chapter 10 – the nervous system

The Nervous System

Functions of the Nervous System

Coordinates and controls all bodily activities

Structures of the Nervous System

Brain

Spinal cord

Nerves

Sensory organs

The Nervous System Is Divided Into 3 Parts

The central nervous system (CNS)Brain and spinal cord

The peripheral nervous system 12 pairs of cranial nerves31 pairs of spinal nerves

The autonomic nervous systemPeripheral nervesGanglia

The Nerves

A tract is a bundle of nerve fibers located within the brain or spinal cord.Ascending tracts carry impulses toward

the brain.Descending tracts carry nerve impulses

away from the brain.

A ganglion is a knotlike mass of nerve cell bodies outside the CNS.

The Nerves

A plexus is a network of intersecting nerves and blood or lymphatic vessels.Innervation is (a) the supply of nerves to a body part or (b) the stimulation of a body part by the

nerves.

Receptors are sites in the sensory organs that receive external stimulation. The receptors send this information to the brain for interpretation.

The Nerves

A stimulus is anything that activates a nerve and causes an impulse.

An impulse is a wave of excitation transmitted through nerve fibers.

The Reflexes

A reflex is an automatic, involuntary response to some change.Deep tendon reflexes.Maintenance of heart rate, respiratory

rate & blood pressure are reflex actions.Coughing, sneezing & reactions to pain

are reflex actions.

Neurons

3 types Afferent – (sensory neuron) emerge from skin

or sense organ and carry impulse toward the brain & spinal cord.

Connecting – (associative neurons) carry impulses from one neuron to another.

Efferent – (motor neurons) carry impulses away from the brain and spinal cord toward the muscles and glands.

Neurons

Dendrites are rootlike

structures that receive impulses & conduct them to the cell body.

The axon conducts impulses away from the nerve cell. Some are covered with myelin.

Terminal end fibers lead the nervous impulse toward the synapse.

Synapses

Synapses are the spaces between 2 neurons or between a neuron and a receptor organ.

A neurotransmitter is a chemical that transmits messages between nerve cells . they allow nerve impulses to jump across the synapse from one neuron to another.

Neurotransmitter

Glial cells are the supportive and connective cells of the nervous system. Glial means pertaining to glue.

Myelin sheath is the protective covering over some nerve cells. White in color.

Gray matter – portions of nerves that do not have a myelin sheath.

The CNS

The meninges are 3 layers of membrane that enclose the brain and spinal cord. The dura mater – thick, tough outer

membrane. The arachnoid membrane – resembles a

spider web& is 2nd layer. The pia mater – layer nearest the brain &

spinal cord. Made of delicate connective tissue with rich blood supply.

Cerebral spinal fluid: is clear, colorless, watery fluid produced by special capillaries within the ventricles. flows throughout the brain & around the spinal cord. cools, nourishes and cushions these organs.

Cerebrum

Cerebrum largest and uppermost portion of brain.Responsible for thought, judgment, memory , association and discrimination. Cerebral cortex made up of gray matter & is outer layer of cerebrum. Arranged in folds.

Cerebral Hemispheres

Rt and left hemispheres connected at midpoint at the corpus callosum

Lobes

Each hemisphere is divided into 4 lobes

Frontal lobe – motor function

Parietal lobe – receives and interprets nerve impulses from the sensory receptors.

Occipital lobe – eyesight

Temporal lobe – controls senses of hearing and smell

Thalamus

Located below the cerebrum –.

Produces sensations by relaying impulses to & from the cerebral cortex and the sense organs of the body.

Hypothalamus

Controls heart rate, BP, respiratory rate, & digestive tract activityRegulates:Emotional responses & behaviorBody temp Food intake/hunger, thirst/water balanceSleep-wake cyclesEndocrine activity

Cerebellum

Receives incoming messages regarding movement within joints, muscle tone & positions of the body. From here messages are relayed to different parts of the brain.

Brainstem

Stalklike portion of brain that connects cerebral hemispheres with spinal cord.

Made up ofMidbrainPonsmedulla oblongata

Midbrain

Extends from lower surface of the cerebrum to the pons.

Provides conduction pathways to and from higher and lower centers.

Pons

Pons – bridge

At base of brain

Nerve cells cross from one side of the brain to control the opposite side of the body

Medulla Oblongata

Located at lowest part of the brainstem.

Controls basic life functions including respiration, heart rate & blood pressure.

Spinal Cord

Spinal cord – pathway for impulses going to and from the brain.

Contains all the nerves that affect the limbs and lower part of the body.

