The Nervous System and Behavioral Disorders

Nervous System Controls body functions with electric

impulses Two physical systems

Central nervous system Brain Spinal cord

Peripheral nervous system All other nerve tissue

Nervous System (con’t) Two functional systems

Somatic nervous system Controls skeletal muscles

Autonomic nervous system Controls:

Smooth muscles Cardiac muscles Glands

The Neuron Basic functional unit of nervous system Two types of fibers extend from cell body

Dendrite Carries impulses toward cell body

Axon Carries impulses away from cell body Some covered with myelin

The Neuron (con’t)

Types of neurons Sensory neurons

Transmit impulses towards CNS Motor neurons

Transmit impulses away from CNS Connecting neurons

Contact at synapse

Nerves

Bundles of neuron fibers in PNS Ganglion = collection of cell bodies

along nerve pathway Most nerves contain both sensory

and motor fibers

The Brain Cerebrum

Largest part of brain Composed mostly of white matter Also houses cerebral cortex

Thin outer layer of gray matter Higher brain functions

Divided into two hemispheres Deep groove separates hemispheres

Called longitudinal fissure

Meninges Set of three protective layers covering

brain and spinal cord Dura mater

Outermost layer Arachnoid

Middle layer Pia mater

Thin, vascular inner layer Attached directly to brain and spinal cord tissue

The Spinal Cord Extends from medulla oblongata to

between 1st and 2nd lumbar vertebrae

Consists of: Gray matter

Central area surrounded by white matter White matter

Contains tracts for impulses

Vascular Disorders Stroke or cerebrovascular accident

Any occurrence of brain tissue not getting oxygen

3rd leading cause of death in developed world Leading cause of neurologic disability Risk factors:

Hypertension Atherosclerosis Heart disease Diabetes mellitus Cigarette smoking Heredity

Trauma Epidural hematoma

Bleeding between dura mater and skull bone Usually results from blow to side of head

Subdural hematoma Bleeding between dura mater and arachnoid Usually results from blow to front or back of

head Concussion

Can result from blow to head or fall May also encounter contrecoup injury

Infections Bacterial meningitis

Inflammation of meninges Common symptom is stiff neck Diagnosed with lumbar puncture

Viral meningitis (another form) Encephalitis (inflammation of the brain) Also includes other viruses that affect CNS:

Rabies Polio HIV

Neoplasms Tumors originating in nervous system,

usually involving neuroglia Called gliomas Symptoms are dependent on size and

location: Seizures Headaches Vomiting Muscle weakness Interference with one of the senses (hearing,

vision)

Degenerative Diseases Multiple sclerosis

Patchy loss of myelin with hardening of tissue in CNS

Symptoms: Vision problems Tingling, numbness in arms Urinary incontinence Tremor Stiff gait

Exact cause is unknown

Degenerative Diseases (con’t)

Parkinson disease Failure of midbrain neurons to secrete

dopamine Leads to:

Tremors Muscle rigidity Flexion at joints Akinesia Emotional problems

Treated with L-dopa

Degenerative Diseases (con’t)

Alzheimer disease Unexplained degeneration of

neurons Atrophy of cerebral cortex May cause:

Progressive loss of recent memory Confusion Mood changes

Epilepsy Seizures caused by abnormal electric brain activity Seizures vary:

Brief and mild (petit mal) Major (grand mal)

Serious seizures result in loss of consciousness and convulsions

Diagnosed with EEG revealing brain activity abnormalities

Treated with antiepileptic and anticonvulsive drugs

Sleep Disturbances Dyssomnia = general term for sleep

disorders Insomnia

Insufficient or nonrestorative sleep Narcolepsy

Brief, uncontrollable “attacks” of sleep Treated with:

Stimulants Regulation of sleep habits Short daytime naps

Sleep apnea Failure to breathe for brief periods during sleep Usually results from upper airway obstruction

Behavioral Disorders Anxiety disorders

Generalized anxiety disorder Chronic excessive and uncontrollable

worry May be accompanied with:

Muscle tensing Restlessness Dyspnea Palpitations Insomnia Irritability

Behavioral Disorders (con’t) Panic disorder

Anxiety with episodes of intense fear Phobias

Extreme, persistent fears centered around objects or situations

Obsessive-compulsive disorder Condition w/ repetitive behaviors to relieve

anxiety Attention-deficit-hyperactivity disorder

Difficult to diagnose due to overlapping symptoms

Treated with stimulant drugs

Depression Usually coexists with physical or

emotional conditions Characterized by feelings of:

Feelings of sadness Hopelessness Lack of interest

Dysthymia Form of depression triggered by

serious event Bipolar disorder

Depression with episodes of mania

Psychosis Mental state with gross

misconception of reality Characterized by:

Delusions Paranoia Hallucinations

Schizophrenia From of chronic psychosis

Drugs Used in Treatment Psychotropic drugs

Acts on mental state Category of drugs includes:

Antianxiety (anxiolytics) Mood stabilizers Antidepressants Antipsychotics (neuroleptics)