The Nervous System

Functions of the Nervous System

  • Brain as its center:

    • Coordinates and controls all bodily activities

    • When brain ceases to function, body is no longer able to live on its own

Structures of the Nervous System

  • Brain

  • Nerves

  • Spinal cord

  • Sensory organs

Divisions of the Nervous System

  • Central nervous system

    • Receives and processes information

    • Regulates all bodily activities

    • Brain and spinal cord

  • Peripheral nervous system

    • Transmits nerve signals to and from the CNS

    • 12 pairs of cranial nerves

      • extend from brain

    • 31 pairs of peripheral spinal nerves

      • extend from the spinal cord

Neurons

  • Basic cells of the nervous system

  • Allow different parts of the body to communicate with each other via and electrochemical process

  • Billions of them!

  • Parts:

    • Dendrites: Root-like processes that receive impulses and conduct them toward the cell body

    • Axon: Process that conducts impulses away from the nerve cell

      • Can be >3 feet long!

      • Protected my a myelin sheath

    • Terminal end fibers: Branching fibers at the end of the axon

    • Synapse: Space between 2 neurons

Types of Neurons

  • Afferent nuerons

    • Sensory neurons

    • Carry impulses from sensory neurons toward brain and spinal cord

  • Connecting neurons

    • Associative neurons

    • Link afferent and efferent neurons

  • Efferent neurons

    • Motor neurons

    • Carry impulses away from the brain/spinal cord toward muscles and glands

Myelination

  • Myelin

    • Fatty substance created by glial cells that provides insulation around the axon increasing the efficiency of impulse transmission

  • Myelin sheath

    • Protective covering made up of glial cells and the myelin that comes from them

    • Support and protect the nerve cells by

      • Holding them in place

      • Supply nutrients and oxygen

      • Insulate one neuron from another

      • Destroy and remove dead neurons

  • Myelinated

    • White natter of the brain and covers some parts of the spinal cord and the axon of most perpheral nerves

  • Unmyelinated

    • Known as gray matter

    • In the brain and spinal cord

Neurotransmitters

  • Chemical substances that make it possible for messages to cross from the synapse of the neuron to its target

  • Acetylcholine

    • Released in spinal cord and neuromuscular junctions

      • Influences muscle action

  • Dopamine

    • Released in the brain

      • Involved in mood/thought disorders and in movement disorders like Parkinson’s

  • Endorphins

    • Produced by brain

      • Pain relief

  • Epinephrine and Norepinephrine

    • Released by adrenal gland

      • Affect alertness; part of fight or flight response

  • Serotonin

    • Released by the brain

      • Has roles in hunger, sleep and pleasure recognition

      • Linked to mood disorders

Nerves Vocab

  • Nerve

    • 1 or more bundles of neurons that connect the brain and spinal cord with other parts of the body

  • Innervation

    • Supply of nerves to a specific body part

  • Stimulus

    • Anything that excites (activates) a nerve and causes an impulse

  • Plexus:

    • Network of intersecting spinal nerves

    • …or blood vessels of lymphatic vessels

  • Reflect

    • Automatic involuntary response to a change either inside or outside the body

      • Changes in HR, RR, B/P

      • Coughing/sneezing

      • Responses to painful stimuli

Central Nervous System

  • Brain and spinal cord

  • Protected by bones of cranium and vertebrae

  • Cerebrospinal fluid

    • Produced in the cerebrum, watery fluid, cools, cushions and nourishes the brain and spinal cord

  • Meninges

  • System of membranes that encloses the CNS

  • Dura mater: thick, tough, outermost membrane

  • Arachnoid membrane: resembles a spiderweb, second layer

  • Pia mater: third layer, located nearest to brain and spinal cord

Rich supply of blood vessels

Parts of the Brain

Cerebrum

  • Largest and uppermost part of brain

  • Responsible for the highest level of thought

  • Processes sensations and controls voluntary muscle activity

  • Cerebral hemispheres: cerebrum divided in 2 hemispheres that are connected at the lower midpoint by the corpus callosum

    • Left cerebral hemisphere: controls right side of body

    • Right cerebral hemisphere: controls left side of body

  • Cerebral lobes: subdivisions of the cerebral hemispheres

    • Frontal, parietal, occipital, temporal

    • Each lob controls specific functions like memory, taste, eyesight, hearing, etc.

