Nervous System Disorders

Flashcards covering the key concepts of nervous system disorders, including anatomy, physiology, and pathology.

What are the two main components of the Central Nervous System (CNS)?

Brain and spinal cord

What are the components of the Peripheral Nervous System (PNS)?

Cranial and spinal nerves, sensory neurons, neuromuscular junctions

List the layers of the meninges from outermost to innermost.

Dura mater, arachnoid, pia mater

Where is cerebrospinal fluid (CSF) found?

Subarachnoid space

What are the functions of cerebrospinal fluid (CSF)?

Provides cushion for brain and spinal cord; Changes in CSF characteristics are diagnostic; Maintains intracranial pressure (ICP)

What forms the blood-brain barrier?

Capillaries in the brain

What substances can easily pass through the blood-brain barrier?

Lipid-soluble substances

Where is the blood-CSF barrier located?

Choroid plexus

What connects the cerebral hemispheres?

Corpus callosum

Which hemisphere is usually dominant and what functions does it control?

Left; controls language (Broca's area for expressive speech, Wernicke's area for comprehension)

What is the function of the prefrontal cortex?

Coordinates complex cognitive behavior, personality expression

What is the function of the basal nuclei?

Controls skeletal muscle activity

What is the limbic system responsible for?

Emotional reactions/feelings

What is the function of the thalamus?

Relay station for incoming sensory impulses

What are the key roles of the hypothalamus?

Homeostasis; controls ANS and endocrine system; regulates body temperature, fluid/food intake, sleep cycles, stress response, emotional responses, sex drive

What is the function of the midbrain?

Reticular formation/RAS (degree of awareness)

What is the function of the pons?

Bundles of afferent/efferent fibers; bridge between cerebellum/cerebrum; cranial nerve nuclei

What are the functions of the medulla oblongata?

Control center for respiratory and cardiovascular function; coordinates cough, swallowing, vomiting reflexes; nuclei for cranial nerves

What are the functions of the cerebellum?

Coordination of movements, posture, equilibrium

What arteries supply blood to the brain?

Internal carotid and vertebral arteries

What is the function of the Circle of Willis?

Provides collateral circulation in the brain

How does the brain regulate blood flow?

Autoregulation: increased CO2, decreased pH, decreased BP lead to local vasodilation

Where does venous blood collect from the brain?

Dural sinuses, drains into internal jugular veins

Where does the spinal cord end?

L1 vertebra

What composes the gray matter of the spinal cord?

Anterior horns (motor neurons), Posterior horns (interneurons), Lateral horns (visceral motor neurons)

What fibers compose the white matter of the spinal cord?

Afferent (sensory) and efferent (motor) fibers organized into tracts (ascending/descending)

What are reflexes?

Automatic, rapid, involuntary responses to stimuli

What are the main components of a neuron?

Cell body, axons (conduct away), dendrites (receptor site, conduct toward)

What cells form the myelin sheath in the PNS and CNS?

Schwann cells (PNS) or oligodendrocytes (CNS)

What are the types of glial cells and their functions?

Astroglia (blood-brain barrier), Oligodendroglia (myelin in CNS), Microglia (phagocytotic), Ependymal cells (line ventricles, choroid plexus)

Which axons may regenerate: PNS or CNS?

PNS

What is the basic process of nerve impulse conduction?

Stimulus increases membrane permeability -> depolarization (Na+ influx) -> action potential -> repolarization (K+ outward) - > Na-K pump restores ions

What is saltatory conduction?

Rapid conduction in myelinated fibers

What are the components of a synapse?

Presynaptic axon terminal (neurotransmitter vesicles), synaptic cleft, postsynaptic receptor

Give examples of neurotransmitters and whether they are excitatory or inhibitory.

Acetylcholine (excitatory), Norepinephrine/Epinephrine (excitatory), Dopamine/Serotonin (excitatory), GABA (inhibitory), Glycine (inhibitory)

What are the divisions of the Autonomic Nervous System (ANS)?

Sympathetic Nervous System (SNS) and Parasympathetic Nervous System

What are the main characteristics of the Sympathetic Nervous System (SNS)?

Fight-or-flight, increases general activity, preganglionic fibers in thoracic and first two lumbar segments, ganglia in chains/trunks, preganglionic neurotransmitter (acetylcholine), postganglionic neurotransmitter (norepinephrine), receptors (alpha and beta)

What are the main characteristics of the Parasympathetic Nervous System?

Originates in brainstem and sacral spinal nerves, dominates digestive system, aids recovery after sympathetic activity, ganglia scattered close to target organ, neurotransmitter (acetylcholine both pre- and postsynaptic), receptors (nicotinic and muscarinic)

What are local (focal) effects of neurologic dysfunction?

Signs related to the specific area of brain/spinal cord lesion

Where are supratentorial lesions located and what are their characteristics?

Cerebral hemispheres (above tentorium cerebelli); specific dysfunction in discrete area

Where are infratentorial lesions located and what are their characteristics?

