Chapter 3 Flashcards
Explain the results of the voltage clamp method
- voltage can cause permeability changes, which can change the current
Hodgkin and Huxley and the squid
Na+ produces an early current and K+ produces a late current
Tetrodotoxin (TTX)
blocks voltage-gated Na+ channels
Tetraethylammonium (TEA)
blocks K+ voltage-gated channels
2 conclusions of HH experiments
- Na+ and K+ require time to activate (Na+ will eventually deactivate); as voltage becomes less negative, speed increases
- Conductance/permeability is related to voltage; As membrane potential becomes less negative, conductance increases
refractory period
no action potential is fired
Relation of feedback loops and action potentials
a positive feedback loop generates action potentials
Where are voltage-gated sodium channels located?
nodes of ranvier
saltatory conduction
myelin insulation allows current action potential to jump from node to node
What is the velocity of action potential dependent on?
myelination and diameter of axon
Multiple sclerosis description
- chronic demyelination and inflammation of axons
- onset 20-40 years
- females at a greater risk
- lifespan 7.5 years shorter
What causes multiple sclerosis?
Autoimmune system destroys myelin
Symptoms of MS
- vision (double vision)
- muscle weakness & clumsiness
- tingling and numbness
- bladder issues/constipation
- mood changes/cognitive impairment
MS treatment
- drugs
- interferon-beta stabilizes blood brain barrier and lymphocytes
- blocking K+ channel for symptoms
Does an action potential require passive or active flow?
Both
