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Psyco 275 > Resting Membrane and Action Potentials > Flashcards

Resting Membrane and Action Potentials Flashcards

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1
Q

What is a neuron at rest?

A

Unstimulated/inactive

Can change when excited by input

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2
Q

How does a negative charge build-up inside the cell?

A

The membrane bilayer is selectively permeable
Ions cannot cross easily which results in a polarized membrane (-70 mV)
Ions are unequally distributed across the membrane

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3
Q

How do we record membrane potential?

A

Use intracellular and extracellular electrodes to detect the difference between the inside and outside of cells

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4
Q

What is the ionic distribution outside of the cell?

A

Higher [Na+] outside of the cell

  • the membrane extremely resists passage
  • driven inside cell by electrostatic forces and concentration gradient

Higher [Cl-] concentration outside of the cell

  • membrane slightly resists passage
  • more at equilibrium
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5
Q

What is the ionic distribution inside of the cell?

A

Higher [K+] inside of the cell

  • driven inside by electrostatic pressure and outside by a concentration gradient
  • membrane is highly permeable to K+ because they are more leaky channels

Negatively charged proteins inside
-cannot cross the membrane

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6
Q

What are the factors that maintain resting potential?

A

Concentration gradient
Electrostatic pressure
Passive forces
Active forces

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7
Q

What is a concentration gradient?

A

Tend to equally distribute

Move from high to low concentration

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8
Q

What is electrostatic pressure?

A

Like repels like

Opposites attract

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9
Q

What are passive forces?

A

Random motion due to selective permeability to ions

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10
Q

What are active forces?

A

Sodium-potassium pumps; maintain the stability of resting membrane potential
Re-distribution of ions

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11
Q

How do sodium-potassium pumps provide long-term maintenance of resting membrane potential?

A

Active transporter

Maintains equilibrium potential by continuously transferring 3Na+ out and 2K+ in

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12
Q

How do postsynaptic potentials create excitatory signals?

A

Excitatory neurotransmitters bind and cause rapid change to the postsynaptic cell
Causes depolarization of the cell (cell becomes less negative)
An excitatory postsynaptic potential increases the likelihood of an action potential

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13
Q

What is an EPSP?

A

Excitatory postsynaptic potential
Graded response
Bigger stimulation = bigger PSP
larger positive ion influx = larger EPSP

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14
Q

How do postsynaptic potentials create inhibitory signals?

A 
Inhibitory neurotransmitters bind and cause rapid change to the postsynaptic cell
Causes hyperpolarization (cell becomes more negative) 
An inhibitory postsynaptic potential decreases the likelihood of an action potential
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15
Q

What is an IPSP?

A

Inhibitory postsynaptic potential

Large negative ion influx = larger IPSP

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16
Q

What is a graded response?

A

The amplitude of the signal proportional to stimulus intensity
Passive decay over space and time

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17
Q

What is a rapid transmission?

A

Instantaneous rate of transmission

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18
Q

How does the integration of PSPs help the cell depolarization reach threshold?

A

One EPSP will not generate an action potential

We need to add or combine incoming signals within a given neuron

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19
Q

What is the threshold of excitation?

A

Synapses closer to the axon hillock have a larger effect on firing due to the incremental transmission of far away PSPs
The integration of inputs must result in about -65 mV at hillock for an action potential

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20
Q

What is spatial summation?

A

Occurs at axon initial segment
Integration of PSPs across postsynaptic locations
Local EPSPs and IPSPs occurring simultaneously combine to amplify or cancel out

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21
Q

What is temporal summation?

A

Integration across time on the same synapse

Multiple rapid inputs from the same presynaptic site

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22
Q

What is an action potential?

A

Reversal of membrane potential by stimulation

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23
Q

Why doesn’t an action potential degrade?

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A

Does not degrade along the length of the axon due to the voltage-gated channels

24
Q

What type of response is an action potential?

