When might ECF composition deviate from normal
- in extreme environments
- abnormal dietary conditions
- high work rates
- medications
- health conditions
Hypokalemia
low ECF K+
How does hypokalemia typically occur
- loss from digestive tract
- loss from body fluid
Hyperkalemia
High ECF K+
What can cause hyperkalemia
- inability to clear K+
- Addison’s disease
- K+-rich diet
- tissue trauma
- medications
How can you lose K+ from your digestive tract
- vomiting
- diarrhea
How can you lose K+ from body fluid
- excessive sweating
- diuretics
Why might you be unable to clear K+
Kidney disease - inability to regulate osmolarity
Why does Addison’s disease cause high potassium
Low aldosterone for the RAAS regulation
Why can tissue trauma cause hyperkalemia
Release of high K+ ICF
What are some examples of medications that cause hyperkalemia
ACE inhibitors
NSAIDs
Is a change in K+ or Na+ or serious
K+ because the RMP is more dependent on K+
What effect does hypokalemia have on AP generation
Harder to reach spike threshold
What effect does hyperkalemia have on AP generation
- highly excitable
OR - depolarisation block
What causes a depolarisation block
Na+ channels become stuck in an inactive form
What are the symptoms of hypokalemia
- weakness
- confusion
- fatigue
- memory loss
- muscle cramps
- arrhythmia
What are the symptoms of hyperkalemia
- weakness
- fatigue
- paresthesias
- life-threatening arrhythmia
What neurological diseases cause a loss of myelin
- multiple sclerosis (CNS)
- Guillain Barré syndrome (PNS)
why are symptoms of myelin loss more variable
Depends on nerve pathways disrupted
Why does MS cause a loss of myelin
It’s an autoimmune disease targeting myelin
What does loss of myelin cause
- Increased current loss from leak channels
- exposure of unmyelinated areas with no Na+ channels
What is the end result of demyelination
Slowed action potentials
Or
Conduction failure
Why does MS worsen with increased body temp
- Na+ channels open quicker and inactivate quicker
- less time for Na+ flux
What is fampridine
potassium channel blockers - used to treat MS
