2.2 Neurophysiology Flashcards

1
Q

Neurons are highly

A

irritable

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2
Q

Plasma membranes are peppered with a variety of

A

ion channels

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3
Q

two types of channels

A
  1. passive or leakage channel (always open)
  2. active or gated channel
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4
Q

two types of gated channel

A
  1. chemically gated channels
  2. voltage gated channel
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5
Q

Body is electrically _____. But there are small differences in electrical charge between inside and outside of cell membranes due to differences in __________ on inside and outside of cell membrane.

A

neutral;
+ and – ions

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6
Q

differences in charge = _________

A

potential (stored energy)

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7
Q

resting cells (all cells in body) have potential difference (-50 to -200 mV)

A

membrane potential

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8
Q

average muscle and nerve cells membrane potential

A

-70 mv

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9
Q

Resting Membrane Potential is in _______ state

A

polarized state

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10
Q

3 major processes of Resting Membrane Potential

A
  1. Different kinds concentration of ions inside and outside the cell membranes
  2. The differential permeability of the plasma membrane to Na+ and K+ ions
  3. The operation of the sodium-potassium pump
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11
Q

There are different kinds and concentrations of ions inside and outside cell membranes: there are more ________ ions inside cell (especially ________)

A

negative ions, especially proteins

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12
Q

Both Na+ and K+ can diffuse across cell membrane by ________ via leakage channels

A

facilitated diffusion

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13
Q

In resting membrane potential, ___+ is more permeable than ___+

A

K+ > Na+

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14
Q

a change in resting membrane potential can be produced by anything that changes _________

A

membrane ion permeability (opens or closes ion gates)

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15
Q

Two kinds of potential changes

A
  1. Graded potentials
  2. Action Potential
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16
Q
  • local phenomenon, signal over short distances
  • small to large changes in membrane potential due to opening and closing of chemical gates
A

Graded potential

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17
Q

membrane potential decreases

A
  • Depolarization
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18
Q

membrane potential increases

A
  • Hyperpolarization
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19
Q

true or false

Graded potentials are given different names depending on where they occur and the functions they perform

A

True

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20
Q

What do you call the graded potential in receptor region of dendrites and cell bodies of neurons? What are the two types?

A

Postsynaptic potentials

  • Excitatory postsynaptic potential (EPSP)
  • Inhibitory postsynaptic potential (IPSP)
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21
Q
  • local depolarization occurs and response stimulatory
  • depolarization might reach threshold producing an action potential and cell response
A

Excitatory postsynaptic potential (EPSP)

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22
Q
  • local hyperpolarization and response inhibitory
  • decrease action potentials by moving membrane potential farther from threshold
A

Inhibitory postsynaptic potential (IPSP)

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23
Q

True or False

The EPSP is an all-or-none response.

A

False

The EPSP is not an all-or-none response but is proportionate in size to the strength of the afferent stimulus

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24
Q

Two types of summation of post-synaptic potentials

A

Temporal and Spatial Summation

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25
Q

summation of EPSP’s or IPSP’s due to repeated stimulation by one neuron

A

Temporal Summation

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26
Q

summation of EPSP’s or IPSP’s due to stimulation by more than one neuron simultaneously

A

Spatial Summation

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27
Q
  • long-distance signals
  • a rapid, all-or-none change in the membrane potential, followed by a return to the resting membrane potential
A

Action potential

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28
Q

In action potential, there is a ______ depolarization and polarization of membrane due to sequential opening and closing of several voltage gates and active transport

A

complete

29
Q

what cells can generate action potential

A

neuron and muscle cells only

30
Q

how fast is an action potential

A

10ms

31
Q

true or false

Do not decrease in strength with distance

A

true

32
Q

In a neuron, a transmitted action potential is called

A

nerve impulse

33
Q

Only _____ are capable of generating action potentials

A

axon (axon hillock)

34
Q

three phases of action potential

A
  1. depolarization
  2. repolarization
  3. undershoot
35
Q

5 steps of action potential

A
  1. Resting state
  2. Depolarization
  3. Rising phase of the action potential
  4. Falling phase of the action potential
  5. Undershoot
36
Q

How does depolarization happens in the membrane?

A

due to the Na+ influx through Na+ channels that opens due to a stimulus

37
Q

During the rising phase of action potential, most Na+ channels open while K+ channels ____?

A

remain closed

38
Q

During falling phase of action potential, most Na+ channel close, blocking Na+ influx and K+ channels _____ which again makes the inside of the cell negative.

A

open

39
Q

what step does the membrane return to its resting membrane phase?

