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Physiology Test 2 > Chapter 8 > Flashcards

Chapter 8 Flashcards

(41 cards)

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1
Q

Factors affecting Ion flux across membranes

A

-Ion (membrane) conductance
-Ion Gradient

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2
Q

Does Ion gradient have much affect

A

Renal system maintains near constant internal environment, so ion gradient changes are minimal

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3
Q

What has the biggest influences on ion flux for neurons

A

Membrane permeability

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4
Q

Action Potential Synonym

A

Nerve impulse
Spike

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5
Q

Axon Synonym

A

Nerve Fiber

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6
Q

Axon Terminal Synonym

A

-Synaptic Knob
-Terminal Bouton
-Presynaptic Terminal
-Axon Knob

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7
Q

Cell Body Synonym

A

Soma

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8
Q

Cell Membrane Synonym

A

Axolemma

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9
Q

What are the parts of an unexcitable neuron

A

Cell body and Dendrites

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10
Q

What does unexcitable mean

A

-Will not have voltage-gated channels
-Will have ligand-gated channels and mechanically gated channels

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11
Q

What is excitable on a neuron

A

The hillock through the axon

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12
Q

What does it mean to be excitable

A

-will have voltage-gated channel
-will not have ligand-gated or mechanically gated channels

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13
Q

Disrupting Events

A

-Graded potentials
-Action Potentials

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14
Q

What does the disrupting event do

A

It disturbs the membrane potential

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15
Q

Graded Potentials

A

A change in membrane potential that varies in size

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16
Q

Where is a grade potential found

A

Unexcitable membrane
-dendrites and cell body

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17
Q

Three characteristics of graded potentials

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A

-A magnitude of response is directly proportional to the magnitude of stimulus
*having more stimulus open more channels causing a greater ion flux, smaller amount of stimulus opens a smaller amount of channels having a smaller ion flux
-does not transmit over long distances
*as it goes it diminishes
-effects can be summated, added together

18
Q

Action potential

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A

Change in a membrane potential of excitable membranes

19
Q

Where are action potentials found

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A

Found in neurons and some non-neural tissue, muscle

20
Q

Three characteristics of action potential

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A

-Action potential are “all-or-nothing”, magnitude is “fixed” after threshold (fixed at about +30mV)
-Capable of transmitting over ling distances
-Do not summate

21
Q

Threshold

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A

the minimum stimulus necessary to elicit a response

22
Q

Threshold is applied

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A

Apply a threshold stimulus to a membrane going to change the voltage by about 15mV, and that will result in the opening of voltage gated channels

23
Q

In a neuron when does threshold have an effect

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A

In the hillock and axon due to being the only place voltage-gated channels are located

24
Q

Go through threshold graphs

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A
  • Small stimulus, 1 messenger, bind to 1 receptor open 1 channel, Ion influx, depolarize cell, did not enough to get to threshold at hillock, get degraded channel closes, back to rest
  • Bigger stimulus, 5 messenger, bind to receptors, open channels, ion influx, did not depolarize it enough, not get the 15mV difference at hillock, det degraded, channel closes, back to res
  • 20 messengers, bind to 20 receptors, open 20 receptors, massive ion flux, ion gated-channel to depolarize, get a 15mV difference and get an action potential, rapid depolarization, sodium channels close, repolarize the cell
  • Once you get to threshold, even if you have 80 messenger you will still only get the same height action potential
25
Voltage-Gated Na Channel at resting potential
At normal situation when the cell is at resting potential the channel is closed but has the potential to be open
26
Voltage-gated Na Channels Open
Threshold change of 15mV to depolarize the sodium channel can pop-open, allowing free passage through the channel based on the gradient
27
Voltage-gated Na channel after open
Close channel and not capable of opening
28
Voltage-Gated Potassium Channel closed
Closed: At resting potential; delayed opening triggered at threshold; remains closed to peak potential
29
Voltage Gated Potassium channel open
Open: From peak potential through after hyper polarization
30
Votage-gated potassium channels react
Open in response to change in Vm but 10x slower than sodium channels
31
What happens to potassium channels when Vm returns to normal
K+ channels don't inactivate like Na+ channels, only close when Vm returns to normal
32
What is taking place once the potassium pump close
The membrane will reset back to -70 to mV from the sodium potassium pump working
33
Na+and K+ graph
-Resting membrane potential -Depolarizing stimulus -Membrane depolarizes to threshold. Voltage-gated Na+ channels open and Na+ enters cell. Voltage-gated K+ channels begin to slowly open. -Rapid Na+ entry depolarizes cell -Na+ channels close and slower K+ channels open -K+ channels remain open and additional K+ leaves cell, hyperpolarizing it -Voltage gated K+ channels close, less K+ leaks out of the cell -Cell returns to resting ion permeability and resting membrane potential
34
Long distance
* In the middle of the axon loaded with voltage-gated channels * There is going to be a disrupting event * It is going to depolarize a chunk of membrane to threshold * Opening Voltage-gated sodium channels * Also activated potassium channels just slower to open * Getting massive sodium ion influx * The ions are going to diffuse randomly * As sodium comes in a start to diffuse * Going to depolarize another chunk of membrane and get it to threshold * Opening more voltage-gated sodium channels * Leading to sodium influx * Activating slower to open potassium channels * Sodium diffusing randomly is going to depolarize another chunk of membrane reaching threshold * Opening more voltage-gated sodium channels * Leading to sodium influx * Sodium will diffuse * Depolarize threshold, opening more voltage-gated sodium channels * And keeping doing it till get to the end of the axon terminus
35
What are the channels doing as the next chunk gets depolarized
* As the depolarizing of the next chunk of membrane occurs the previous voltage-gated sodium channels are closing and locking, and the slowly opening potassium channels are open, and efflux occurs
36
What is an action potential an example of
Positive Feedback loop
37
Local Current
Process of moving down the membrane to depolarize -Few neurons and every muscle cell does it
38
Does the diffusion of sodium effect all parts of the membrane
* Sodium diffuses in all directions, but it does not affect the portion of the membrane that just depolarized because the sodium channel is closed and locked
39
As sodium has lock what is potassium doing
While sodium locked, the voltage-gated potassium pump is wide open leaving the cell repolarizing
40
What is considered the refractory Period
The sodium channels are locked, potassium channel is wide open, and you cannon get this membrane to depolarize
41
What is the outcome of the refractory period
The signal (action potential) will only go in one direction

Physiology Test 2 (4 decks)

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