

Spinal Cord (cont.) Ascending tracts – sensory
Descending tracts – motor Reflexes – predictable automatic responses Stimulus Receptor Sensory Neurons Interneurons Learning Outcome: Describe the structures and functions of the central nervous system. Ascending and Descending Tracts One function of the spinal cord is to carry sensory information up to the brain. Ascending tracts – carry sensory information up to the brain Descending tracts – carry motor information down from the brain to muscles and glands. Reflexes Predictable, automatic responses to a stimulus The information that flows through a typical reflex moves These receptors send their information to sensory neurons that relay the information to interneurons in the spinal cord. The interneurons immediately relay the information to motor neurons that activate the muscles (effectors) The muscles coordinate the movement A person can consciously inhibit a reflex because the information also goes to the cerebral cortex which handles conscious decisions. Effectors Motor Neurons Response

Brain Four sections Cerebrum Cerebrum Diencephalon Brain stem
Cerebellum Cerebrum Two hemispheres Corpus callosum Sulci Gyri Longtidtudinal fissure Learning Outcome: Describe the structures and functions of the central nervous system. Cerebrum Largest part of the brain Corpus callosum – thick bundle of nerve fibers connecting the two hemispheres. Sulci – the grooves on the surface of the cerebrum. Gyri, or convolutions – the “bumps” of brain matter between the sulci. Longitudinal fissure - a deep groove between the two longitudinal hemispheres. Brain

Brain (cont.) Lobes – divisions of the cerebral hemispheres Frontal
Parietal Temporal Occipital Learning Outcome: Describe the structures and functions of the central nervous system. Frontal lobes – motor areas that allow a person to consciously decide to produce a body movement. Parietal lobes – somatosensory areas interpret sensations felt on or within the body. Temporal lobes – auditory areas interpret sounds. Occipital loves – visual areas interpret what a person sees.

Brain (cont.) Cerebral Cortex Ventricles Diencephalon Gray matter
Functions Sensory information Body movement Memories Emotions Ventricles Interconnected cavities within the brain CSF Diencephalon Thalamus Hypothalamus Learning Outcome: Describe the structures and functions of the central nervous system. Cortex Outermost layer of the cerebrum Contains neuron cell bodies and dendrites; nearly 75% of all neurons Beneath the cerebral cortex is white matter. Functions Interprets sensory information Initiates body movements Stores memories Creates emotions Ventricles – filled with CSF which protects and cushions the central nervous system. Diencephalon Located between the cerebral hemispheres and superior to the brain stem. Thalamus – relay station for sensory information that must pass through the thalamus before it reaches the cerebral cortex for interpretation. Hypothalamus – maintains homeostasis by regulating hunger, thirst and body temperature; links the nervous system and the endocrine system.

Brain (cont.) Brain Stem Midbrain Pons Medulla oblongata Cerebellum
Complex body movements Fine muscle movements Learning Outcome: Describe the structures and functions of the central nervous system. Brain Stem Connects the cerebrum to the spinal cord. The midbrain – lies beneath the diencephalon; controls visual and auditory reflexes. The pons – a rounded bulge on the underside of the brain stem; nerve tracts connect the cerebrum and cerebellum; it regulates respiration. The medulla oblongata – directly connected to the spinal cord; it controls many vital activities such as heart rate, blood pressure, and respiration as well as reflexes associated with coughing, sneezing, and vomiting. Cerebellum Inferior to the occipital lobes of the cerebrum; posterior to the pons and medulla oblongata. Coordinates complex skeletal muscle contractions needed for body movements. Coordinates fine movements such as threading a needle, playing an instrument, and writing. Brain

Brain (cont.) Previous slide
Learning Outcome: Describe the structures and functions of the central nervous system. Previous slide

Apply Your Knowledge Answer: Match the following:
SUPER! Answer: Match the following: ___ Meninges A. Carry motor information from brain ___ Ascending tracts B. Stores memories and creates emotions ___ Descending tracts C. Grooves on the surface of the cerebrum ___ Cerebral cortex D. Carry sensory information to the brain ___ Hypothalamus E. Predictable, automatic response to stimuli ___ Sulci F. Maintains homeostasis ___ Cerebellum G. Coordinates skeletal muscle contractions ___ Reflexes H. Protects the brain and spinal cord H D A B F Learning Outcome: Describe the structures and functions of the central nervous system. C G E

Peripheral Nervous System
Nerves that branch off the CNS Cranial nerves Spinal nerves Learning Outcome: Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system.

