Exam 1 -Clinical Correlations Flashcards
what happens with patients who have low serum Na+?
makes the cell more prone to spontaneous discharge (lowers resting potential) -> seizures, confusion
how can one get low serum Na+?
psychological polydipsia
describe seizure disorders in general
- channelopathies
- unstable/extra-leaky Na+ channels
- membrane potential fluctuates -> get unwanted APs
how do you treat seizure disorders?
Alantin/phenytoin (stabilizes Na+ channels)
describe hyperkalemic periodic paralysis
- channelopathy
- increased serum K+ causes slight depolarization of the cell, which counterintuitively prevents APs from happening because the sustained depolarization keeps Na+ inactivation gates closed constantly
- become limp and can’t move muscles
- impairs mostly motor neurons
how do you treat hyperkalemic periodic paralysis?
glucose + insulin -> drives K+ into cells
describe hypokalemic periodic paralysis
- channelopathy
- happens in horses and humans after strenuous activity
- low K+ prevents AP from being generated
- impairs mostly motor neurons
how do you treat hypokalemic periodic paralysis?
give K+
what is Marie-Charcot-Tooth disease?
- individuals develop weakness starting in lower limbs
- defective myelin that dies out -> then neuron dies
- no treatment
- autosomal recessive/ X-linked recessive
- gap junctions don’t form properly -> nutrients don’t diffuse all the way down through spiral cell
how do local anesthetics work?
temporarily block voltage gated Na+ channels of axons
-small lipid-soluble molecules that act by binding w/
hydrophobic sites of the voltage-gated transmembrane
protein molecule -> decreased conductance of Na+
Guilliane-Barre disease
-peripheral neuropathy w/ longest nerves affected before shorter nerves (b/c something toxic in blood)
-due to circulating myelin Abs in blood
-50% of patients give history of GI issues 3/4 weeks ago
-viral infection -> develop viral Abs -> these co-react w/
myelin -> demyelinating neuropathy
how do you treat Guilliane-Barre disease?
- give IgG - downregulate body’s own production of Abs
- remove Ab’s by plasmaphoresis
multiple sclerosis
-get Abs to central myelin, but not peripheral -> lost myelin -> no axonal conduction in CNS -> lose function
how do you treat multiple sclerosis?
selective immunosuppressive drugs - don’t cure it, but lessen accumulation of symptoms and disabilities
myasthenia gravis
- autoimmune Abs bind specifically to AChR, blocking some of them
- results in weakness
how do you treat myasthenia gravis?
- AChE inhibitors (vestinone) - leaves ACh in cleft longer, so get a greater chance of finding an open AChR
- other treatments to reduce/remove Ab
botulism
- toxin: enzyme that acts on SNAREs -> prevents release ACh from vesicles -> no muscle movement
- develop paralysis
- die without treatment
how do you treat botulism?
treat with ventilators until toxin clears (7-10 days)
autosomatotopagnosia
visual-spatial neglect
- remember story about dude hitting his arm against bed
- lesion in R cerebral hemisphere
- happens b/c spatial map is in R hemisphere -> if damaged, you get spatial neglect
malignant hyperthermia
- autosomal dominant
- triggered by exposure to certain drugs in general anesthesia (succinylcholine) or excess caffeine
- uncontrolled muscle contraction + increased oxidative metabolism -> overwhelms supply of O2, removal of CO2, and control of temperature -> if untreated, results in circulatory collapse and death
- mutation in ryanodine receptor in SR -> lowered activation threshold -> increased Ca2+ release -> prolonged contraction + increased ATP consumption in attempt to remove intracellular Ca2+
how do you treat malignant hyperthermia?
dantrolene sodium - muscle relaxant that works on ryanodine receptor to prevent release of Ca2+ -> reduces mortality from 80% to 10%
symptoms of malignant hyperthermia?
- generalized muscle rigidity post-op
- rapid rising temperature to high levels
- elevated CK
symptoms of myotonic dystrophy?
- prefrontal baldness
- hatchet face
- myotonia
- cataracts
- heart disease
- weakness with delayed relaxation
myotonic dystrophy
- one of the muscular dystrophies
- autosomal dominant
- paucity of muscle Cl- channels -> delayed repolarization of muscle cells
- live to late 40s/50s - die most often from weakness of respiratory muscles
how do you treat myotonic dystrophy?
- quinine (not on market anymore) - decrease muscle excitability
- anti-arrhythmia drugs