Thalamus

  • Relays impulses between cerebrum and sense organs

Hypothalamus

  • Regulates autonomic nervous system (HR, B/P, RR, digestion)

  • Emotions like fear/pleasure

  • Temperature

  • Hunger and thirst

  • Sleep cycles

  • Endocrine activity

Cerebellum

  • Receives and transmits information concerning skeletal muscles to different parts of the brain

  • Produces smooth and coordinated movements and maintain equilibrium and posture

Brainstem

  • Connects the cerebral hemispheres with the spinal cord

  • Divided into 3 parts: midbrain, pons, and medulla oblongata

Spinal Cord

  • Begins at brainstem and continues thru the spinal column

    • Pathway for all impulses going to and from the brain

Peripheral Nervous System

  • Cranial nerves originate from underside of the brain

    • 12 pairs

    • Each nerve of a pair is identical, but serves only half of the body

  • Peripheral spinal nerves

    • 31 pairs; cervical nerves- C1-C8, Thoracic nerves T1-T12, Lumbar nerves - L1-L5, Sacral nerves - S1-S5

Autonomic Nervous System

  • Controls the involuntary actions of the body

  • Split into 2 divisions

  • Each division balances the activities of the other

    • Maintains homeostasis

  • Sympathetic nerves

    • Prepares the body for emergencies and stress - fight or flight response

    • Increases HR, RR, blood flow to muscles

  • Parasympathetic nerves

    • Returns the body to normal after a response to stress

    • Maintains normal body functions during ordinary non-emotional, non-stressful circumstances

Medical Specialties

  • Anesthesiologist

    • MD who administers anesthetics

  • Anesthetist

    • Medical professional who administers anesthetics but is not a physician

    • Nurse Anesthetist

  • Psychiatrist

    • MD specializing in dx and tx of mental illness

    • Can prescribe medications

  • Psychologist

    • Has a doctoral degree (PhD or PsyD) but is not a medical doctor (MD)

    • Can evaluate and treat mental illness and emotional problems but cannot prescribe medications

  • Neurologist

    • MD specializing in dx and tx of diseases and disorders of the nervous system

  • Neurosurgeon

    • MD specializing in surgery of the nervous system

Pathology

Head and Meninges

  • Cephalalgia

    • Pain in the head (headache

  • Migraine headache

    • Cephalalgia characterized by throbbing pain on one side of the head

      • More often in women

      • Can be accompanied by N/V,

      • Can be preceded by warning aura

  • Cluster headache

    • Intense painful headaches that affect 1 side of head

    • May associate with tearing of eyes and nasal congestion

    • Repeated occurrence

    • Primarily affect men

  • Hydrocephalus

    • Excess CSF accumulates in the brain

      • Can be present at birth or can develop later due to obstructions

      • No cure, but can be controlled via a shunt

  • Meningitis

    • Inflammation of the meninges of the brain and spinal cord

      • Can be bacterial, viral, or fungal

  • Meningioma

    • Slow growing benign tumor of meninges

  • Meningocele

    • Congenital herniation of the meninges thru a defect in the skull or spinal column

  • Encephalocele

    • Congenital herniation of brain tissue through gap in skill

      • Only 20% of fetuses with encephalocele are born alive

Brain

  • Cognition

    • Mental activities associated with thinking, learning and memory

  • Dementia

    • Slow progressive decline in mental abilities (memory, thinking, judgment)

      • Can be accompanied by personality changes

  • Encephalitis

    • Inflammation of the brain

  • Reye’s Syndrome

    • Serious/deadly disorder in children

    • Vomiting and confusion

    • Swelling of liver and brain

    • Caused by viral infection + Aspirin

Neurodegenerative Diseases

  • Disorders in which there is a progressive loss of the structure or function of the neurons

  • Alzheimer’s diseases

    • Most common cause of dementia—gen. term for memory loss

    • Progressive disorder involving thought, memory and language

    • Leading cause of dementia – progressive

    • Inability to form new memories

    • Abnormal clumps (amyloid plaques) and tangled bundles of fibers (neurofibrillary, or tau, tangles).

    • These plaques and tangles in the brain are the main features of Alzheimer’s disease

  • Parkinson’s Disease

    • Inadequate dopamine (neurotransmitter in brain

    • Affects 1 in 1000 Americans over age 60

    • No definite test to diagnose at this time - makes diagnosis difficult

Brain Injury

  • Cerebral contusion

    • Bruising of the brain tissue as the result of a head injury that causes the brain to bounce against the skull

