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Be it, feel it > Item 5 > Flashcards

Item 5 Flashcards

1
Q

Action potentials occur in the membranes of _ tissue (whether nerve or muscle)

A

excitable

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2
Q

During an action potential, a large, rapid _polarization occurs in which the polarity of the membrane potential actually reverses; that is, the membrane potential becomes positive for a brief time

A

de-polarization

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3
Q

The initial membrane potential changes very quickly (in about 1 msec) from a resting level of approximately -70mV to __ mV

A

+30 mV

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4
Q

Once initiated, an action potential, unlike a graded potential is capable of being propagated long distances along the length of _ _ without any decrease in strength

A

an axon

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5
Q

The generation of an action potential is based on…and the Na+ and K+ electrochemical gradients that exist across the membrane

A

the selective permeability of the plasma membrane

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6
Q

At rest, the plasma membrane is _ times more permeable to potassium than to sodium ions because of the presence of more K+ leak channels to sodium channels

A

25 times

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7
Q

Changes in the permeability of the plasma membrane in excitable cells resulting from the opening and closing of _ _ _ can produce action potentials

A

gated ion channels

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8
Q

An action potential in a neuron consistws of 3 distinct phases:
1. rapid depolarization
2. repolarization
3. _

A

after-hyperpolarization

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9
Q

depolarization leads to a mV reading of _ due to influx of sodium ions into the cell

A

+30 mV (note it is yet not the equivalent of the sodium equilibrium potential of +60 mV)

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10
Q

The repolarization of the membrane potential brings the membrane potential down to _ mV due to a reduction in sodium permeability, and increase of potassium permeability, with potassium moving DOWN its electrochemical gradient out of the cell, repolarizing the membrane potential to bring it back to resting levels

A

-70 mV

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11
Q

Potassium permeability at after-hyperpolarization remains elevated for a brief time (_ - _ msec) after the membrane potential reaches the resting membrane potential, resulting in an after-hyperpolarization

A

5 - 15 msec

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12
Q

During after-hyperpolarization, the membrane potential is even more _ than at rest as it approaches the potassium equilibrium potential

A

negative (close to -94 mV)

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13
Q

Voltage-gated sodium and potassium channels are mostly found in the plasma membrane of the __ and axon, as well as of some muscle cells

A

axon hillock

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14
Q

In _ axons, voltage-gated sodium and potassium channels are at a greater concentration at the nodes of Ranvier; in _ axons, these channels are evenly distributed along the entire axon

A

myelinated;
unmyelinated

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15
Q

Are the exact mechanisms of gating in the voltage-gated sodium and potassium channels known?

A

no, that’s why models are used

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16
Q

In/activation gates are responsible for the opening of sodium channels during the depolarization phase of an action potential

A

Activation

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17
Q

In/activation gates are responsible for the close of sodium channels during the repolarization phase of an action potential

A

Inactivation

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18
Q

For a sodium channel to be open, the activation gate has to be _, and the inactivation gate has to be _

A

both open!

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19
Q

A sodium channel can exist in _ conformations

A

3

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20
Q

The first confirmation for the sodium channel is closed…

A

but capable of opening

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21
Q

The first confirmation for the sodium channel is closed but capable of opening. At rest, the _ gate is open, but the _ gate is closed. In this state, the channel is closed, but it can be opened by a depolarizing stimulus that causes the activation gate to open.

A

the inactivation gate is open but the activation gate is closed, meaning the channel is closed but capable of opening

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22
Q

The activation gate is on the _ of the cell, whereas the inactivation gate is on the _ of the cell

A

exterior;
Interior

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23
Q

On depolarization, the _ gate opens and with both gates in their open position, the channel is open and sodium ions move through the channel into the cell

A

activation gate opens (inactivation gate is already open) - part of depolarization of an action potential

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24
Q

The 3rd sodium channel conformation is _ and in/capable of opening

A

closed and incapable of opening

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25
Q

The 3rd sodium channel conformation is closed and incapable of opening. Within 1 msec of initial stimulus opening the activation gate, the _ gate closes

A

inactivation gate closes

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26
Q

The closing of the inactivation gate in the 3rd sodium channel conformation is a delayed response initiation by…

