Nervous System

Please be sure to study and take notes.

What is the nervous system?

• A complex, organized system that coordinates all the activities of the body

• ***Enables the body to respond and adapt to changes that occur both inside and outside the body ***

• Neuron (nerve cell) is the basic structural unit of the nervous system– The neuron consists of :

• Cell body containing a nucleus• Nerve fibers called dendrites which carry impulses toward the

cell body• Single nerve fiber called an axon which carries impulses away

from the cell body (Axons have a lipid covering called myelin sheath, which increases impulse transmission and insulates the axon)

• Axon of one neuron lies close to the dendrites of many other neurons----Space between them are know as synapses

-Impulses coming from an axon “jump” the synapse to get to the dendrite that will carry the impulse in the right direction

-Neurotransmitters located at the end of each axon allow nerve impulses to pass from one neuron to another

YOU ARE GETTIN’ ON MY NERVES

• So, what are “nerves”– Combination of nerve fibers (bundles of axons)– Located outside the brain and spinal cord– Afferent (sensory) nerves carry messages from all

parts of the body to the brain and spinal cord– Efferent (motor) nerves carry messages from the

brain and spinal cord to muscles and glands– Associative nerves carry both sensory and motor

messages

2 divisions of the nervous system

1. Central nervous system (CNS)- Consists of the brain and spinal cord

-BRAIN- Mass of nerve tissue, protected by the cranium (skull)- Sections of the brain

- 1. Cerebrum= largest section of the brain- Outer part is arranged in folds called convolutions - Separated into lobes- frontal, parietal, temporal, occipital- Responsible for reasoning, thought, memory, judgment,

speech, sensation, sight, smell, hearing, and voluntary body movements

Sections of the brain continued

• 2. Cerebellum– Section below the back of the cerebrum– Responsible for muscle coordination, balance, posture, and

muscle tone

3. Diencephalon- Located between the cerebrum and midbrain- Contains two structures

- 1. thalamus- allows conscious recognition of pain and temperature- 2. hypothalamus-regulates and controls the autonomic nervous

system, temperature, appetite, water balance, sleep, and blood vessel constriction and dilation; also involved in emotions such as anger, fear, pleasure, pain, and affection

Sections of the brain continued• 4. Midbrain

– Located below the cerebrum at the top of the brainstem– Responsible for impulses between brain parts and for certain eye and auditory

reflexes

5. Pons-located below the midbrain and in the brainstem-Responsible for conducting messages to other parts of the brain and for reflex actions like chewing, tasting, producing saliva, and assisting with respiration

6. Medulla Oblongata-lowest part of the brainstem, connects with the spinal cord-Responsible for regulating heartbeat, respiration, swallowing, coughing, and blood pressure

•SPINAL CORD• Continues from the medulla oblongata and ends at the first or second vertebrae• Surrounded and protected by the vertebrae• Responsible for carrying afferent (sensory) messages up to the brain and carrying efferent (motor)

messages from the brain to the nerves that go muscles and glands

-You have three membranes called meninges that cover and protect the brain and spinal cord- Dura mater- thick, tough, outer layer- Arachnoid membrane- middle layer; delicate weblike layer that is attached to other meninges to allow space for fluid to flow between the layers-Pia Mater- innermost layer, closely attached to the brain and spinal cord; contains blood vessels that nourish the nerve tissue

Ventricles

• Brain has 4 ventricles• What are they? Hollow spaces that

connect with each other and with the space under the arachnoid membrane (middle layer membrane that covers and protects the brain and spinal cord)

• Ventricles are filled with clear, colorless fluid called cerebrospinal fluid

Functions of cerebrospinal fluid

• Circulates continually between the ventricles• Serves as shock absorber to protect the brain and

spinal cord• Carries nutrients to some parts of the brain and

spinal cord• Helps remove wastes• After circulating it is absorbed into the blood vessels

of the dura mater (thick, tough, outer layer membrane that covers and

protects the brain and spinal cord) and returned to the bloodstream

• 2. Peripheral Nervous System (PNS)• Consists of the somatic and the autonomic nervous systems

• - Somatic Nervous System– Consists of 12 pairs of cranial nerves and 31 pairs of

spinal nerves» Spinal nerves carry messages to and from the spinal

cord and are mixed nerves—afferent (sensory) and efferent (motor)• 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 pair

of coccygeal

12 pairs of cranial nerves• I. Olfactory Nerve– smell• II. Optic nerve- vision• III. Oculomotor nerve- eye movement, pupil regulation• IV. Trochlear nerve- eye movement• V. Trigeminal nerve- (largest cranial nerve)sensations to head and face, mastication

