Nervous System

Chapter 14

Medical Terminology

Nervous System

• System of conducting tissues (nerves) that receive information from the environment and control both voluntary and involuntary functions of the body and consciousness

Cellular Anatomy

• Two types of cells:– Neurons

• Transmit impulses (conduct)– Sensory neurons (afferent)

– Motor neurons (efferent)

– Mixed (both afferent and efferent)

– Neuroglia• Supporting cells

Neurons: Structure

• Cell body– Nucleus, cytoplasm, organelles

• Dendrites– Projections of the cell body– Receive and carry impulses

• Axons– Single, long projections from cell body– Also transmit impulses

Neurons: Structures

• Myelin sheath– Covering outer layer of axon– Lipid layer– White color– Makes up the white matter in CNS– Acts as an insulator – Speeds up impulse transmission in the axon

More about myelin

• Unmyelinated structures– Appear gray, gray matter– CNS and spinal column

• Peripheral nerve (PNS)– Schwann cell = myelin sheath– Neurilemma/neurolemma = this thin layer– Node of Ranvier = space between Schwann

cells

Neurons: Other terms

• Synapse– Space between neurons– Between axon terminal and dendrites of

adjacent neurons

• Axon terminal

• Neurotransmitter

Neuroglia: Four Types

Astrocytes

star shaped support cells for neurons

form capillary sheaths (BBB)

Oligodentrocytes

help in CNS myelin development

Microglia:

phagocytes

Neuroglia: Four Types

• Ependyma– Ciliated cells– Line cavities in CNS (ventricles)– Help CSF circulation

Nervous System Anatomy

• Central Nervous System (CNS)– Brain– Spinal Cord

• Peripheral Nervous System (PNS)– 12 pairs of cranial nerves (CN I-XII)

• From basilar surface of brain

– 31 pairs of spinal nerves• From spinal cord

CNS Anatomy: Brain

Meninges

three protective membranes around CNS

Cerebrum

corpus callosum

structures connecting hemispheres

gyri (gyrus) = folds or convolutions

sulci (sulcus) =fissues, furrows

CNS Anatomy: Brain

• Lobes of the brain:– Frontal– Parietal– Temporal– Occipital– Insula

Brain Anatomy

• Cerebral Cortex– Thin outer layer– Gray matter due to millions of cell bodies– Rest of cerebrum is myelinated axons (white)

• Cerebrum: Functions– Sensory perception, interpretation– Voluntary movement, language, memory– Emotional aspects of behavior

Other Structures in the Brain:

• Cerebellum– Posterior aspect– Coordinates and refines movement– Balance and equilibrium

Other Brain Structures

• Diencephalon (interbrain)– Thalamus

• Receives & transmits all sensory info except smell to the cerebrum

• Transmits impulses from cerebrum to efferents

– Hypothalamus• Coordinates autonomic impulses• Temperature regulation• Control of endocrine system

Other Brain Structures:

• Brainstem: control of respiration, cardiac activity

• Pathway between brain and spinal column– Midbrain (mesencephalon)– Medulla (oblongata)– pons

CNS structures: Spinal Cord

• Ascending tracts– Bring sensory input to CNS

• Descending tracts– Send impulses to muscles, end organs

• Cross-section:– Gray matter-inner part of cord– White matter—outer part of cord

• Spinal cavity– Spinal nerves exit from intervertebral spaces– Cauda equina

CNS: Meninges

• Dura– Outermost, very fibrous– Subdural space: filled with serous fluid

• Arachnoid– Thinner, looks like a spider web– Subarachnoid space: contains CSF

• Pia– Innermost layer, also thin– Contains blood vessels and lymphatics

Peripheral Nervous System (PNS)

• Cranial Nerves

• Spinal Nerves

• Somatic Nervous system (SNS)

• Autonomic Nervous system (ANS)

PNS: Cranial Nerves

• Exit mostly from base of the brain

• Named and denoted by I through XII

• Mostly involve facial, eye, mouth movement and sensation and the special senses of hearing, taste, sight

• Are afferent, efferent, and mixed nerves

PNS: Spinal Nerves

• Exit from spinal cord and go to muscles and organs

• Each has two attachments to spinal cord:– Anterior root: motor fibers– Posterior root: sensory fibers