Cranial Nerves Olfactory nerves Optic nerves Oculomotor nerves
Trochlear nerves Trigeminal nerves Abducens nerves Learning Outcome: Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system. Olfactory nerves carry smell information to the brain for interpretation. Optic nerves carry visual information to the brain for interpretation. Oculomotor nerves are found in the muscles that move the eyeball, eyelid, and iris. Trochlear nerves act in the muscles that move the eyeball. Trigeminal nerves Carry sensory information from the surface of the eye, the scalp, facial skin, the lining of the gums, and the palate to the brain for interpretation. Also are found in the muscles needed for chewing. Abducens nerves act in the muscles that move the eyeball. Diagram

Cranial Nerves (cont.) Vagus nerves Facial nerves Accessory nerves
Hypoglossal nerves Facial nerves Vestibulocochlear nerves Glossopharyngeal nerves Learning Outcome: Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system. Facial nerves are found in the muscles of facial expression as well as in the salivary and tear glands. These nerves also carry sensory information from the tongue. Vestibulocochlear nerves carry hearing and equilibrium information from the inner ear to the brain for interpretation. Glossopharyngeal nerves carry sensory information from the throat and tongue to the brain for interpretation. They also act in the muscles of the throat. Vagus nerves carry sensory information from the thoracic and abdominal organs to the brain for interpretation. These nerves are also found in the muscles in the throat, stomach, intestines, and heart. Accessory nerves are found in the muscles of the throat, neck, back, and voice box. Hypoglossal nerves are found in the muscles of the tongue. Diagram

Learning Outcome: Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system. Back

Spinal Nerves 31 pairs of spinal nerves 8 pairs of cervical nerves
12 pairs of thoracic nerves 5 pairs of lumbar nerves 5 pairs of sacral nerves 1 pair of coccygeal nerves Learning Outcome: Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system. Spinal nerves are peripheral nerves that originate from the spinal cord There are 31 pairs of spinal nerves: Cervical nerves – numbered C1 through C8 Thoracic nerves – numbered T1 through T12, Lumbar nerves – numbered L1 through L5 Sacral nerves – numbered S1 through S5 Coccygeal nerves – Cx Spinal Nerves

Spinal Nerves (cont.) Dermatome Ventral root – axons of motor neurons
Skin segment innervated by spinal nerve C1 is not associated with a dermatome Ventral root – axons of motor neurons Dorsal root Axons of sensory neurons Dorsal root ganglion ~ cell bodies of sensory neurons Learning Outcome: Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system.

Spinal Nerves (cont.) Nerve plexuses Cervical ~ skin and neck
Brachial ~ arms Lumbosacral ~ lower abdomen, external genitalia, buttocks, thighs, legs, and feet Coccygeal ~ anus and back of thighs Learning Outcome: Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system. Nerve plexuses – the main portions of spinal nerves fuse together to form plexuses, except in the thoracic region. The cervical plexus Supplies the skin and the muscles of the neck. The phrenic nerve originates from the cervical plexus and controls the diaphragm The brachial plexus – includes nerves that control muscles in the arms. The lumbosacral plexus Supplies the lower abdominal wall, external genitalia, buttocks, thighs, legs, and feet. The sciatic nerve originates from this plexus and controls the muscles of the legs. The coccygeal plexus – source of the anococcygeal nerve, which innervates the anus and the back of the thighs. Spinal Nerves

Learning Outcome: Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system. Back

Somatic and Autonomic Nervous System
Somatic Nervous System Nerves that connect the CNS to skin and skeletal muscle “Voluntary” nervous system Controls skeletal muscles Learning Outcome: Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system. The peripheral nervous system is divided into the somatic and autonomic nervous systems.

Somatic and Autonomic Nervous System (cont.)
Connect the CNS to organs and other structures “Involuntary” nervous system Ganglia Organs and blood vessels Learning Outcome: Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system. The autonomic nervous system controls organs not under voluntary control. Ganglia Collections of neuron cell bodies outside the CNS. Motor neurons from the brain and spinal cord communicate to other motor neurons that are located in ganglia. The motor neurons of ganglia then communicate to various organs and blood vessels. Motor neurons in ganglia Motor neurons from brain and spinal cord

Sympathetic division “Fight or flight” Prepares body for stressful or emergency situations Releases norepinephrine Controls constriction of blood vessels Learning Outcome: Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system. The two divisions of the autonomic nervous system are the sympathetic and the parasympathetic divisions The sympathetic division Many neurons are located in the thoracic and lumbar regions of the spinal cord so it is also called the thoracolumbar division Sympathetic neurons release the neurotransmitter norepinephrine into organs and glands. Increases the heart and breathing rates Slows down the activity of the digestive glands Slows down the muscles of the stomach and the intestines, Dilates the pupils. The constriction of blood vessels increases blood pressure, a needed response during an emergency situation.