(chewing)• VI. Abducens nerve-eye movement• VII. Facial nerve- taste receptors, facial expressions• VIII. Vestibulocochlear Nerve- hearing, sense of balance (equilibrium)• IX. Glossopharyngeal Nerve- sensations to tongue and pharynx- swallowing/saliva• X. Vagus nerves- speech (larynx) and swallowing, slows heart rate, digestion• XI.Accessory nerves- controls muscles used in head movement (neck/back-spinal

branch); (cranial branch- transmit impulses of soft palate, pharynx, larynx)• XII. Hypoglossal nerves- tongue movement

• Autonomic Nervous System– Helps maintain a balance in the involuntary

functions of the body and allows the body to react in times of emergency

– Has 2 divisions= sympathetic and parasympathetic nervous systems

– **** These two divisions/systems work together to maintain a balanced state called ___________.

Sympathetic• Acts in times of emergency– “Fight or flight”• Prepares the body to act• Increases heart rate and respirations, raises

blood pressure, slows activity in digestive tract

Parasympathetic• Counteracts actions of sympathetic system

after an emergency• Slows heart rate and respirations, lowers

blood pressure, increases activity in the digestive tract

Diseases/Conditions of Nervous System

• Amyotrophic Lateral Sclerosis (ALS)– AKA Lou Gehrig’s Disease– Chronic, degenerative neuromuscular dz– Cause is unknown (?genetic, ?viral/immune factors)– Nerve cells in the CNS that control voluntary movement degenerate

R/I weakening and atrophy of muscles they control– Initial sx: muscle weakness, abnormal reflexes , tripping/falling,

impaired hand/arm movements, difficulty speaking and swallowing– As dz progresses, more muscles are affected, R/I in total body paralysis– Late stages of dz- loses all ability to communicate, breathe, eat, and

move– * Mental acuity is unaffected– No treatment but meds to slow progression of dz

Carpal Tunnel Syndrome

– Condition occurs when the medial nerve and tendons that pass through a “tunnel” on their way from the forearm to the hands ad fingers are pinched

– Repetitive movement of the wrist causes swelling around this tunnel, which puts pressure on nerves/tendons

– Sx:- pain, muscle weakness in hand, impaired movement– Classic Sx: pain, numbness/tingling in thumb, ring finger,

and middle finger– Tx: anti-inflammatory meds, pain meds, splinting to

immobilize joint; surgery to enlarge the tunnel and relieve pressure on nerves/tendons

Cerebral Palsy

– Disturbance in voluntary muscle action– Caused by brain damage

• Lack of O2 to the brain and/or birth injuries• Prenatal rubella (German measles)• Prenatal infections

Spastic is the most common form of cerebral palsySx: exaggerated reflexes and seizures, tense muscles and development of contractures, speech impairment, spasms, tremors, mental retardation in some casesTx: (no cure) PT, OT, speech therapy. Muscle relaxants, anticonvulsive meds, braces, orthopedic surgery if needed for severe contractures

Cerebrovascular Accident (CVA)

– AKA stroke– Blood flow to the brain is impaired, R/I lack of O2 and

destruction of brain tissue– Causes: cerebral hemorrhage from HTN, aneurysm, or a

weak blood vessel; blockage caused by atherosclerosis or a thrombus

– Risk factors: smoking, high fat diet, obesity, sedentary lifestyle

– Sx: LOC, weakness, vertigo, paralysis on one side of the body, dysphagia (difficulty swallowing). Mental confusion, aphasia (speech impairment), incontinence

CVA (continued)

• Immediate care within the first 3 hours can help prevent brain damage

• Treatment with “clot busting” drugs (TPA) or angioplasty of cerebral arteries can dissolve a clot and restore blood flow to the brain

• CT scans are used to determine cause of CVA (IF CVA is caused by a hemorrhage a “clot busting” drug cannot be used)

• May need PT, OT, speech therapy

Encephalitis

• Inflammation of the brain caused by a virus, bacterium, chemical agent, or as a complication of measles, mumps, chicken pox

• ** frequently contracted from a mosquito (mosquitos carry encephalitis virus)

• Sx– fever, extreme weakness (lethargic), visual disturbances, headaches, vomiting, disorientation, seizures, coma

• Tx- antiviral meds, maintain fluid and electrolyte balance, antiseizure meds, watch respiratory and kidney functions

Epilepsy (Seizures)

• Brain disorder associated with abnormal electrical impulses in the neurons of the brain

• Causes can include brain injury, birth trauma, tumors, toxins, infections, and many are idiopathic

• Petit mal seizures- milder, LOC lasting a few seconds• Grand-mal seizures- most severe, LOC lasting a few minutes,

convulsions with violent shaking, foaming at the mouth (hypersalivation), loss of body functions

• Some people may experience an aura just before a seizure occurs (particular smell, ringing in the ears, visual disturbances