Somatic Nervous System (SNS)

• Voluntary functions

• Mostly supplies skeletal muscles

Autonomic Nervous System (ANS)

• Supplies nerves (ennervates) involuntary functions

• Ennervates glands, smooth & cardiac muscles, etc

• Sympathetic system– Fight or flight

• Parasympathetic system– Functions that are the opposite, resting

Medical Word Elements

• Cerebro: cerebrum

• Cranio: cranium or skull

• Encephalo: brain

• Kinesio: movement

• Ganglio: knot or mass (a ganglion)

• Narco: sleep, stupor

• Neuro: nerve

Medical word elements:

• Radiculo: nerve root (radiculopathy)

• Theco: sheath (intrathecal)

• Tono: tension (tonometry, dystonic)

Medical Word Elements

• Others are from anatomic structure names

• Ventriculo: ventricles

• Thalamo: thalamus

• Myelo: spinal cord or bone marrow

• Meningo: meninges

• Glio: neuroglial tissue

• Dentro: treee-like

Suffixes: Neuro

• -algia or algesia: pain

• -asthenia or –paresis: weakness, disability

• -esthesia: feeling

• -kinesia: movement

• -lepsy: seizure (epilepsy, narcolepsy)

• -phasia: speech

• -plegia: paralysis

Suffixes: Neuro

• -plexy: stroke

• -taxia: coordination (ataxia)

• -trophy: development

Prefixes: Neuro

• Contra- = against/opposite

• Pachy- = thick

• Para- = near

• Syn- = together, joined

Neurological Pathology

• Common symptoms:– Pain (head, neck, back, periphery)

– Abnormal movements

– Gait abnormalities

– Disturbances of special senses

– Speech abnormalities

– Altered level of consciousness

– Focal weakness

– seizures

Bell’s Palsy

• Facial paralysis (unilateral usually))

• Involves CN VII

• Herpes viral infection

• Usually transient

• Facial weakness and numbness, problems with blink reflex and speech

Cerebrovascular Disease

• Cerebrovascular accident (CVA) or stroke– Focal loss of function due to loss of blood

supply– Lasts more than 24 hours– Causes:

• Ischemic: due to thrombus or carotid emboli (75%)

• Hemorrhagic (25%)

• Extrinsic compression of blood vessel (rare)

Cerebrovascular Disease

• Typical CVA symptoms:

• Anterior stroke:– Hemiparesis or hemiplegia– Aphasia or dysphasia– Partial loss vision/ visual field

• Posterior stroke:– Balance problems, ataxia, vertigo

Cerebrovascular Disease

• Transient Ischemic Attack (TIA)– Focal symptoms like a CVA, lasting less than

24 hours– Typical symptoms: weakness or clumsiness of

upper extremity, visual field loss, hemiparesis of the face, paresthesias of upper extremities

– Indicates risk of CVA within next year

Seizure Disorders

• Nerve conduction dysrhythmias

• Epilepsy = chronic seizure disorder

• Generalized Sz (gran mal, tonic clonic)– Movements of entire body– unconsciousness

• Partial Sz (focal) (Jacksonian)

• Petit mal (absence Sz)

Seizure Disorders: Causes

• Congenital anomalies

• Brain injury

• Metabolic disease

• Brain tumors

• Genetic disorders

• Vascular anomalies

Seizures:

• Are often the symptom of the disease

• Status epilepticus– Life-threatening– Lengthy or muliple Sz

• Electroencephalography

• Magnetoencephalography

• Rx: antiepileptic meds

Parkinson Disease

• Parkinsonism also

• A movement disorder

• Progressive neurological disease affected the movement control centers of the brain

• Deficiency of dopamine, a neurotransmitter in the brain

• Rx: L-dopa administration

Parkinson Disease

• Symptoms:

• Bradykinesia or hypokinesia

• Uncontrollable shaking of head

• Shuffling gait, pill rolling of fingers

• Tremors

• Some stiffness,

• Mask-like facial expressions

Multiple Sclerosis (MS)