A

the same depolarization that caused the activation gate to immediately open

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27
Q

The closing of the inactivation gate in the 3rd sodium channel conformation, with the inactivation gate closed and the activation gate open, the channel is closed. The inactivation gate remains closed until…

A

the membrane potential returns to near its resting value

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28
Q

Until the membrane potential returns to near its resting value, the channel cannot open in response to a second depolarizing stimulus because…

A

the inactivation would remain closed; it does not open in response to a depolarization

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29
Q

Once repolarization has occurred, the inactivation gate opens and the activation gate closes, returning the channel to its _ _

A

resting state

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30
Q

The opening of sodium activation gates is a _ mechanism; the opening of some sodium activation gates causes more sodium activation gates to open by _ing the stimulus to open the gates (depolarization)

A

regenerating

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31
Q

Sodium channel opening is part of a _ feedback loop that allows for the rapid depolarization of the cell

A

POSITIVE

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32
Q

What prevents the oversaturation of sodium ions in the cell is…

A

the sodium inactivation gates closure

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33
Q

Threshold occurs when the inward flux of sodium ions…

A

exceed the outward flux of potassium ions

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34
Q

Voltage-dependent potassium channels are part of a _ feedback loop during an action potential

A

negative

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35
Q

Voltage-dependent potassium channels are part of a negative feedback loop during an action potential because the effect of opening potassium channels (repolarization) is an action opposite to…

A

the initial stimulus that opened the potassium channels (depolarization)

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36
Q

As the cell repolarizes, the depolarizing stimulus _, and potassium channels slowly close

A

weakens

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37
Q

The _ principle suggests that whether a membrane is depolarized to threshold or greater, the amplitude of the resulting action potential is the same; if the membrane is not depolarized to threshold, no action potential occurs

A

all=or=none principle

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38
Q

The level of depolarization reached at the peak of an action potential depends not on the strength of the stimulus, but rather on the relative strengths of the electrochemical gradients for so- dium and potassium ions and …

A

the relative permeabilities of the membrane to these ions

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39
Q

During the depolarization phase, sodium permeability exceeds potassium permeability _ fold and the membrane potential approaches the sodium equilib- rium potential of +60 mV

A

several 100 fold

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40
Q

The 4 different phases of an action potential are:
_
depolarization
repolarization
after-hyperpolarization

A

resting

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41
Q

The membrane potential for a resting neuron is:
a. -70 mV
b. -70 mV to 30 mV
c. 30 mV to -70 mV
d. -70 mV to -85 mV

A

a. -70 mV

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42
Q

Voltage-gated sodium channels are _ during a neuron at rest.

A

closed

They can’t be open unless they are triggered by an action potential

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43
Q

Voltage-gated sodium channels are _ during depolarization

A

open

They have to be open, otherwise the sodium couldn’t enter the cell during an action potential

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44
Q

Voltage-gated sodium channels are _ during repolarization

A

closed

Repolarization is all about potassium leaving the cell, not about much sodium movement

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45
Q

Voltage-gated sodium channels are _ during after-hyperpolarization

A

closed

They have to be closed to enable the continued high outward flow of potassium through the voltage-gated channels

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46
Q

The inactivation gate of a voltage-gated sodium channel is only CLOSED during _

A

REPOLARIZATION

It can’t be during depolarization, since they’re all open at that time. It can’t be during resting and after-hyperpolarization the ACTIVATION gate is closed, and it would take extra energy to close both gates the rest of the time

the activation gate is open during depolarization and repolarization, but closed during rest and after-hyperpolarization

the inactivation gate is only CLOSED during repolarization

the voltage-gated sodium channel is only open during depolarization

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47
Q

The voltage-gated sodium channel is only open during _

A

depolarization

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48
Q

The activation gate of the voltage-gated sodium channel is closed during _ and _

A

resting and after-polarization

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49
Q

The depolarization of the membrane is met by _ feedback with sodium flow into the cell, creating a net positive change in the cell

A

positive feedback

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50
Q

The depolarization of the membrane is met by _ feedback with potassium flow into the cell, creating a net negative charge in the cell

A

negative feedback

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51
Q

T or F: the neuron can never meet or exceed the sodim equilibrium potential for the same reason that the resting membrane potential can never equal or exceedthe potassium equilibrium potential

A

true

Sodium movement into the cell is countered by potassium movement out of the cell, primar- ily through potassium leak channels and later through the opened voltage-gated potassium channels.