Brainstem (below tentorium); affects many motor/sensory fibers, widespread impairment, respiratory/circulatory impairment, impaired level of consciousness

What are the effects of left hemisphere damage?

Loss of logical thinking, analytical skills, intellectual abilities, communication

What are the effects of right hemisphere damage?

Impaired appreciation of music/art, behavioral problems, spatial orientation/recognition deficits, self-care deficits

What is an early sign of acute brain disorders?

Decreased level of consciousness (LOC)

What is the Glasgow Coma Scale used for?

Assesses eye opening, motor response, verbal response

What are the characteristics of a vegetative state?

Loss of awareness/mental capabilities due to diffuse brain damage; brainstem function continues; sleep-wake cycle present; unresponsive to stimuli

What are the characteristics of locked-in syndrome?

Aware and capable of thinking, but paralyzed and unable to communicate

What are the criteria for brain death?

Cessation of brain function (cortex and brainstem); flat EEG; absence of brainstem reflexes/responses; absence of spontaneous respirations; confirmation of irreversible damage by two physicians

What are the effects of upper motor neuron damage?

Interference with voluntary movements; weakness/paralysis on contralateral side

What are the effects of lower motor neuron damage?

Weakness/paralysis on ipsilateral side, at and below level of spinal cord damage

What can decorticate and decerebrate posturing indicate?

Severe brain damage

What is the function of the somatosensory cortex?

Receives/localizes basic sensory input (touch, pain, temperature, position), uses dermatomes (useful for spinal cord lesions)

What is hemianopia and what causes it?

Visual loss; depends on site of damage in visual pathway

What are the different types of aphasia and what are their characteristics?

Receptive (Wernicke's): Inability to read or understand spoken word; damage to Wernicke's area (left temporal lobe). Expressive (Broca's): Impaired ability to speak or write fluently/appropriately; damage to Broca's area (dominant frontal lobe). Global: Combination of expressive and receptive; major brain damage. Fluent Aphasia: Normal speech pace, includes made-up words (Wernicke's damage). Nonfluent Aphasia: Slow, labored, short phrases (Broca's damage)

Describe dysarthria.

Motor dysfunction affecting speech muscles (cranial nerve damage or muscle impairment)

Define agraphia, alexia, and agnosia.

Agraphia: Impaired writing ability. Alexia: Impaired reading ability. Agnosia: Loss of recognition or association

What causes seizures?

Spontaneous, excessive discharge of neurons in the brain

Describe status epilepticus.

Continuous seizures without consciousness recovery; life -threatening due to increased glucose/oxygen metabolism

What causes increased intracranial pressure (ICP)?

Increase in fluid/mass causes pressure; common in hemorrhage, trauma, cerebral edema, infection, tumors, abnormal CSF circulation

What are early signs of increased ICP?

Decreasing LOC/responsiveness (lethargy), decreased pupillary responses, severe headache, projectile vomiting, papilledema (swelling of optic disc)

Describe the Cushing reflex and what it indicates.

Cerebral ischemia -> vasomotor centers increase arterial blood supply -> systemic vasoconstriction -> increased BP (with increasing pulse pressure) -> baroreceptor response (slows HR) -> chemoreceptor response (reduces RR). This is a temporary compensatory mechanism for increased ICP

What visual signs are associated with increased ICP?

Pressure on oculomotor nerve (CN III) affects pupils (ipsilateral fixed/dilated, then bilateral); ptosis

What changes occur in CSF with increased ICP?

Elevated pressure on lumbar puncture; composition varies (pinkish/erythrocytes, cloudy/WBCs, abnormal protein)

What is herniation and what are the different types?

Displacement of brain tissue due to increased ICP. Transtentorial: Cerebral hemispheres, diencephalon, midbrain displaced downward. Uncal: Uncus of temporal lobe displaced downward. Infratentorial (Cerebellar/Tonsillar): Cerebellar tonsils pushed through foramen magnum

What diagnostic tests are used for neurologic dysfunction?

CT scans, MRI, Cerebral angiography, Doppler ultrasound, Electroencephalography (EEG), Radionuclide perfusion tracking, Lumbar puncture (for CSF analysis and pressure)

What are gliomas?

Largest category of primary malignant brain tumors

What are common signs and symptoms of brain tumors?

Site-dependent focal signs; seizures (often first sign); headaches (ICP), vomiting, lethargy, irritability, personality/behavioral changes, unilateral facial paralysis/visual problems

What are the treatments for brain tumors?

Surgery (if accessible), chemotherapy, radiation (can damage normal CNS tissue)

What are Transient Ischemic Attacks (TIAs)?

Temporary localized reduction of blood flow in brain

What causes TIAs?

Partial occlusion (atherosclerosis, small embolus, vascular spasm, local loss of autoregulation)

What are signs and symptoms of TIAs?

Intermittent short episodes of impaired function (muscle weakness, visual disturbances, numbness/paresthesia, transient aphasia/confusion)

Define Cerebrovascular Accidents (CVAs) - Stroke.

