Lab 6 Action Potential Flashcards
RMP and where is more negative?
-70, more negative on the inside
depolarization and cause
- voltage is less negative, Na+ enters
hyperpolarization and cause
voltage is more negative, K+ keeps leaving or Cl- enters
stimulated neuron meaning
neuron where Na+ LGIC are open (EPSP generated)
EPSP cause and NT
Na+ LGIC open and Na+ enters causing depolarization, Ach on nicotinic and glutamat e
IPSP cause and NT
Cl- LGIC opens and Cl- enters causing hyperpolarization, GABA in brain and glycine in spine
4 phase of action potential and causes
- EPSP/ graded potential caused by Na+ entering through LGIC
- steep depolarization by Na+ entering through VGIC
- steep repolarization by K+ leaving through K+ VGIC
- after hyperpolarization by K+ still leaving
overall story of action potential generation
NT binds to Na+ LGIC opening it –> Na+ enters causing wave of depolarization going to axon hillock –> Na+ VGIC open causing depolarization and Na+ enters –> K+ VGIC open and K+ leaves causing repolarization –> K+ keeps leaving causing hyperpolarization –> Na+/K+ pump restores RMP
absolute refractory period
- no AP possible
- all Na+ VGIC are inactive closed and must go back to active closed before they can open again
relative refractory period
- AP possible if strong enough stimulation (more frequent or greater duration)
- K+ hyerpolarization makes it hard for threshold to be reached
equilibrium potential meaning
- if no other ion present around cell besides the one being examined and measure the voltage
- balance of electrical and chemical gradient across cell
why RMP closer to equilibrium potential of K+
membrane more permeable to K+ due to leakage channels
equilibrium potential of K+ and Na+
K+ = -90 = Na+ = +66
action potential vs graded potential
- amplitude
- max depolarization
- summation
- refractory period
- initial stimulation
- all or none vs graded
- +40 vs 0
- no summation vs yes summation
- refractory period vs no refractory period
- Na+ VGIC vs Na+ LGIC
summation meaning and temporal vs spatial summation
- summation = graded potentials can add up or cancel each other out
- temporal = higher frequency of graded potential
- spatial = graded potential from multiple presynaptic neurons add up
2 ways intensity is encoded
1) increased frequency of AP
2) recruitment of more neurons to fire in a nerve
all or none meaning and relation to different magnitudes of EPSP
- AP happens or doesnt happen
- if EPSP too weak = no AP, if EPSP stronger AP generated, stronger EPSP generates same AP
E, gNa, gK meaning
E = membrane potential gNa = Na conductance / movement across membrane gK = K+ movement across membrane
normal neuron at time 0
why gNa < gK
E = -63
gNa < gK because increased permeability to K+ due to leakage channels
normal neuron at after hyper-polarization - what is the expected E value
E more negative then -63
Na+ poison name and mechanism, common drug name
- effect on AP and why?
tetrodotoxin blocks Na+ VGIC
- no AP because no depolarization can be created
- lidocaine works the same way
K+ channel poison
- effect on AP and why
- name of poison
- cannot repolarize completely since K+ VGIC dont work
- some repolarization due to leakage channel and Na+/K+ pumps
- tetraehtyl ammonia
hypernatremia
- E at rest and why
- overall magnitude of impact
- more Na+ outside, slightly less negative RMP, very small impact in general
hyponatremia
- E at rest and why
- affect on AP and why
- less Na+ outside, RMP is slightly more negative
- weaker AP because less Na+ available to rush in
mild hypoklemia
- effect on E
- effect on after hyperpolarization
- less K+ outside, K+ leaves cell and RMP is more negative
- after hyperpolarization is more negative since steeper gradient for K+ to rush out
mild hyperkalemia
- effect on E
- effect on gradient
- effect on AP
- relation to lethal injection
- more K+ outside, K+ enters cell and makes RMP less negative
- gradient is weaker
- AP generate one after the other by one stimulus
- K+ lethal injection causes seizures and cardiac arrhythmia
severe hypo and hyper kalemia and why
- both = no AP
- hypo = less K+ in blood, K+ leaves causing hyperpolarzation of RMP that is so negative threshold can never be reached
- hyper = more K+, inside of cell has lot of K+ so RMP less negative, Na+ VGIC open once then stay inactive (not sure why)
second stimulus after relative refractory period
normal AP generated
second stimulus during relative refractory period but is weak
no AP generated because stimulus is not strong enough small spike due to EPSP
second stimulus during relative refractory period but is strong
AP generated but it is weaker due to K+ hyperpolarization