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52
Q

During the depolarization phase of an action potential, is the membrane more permeable to sodium or to potassium?

A

Sodium!

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53
Q

If a neuron had equal permeability to sodium and potassium ions, would the resting membrane potential of that cell be more negative or less negative than -70 mV?

A

less negative (i.e., closer to +60 mV)

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54
Q

What equation does this give regarding sodium, potassium and chloride ions?

Vm = 61log (PNa[Na+]o + PK[K+]o + PCl[Cl-]i) / (PNa[Na+]i + PK[K+]i + PCl[Cl-]o

A

the GHK equation to calculate the MEMBRANE POTENTIAL for a membrane that is somewhat permeable to sodium, potassium and chloride but IMPERMEABLE to other ions

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55
Q

TTX is a toxin that blocks voltage-gated sodium channels, and TEA is a toxin that blocks voltage-gated potassium channels. Predict what effect each of these toxins would have on (1) the resting membrane potential

A

TTX (tetrodotoxin) blocks the voltage-gated sodium channels responsible for the rapid depolarization phase of the action poten- tial and, therefore, blocks the generation of action potentials. Because some of these channels (albeit only a few) are open at rest, TTX would decrease sodium permeability, thereby causing a hyperpolarized resting membrane potential

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56
Q

TTX is a toxin that blocks voltage-gated sodium channels, and TEA is a toxin that blocks voltage-gated potassium channels. Predict what effect each of these toxins would have on the generation of action potentials

A

TEA (tetraethylammonium) blocks the voltage-gated potassium channels responsible for the repolarization phase of the action poten- tial. Thus, once an action potential occurs, the depolarization phase will be prolonged. Because some of these channels are open at rest, TEA would decrease potassium perme- ability, thereby causing a depolarized resting membrane potential

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57
Q

Multiple sclerosis is an autoimmune disease in which the immune system attacks myelin in the central nervous system. What effect does multiple sclerosis have on the conduction of action potentials in the nervous system?

A

By decreasing the amount of myelin, multiple sclerosis slows down the conduction of action potentials in the central nervous system. Eventually, the degree of demyelination causes the cessation of action potentials along some axons

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58
Q

The absolute refractory period does/not allow another action potential to take place, whereas the relative refractory period does/no

A

absolute RP doesn’t, relative RP does

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59
Q

Does a stimulus preclude the absolute refractory period?

A

yes

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60
Q

To generate a second action potential during the relative refractory period, a stimulus must be strong enough to open enough sodium channels such that sodium inflow overcomes the elevated potassium outflow that occurs during the relative refractory period, and the stimulus may have to overcome some sodium _ gates that are still closed

A

inactivation

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61
Q

Peripheral neuropathy, a disease of the peripheral nervous system, can affect the somatic or _ efferent or the afferent branch

A

autonomic

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62
Q

Peripheral neuropathy is correlated with issues with blood _ _

A

glucose regulation

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63
Q

Why does saltatory conduction occur in myelinated axons?

A

because very little current flows across the membrane where myeline insulates it, needing it to flow all the way to the next node of Ranvier

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64
Q

Does the amplitude in current diminish because some current leaks across the axon membrane, even in myelinated axons?

A

yes, but the stimuli that reaches the next node of Ranvier is typically sufficient to create another threshold for action potentials to continue along each node

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65
Q

Conduction velocity is greater in _-diameter axons

A

larger-diameter

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66
Q

We can think of speedy conduction velocity for myelinated axons as…

A

express trains that make fewer stops, getting to their destination in quicker time

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67
Q

Which of the nerve fibers do not have myelin present?
A alpha
A beta
A gamma
A delta
B
C

A

C - it’s the smallest fiber diameter at 0.3 - 1.3 um, and has the slowest conduction velocity at 0.7 - 2.3 m/sec

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68
Q

The largest nerve fiber diameter is A alpha, which is typical of…

A

stimulation of skeletal muscle contraction

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69
Q

Note the missing example of function in the following nerve fiber types (highest to lowest diameter):

A alpha - stimulation of skeletal muscle contraction
A beta - …
A gamma - stimulation of muscle spindle contractile fibers
A delta - pain, temperature sensation
B - visceral afferents, autonomic preganglionics
C - pain, temperature sensation, autonomic postganglionics

A

A beta - touch, pressure sensation

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70
Q

Depolarization of a neuron to threshold stimulates:
a) Opening of sodium channels.
b) Delayed closing of sodium channels.
c) Delayed opening of potassium channels.
d) Both a and c.
e) All of the above.