Parasympathetic division Prepares body for rest and digesting Controls most of the body’s organs Releases acetylcholine Sympathetic and parasympathetic divisions are antagonistic Learning Outcome: Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system. Parasympathetic division is also called the craniosacral division because many of its neurons are located in brain stem and sacral regions of the spinal cord. Most of the body’s organs are under parasympathetic control. Acetylcholine is a neurotransmitter Slows the heart and breathing rates Constricts the pupils Activates digestive glands The muscles of the stomach and intestines. Most blood vessels in the body do not receive communication from parasympathetic nerves.

Apply Your Knowledge Impressive!
What is the difference between the sympathetic and parasympathetic nervous systems? ANSWER: The sympathetic nervous system prepares the body for stress. It releases norepinephrine, causing an increase in heart and respiratory rate, slows down the GI system, and dilates pupils. The sympathetic system also controls constriction of blood vessels. The parasympathetic system prepares the body for resting and digesting. It releases acetylcholine, which slows heart and respiratory rates, constricts pupils, and stimulates the GI system. It has no effect on most blood vessels. Learning Outcome: Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system.

Neurologic Testing Typical neurologic examination
State of consciousness Reflex activity Speech patterns Motor patterns Learning Outcome: Recognize common tests that are performed to determine neurologic disorders. Patients with nervous system disorders may have a wide variety of signs and symptoms, but the most common are headache, muscle weakness, and paresthesias. Neurologic examination can determine the state of consciousness This state can vary from normal to a state of coma. Terms used to describe states of consciousness Stupor Delirium Vegetative Asleep Reflex activity – tests primarily determine the health of the peripheral nervous system. Speech patterns – abnormalities include a loss of the ability to form words correctly or to form sentences that make sense. Motor patterns – abnormalities include the loss of balance, abnormal posture, or inappropriate, involuntary movements of the body.

Diagnostic Procedures
Lumbar puncture Magnetic resonance imaging (MRI) Positron emission tomography (PET) scan Cerebral angiography Computerized tomography (CT) scan Electroencephalogram (EEG) X-ray Learning Outcome: Recognize common tests that are performed to determine neurologic disorders. Lumbar puncture – extraction of CSF from spinal column for analysis. MRI – uses powerful magnets to generate images of the brain and spinal cord from many angles. PET – uses radioactive chemicals that collect in specific areas of the brain and generates images of those areas. Cerebral angiography – uses contrast material that can be visualized in the blood vessels of the brain. CT scan – produces images that provide more information than a standard x-ray. EEG – detects electrical activity in the brain. X-ray – detects skull or vertebral fractures.

Cranial Nerve Tests Olfactory nerve (I) – have patient smell various substances Cranial nerves III, IV, and VI – have patient visually track movement of finger Learning Outcome: Recognize common tests that are performed to determine neurologic disorders.

Cranial Nerve Tests (cont.)
Cranial nerve V – have patient clench teeth, feel jaw muscles Cranial nerve VII – check patient’s facial expression Cranial nerve XII – have patient extend and move tongue Learning Outcome: Recognize common tests that are performed to determine neurologic disorders. Cranial nerve V controls the muscles needed for chewing So ask the patient to clench his teeth. If the jaw muscles feel limp or weak, this nerve may be damaged. .

Reflex Testing Terms Tests Biceps reflex Areflexia Knee reflex
Hyporeflexia Hyperreflexia Tests Biceps reflex Knee reflex Abdominal reflexes Learning Outcome: Recognize common tests that are performed to determine neurologic disorders. Allows a physician to evaluate the components of a reflex as well as the overall health of the individual’s nervous system. Areflexia – absence of a reflex Hyporeflexia – decreased reflex Hyperreflexia – stronger than normal reflex The following are common reflex tests: Biceps reflex – absence of this reflex may indicate spinal cord damage in the cervical region. Knee reflex – absence of this reflex may indicate damage to lumbar or femoral nerves. Abdominal reflexes – evaluate damage to thoracic spinal nerves.