Peripheral Nervous System

1. Cranial nerves

2. Spinal nerves

There are 31 pairs of spinal nerves.

Specialties

Anesthesiologist –

Anesthetist –

Neurologist –

Neurosurgeon –

Psychiatrist –

Psychologist -

Cephalagia -

Cephal = head

Algia = pain

Headache

Migraine – sudden, severe,sharp headache, usually present on only one side.

Meningocele – cystlike sac covered with membrane protruding thru bony defect in the vertebrae containing meninges and CSF.

Meningomyclocele – cystlike sac with membrane protruding thru bony defect in vertebrae & contains meninges, CSF, & spinal cord segments.

Spina bifida occulta – congenital defect in which back portion of the vertebrae is not closed. A dimpling over the area may occur.

Hydrocephalus (hydro = water +cephal = head + us = singular noun ending).Abnormally increased CSF within the

brain.

Meningitis = inflammation of the meninges of the brain or spinal cord.

Disorders of the Brain

Alzheimer’s disease = group of disorders associated with degenerative changes in brain structure leading to characteristic symptoms including progressive memory loss, impaired cognition and personality changes.

Cognition = mental activities associated with thinking, learning and memory.

Encephalitis (encelphal means brain + itis means inflammation) = inflammation of the brain.

Parkinson’s disease = chronic, slowly progressive, degenerative CNS disorder. Characterized by fine muscle tremors, a mask like facial expression and a shuffling gait.

Tetanus also known as lockjaw = acute and potentially fatal bacterial infection of the CNS caused by the tetanus bacillus.

Tetanus can be prevented through immunization

Brain Injuries

Amnesia = disturbance in the memory marked by total or partial inability to recall past experiences. Caused by a brain injury, illness or psychological disturbance.

•Concussion (concuss means shaken together and ion means condition). This is a violent shaking up or jarring of the brain.

Cerebral contusion (contus = bruise + ion = condition) the bruising of brain tissue as the result of a head injury.

Cranial hematoma (hemat means blood + oma means tumor). This is a collection of blood trapped in the tissues of the brain. They are named for their locations.Epidural hematoma.Subdural hematoma.Intracerebral hematoma.

Altered States of Consciousness

Conscious = being alert, awake aware and responding appropriately.Syncope = fainting, the brief loss of consciousness caused by a lack of oxygen to the brain.Lethargy – lowered level of consciousness, marked by listlessness, drowsiness, and apathy.

Stupor = state of impaired consciousness marked by a lack of responsiveness to environmental stimuli.

Coma = a profound deep state of unconsciousness marked by the absence of spontaneous eye movements, no response to painful stimuli, and no vocalization.

Delirium and Dementia

Delirium = potentially reversible condition often associated with a high fever that comes on suddenly in which the patient is confused, disorientated and unable to think clearly.

Dementia = slowly progressive decline in mental abilities including memory, thinking, judgment and the ability to pay attention.

Brain Tumors

An abnormal growth within the brain.

May be benign or malignant.

Can cause damage through. Invasively destroying brain tissue or.By causing pressure on the brain.

Cerebral Vascular Accident (CVA) or Stroke

Damage to brain caused when blood flow to the brain is disrupted because a blood vessel supplying it either became blocked or ruptured.

Ischemic Attacks

TIA – transient ischemic attack = temporary interruption in blood supply to the brain.

Symptoms include Weakness Dizziness Loss of balance

Symptoms last a few minutes but may be warning of an impending stroke.

Ischemic Stroke

Carotid artery is narrowed, blocking flow of blood to brain

OR

Cerebral thrombus blocks the artery

The lack of blood flow damages the cerebrum and affects movement, language and senses.

Aphasia (a = without + phasia = speech) loss of ability to speak, write or comprehend the written or spoken word.

Carotid endarterectomy opens blocked artery to prevent ischemic stroke.

Sleep Disorders

Insomnia = prolonged or abnormal inability to sleep.

Narcolepsy –recurrent uncontrollable seizures of drowsiness and sleep.(narco = stupor and lepsy = seizure).

Sleep Disorders

Somnambulism = sleepwalking. (somm means sleep = ambul means to walk and ism means condition of ).

Spinal Cord

Myelitis = inflammation of the spinal cord. (myel = spinal and itis = inflammation.

Also means inflammation of the bone marrow)

Multiple sclerosis = progressive autoimmune disorder scattered patches of demyelianation or nerve fibers of brain and spinal cord.