A

e) all of the above

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71
Q

Neurotransmitters are released most commonly from the
a) Cell body.
b) Dendrites.
c) Axon terminals.
d) Axon hillock

A

c) Axon terminals.

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72
Q

If a cation is equally distributed across the cell membrane (that is, its concentration inside the cell equals its concentration outside the cell), then which of the follow- ing statements is false?
a) At —70 mV, the chemical force on the ion is zero.
b) At —70 mV, the electrical force on the ion acts to move it into the cell
c) At +30 mV, the chemical force on the ion is zero.
d) The equilibrium potential for the ion is zero.
e) At —70 mV, the electrochemical force on the ion acts to move it out of the cell

A

e) At —70 mV, the electrochemical force on the ion acts to move it out of the cell

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73
Q

The depolarization phase of an action potential is caused by the
a) Opening of potassium channels.
b) Closing of potassium channels.
c) Opening of sodium channels.
d) Closing of sodium channels

A

c) Opening of sodium channels.

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74
Q

During the relative refractory period, a second action potential
a) Cannot be elicited.
b) Can be elicited by a threshold stimulus.
c) Can be elicited by a subthreshold stimulus.
d) Can be elicited by a suprathreshold stimulus

A

d) Can be elicited by a suprathreshold stimulus

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75
Q

Nerves are found
a) In the central nervous system.
b) In the peripheral nervous system
c) Both a and b.
d) Neither a nor b

A

b) In the peripheral nervous system

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76
Q

If the membrane potential of a neuron becomes more negative than it was at rest, then the neuron is _. In this
state, the neuron is _ excitable.
a) depolarized; more
b) hyperpolarized; more
c) depolarized; less
d) hyperpolarized; less

A

d) hyperpolarized; less

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77
Q

Oubain is a poison that blocks the Na+/K+ pump. If this pump is blocked, then the concentration of potassium inside the cell would
a) Increase.
b) Decrease.
c) Not change

A

b) Decrease.

read the question - the answer is specific to increasing inside the cell, not outside the cell, or elsewhere

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78
Q

If potassium concentrations in the extracellular fluid of the brain increased, activity in the brain would
a) Increase.
b) Decrease.
c) Not change

A

a) Increase

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79
Q

Which of the following neurons are part of the peripheral nervous system?
a) Motor neurons innervating skeletal muscles
b) Parasympathetic neurons
c) Sympathetic neurons
d) All of the above

A

d) All of the above

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80
Q

Which of the following axons exhibits the greatest conduction velocity?
a) An unmyelinated axon with diameter 5 fxm
b) A myelinated axon with diameter 5 fxm
c) An unmyelinated axon with diameter 20 luim
d) A myelinated axon with diameter 20 [xm

A

d) A myelinated axon with diameter 20 [xm

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81
Q

Which of the following best describes the status of sodium channels at the resting membrane potential?
a) Activation gates are open and inactiva- tion gates are closed.
b) Activation gates are closed and inacti- vation gates are open.
c) Activation gates and inactivation gates are closed.
d) Activation gates and inactivation gates are open

A

b) Activation gates are closed and inacti- vation gates are open.

inactivation gates are only closed during repolarization

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82
Q

Which of the following is not a part of the efferent division of the nervous system?
a) Parasympathetic nervous system
b) Sympathetic nervous system
c) Motor neurons
d) Sensory receptors

A

d) Sensory receptors

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83
Q

Of the following ions, which is (are) lo- cated in greater concentration inside the cell?
a) Sodium only
b) Potassium only
c) Chloride only
d) Sodium and potassium
e) Potassium and chloride

A

b) Potassium only

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84
Q

Which of the following statements about graded potentials is false?
a) The magnitude of a graded poten- tial varies with the strength of the stimulus.
b) Some graded potentials are hyperpo- larizations; others are depolarizations.
c) Graded potentials are produced at ligand-gated ion channels.
d) Graded potentials can sum over space and time.
e) Graded potentials are limited in dura- tion by the refractory period

A

e) Graded potentials are limited in dura- tion by the refractory period

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85
Q

What are the subdivisions of the periph- eral nervous system?