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A

All or nothing is the membrane depolarizes to the threshold voltage

25
How are action potentials affected by higher or longer stimulation?
The firing frequency increases
26
What happens to the action potential when it just meets the threshold?
There are fewer action potentials produced
27
What happens to the action potential when it goes way about the threshold?
There are many action potentials produced
28
What channels generate and propagate action potentials?
Voltage-gated sodium channels
29
Where are voltage-gated ion channels found?
Along the axon
30
When do voltage-gated ion channels open?
in response to membrane potential depolarization
31
When do voltage-gated ion channels close?
Close to continued depolarization
32
What happens when sodium channels open?
Sodium rushes into the cell based on the electrostatic and concentration gradient The membrane potential reaches +50 mV
33
When do sodium channels close?
When depolarization reaches a threshold
34
What happens when potassium channels open?
Potassium rushes out of the cell based on the electrostatic and concentration gradient Membrane repolarizes and becomes slightly hyperpolarized These channels close gradually
35
How is membrane potential reestablished?
By random motion of ions and the sodium-potassium pump
36
What are the differences between PSPs and APs?
EPSPs/IPSPs - decremental over space and time - fast - passive APs - non-decremental - conducted more slowly than PSPs - passive and active
37
What is the absolute refractory period?
Voltage-gated sodium channels are inactivated for about 1 msec post-AP initiation Cannot start a new AP in the same location on the axon
38
What is the purpose of the absolute refractory period?
Prevents backwards movement of the AP
39
What is the relative refractory period?
Happens during the after hyperpolarization Requires larger than threshold stimulus to initiate new AP More intense stimulation can overcome hyperpolarization to increase the firing rate
40
How are action potentials conducted across the axon?
A row of voltage-gated sodium channels creates a domino effect that causes a wave of depolarization Spreading can occur in two directions -anterograde -retrograde
41
What is orthodromic conduction?
Anterograde movement | -hillock to boutons
42
What is antidromic conduction?
Retrograde movement | -boutons to hillock
43
What is the velocity of axonal conduction of APs?
Large diameter = faster because there is less friction Myelinated = faster Large are myelinated = really fast
44
What is saltatory conduction?
AP jumps from node to node Requires less energy Sodium channels are only located on nodes
45
What is conduction in myelinated axons like?
Faster action potentials Passive (rapid and decremental) from node to node -diminished before the next node but is enough to open the next sodium channel
46
Are all axons myelinated?
Long, peripheral nerves | Cells spanning locations within the CNS
47
What does myelin degeneration do?
Impairs AP conduction
48
What does MS attack?
Immune system attacks myelin - schwann cells - oligodendrocytes
49
What are the steps of chemical transmission?
1. AP reaches the end of the axon terminal 2. Calcium enters the cell 3. Presynaptic density release neurotransmitter into the cleft via exocytosis 4. Neurotransmitter binds receptors on post synaptic density 5. Receptors influence post synaptic neurons 6. Neurotransmitter degradation/recycling
50
What are the 5 types of synaptic contacts?
``` Axodendritic Axosomatic Dendrodendrtic Dendroaxonic Axoaxonic ```
51
What is an axodendritic synaptic contact?
Axon to dendrite | Most common
52
What is an axosomatic synaptic contact?
Axon to soma
53
What is a dendrodendritic synaptic contact?
Dendrite to dendrite Reciprocal -can be transmitted in either direction
54
What is a dendroaxonic synaptic contact?
Dendrite to axon
55
What is an axoaxonic synaptic contact?
Axon to axon Mediate presynaptic inhibition or facilitation -selectively influence synapse rather than entire neuron
56
What is a directed synapse?
Site of neurotransmitter release close to postsynaptic contact Most common
57
What is an undirected synapse?
The site of release and contact is far Has varicosities Common for monoamines The neuroendocrine system releases neurohormones into the bloodstream

Psyco 275 (9 decks)

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