Exam 2: Common Neurological Disorders Flashcards
Nervous System
What is the structure of the CNS?
Brain and spinal cord
Overall “command center”
Processing and integrating information
Nervous System
What is the structure of the PNS?
Nerves and ganglia
Receives and projects information to and from the CNS
Mediates some reflexes
Nervous System
What is the function of the motor nervous system?
Some CNS and PNS components - includes all axons that transmit nerve impulses from the CNS to a muscle or gland
Somatic
Autonomic
Nervous System
Sensory Nervous System
Includes all axons that transmit impulses from a peripheral structure to the CNS (includes Eyes and Ears)
Somatic sensory
Visceral sensory
Special Senses: Glaucoma
Pathogenesis of Glaucoma
Increased intraocular pressure
blocks blood flow through intraocular vessels (in the uvea)
Reduced blood flow deprives retina of nutrients (atrophy of retinal layer)
Special Senses: Glaucoma
What causes increased intraocular pressure?
Increased production of vitreous humor
Decreased drainage of vitreous humor
Accumulation of vitreous humor
Special Senses: Glaucoma
What causes atrophy of retinal layer?
reduced blood flow deprives retina of nutrients
Special Senses: Glaucoma
What is the pathology of glaucoma?
Retinal Atrophy
* Disrupted nerve fiber layer (axon layer)
* Fewer cells in ganglion cell layer
* Damage to layer of rods and cones
* Overall thinning of retina
Plexiform laters are barely visible
Special Senses: Glaucoma
What are the clinical symptoms of Glaucoma?
Retinal damage - blurred vision, impaired dark adaptation
Corenal damage - halos around lights
Optic Nerve Atrophy
Special Senses: Ostosclerosis
Otosclerosis
Disease of the middle ear
Hardening of the tissue in the ear
May be asymptomatic
Genetic Component
Special Senses: Ostosclerosis
What causes ostosclerosis?
Bony growth around oval window
* failure of resorption results in excess bone
* Immobilizes stapes (prevent vibration transmission)
Special Senses: Ostosclerosis
What is the pathogenesis of Otosclerosis?
Starts with bone resorption
* uncoupling of resorption/deposition
Proceeds with fibrosis and vascularization of the temporal bone
Dense new bone replaces fibrotic tissue
* anchors the footplate of the stapes (cant vibrate againt oval window - deaf)
Special Senses
Tinnitus
disease of the inner ear
ringining, hissing, whistling, humming, and/or roaring in the ears
Special Senses: Tinnitus
Transient Tinnitus
not associated with disease
excessive stimulation of hair cells
Signalling hasnt stopped - usually goes away within a day or 2
Loud concert, club, loud party, etc.
Special Senses
Persistent Tinnitus
Associated with hearing loss
associated with cochlear dysfunction or cranical nerve VIII dysfunction
hair cell damage w/hearing loss
Diseases of the PNS
What are the types of PNS Diseases?
Neuromuscular
Myelin sheath
PNS: Neuromuscular disease
Neuromuscular junctions
Terminals of motor axons synapse with sarcolemma
Neurotransmitter is acetylcholine
PNS: Neuromuscular disease
Neurotransmitters
Can be excitatory or inhibitory
Usually amines, amino acids, or small peptides
Degraded in synaptic cleft, or taken up by endocytosis (prevent prolonged stimulation)
May act as paracrine hormones outside the nervous system
PNS: Neuromuscular disease
How does Myasthenia gravis affect neuromuscular junctions?
Autoantibodies bind ACh receptors
PNS: Neuromuscular disease
How does Botulism toxin affect neuromuscular junctions?
Directly effects ACh release
PNS: Neuromuscular disease
How does Lambert-Eaton Syndrome affect neuromuscular junctions?
Attacks voltage-gated Ca2+ channels
PNS: Neuromuscular disease: Myasthenia Gravis
Myasthenia Gravis
Antibody-mediated autoimmune disease
* Autoantibodies against ACh receptors (85% of patients)
* Induce aggregation and degredation of receptors (decreased number of receptors)
Reduced ACh receptors
* On post-synaptic membranes
* Reduced responsiveness to ACh - muscle weakness
Antibodies also interact with the thymus
* benign thymoma (10% of cases)
* Thymic Hyperplasia (30%)
* B-cell follicles in thymus
PNS: Neuromuscular disease: Myasthenia Gravis
What are the clinical symptoms of Myasthenia Gravis?
