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PSIO 258: Elementary Physiology I > Nerve Cells and Neuron Potentials 2 > Flashcards

Nerve Cells and Neuron Potentials 2 Flashcards

1
Q

Electrical signals in neurons result in …

A

membrane potential changes

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2
Q

Electrical signals are due to …

A

gated channels (voltage, ligand, mechanically gated)

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3
Q

Describe gated channels.

A
  • open or close in response to stimuli
  • affect movement of ions
  • ion movement = electrical signal
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4
Q

What are the 2 types of electrical signals?

A
  • graded potentials

- action potentials

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5
Q

Graded potentials are (small/large) and communicate over (short/long) distances.

A
  • small

- short

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6
Q

Action potentials are (small/large) and communicate over (short/long) distances.

A
  • large

- long

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7
Q

Describe graded potentials.

A
  • initiated by a stimulus
  • small change in membrane potential
  • magnitude varies (graded)
  • spread by electronic conduction
  • are decremental (magnitude decays as it spreads)
  • communicate over short distances
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8
Q

What is the purpose of graded potentials?

A

determine whether an action potential will occur

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9
Q

What is the threshold?

A

level of depolarization necessary to elicit action potential

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10
Q

Excitatory is …

A

depolarization

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11
Q

Inhibitory is …

A

hyperpolarization

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12
Q

What is temporal summation?

A

same stimulus repeated close together in time

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13
Q

What is spatial summation?

A

different stimuli that overlap in time

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14
Q

Describe action potentials?

A
  • rapid, large depolarization of membrane
  • used for communication
  • travel from cell body –> axons –> axon terminal
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15
Q

What can generate action potentials?

A

excitable membranes

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16
Q

What are the phases of an action potential?

A
  • depolarization
  • repolarization
  • hyperpolarization
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17
Q

What happens to trigger depolarization?

A

Na+ channels open

18
Q

What happens to trigger repolarization?

A

K+ channels open

19
Q

Name 2 threshold triggers (depolarization).

A
  • graded potentials bring membrane to threshold

- rapid opening of Na+ channels

20
Q

What parts of the neuron are responsible for graded potentials?

A
  • dendrites
  • cell body
  • receptors
21
Q

Rapid opening of Na+ channels means …

A
  • slow closing of Na+ channels

- slow opening of K+ channels

22
Q

Why does the action potential not reach the equilibrium potential of sodium?

A
  • K+ channels opening

- Na+ channels closing

23
Q

What happens during repolarization?

A
  • Na+ channels closed

- K+ channels opened

24
Q

What happens during hyperpolarization?

A
  • K+ channels remain beyond -70 mV

- membrane potential gets close to the equilibrium potential of potassium

25
Q

What restores resting potential?

A

Na+/K+ pump

26
Q

What are the 2 gates associated with voltage-gated sodium channels?

A
  • activation gate

- inactivation gate

27
Q

Describe the activation gate.

A
  • voltage dependent
  • opens at threshold and depolarization
  • positive feedback
28
Q

Describe the inactivation gate.

A
  • voltage and time dependent
  • opens during depolarization
  • closes during repolarization
29
Q

Describe voltage-gated potassium channels.

A
  • one gate
  • voltage/time dependent
  • negative feedback: restores resting membrane potential, prepares the neuron for another AP
30
Q

What is the refractory period? What are the 2 categories?

A
  • follows an action potential
  • decreased excitability
  • absolute and relative
31
Q

Describe the absolute refractory period.

A
  • all of depolarization + most repolarization phase
  • second action potential cannot be generated
  • Na+ gates are inactivated
32
Q

Describe the relative refractory period.

A
  • spans the last part of the repolarization phase and hyperpolarization
  • second action potential can be generated with a stronger stimulus
  • some Na+ gates are closed; some are inactivated
33
Q

What kind of stimulus can generate an AP during the absolute refractory period?

A

no stimulus of any strength can

34
Q

What kind of stimulus can generate an AP during the early parts of relative refractory period?

A

a much stronger stimulus than normal

35
Q

What kind of stimulus can generate an AP during the late parts of relative refractory period?

A

a stimulus a little stronger than normal

36
Q

What is the all or none principle in reference to threshold stimulus?

A
  • threshold depolarization = AP
  • sub threshold depolarization = no AP
  • suprathreshold depolarization = AP
37
Q

What are 3 consequences of refractory periods?

A
  • all or none principle
  • frequency: greater frequency of AP for greater stimuli
  • unidirectional propagation of action potentials
38
Q

What 3 factors affect propagation?

A
  • refractory period (unidirectional)
  • axon diameter
  • myelination
39
Q

Describe how axon diameter affects propagation.

A
  • larger: less resistance, faster

- smaller: more resistance, slower

40
Q

Describe how myelination affects propagation?

A
  • saltatory conduction

- faster propagation

41
Q

Mechanisms of action potential conduction depends on the presence or absence of _______.

A

myelin

42
Q

What are the 2 effects of graded potentials/APs?

A
  • dissipate Na+ and K+ concentration gradients

- the Na+/K+ pump prevents dissipation

PSIO 258: Elementary Physiology I (14 decks)

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