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Physiology Fall 21' > CH. 7 Nerve Cells and Electrical Signaling > Flashcards

CH. 7 Nerve Cells and Electrical Signaling Flashcards

1
Q

What are the cells of the nervous system?

A
  1. neurons - excitable cells

2. glial cells - support cells

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2
Q

What are the 5 components of a neuron?

A
  1. soma
  2. dendrites
  3. axon
  4. axon hillock
  5. axon terminal
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3
Q

What is the function of the soma?

A

contains nucleus and most organelles

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4
Q

What is the function of dendrites?

A

reception of incoming information

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5
Q

What is the function of the axon?

A

transmits electrical impulses called action potentials

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6
Q

What is the function of the axon hillock?

A

where axon originates and action potentials are initiated

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7
Q

What is the function of the axon terminal?

A

releases neurotransmitter

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8
Q

What are the two types of neuron transport?

A

1, anterograde transport - from soma to axon terminal (A to B)

  1. retrograde transport - from axon to soma (B to A)
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9
Q

What is a synapse?

A

site of communication between two neurons or between a neuron and an effector organ

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10
Q

What is synaptic flexibility?

A

with continued use, synapse changes anatomically which produces a different synapse

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11
Q

What are the 3 ion channels of a neuron?

A
  1. leak channels

2, ligand-gated channels

  1. voltage-gated channels
    - sodium and potassium channels
    - calcium channels
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12
Q

What are the characteristics of leak channels?

A
  • always open
  • located throughout the neuron
  • has a resting membrane potential
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13
Q

What are the characteristics of ligand-gated channels?

A
  • open or close in response to ligand binding
  • located on dendrites and cell body
  • synaptic potentials?
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14
Q

What are the characteristics of voltage-gated channels?

A
  • open or close in response to changes in membrane potential
  • sodium/potassium channels are found throughout but more in the axon (action potentials)
  • calcium channels found at axon terminal (releases neurotransmitter)
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15
Q

What are the three structural classes of neurons?

A
  1. bipolar
  2. pseudo-unipolar
  3. multipolar
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16
Q

What are the three functional classes of neurons?

A
  1. afferent neurons
  2. efferent neurons
  3. interneurons
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17
Q

What are the four types of glial cells?

A
  1. astrocytes
  2. microglia
  3. oligodendrocytes
  4. schwann cells
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18
Q

What are the characteristics of oligodendrocytes?

A
  • located in the central nervous system

- one oligodendrocyte forms several myelin sheaths and myelinates sections of several axons

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19
Q

What are the characteristics of schwann cells?

A
  • located in the peripheral nervous system

- one schwann cell forms one myelin sheath and myelinates one section of an axon

20
Q

Why do resting membrane potentials exist?

A

there are more negative charges inside the cell and more positive charges outside the cell

21
Q

What is the resting membrane potential of neurons?

A

-70 mV

22
Q

What are the two factors that are critical in determining resting membrane potential?

A
  1. ion concentration gradients

2. membrane permeability to these ions (ion channels)

23
Q

What is a graded potential?

A

relatively small change in the membrane potential produced by some type of stimulus that triggers the opening or closing of ion channels

24
Q

What is the concentration gradient produced by the Na+/K+ pump?

A

high sodium outside, low inside

low potassium outside, high inside

25
Q

How does electrical driving force respond when K+ diffuses out of cell that is permeable to potassium only?

A

wants to pull K+ back into the cell to make less negative

26
Q

When is an ion at equilibrium?

A

when there is no net force for it to move across the membrane

i.e chemical force = negative electrical force
or
electrochemical force = 0

27
Q

What is the ion permeability of neurons?

A

neuron is 25 times more permeable to potassium than sodium

  • more potassium leaves the cell than sodium enters
  • makes the inside of the cell more negative
28
Q

What are the chemical driving forces of a typical neuron?

A

potassium out

sodium in

29
Q

What is the steady state of a neuron?

A

inflow of sodium is balance by outflow of potassium

- creates a resting membrane potential of -70mV

30
Q

What are the different types of gated channels in neurons?

A
  1. voltage gated
  2. ligand (chemically) gated
  3. mechanically gated
31
Q

What are the phases of an action potential?

A

resting - depolarization - repolarization - hyperpolarization

32
Q

What does it mean when graded potentials are decremental?

A

magnitude decays as it spreads

33
Q

What is temporal summation?

A

a graded potential where the same stimulus is repeated close together in time

34
Q

What is spatial summation?

A

a graded potential where different stimuli overlap in time

35
Q

What is an action potential?

A

rapid large depolarization is used for communication

36
Q

How do action potentials travel in neurons?

A

along axons from cell body to the axon terminal

- if afferent neuron, from receptor to terminal

37
Q

What occurs that prevents an action potential from reaching the equilibrium constant of sodium?

A

the slow opening of potassium channels and the slow closing of sodium channels

38
Q

What restores the resting membrane potential when an action potential has reached hyperpolarization?

A

sodium/potassium pump

39
Q

What are the two gates associated with the voltage gated sodium channel?

A

activation gate and inactivation gate

40
Q

What is the “all-or-nothing” principle?

A

a threshold depolarization needs to be met in order to induce the regenerative mechanism for the opening of sodium channels

i.e for action potential to occur

41
Q

What is the refractory period?

A

period of time following an action potential

  1. absolute
  2. relative
42
Q

How long does the absolute refractory period last?

A

spans all of depolarization and most of the repolarization phase
- second action potential cannot be generated

43
Q

How long does the relative refractory period last?

A

spans the last part of the repolarization phase and hyperpolarization
- second action potential can be generated but with a stronger stimulus

44
Q

What are the 3 consequences of refractory periods?

A
  1. all-or-nothing principle
  2. frequency coding
  3. unidirectional propagation of action potentials
45
Q

What needs to be present for the propagation of action potentials?

A

myelin

Physiology Fall 21' (15 decks)

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