  • Concussion

    • Violent shaking up of the brain

  • Cranial hematoma

    • Collection of blood trapped in the tissues of the brain

      • Named for location

  • Amnesia

    • Memory disturbance

      • Inability to recall past experiences

Shaken Baby Syndrome

  • Term that describes the results of a child being violently shaken by someone

  • Can cause brain injury, blindness, fractures, seizures, paralysis and death

Levels of Consciousness

  • Altered levels of consciousness

    • Decrease in consciousness due to injury, disease, drugs

  • Lethargy

    • Lowered level of consciousness

  • Stupor

    • unresponsive state from which a person can be aroused only briefly despite vigorous repeated attempts

  • Unconscious

    • States of being unaware and unable to respond to any stimuli including pain

  • Delirium

    • Acute condition

    • Confusion, disorientation

  • Syncope

    • AKA fainting

    • Brief loss of consciousness due to blood flow to the brain

  • Coma

    • Profound state of unconsciousness marked by the absence of spontaneous eye movements

    • No response to painful stimuli and the lack of speech

  • Persistent vegetative state

    • Type of come in which the patient exhibits alternating sleep and wake cycles, but because of severe brain damage, is still unconscious even when appearing to be awake

Cerebrovascular Accident (CVA)

  • AKA stroke

  • Brain damage causes by disrupted blood flow

  • Ischemic stroke

    • Blood flow to brain blocked by the narrowing or blockage of a carotid artery, or other artery within the brain

  • Hemorrhagic stroke

    • Occurs when a blood vessel in the brain leaks or an aneurysm ruptures

    • This type of stroke is less common but often fatal

  • Transient ischemic attack (TIA)

    • Mini stoke

    • Temporary interruption (decrease) in the blood supply to the brain

  • Aphasia

    • Loss of the ability to speak, write, and/or comprehend the written or spoken word often caused by CVA

Sleep Disorders

  • Insomnia

    • Prolonged or abnormal inability to sleep

  • Narcolepsy

    • Sleep disorder consisting of sudden and uncontrollable brief episodes of falling asleep during the day

  • Somnambulism

    • Sleepwalking

Spinal Cord

  • Myelitis

    • Inflammation of the spinal cord

  • Poliomyelitis

    • Polio

    • Highly contagious viral infection of the brainstem and spinal cord that sometimes leads to paralysis

  • Radiculitis

    • Pinched nerve

    • Inflammation of the root of a spinal nerve causing pain and numbness radiating down the affected limb

Multiple Sclerosis

  • Progressive autoimmune disorder

  • Inflammation that causes demyelination of the myelin sheath

  • Scars the brain, spinal cord, and optic nerves

  • Disrupts transmission of nerve impulses

Amyotrophic lateral sclerosis

  • AKA ALS, Lou Gehrig’s disease

  • Rapidly progressive neurological disease that attacks the nerve cells responsible for controlling voluntary muscles

Bell’s Palsy

  • Temporary paralysis on only one side of the face (numbness)

Nerves

  • Sciatica

    • Inflammation of the sciatic nerve

  • Trigeminal neuralgia

    • Inflammation of the 5th cranial nerve

    • Severe lightning-like pain in the cheek, lips and gums on one side of the face

  • Guillain-Barre syndrome

    • inflammation of the myelin sheath of peripheral nerves

    • Muscle weakness and temporary paralysis

  • Cerebral Palsy

    • Cerebrum is damaged/injured during pregnancy, birth or soon after birth

    • Poor muscle control, spasticity, speech defects

    • Occurs most frequently in preemies or low birth weight infants

  • Epilepsy

    • Recurrent, unprovoked episodes of seizures of varying severity causes by a sudden surge of electrical activity in the brain

    • Chronic neurological condition

Abnormal Sensations

  • Causalgia

    • Persistent severe burning pain following an injury to a sensory nerve

  • Hyperesthesia

    • Excessive sensitivity sensory stimuli like touch or pain

  • Paresthesia

    • Burning or prickling sensation felt in hands, feet, arms, or legs

  • Peripheral neuropathy

    • Disorder in peripheral nerves

    • Pain, loss of sensation, decreased muscle control

Diagnostic Procedures

  • Carotid ultrasonography

    • Create ultrasound image of carotid artery

    • Looking for plague buildup (ischemic stroke predictor)

  • Echoencephalography

    • Create an ultrasound image of the brain

  • Electroencephalography

    • Recording electrical activity in the brain

    • Uses electrodes attached to scalp-min 21 electrodes

  • Myelography

    • Radiographic study of spinal cord

    • Uses a contrast medium

Treatment Procedures

  • Sedative

    • Depressive the CNS to produce calm without producing sleep

  • Anesthesia

    • Absence of normal induce anesthesia

    • May be topical, local, regional, or general

  • Epidural anesthesia

    • Regional anesthesia produced by injecting medication into the epidural space in the lower space