Infarction of brain tissue due to lack of blood (occlusion or rupture of cerebral vessel)

What are the different types of CVAs?

Thrombus: Occlusion by atheroma (large arteries); gradual onset, often at rest; minimal ICP; localized effects. Embolus: Sudden obstruction by embolus (cerebral artery); sudden onset; minimal ICP; localized unless multiple emboli. Hemorrhage: Rupture of cerebral artery (hypertension); sudden onset with activity; high ICP; widespread and severe, often fatal

What are the general signs and symptoms of CVAs?

Depend on obstruction location/size, collateral circulation; lack of voluntary movement/sensation on opposite side (initially flaccid, then spastic paralysis). NIH Stroke Scale (NIHSS) for rapid diagnosis

What are cerebral aneurysms and what causes them?

Localized weakness in arterial wall, often multiple, at Circle of Willis bifurcations (Berry aneurysms); aggravated by hypertension

What are the signs and symptoms of cerebral aneurysms?

Loss of visual field/disturbances, headache, photophobia, intermittent dysfunction, nuchal rigidity (meningeal irritation), vomiting, seizures, loss of consciousness

What are the treatments for cerebral aneurysms?

Surgical clipping/tying (if diagnosed before rupture, or after with rebleeding risk), reduce ICP, manage cerebral vasospasm

What is meningitis?

Inflammation of the meninges, usually caused by bacterial infection

How does meningitis spread?

Microorganisms reach brain via blood, nearby tissue, or direct access; rapid spread through meninges

What are the signs and symptoms of meningitis?

Sudden onset; severe headache, back pain, photophobia, nuchal rigidity, Kernig sign, Brudzinski sign, vomiting, irritability, lethargy, fever, chills with leukocytosis; progression to stupor/seizures

What are the diagnostic tests and treatments for meningitis?

Diagnostic Tests: CSF examination (lumbar puncture), identification of causative organism. Treatment: Aggressive antimicrobial therapy, specific ICP/seizure measures, glucocorticoids (reduce inflammation/edema), vaccines available

Describe a brain abscess.

Localized infection (often frontal/temporal lobes); necrosis and edema

What is encephalitis and what are the common causes?

Infection of parenchymal/connective tissue in brain/spinal cord; necrosis/inflammation -> permanent damage; usually viral (Western equine, St. Louis, West Nile, Herpes simplex)

What are the signs of encephalitis?

Severe headache, stiff neck, lethargy, vomiting, seizures, fever

How does rabies spread and what are its signs?

Viral (animal bite, contaminated tissue); travels along peripheral nerves to CNS/salivary glands; headache, fever, hyperirritability, sensitivity to touch, seizures, difficulty swallowing, fear of fluids, respiratory failure, death

What causes tetanus and what are its signs?

Clostridium tetani (spores in soil); exotoxin enters nervous system; tonic muscle spasms (jaw stiffness, difficulty swallowing, stiff neck), headache, skeletal muscle spasm, respiratory failure

How does poliomyelitis spread and what are its effects?

Polio virus (immunization available); highly contagious (direct contact, oral droplets); attacks motor neurons of spinal cord/medulla; fever, headache, vomiting, stiff neck, pain, flaccid paralysis

What causes Herpes Zoster (Shingles) and what are its signs?

Varicella-zoster virus in adults (reactivation); affects cranial nerve or dermatome; pain, paresthesia, vesicular rash

When does Post-Polio Syndrome (PPS) occur and what are its signs?

10-40 years after original infection; progressive debilitating fatigue, weakness, pain, muscle atrophy

What is Reye's Syndrome and what are its effects?

Cause not fully determined; linked to viral infection in children treated with aspirin; pathological changes in brain/liver (cerebral edema, enlarged/fatty liver, acute failure)

What is Guillain-Barre Syndrome?

Inflammatory condition of PNS; exact cause unknown; local inflammation, demyelination, axon destruction -> impaired nerve conduction

What is a concussion?

Reversible interference; sudden excessive brain movement (mild blow, whiplash); amnesia, headaches; recovery usually within 24 hours

What is a contusion?

Bruising of brain tissue, small vessel rupture, edema; blunt blow; possible residual damage

What is a closed head injury?

Skull not fractured; brain tissue injured, blood vessels ruptured; extensive damage with head rotation

What is an open head injury?

Fractures or penetration of brain

What is a depressed skull fracture?

Bone displacement below skull level; compression of brain tissue; impaired blood supply

What is a basilar fracture?

At base of skull; CSF leakage through ears/nose possible

What is a contrecoup injury?

Injury to brain area contralateral to direct damage (brain bounces off skull); secondary to acceleration/deceleration

What are primary brain injuries?

Direct: Laceration/compression of tissue, rupture/compression of vessels, damage from skull's inner surface, lobe movement

What are secondary brain injuries?

Additional effects of cerebral edema, hemorrhage, hematoma, vasospasm, infection, ischemia