Apply Your Knowledge ________ Match the following:
___ State of consciousness A. Determines the health of peripheral nerves ___ Reflex activity B. Loss of balance, abnormal posture ___ Speech patterns C. Stupor, delirium, vegetative ___ Motor patterns D. Loss of ability to form words ANSWER: C A Learning Outcome: Recognize common tests that are performed to determine neurologic disorders. D B

Common Diseases and Disorders of the Nervous System
Brain and spinal cord injuries Causes Motor vehicle accidents Sports and recreational accidents Violence Children and teens at highest risk Most are preventable Learning Outcome: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system. Refer to Educating the Patient : Preventing Brain and Spinal Cord Injuries In the United States alone, almost half a million people a year suffer brain and spinal cord injuries. Refer to CONNECT to see an animation about Spinal Cord Injury .

Common Diseases and Disorders of the Nervous System (cont.)
Disease/Disorder Description Alzheimer’s disease Progressive, degenerative disease of the brain Amyotrophic lateral sclerosis (ALS) Degeneration of neurons in the spinal cord and brain; Lou Gehrig’s disease; fatal Learning Outcome: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system. Alzheimer’s disease Cause of symptoms – fiber tangles within neurons, degenerating nerve fibers, and a decreased production of neurotransmitters. Associated with advanced age, family history, certain genes, and possibly some environmental factors. Amyotrophic lateral sclerosis (ALS) – most causes are unknown, but they are likely to involve hereditary and environmental factors.

Disease/Disorder Description Bell’s palsy Weak or paralyzed facial muscles Brain tumors and cancers Abnormal growths Can be primary or secondary tumors; most common – gliomas Learning Outcome: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system. Bell’s palsy Can result from damage to cranial nerve VII (the facial nerve), but many times the cause is unknown. It is more common in people with diabetes, the flu, or a cold. Brain tumors and cancers A brain tumor with cancer cells is malignant. Those that start in other body parts and spread to the brain are classified as secondary brain cancers. The most common primary brain tumors are gliomas that arise from neuroglial cells. The causes are gene mutations and associated factors include exposure to toxins, an impaired immune system, and hereditary factors.

Disease/Disorder Description Epilepsy and seizures Occurs as a result of bursts of electrical signals that disrupt normal brain functioning Guillain-Barré Syndrome Body’s immune system attacks the PNS; sudden and unexpected onset Learning Outcome: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system. Epilepsy and seizures Seizures may be either petit mal or grand mal. Petit mal seizures may appear as loss of awareness of the present. Grand mal seizures result in the classic tonic-clonic seizure. Epilepsy – the condition of having repeated, long-term seizures. Causes are unknown but may include birth trauma, high fevers, alcohol and drug withdrawal, head trauma, infections, brain tumors, and certain medications Guillain-Barré syndrome The destruction of myelin by the body’s immune system Viral infections, immunizations, and pregnancy sometimes trigger the disease.

Disease/Disorder Description Headaches Tension Migraines Cluster Episodic or chronic Most severe form of headache Severe form of migraines; attacks occur in groups Learning Outcome: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system. Headaches – a physician should evaluate repetitive and severe headaches. Tension headaches are classified as Episodic tension headaches – the most common type of tension headache; the result of temporary stress or anger. Chronic tension headaches – the result of stress or fatigue, but it may also be associated with physical problems, psychological issues, or depression. Migraines Responsible for more “sick days” than any other headache type Hormones may influence migraines More frequent in women Associated with the distension of the arteries of the brain. Cluster headaches Named because the attacks come in groups. The most severe type of migraines. Some research indicates that alcohol consumption can bring on attacks of cluster headaches.

Disease/Disorder Description Meningitis Inflammation of meninges Multiple sclerosis (MS) Chronic disease of CNS; myelin is destroyed Neuralgias Disorders causing nerve pain Learning Outcome: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system. Meningitis Causes may include bacterial, viral, and fungal infections. Some types of meningitis can be prevented with vaccines. Multiple sclerosis (MS) – the causes are mostly unknown, but some known causes are viruses, genetic factors, and immune system abnormalities. Neuralgias They most frequently occur in the nerves of the face. There are many causes of neuralgia, including trauma, chemical irritation of the nerves, bacterial infections, and diabetes. Many times the causes are unknown