A

afferent and efferent ns

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86
Q

Information from the periphery is brought to the central nervous system by (afferent/ efferent) pathways

A

afferent pathways

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87
Q

Which cell type is more abundant in the nervous system — glial cells or neurons?

A

glial cells - workers behind the scenes outnumber the stars of the show

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88
Q

Voltage-gated calcium channels are lo- cated in which region(s) of a neuron?

A

axon terminal

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89
Q

(Schwann cells/Oligodendrocytes) form myelin in the peripheral nervous system, and (Schwann cells/oligodendrocytes) form myelin in the central nervous system

A

Schwann cells in PNS, oligodendrocytes in the CNS

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90
Q

Myelin (increases/decreases) conduction velocity in axons

A

increases

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91
Q

If an anion is present in greater concentration outside the cell compared to inside the cell, would the equilibrium potential for that anion be positive, negative, or zero?

A

negative

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92
Q

Which ion is closer to equilibrium at the resting membrane potential of -70 mV— sodium or potassium?

A

potassium

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93
Q

In the peripheral nervous system, cell bodies of afferent neurons are located in _

A

ganglion (as opposed to…?)

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94
Q

The electrochemical force for potassium ions when the membrane potential is at the peak of an action potential is (greater than/less than) the electrochemical force for potassium ions when the membrane potential is at rest

A

greater than

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95
Q

Both sodium and potassium channels have inactivation gates that close shortly after the activation gates open, (true/ false)

A

false

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96
Q

When sodium inactivation gates are closed, a second action potential is im- possible, (true/false)

A

true - this occurs during repolarization, which is the absolute refractory period

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97
Q

In myelinated axons, action potentials are propagated by _ conduction

A

saltatory

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98
Q

The Na+/K^ pump causes the repolariza- tion phase of an action potential, (true/ false)

A

false -

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99
Q

When a neuron is at the peak of an ac- tion potential (+30 mV), the direction of the electrical force for potassium ions is (into/out of) the cell

A

out of the cell

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100
Q

Electrical synapses operate by al- lowing electrical signals to be transmitted from one neuron to another or a neuron to a glial cell through _ _

A

gap junctions

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101
Q

Chemical synapses operate through the release of neurotransmitters that activate signal _ mechanisms (described in Chapter 5) in the target cell

A

transduction

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102
Q

When an elec trical signal is generated in one cell, it is directly transferred to the adjacent cell by means of … through the gap junctions

A

ions flowing through

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103
Q

Can second messenger molecules move through gap junctions, in addition to other ions flowing through them?

A

yes

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104
Q

Rapid communication between adjacent neurons that synchronizes the electrical activity in these cells can be _l

A

bidirectional

105
Q

Electrical synapses are found in:
a. retina of the eye
b. certain areas of the cortex
c. the brainstem for regulating breathing
d. synchronizing the neurons responsible for inspiration
e. all of the above

A

e. all of the above

106
Q

Hypothalamic neurons release tropic hormones by _ _ thereby synchronizing their activity and resulting in bursts of tropic hormone release

A

gap junctions - electrical activity

107
Q

T or F: much is unknown about the function of electrical synapses

A

true

108
Q

A synapse between a neuron and an effector cell is called a _ junction

A

neuroeffector

109
Q

Synapses can occur at dendrites, cell bodies, or with other _s

A

axon
(axondendritic, axosomatic or axoaxonic)

110
Q

Signaling across a chemical synapse is _directional

A

unidirection: pre to post-synaptic neuron

111
Q

voltage-gated _ channels open when the axon terminal is depolarized, which occurs upon arrival of an action potential at the axon terminal

A

calcium

112
Q

When the calcium channels open, they allow cal- cium to flow down its electrochemical gradient into the _ _, thereby increasing the concentration of cytosolic calcium in the axon terminal

