Action Potentials and Graded Potentials Flashcards Preview

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Flashcards in Action Potentials and Graded Potentials Deck (20)
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1
Q

Graded potentials

A

Small-scale local changes that degrade over a dfistance

Within a neuron
Magnitude can change

Can be depolarising or hyper (synaptic are either but receptor are depolarizing)

2
Q

Action potentials

A

Large all or none changes that propogate long distances

Between neurons

3
Q

initiation of graded potential

A

Chemical signal
Gated ion channel opens
Current at cell membrane, charge carried by ions
Local depolariszation or hyperpolarization
Depolarization spreads

4
Q

Graded potential variable amplitude

A

Size is porportional to stimulus intensity

5
Q

Graded potentials decremental

A

Decary of distance because of leakage of K+

6
Q

RC circuit of a nerve cell

A

Ion channel acts as a resistor…more ion channels decreases resistance

PLasma membrane capacitor that separates charge…larger membrane surface area means greater capacitance

7
Q

membrane time constant

A

Time to get to 63% of steady state value

More channels means less resistance so shorter time
Increased membrane SA means more capacitance so greater

8
Q

Space (length) constant

A

Distance over whic ha potnetial can change

INcrease in membrane resistance (from decrease in resistors) means lengthen

Increased axial resistace - shorten

9
Q

All or none of action potentials

A

Weak stimuli are termed subthreshold potentials
Strong will hit the threshold potnetial

A single AP cannot convey stimulus intensity BUT multiple APs together can

10
Q

Voltage gated Na and K channels

A

Will open at a certain voltage

Inactivation gate blocks Na gate quickly

K open and close slower

11
Q

Permeability at resting potential

A
K = 1 
Na = .04
Cl = .45
12
Q

K vs Na voltage gated

A
Na = faster opening and closing and inactivate spontaneously 
K = slower and only inactivate once repolarization occurs
13
Q

Absolute refreacto yperiod

A

Second AP CANNOT occur during this time (Na in the open or inactivated state)

1) Allows re-establishment of membrant potential
2) Limits # of APs
3) Directs towasrd terminal
4) Separates APs

14
Q

Relative refractory

A

Can occur during hyperpolarization but only if strong enough

Cotrol over frequency of APs

15
Q

Na channel structure

A

6 TM segments with 4 subunits
Voltage sensor
Inactivation particle that blocks the gate

16
Q

K+ channel structure

A

A gene encodes 1 of 4 subunits whcih form a functional channel

17
Q

Procaine/lidocain and tetrodoxin

A

Block voltage gated Na channels and prevent AP

18
Q

Ca channel family

A

Happens after each AP…as more calcium accumulates, opens K channels and causes hyperpolarization….prevents formation of AP over and over again

Longer lasting AHP

19
Q

Propogation

A

Initated at axon hillock…once it moves to 2, then 1 is refractory and 2 is depolarizing toward the threshold potentia l

20
Q

Saltatory conduction

A

Myelin increases speed and fidelity of AP

Path of least resistance at next node
Na+ channel concentration higher at nodes of ranvier