A

undershoot

40
Q

During action potential, _____ is more permeable than ______

A

Na+ is more permeable than K+

41
Q
  • in the interval from the onset of the action potential until repolarization is about one-third complete, no stimulus can elicit another response
  • to ensure that each action potential is separate
  • to enforce one-way transmissionof the AP
A

the dead phase (absolute refractory phase)

42
Q

each action potential has the same amplitude independently from the strength of the stimulus

A

all or none

43
Q

a second action potential cannot occur during this period

A

refractory period

44
Q

During the ________, it is possible to generate a second action potential, but only if the stimulus is stronger than usual. Is important for regulating the frequency of action potentials and allowing the neuron or muscle cell to respond to stronger stimuli.

A

relative refractory period

45
Q

is like a fast and efficient way for nerve signals to travel through jumping with the help of myelin sheath

A

saltatory conduction

46
Q

Cellular junctions where signals are transmitted from neurons to target cells

A

synapses

47
Q

Synapses target cells (3)

A
  1. Other neurons:
    - Axodendritic synapse
    - Axoaxonic synapse
    - Axosomatic
  2. Muscle cell (Neuromuscular junctions)
  3. Gland cells (Neuroglandular junctions)
48
Q

Two types of communicating junctions or synapses

A
  1. Electrical synapses via gap junctions
  2. Chemical synapses involving neurotransmitters
49
Q
  • allows current to flow directly from one cell to another
  • allows the exchange of small molecules between cells
  • a patch where cells are separated by a narrow gap of ________
A

Electrical synapses (Gap junctions);
2-4 nm

50
Q

Gap junctions are formed where hexameric pores called ______ connect with one between cells

A

connexons

51
Q

Each connexon is comprised of ____ identical subunits called _____

A

six; connexins

52
Q

in electrical synapses, permeability of junction is mediated by conformation of the ________

A

connexons

53
Q

in electrical synapses, impulses can go in _____ direction, while chemical synapses are _______

A

either direction (bidirectional);
one direction only (unidirectional)

54
Q
  • allows the flow of ions between neuron and are specialized for the release and reception of chemical neurotransmitters
  • actual gap or space between nerve cells
  • prevents direct transmission of action potential
A

chemical synapses

55
Q

chemical synapses are separated by the ______ (___ to ____ nm wide)

A

synaptic cleft (30-50 nm wide)

56
Q

two parts of chemical synapses

A
  1. axon terminals: synaptic vesicles
  2. receptor region of the postsynaptic neuron
57
Q

Criteria that define a neurotransmitter: (3)

A
  1. present at presynaptic terminal
  2. must be released by depolarization, Ca++-dependent
  3. Specific receptors must be present
58
Q

Synaptic vesicle release consists of three principal steps:

A
  1. docking
  2. priming
  3. fusion
59
Q

During ____, vesicles lie close to plasma membrane (within _____)

A

docking, 30nm

60
Q

During _____, vesicles can be induced to fuse with the plasma membrane by :
* sustained depolarization,
* high K+,
* elevated Ca++,
* hypertonic sucrose treatment

A

priming

61
Q

During ______, vesicles fuse with the plasma membrane to release transmitters. Physiologically this occurs near ________, but can be induced experimentally over larger area.

The ________ is the site of physiological release, and can sometimes be recognized as an electron-dense structure.

A

fusion, calcium channels

active zone

62
Q

is a protein that helps in priming during the release of synaptic vesicle

A

Munc-13

63
Q

complexes that forms during docking to pull the two membranes together

A

SNARE complexes:
* Vesicle
- Synaptobrevin
- Synaptotagmin
* Postsynaptic cell
- Syntaxin
- SNAP-25

64
Q

What is the purpose of calcium during signal transmission at a chemical synapse? And how do they go in the presynaptic cell?

A

Calcium signals the vesicles to fuse with the presynaptic membrane and release the messenger chemicals.

Depolarization of presynaptic terminal causes opening of voltage-gated Ca2+ channels.

65
Q

Two types of synapse according to how they affect the membrane potential of the postsynaptic neuron (2)

A
  1. Excitatory Synapses - Excitatory postsynaptic potentials (EPSPs)
  2. Inhibitory Synapses - Inhibitory postsynaptic potentials (IPSPs)
66
Q

What determines whether a stimulus will be strong enough to produce an action potential in a nerve cell?

A
  1. The resting membrane potential is about -70mV.
    A threshold stimulus will sufficiently increase the permeability of the membrane to sodium ions to raise the membrane potential to about -55mV. Once this threshold potential has been reached, complete depolarization and repolarization occur and an action potential is generated.
67
Q

Is the size of the action potential related to the strength of the stimulus?

A

No. Nerve and muscles obey the all-or-none law, which states that a threshold stimulus evokes a maximum response and that a subthreshold stimulus evokes no response.

68
Q

What factors influence the speed at which impulses are conducted along excitable cell membranes?

A
  • Diameter of the conducting fiber: proportional
  • Temperature of the cell: proportional
  • Presence or absence of the myelin sheath through Saltatory conduction: proportional