Neurophysiology Flashcards
Resting membrane potential is dependent of? range?
Dependent on the permeability of ions that travel across the membrane (-40 to -90mv)
Describe what the initial concentration of ions are intracellularly and extracellularly. What creates this gradient.
There is more Na+ outside than K+.
Extracellular : 150mM of Na+ & 5mM of K+
Intracellular: 5mM of Na+ and 150mM of K+
The Na+/K+ ATPase keeps this gradient
What happens when there is a higher concentration of K+ extracellularly?
There will be less K+ diffusing out bc the concentration difference is lower. More K+ inside the cell means that there is a more positive resting membrane / less negative (-40 mv)
What happens when there is a a lower concentration of Na+ extracellularly?
There will be less Na+ diffusing in because the concentration difference is lower. Less Na+ entering results in am more negative resting potential. (-72)
Why is there a greater change when K+ concentration is changed vs. Na+
bc the resting membrane potential is dependent on the permeability of ions and there are more K+ ions
Where are AP initiated?
Axon Hillock, axon initial segment, trigger zone
does the AP become larger with a stronger stimuli
No AP are all or nothing so it just has to pass the threshold
What does TTX and lidocaine do and how are they different
they block Na+ channels which inhibits AP to propagate downstream. TTX is irreversible but lidocaine is reversible which is why it is used by dentists
When do Na+/K+ channels open vs close
Both Na+ and K+ channels open at the same time during initial depolarization. K+ open more slowly and stays open for a longer time. Na+ channels close at peak.
How does mylenation and diameter affect conduction velocity?
the more mylenation and larger diameter, the faster the conduction.
A fiber vs. B fiber vs. C fiber
A fiber is a the most myelinated with largest diameter (afferent and efferent neurons)
B has medium mylenation and medium diameter (afferent neuron)
C has least mylenations and smallest diameter (afferent neuron)
The release of ACH by exocytosis depends on?
The strong enough AP to activate the opening of Ca2+ channels and enough extracellular Ca2+ concentration .
How does Mg2+ affect ca2+ channels?
Mg2+ has the same charge as Ca2+ but is larger so it blocks the ca2+ channels
ESPS vs IPSP
ESPS = excitatory, IPSP = inhibitory
supra threshold
larger than threshold