Fluctuating weakness
* Increases over the course of the day
* increass upon exertion
* decreased muscle responsiveness upon repeated stimulation
Involvement of extra-ocular muscles
PNS: Neuromuscular disease: Myasthenia Gravis
What is the treatment for Myasthenia Gravis?
Acetylcholinedterase inhibitors (ACh persists in synaptic cleft)
Immunosuppressive therapy (glucocorticoids) or Plasmapheresis
Thymectomy for patients with thymoma
PNS: Neuromuscular disease: Myelin Sheath Disease
Myelin Sheath
Layers of membrane surround an axon
In CNS, gives white matter its characteristic macroscopic appearance
Function: important for signal transmisison
Transmit signal through salatory conduction
PNS: Neuromuscular disease: Multiple Sclerosis
Multiple Sclerosis
Myelin Sheath Disease
Autoimmune demyelinating disorder - Both genetic and environmental components
Lesions in myelin sheath reduce nerve transmission efficiency
Relapsing episodes of neurologic deficits
Freqiency increases with time, while recovery decreases
Linked to MHC component (DR2)
Also IL-2/IL-7 receptors
PNS: Neuromuscular disease: Multiple Sclerosis
Describe the replasing episodes of multiple sclerosis
variable duration (weeks to years)
gradual, partial recovery
don’t have full recovery
episodes increase over time but recovery decreases
PNS: Neuromuscular disease: Multiple Sclerosis
Why is MS an autoimmune disease?
Immune response to components of the myelin sheath
Presence of chronic immune cells (especially T cells and macrophages) around myelin sheath plaques
PNS: Neuromuscular disease: Multiple Sclerosis
What is the immune response of MS?
T helper cells initiate immune response against myelin antigens
Cytokine release promotes macorphage and leukocyte infiltration
Macrophages and leukocytes release agents to damage invaders
agents damage myelin sheath indtead - b/c no invaders
PNS: Neuromuscular disease: Multiple Sclerosis
Describe the tissue damage in MS
Consistent with other immune diseases
Immune response itself produces tissue damage
Lesions are firmer than surround tissue (sclerosis)
Myelin is very soft - soft tissue gets replaces with harder tissue
PNS: Neuromuscular disease: Multiple Sclerosis
What are common signs and symptoms of MS?
Unilateral visual impairment
Brainstem involvement
Spinal cord lesions
PNS: Neuromuscular disease: Multiple Sclerosis
How is the brainstem involved in MS?
Cranial nerve signs
ataxia
nystagmus
internuclear opthalmoplegia
PNS: Neuromuscular disease: Multiple Sclerosis
What causes unilateral visual impairment?
Signal transmitted to axon as well
only one eye
PNS: Neuromuscular disease: Multiple Sclerosis
What causes/results from spinal cord lesions?
Cause: motor or sensory nerves (tingly)
Spasticity and loss of bladder control
Signal in spinal cord is slow/glitchy
Diseases of the CNS
Types of diseases of the CNS
Ethanol Toxicity
Cerebrovascular Disease
Prion Disease
Motor Neuron diseases (degenerative)
Degenerative Diseases
Dementia (degenerative)
Diseases of the CNS: Ethanol Toxicity
Toxic Nerve Damage
Cellular and tissue loss due to toxicity
Carbon monoxide
Methanol
Ethanol
Radiation
Diseases of the CNS: Ethanol Toxicity
Toxic Nerve Damage: Unique considerations in the CNS
Isolation (BBB) - only toxins that can cross the BBB get into the CNS
Meabolic needs
repair capacity
Diseases of the CNS: Ethanol Toxicity
Ethanol-induced toxicity
Acute abuse is generally reversible
Chronic alcohol abuse associated with metabolic disturbances as well
Diseases of the CNS: Ethanol Toxicity
What are the 3 mechanisms that cause CNS damage due to ethanol abuse?
Mostly associated with liver damage
Hepatic encephalopathy - damage secondary to liver
Thiamine deficiency
Ethanol toxicity
Diseases of the CNS: Ethanol Toxicity
Hepatic Encephalopathy
Glial response within the CNS (cerebral cortex and basal ganglia)
Elevated ammonia and pro-inflammatory cytokines
Astrocytes will be altered
Diseases of the CNS: Ethanol Toxicity
How are astrocytes altered in hepatic encephalopathy?
Enlarged nuclei
Minimal reactive cytoplasm