    • Useful during childbirth

Brain and Nerves

  • Gamma knife surgery

    • Type of radiation treatment for brain tumors performed without a knife or incision

  • Lobectomy

    • Surgical removal of a portion of the brain to treat brain cancer or seizure disorders that cannot be controlled with medications

  • Neurorrhaphy

    • Surgically suturing together the ends of a severed nerve

Mental Health

Anxiety Disorders

  • Conditions characterized by excessive, irrational dread of everyday situations or fear that is out of proportion to the read danger, such as:

  • Panic Attack

    • Unexpected, sudden experience of fear in the absence of danger

    • Signs include heart palpitations, SOB, chest tightness, dizziness, sweating, nausea

    • Unneeded activation of the fight or flight response

  • Generalized anxiety disorder (GAD)

    • Chronic excessive worrying

    • Signs include muscle tension, sleep disturbance, irritability, trouble concentrating, restlessness

  • Obsessive compulsive disorder (OCD)

    • Makes a person feel he/she must do compulsive behaviors to prevent harm or stop the obsession

      • Obsessions: repetitive, intrusive, distressing thoughts

      • Compulsions: repeatedly feeling compelled to do things

  • Post traumatic stress disorder (PTSD)

    • Develops after an event involving actual or threatened death or injury

    • During this time, the person felt intense fear, helplessness or horror

    • Results in emotional numbing hyperarousal, anxiety, sleep disorders persistent reliving of the event

Phobias

  • Persistent irrational fear of a specific thing or situation

    • Causes distress, and can interfere with functioning

  • Acrophobia

    • Fear of heights

  • Claustrophobia

    • Fear of being in a small enclosed space

Developmental Disorders

Learning Disabilities

  • Disorders found in children of normal intelligence who have difficulties in learning specific skills

    • Processing language or grasping mathematical concepts

      • Dyslexia: Learning disability due to inability of the brain to process symbols

      • Intellectual disability: Dx of significant below-average intellectual present at birth or early infancy

  • Autistic spectrum disorders (ASD): Group of conditions where:

    • Children have difficulty with social relations, and communication

    • May compulsively follow repetitive

    • Interests are narrowly focused and intense

      • Autism: Subset of ASD - speech/language delays, normal social relationships

      • Asperger’s syndrome: subset of ASD - Normal or above normal intelligence, impaired social an nonverbal interaction

More Mental Health Disorders

  • Dissociative identity disorder

    • Formally known as multiple personality disorder

    • Presence of 2 or more distinct personalities within the same individual

  • Personality Disorder

    • Chronic pattern of inner experience and behavior that causes serious problems with relationships and work

    • Examples are antisocial, borderline, or narcissistic personality disorders

  • Factitious disorder

    • Individual acts as if he or she has a physical or mental illness, but is not really sick

  • Malingering

    • Intentional creating of a false or grossly exaggerated physical psychological symptoms

      • Different from factitious disorders in that it is motivated by incentives like avoiding work

  • Somatoform disorder

    • Physical complaints or concerns about one’s body that are out of proportion to any physical findings

      • Hypochondriasis: Fearing that one has a serious illness despite medical evaluation and reassurance

Psychotic Disorders

  • Loss of contact with reality and deterioration of normal social function

    • Delusion: false personal belief that is maintained despite proof to the contrary

    • Hallucination: sensory perception experienced in the absence of external stimulation (sight, touch, smell or taste)

    • Schizophrenia

      • Withdrawal from reality, illogical patterns of thinking, delusions, hallucinations

Substance-Related Disorders

  • Alcoholism

    • Chronic alcohol dependence with signs of withdrawal if abrupt cessation

      • Delirium tremens (DTs): sudden and severe mental changes or seizures caused by abruptly stopping the use of alcohol

  • Drug Abuse

    • Excessive use of drugs (illegal, recreational, prescription)

      • Drug overdose: accidental or intentional use of a drug in a higher-than-safe amount

Treatments For Mental Disorders

  • Anxiolytic drug

    • AKA antianxiety drug or tranquilizer

    • Temporarily relieve anxiety and reduce tension

  • Stimulant

    • Increasing activity in parts of the brain to increase concentration and wakefulness

      • For attention deficit disorder, narcolepsy

  • Behavioral therapy

    • Focuses on changing problem behaviors by replacing them with appropriate behaviors (rewards and consequences

    • Cognitive therapy focuses on changing cognitions or thoughts that are affecting a person’s emotions or actions

      • Logic, gathering evidence, testing in action

      • Goal to change problematic beliefs