Exam 1 -Clinical Correlations

Question 1

what happens with patients who have low serum Na+?

Answer 1

makes the cell more prone to spontaneous discharge (lowers resting potential) -> seizures, confusion

Question 2

how can one get low serum Na+?

Answer 2

psychological polydipsia

Question 3

describe seizure disorders in general

Answer 3

• channelopathies
• unstable/extra-leaky Na+ channels
• membrane potential fluctuates -> get unwanted APs

Question 4

how do you treat seizure disorders?

Answer 4

Alantin/phenytoin (stabilizes Na+ channels)

Question 5

describe hyperkalemic periodic paralysis

Answer 5

• 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

Question 6

how do you treat hyperkalemic periodic paralysis?

Answer 6

glucose + insulin -> drives K+ into cells

Question 7

describe hypokalemic periodic paralysis

Answer 7

• channelopathy
• happens in horses and humans after strenuous activity
• low K+ prevents AP from being generated
• impairs mostly motor neurons

Question 8

how do you treat hypokalemic periodic paralysis?

Answer 8

give K+

Question 9

what is Marie-Charcot-Tooth disease?

Answer 9

• 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

Question 10

how do local anesthetics work?

Answer 10

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+

Question 11

Guilliane-Barre disease

Answer 11

-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

Question 12

how do you treat Guilliane-Barre disease?

Answer 12

• give IgG - downregulate body’s own production of Abs

- remove Ab’s by plasmaphoresis

Question 13

multiple sclerosis

Answer 13

-get Abs to central myelin, but not peripheral -> lost myelin -> no axonal conduction in CNS -> lose function

Question 14

how do you treat multiple sclerosis?

Answer 14

selective immunosuppressive drugs - don’t cure it, but lessen accumulation of symptoms and disabilities

Question 15

myasthenia gravis

Answer 15

• autoimmune Abs bind specifically to AChR, blocking some of them
• results in weakness

Question 16

how do you treat myasthenia gravis?

Answer 16

• AChE inhibitors (vestinone) - leaves ACh in cleft longer, so get a greater chance of finding an open AChR
• other treatments to reduce/remove Ab

Question 17

botulism

Answer 17

• toxin: enzyme that acts on SNAREs -> prevents release ACh from vesicles -> no muscle movement
• develop paralysis
• die without treatment

Question 18

how do you treat botulism?

Answer 18

treat with ventilators until toxin clears (7-10 days)

Question 19

autosomatotopagnosia

Answer 19

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

Question 20

malignant hyperthermia

Answer 20

• 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+

Question 21

how do you treat malignant hyperthermia?

Answer 21

dantrolene sodium - muscle relaxant that works on ryanodine receptor to prevent release of Ca2+ -> reduces mortality from 80% to 10%

Question 22

symptoms of malignant hyperthermia?

Answer 22

• generalized muscle rigidity post-op
• rapid rising temperature to high levels
• elevated CK

Question 23

symptoms of myotonic dystrophy?

Answer 23

• prefrontal baldness
• hatchet face
• myotonia
• cataracts
• heart disease
• weakness with delayed relaxation

Question 24

myotonic dystrophy

Answer 24

• 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

Question 25

how do you treat myotonic dystrophy?

Answer 25

• quinine (not on market anymore) - decrease muscle excitability
• anti-arrhythmia drugs