• Tx: anticonvulsant meds

Hydrocephalus

• Excessive accumulation of cerebrospinal fluid (CF) in the ventricles

• Cause- usually by a congenital defect, infection, or tumor that obstructs the flow of CF out of the brain

• Sx- abnormally enlarged head, bulging eyes, irritability, distended scalp veins; retardation when pressure prevents proper development of the brain

• Tx- surgical implantation of a shunt to provide drainage of the excess fluid (implant between the ventricles and veins, heart, or abd. cavity)

Multiple Sclerosis (MS)• Chronic, progressive condition resulting from degeneration of the

myelin sheath in the CNS• Usually occurs between ages of 20 and 40• Cause- unknown but genetics and viral infections of immune

system are suspected• May have periods of remission• Early Sx- visual disturbances like diplopia (double vision),

weakness, fatigue, poor coordination, numbness and tingling• Sx with disease progression- tremors, paralysis, speech

impairment, muscle spasms, incontinence• * NO CURE* but treat with PT , muscle relaxants, steroids, pysch

counseling

Neuralgia

• Nerve pain• Caused by inflammation, pressure, toxins,

disease• Tx- directed toward eliminating cause of the

pain

Paralysis

• Usually results from a brain or spinal cord injury• Hemiplegia- paralysis on one side of the body (tumor,

stroke, injury)• Paraplegia- paralysis in the lower extremities or lower

part of the body ( spinal cord injury)• Quadriplegia- paralysis of arms, legs, and body below

the spinal cord injury• *NO CURE*, research is being directed toward

repairing spinal cord damage• Tx: PT, OT, pysch counseling

Parkinson’s Disease

• Chronic, progressive condition involving degeneration of brain cells

• Sx- tremors, stiffness, shuffling gait, loss of facial expression, drooling, forward leaning position

• *NO CURE* but meds to help with sx, PT• Surgery can be performed to destroy a small

area of the brain and control involuntary movements

Shingles (Herpes Zoster)

• Acute inflammation of nerve cells• Cause- herpes virus, which also causes chicken

pox• Occurs on one side of the body and follows a

the path of the affected nerves• Sx- Fluid filled vesicles appear on the skin,

severe pain, redness, itching, fever• Tx- pain meds, antiviral meds

WHO AM I ??????

• I am the basic structural unit of the nervous system………

• I am the space between the axon of one neuron and the dendrite of other neurons…….

• I am also known as afferent nerves……

• I am a single nerve fiber……..

• We are two main divisions of the nervous system…..

• I can contain 12 pairs of cranial nerves and 31 pairs of spinal nerves…..

• I carry both afferent and efferent nerves…..

• We work together to maintain homeostasis…..

• I am cranial nerve # 1….. And I provide you a sense of ……..

• You would ask me to stick out my tongue and move it side to side to test me……

• You would test me by having me read the Snellen chart…….

• I help with digestion, decrease heart rate, and the movement of organs……

• You might give me a piece of gum to test me….

• Use a pen light to test me, have me follow your finger…..

• Give me a hearing test to test me…….

• Give me a lemon and watch me swallow….

• I am responsible for conducting impulses between brain parts for eye and auditory reflexes………

• I am responsible for respiration and cardiac regulations………

• I am responsible for posture, balance and muscle tone and coordination………..

• I am the largest section of the brain….. And I am responsible for………

• We cover and protect the brain and spinal cord…. There are 3 of us…..

• I am the thick outer membrane that protects the brain and spinal cord……

• I am hollow space and the brain has four of me……

• I am a clear, colorless fluid…..

Diagnose ME……..• I am caused by the herpes virus and cause you

a lot of pain because I am inflammed nerve cells…….

• I weaken your muscles causing you to trip and fall and make it difficult for you to speak and swallow while I leave your mind intact….. Over time you become an active mind trapped in a paralyzed body……..

• I happen sometimes after a stroke, injury, or tumor….. I affect one side of your body…..

• I cause your thumb, ring finger, and middle finger to hurt, tingle and have numbness….You may have to splint me…..

• I result from degeneration of your myelin sheath…..

• I am caused by brain damage that leads to a disturbance in my voluntary muscle actions…

• I cause you to have high fever, headaches, neck pain, N/V….. I have inflammed your meninges of your brain and spinal cord….

• You may get me if you have a brain disorder associated with abnormal electrical impulses in the neurons of the brain…..

• I could happen if you damage your spinal cord…. I affect your lower extremities…..

• You might need a shunt if you have me…. I cause an excessive accumulation of CF in the ventricles….

• If you think I am happening give me a thrombolytic drug within 3 hours….

• I cause you to tremor, shuffle your feet, lean forward, and lose your facial expressions…..