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Physiology Exam #2 > Neurons and Action Potentials > Flashcards

Neurons and Action Potentials Flashcards

1
Q

Neurons (what they are and structure)

A

-specialized nerve cells that transmit messages

Structure

  • soma (cell body)
  • processes
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2
Q

Cell body (soma)

A
  • contains nucleus

- site of metabolism

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3
Q

Processes (what they are and types)

A

-fibers that extend from the soma

Types:

  • dendrites: receives information
  • axons: sends information
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4
Q

Function properties

A
  • irritability: ability to respond to a stimulus

- conductivity: ability to transmit an impulse

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5
Q

Resting Neurons

A
  1. plasma membrane polarized
  2. high concentration of sodium outside
  3. high concentration of potassium inside
  4. fewer + ions inside vs outside –> resting membrane potential
  5. RMP= -70mV
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6
Q

How is RMP maintained?

A
  • Na+/K+ pumps

- leak channels

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7
Q

Na+/K+ pumps

A
  • generate concentration gradient
  • 3 Na+ out, 2 K+ in
  • Cost: 1 ATP
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8
Q

Leak channels (types, why)

A
  • small Na+ leak at rest
  • WHy? high force (large gradient), low permeability (less channels)
  • small K+ leak at rest
  • Why? Low force (less gradient), high permeability (more channels)
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9
Q

Channels on neurons

A
  • leak channels
  • voltage-gated channels
  • ligand-gated channels
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10
Q

Leak channels (when they are open and location)

A

-always open

Location: throughout neuron

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11
Q

Ligand- gated channels (when they are opened or closed and location)

A
  • open or closed when ligand binds to receptors on the membrane
  • location: usually dendrites and soma
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12
Q

Voltage gated channels (when they are opened/closed and location)

A
  • open or closed when membrane potential changes

- location: mostly on axon but throughout

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13
Q

Action potential (what it is, stages, time, properties)

A

-rapid, large depolarization used for communication

stages:

  • depolarization
  • repolarization
  • hyperpolarization

Time: 1-2 ms

Properties:

  • all-or-nothing principle
  • unidirectional propagation
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14
Q

Depolarization, depolarization, hyperpolarization (what happens in each event and the RMP)

A

Depolarization:

  • Na+ gates open –> Na+ rushes in
  • RMP: -70mV –> 30mV

Repolarization:

  • K+ gates open –> K+ rushes out
  • Na+ gates close
  • RMP: 30mV –> -70mV

Hyperpolarization

  • K+ gates close after RMP
  • RMP drops below -70mV
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15
Q

All-or-nothing principle (threshold, what happens if stimulus is at or above threshold, terminology)

A

Threshold: -55mV

  • minimum depolarization necessary to open Na+ channels –> AP
  • if stimulus is at or above threshold –> AP of some magnitude (100mV)

Terminology

  • subthreshold depolarization –> no AP
  • threshold depolarization –> AP
  • suprathreshold depolarization –> AP
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16
Q

Unidirectional propagation

A
  • AP moves down axon toward axon terminal

- depolarization in one patch –> depolarization in adjacent patch

17
Q

Voltage gated Na+ channels (how many and types)

A

-2 gates

  • activation gate
  • inactivation gate
18
Q

activation gate (dependent on what, when it is opened)

A
  • voltage dependent

- opened: threshold and depolarization

19
Q

inactivation gate (dependent on what, when it is opened, when it is closed)

A
  • voltage and time dependent
  • opened: first part of depolarization
  • closed: second part of depolarization
20
Q

3 stages of gates of activation and inactivation gates

A
  1. activation closed- inactivation opened
    - during resting state
    - activation gate capable of opening with stimulus
  2. activation opened- inactivation opened
    - during depolarization
    - allows Na+ to rush into cell
  3. activation opened- inactivation closed
    - during 1 msec following depolarization
    - will not open until it returns to resting state
21
Q

refectory period (how many types, types)

A

-2 types

  • absolute
  • relative
22
Q

Absolute refractory period

A
  • second AP cannot be generated
  • Na+ gates are inactivated
  • time: all of depolarization and part of depolarization
23
Q

relative refractory period

A
  • second Ap can be generated but with stronger stimuli
  • Na+ gates: closed, some inactive
  • Time: end of repolarization, and hyperpolarization
24
Q

consequences of relative refractory period

A
  1. all-or-nothing principle
  2. unidirectional propagation
  3. frequency coding
25
Q

frequency coding

A

-intensity of stimulus is coded by AP frequency

  • high intensity=higher frequency
  • lower intensity=lower frequency

Physiology Exam #2 (9 decks)

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