Demyelination is progressive loss of protective myelin covering. This disrupts the transmission of nerve impulses and causes symptoms including tremors, paralysis and speech disturbances.

Poliomyelitis = viral infection of the gray matter of the spinal cord that may result in paralysis. (Polio = gray + myel = spinal cord + itis = inflammation)

Radiculitis = (pinched nerve) – inflammation of the root of a spinal nerve. (radicul = root and itis = inflammation)

Nerves

Amyotrophic lateral sclerosis – ALS or Lou Gehrig’s disease = degenerative disease of motor neurons in which patients become progressively weaker until they are completely paralyzed. Intellect, eye motion, bladder function and sensation are spared.

Bell’s palsy = paralysis of the facial nerve (7th cranial). Causes drooping on the affected side of the face.

Guillain-Barre syndrome (ascending polyneuritis) – rapidly worsening muscle weakness that may become a temporary paralysis. Thought to be an autoimmune reaction that may occur after a mild infection, surgery, or an immunization.

Nerves

Nerves

Cerebral Palsy

Condition of poor muscle control, spasticity and other neurological deficient caused by injury to the part of the brain that controls muscle movements.

This injury occurs during pregnancy, birth or soon after.

Convulsions and Seizures

Sudden violent, involuntary contraction of a group of muscles caused by a disturbance in brain function. Have many causes such as brain injury lesions extreme high fevers.

Convulsions and Seizures

Generalized tonic-clonic seizure = generalized seizure. Loss of consciousness and tonic and clonic convulsions.Tonic convulsion – state of continuous muscular contraction that results in rigidity and violent spasms.Clonic convulsion – alternative contraction and relaxation of muscles resulting in jerking movements of the face, trunk or extremities.

Epilepsy

A group of neurological disorders characterized by recurrent episodes of seizures.Grand mal – more severe form.

Generalized tonic-clonic seizures.Petit mal – sudden temporary loss of

consciousness, lasting only a few seconds. Does not involve convulsive movements.

Epileptic aura – manifested as a smell or light that may be experienced just before a seizure.

Developmental Disorders

Mental retardation – significant below average intelligence and adaptive functioning.

Autistic disorder - does not develop normal social behaviors, or communication skills and behaves in compulsive and ritualistic ways.

Developmental Disorders

Attention deficit disorder – short attention span and impulsiveness

ADHD – as above with hyperactivity

Substance-related D/O’s

Addiction – compulsive, overwhelming involvement with a specific activity.

Withdrawal – psychological or physical syndrome caused by abrupt cessation of the drug after habituation.

Delirium tremens – an organic brain syndrome characterized by sweating, tremor, restlessness, anxiety, mental confusion and hallucinations.

Psychotic D/O’s

Psychotic D/O – loss of contact with reality

Schizophrenia - Psychotic D/O characterized by delusions, hallucinations, disorganized speech disruptive behavior

Mood d/O’s

Manic episode – abnormally and persistently elevated, expansive and irritable mood.

Major depressive D/O – prolonged peroid with depressed mood and loss of interest or pleasure in most activities.

ECT

Bipolar D/O – manic episodes alternating with depressive episodes.

Panic D/OPanic D/O – sudden, unanticipated recurrence of panic attacks (apprehension, fearfulness, terror, & impending doom). Have shortness of breath profuse sweating heart palpitations chest pain choking sensation.

Anxiety D/O

Anxiety D/O – feeling of apprehension, tension, or uneasiness that stems from anticipation of danger, the source of which is unknown or unrecognized.Obsessions are persistent ideas, thoughts or images that cause an individual stress or anxiety.Compulsions – repetitive behaviors to prevent or reduce anxiety or stressObsessive-compulsive D/O –

Phobias

Phobias –

Acrophobia – excessive fear of high places

Agoraphobia – irrational fear of leaving familiar setting/home

Claustrophobia -

Somatoform D/O

Somatoform D/O – presence of physical symptoms that suggest general medical conditions not explained by the pt’s actual medical condition

Somatoform D/O

Conversion reaction –

Hypochondriasis -

Impulse Control D/O’s

Kleptomania –

Pyromania -

Personality D/O’s

Personality D/O is an enduring pattern of inner experience and behavior that deviates markedly from normal. It has it’s onset in adolescence.

Personality D/O’s

Antisocial personality –

Narcissistic -

Other Conditions

Malingering –

Munchausen syndrome –

Munchausen syndrome by proxy –

Diagnostic Exams

CAT scan

MRI

Echoenchalohraphy

Electroencephalography – (EEG)

Myekography – contrast study of spinal cord

LOC -