Disease/Disorder Description Parkinson’s disease Progressive and degenerative motor system disorder Sciatica Damage to sciatic nerve Stroke Brain cells die because of an inadequate blood flow; “brain attack” Learning Outcome: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system. Parkinson’s disease Most causes are undetermined, however, patients with this disease lack certain chemicals (neurotransmitters) in the brain. Brain tumors, certain drugs, carbon monoxide, or repeated head trauma may produce Parkinson’s disease. Sciatica The sciatic nerve is commonly damaged by excessive pressure on the nerve from prolonged sitting or lying down. The nerve is easily damaged by trauma to the pelvis, buttocks, or thighs. Stroke Cerebrovascular accident (CVA). May be preceded by transient ischemic attacks (TIAs) or “mini strokes,” which are caused by brief interruptions of blood supply to the brain. Caused by the blockage of an artery in the neck or brain or by aneurysms that burst. Refer to CONNECT to see an animation about Stroke .

Bravo! Apply Your Knowledge ANSWER: True or false:
___ Alzheimer’s disease is a progressive degenerative disease of the brain. ___ Epilepsy is due to degenerative neurons in the spinal cord and brain. ___ Neuralgias are motor system disorders. ___ Stroke occurs when brain cells die because of inadequate blood flow. T F Due to a burst of electrical signals that disrupt brain function. Learning Outcome: Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system. F They are group of disorders referred to as nerve pain. T

In Summary 30.1 The central nervous system is composed of the brain and spinal cord. The peripheral nervous system consists of the peripheral nerves located throughout the body. Three types of neurons carry out the functions of the nervous system: the afferent (sensory) nerves detect sensation or other stimuli from the body or environment and bring it to the CNS for interpretation, the efferent (motor) nerves produce movement or other functions at the direction of the CNS, and the interpretive interneurons act as “interpreters” between the afferent and efferent nerves.

In Summary (cont.) 30.2 All neurons are composed of a cell body, the shorter and more numerous dendrites that receive information for the cell body, and the longer axons that function to bring impulses from the cell body to the dendrite of the next neuron.

In Summary (cont.) 30.3 Nerve impulses send information either from the CNS to the PNS or vice versa. A synapse is the space between the axon of one neuron and the dendrite of the next. At the end of each axon is the synaptic knob, which contains vesicles that produce neurotransmitters. These are released by the synaptic bulb to allow impulse transmission to continue to the next neuron.

In Summary (cont.) 30.4 The brain consists of the cerebrum, diencephalon, brain stem, and cerebellum. Other structures include the blood-brain barrier and the meninges. The spinal cord consists of 31 spinal segments. The basic function of the spinal cord is to carry sensory information to the brain and motor information to the muscles and glands of the body. Cerebrospinal fluid (CSF) is located within the subarachnoid space and the central canal of the spinal cord. It cushions the brain and spinal cord. 30.4 The brain consists of the cerebrum, diencephalon, brain stem, and cerebellum. The blood-brain barrier is a layer of tightly woven capillaries that protects the delicate tissues of the CNS. The meninges are a triple-layered membrane protecting the brain and spinal cord. The spinal cord is continuous with the brain and consists of 31 spinal segments. The basic function of the spinal cord is to carry sensory information from the body to the brain and motor information from the brain to the muscles and glands of the body. Cerebrospinal fluid (CSF) is located within the subarachnoid space of the brain and within the central canal of the spinal cord. It cushions the brain and spinal cord.

In Summary (cont.) 30.5 The somatic nervous system connects the CNS to the skin and skeletal muscle (voluntary functions). The autonomic nervous system connects the CNS to the internal organs (involuntary functions). The autonomic nervous system is divided into the sympathetic system, which prepares the body for “fight or flight” (stressful) situations, and the parasympathetic system, which is the body’s everyday “resting” system for normal situations.

In Summary (cont.) 30.6 Tests commonly used to determine neurologic disorders include tests of the reflexes and cranial nerves, as well as diagnostic procedures such as lumbar puncture, MRI, PET, cerebral angiography, CT scan, EEG, and X-ray Many types of diseases and disorders are related to the nervous system. The signs, symptoms, and treatments of these diseases are as varied as the diseases themselves. Many of the more common diseases are included in the pathophysiology section at the end of this chapter.

End of Chapter 30 Activity of the nervous system improves the capacity for activity, just as exercising a muscle makes it stronger.” ~ Dr. Ralph Gerard

30 The Nervous System.

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