• Progressive demyelinating disease of CNS

• Impeding nerve conduction

• Disease of young adults, usually females

• Autoimmune disease suspected, fatal

• Symptoms:– Tremors, bradykinesias– Visual disturbances, muscle weakness

Alzheimer Disease

• Progressive, fatal neurological degenerative disease of the elderly

• Memory loss, cognitive dysfunction, anxiety, decline in social skills and ADL

• Plaques develop in cerebral cortex

• Common cause of senile dementia in US

• Some medications slow progress of disease

Mental Illnesses

• Alterations in behavior, mood, thought

• Some general terminology:– Phobia– Delusion– Hallucinations– Obsessive compulsive disorders (OCD)– Psychiatrist or clinical psychologist

Categories of Mental Illnesses

• Affective (mood) disorders– Mania– Depression– Manic-depressive disorder (bipolar disorder)

• Eating disorders– Anorexia nervosa– Bulimia nervosa

Categories of Mental Illnesses

• Anxiety disorders

• Panic attacks

• Attention-deficit hyperactivity disorder (ADHD)

• Schizophrenia (thought disorder)

Neuro Oncology

• Most intracranial neoplasms are primary brain tumors

• Papilledema = classic sign of intracranial tumor, slowly rising ICP

• Metastatic tumors to brain– Fairly common, slower growing than their

primary tumors, more easily resected than primary CNS tumors

Neuro Infections

• Meningitis– Bacterial = most rapid, meningococcal– Viral or fungal

• Encephalitis– Usually viral

• Brain or Spinal Cord abscesses– Usually bacterial– Parasitic also possible

Intracranial Hemorrhages

• Epidural hemorrhage

• Subdural hemorrhage

• Subarachnoid hemorrhage

• Intracerebral hemorrhage

Epidural Hemorrhage

• Arterial bleeding

• Often involves parietal skull fracture

• Disrupts the middle meningeal artery

• Famous “lucid interval” symptoms

• Usual symptoms: headache, unconsciousness, unilateral weakness or abnormal reflexes

Subdural Hemorrhage

• Venous bleeding from the bridging veins

• Slower bleed

• Symptoms: similar to EDH but no lucid interval

Subarachnoid Hemorrhage

• Thin filmy layer of blood around the brain and cord

• May be spontaneous or due to trauma• Symptoms and Signs:

– “the worst headache of my life”– Sudden onset– Nuchal rigidity– Photophobia, nausea, vomiting

Intracerebral Hemorrhage

• May also be spontaneous or traumatic

• Hemorrhage is deep in the CNS tissue

• Creates raised intracranial pressure (ICP) due to space-occupying mass

• Like all of these bleeds, may cause herniation.

Diagnostic & Symptomatic Terms

• Agnosia = inability to process sensory input

• Aura

• Autism = withdrawal, inability to communicate

• Cerebral palsy = developmental defects in brain or birth trauma to brain

• Closed head injury

Diagnostic & Symptomatic Terms

• Coma• Concussion• Dementia• Dyslexia: inability to learn/process written

language• Guillain-Barre Syndrome• Huntington Chorea: inherited movement

disorder (also speech & mental symptoms)

Diagnostic & Symptomatic Terms

• Hydrocephalus

• Lethargy

• Neurosis

• Psychosis

• Spina bifida/ occulta

• Meningocele

• myelomeningocele

Diagnostic & Symptomatic Terms

• Paraplegia / quadriplegia

• Paresthesia

• Poliomyelitis

• Reye Syndrome

• Sciatica

• Syncope

Diagnostic Procedures

• Electroencephalography (EEG)• Electromyography (EMG)• Lumbar puncture (LP)• Nerve conduction velocity (NVC)• CSF analysis

– Glucose concentration– Types of blood or other cells present– Culture to grow bacteria

Diagnostic Procedures

• Cerebral angiography

• Myelography

• Scans: CT, MRI, PET

Pharmacology

• Analgesics

• Anesthetics– Local & general

• Anticonvulsants– Tegretol, Depakote, Lamictal

• Antiparkinsonian drugs– Levodopa, Sinemet

Pharmacology

• Hypnotics (sedate)– Barbiturates and valium derivatives

• Antipsychotics– Haldol, Zyprexia, etc

• Antidepressants– Paxil, Prozac, TCA’s

• Psychostimulants– Ritalin