A

axon terminal

113
Q

Calcium then causes the membranes of synaptic vesicles to fuse with vesicle attachment sites on the inner surface of the axon terminal membrane and undergo _, which re- leases the neurotransmitters into the synaptic cleft

A

exocytosis

114
Q

The amount of neurotransmitter released depends on the con- centration of calcium in the cytosol of the axon terminal, which depends on the …

A

frequency of action potentials in the presynaptic neuron

115
Q

Following a single action potential, neurotransmitter re- lease stops within a few milliseconds because the voltage-gated calcium channels close soon after opening, and because calcium ions are _ively transported in/out of the axon terminal on a continual basis, bringing the cytosolic calcium concentration back to its rest- ing level

A

actively;
out

116
Q

If neurotransmitter molecules were to remain indefinitely in the synaptic cleft following their release, they would bind to re- ceptors over and over again, inducing a …

A

continual response in the postsynaptic neuron

117
Q

Ways to prevent neurotransmitter continually binding to receptors is its degradation by enzymes: -
on the postsynaptic neuron’s plasma membrane
- on the presynaptic neuron’s plasma membrane
- on the plasma membrane’s nearby glial cells
- in the interstitial fluid of the synaptic cleft
…

A

in the cytoplasm of the presynaptic neuron or glial cells

118
Q

Reuptake involves neurotransmitter molecules actively being transported back…

A

into the presynaptic neuron that released them

119
Q

what prevents neurotransmitter degradation by enzymes, etc.?

A

binding to receptorsin the post-synaptic neuron

120
Q

Neurotransmitter is usually present in the synaptic cleft for a fair amount/only a few ms after its release from the presynaptic neuron

A

only a few ms; they are dealt with quickly to prevent over-stimulation of the post-synaptic neuron

121
Q

Several pharnnaceutical agents work by decreasing the activity of specific neurotransnnitter reuptake proteins or enzynnes that degrade neurotransnnitters. Describe the effects of each type of inhibitor on the concentration of neurotransnnitter in the synaptic cleft and, therefore, on communication across specific synapses

A

Drugs that block the degradation or reuptake of neurotransmitter increase the concentra- tion of neurotransmitter in the synaptic cleft of active neurons, enhancing the communication. However, if a neuron is not releasing neurotrans- mitter, then these drugs will have no effect

122
Q

The time it takes for an action potential arriving at the axon terminal before a response occurs in the postsynaptic cell is called _ _

A

synaptic delay

123
Q

The time lag for an action potential arriving at the axon terminal before a response occurs in the postsynaptic cell is mostly due to the time required for…

A

calcium to trigger the exocytosis of neurotransmitter

124
Q

A fast response whenever a neurotransmitter binds to a post-synaptic receptor is a _-gated channel, or a channel-linked receptor

A

ligand-gated channel

125
Q

A slow response of a neurotransmitter absorbed by a postsynaptic neuron is through _ _-linked receptors called metabotropic receptors

A

G protein-linked

126
Q

Fast responding signal transduction is associated with a change in the membrane potential, called a _ potential

A

postsynaptic potential (PSP)

127
Q

PSPs occur _ and terminate _

A

rapidly; rapidly

128
Q

Slow response neurotransmitter binds occur _ and terminate _

A

slowly (milliseconds to hours)

129
Q

A slow response, direct coupling synaptic transmission involves more than one _, produced by activation or inhibition of an enzyme after the metabotropic receptor binds to a neurotransmitter to activate a G protein

A

messenger
the enzyme from the G protein activation can create a second messenger

130
Q

In a slow response, direct coupling synaptic transmission, the… can produce a second messenger which can produce other cell responses as well as open or close ion channels

A

G protein, which activates or inhibits an enzyme that produces the second messenger

131
Q

_ synapses depolarize the post- synaptic neuron

A

excitatory

132
Q

ESPSs or _ postsynaptic potentials, can occur as either a fast response or a slow response

A

excitatory

133
Q

T or F: EPSPs are action potentials

A

false - they’re graded potentials, with the amplitude of depolarization increasing as more neurotransmitter molecules bind to receptors

134
Q

Fast EPSPs are generally caused by the binding of neurotrans- mitter molecules to their receptors on the postsynaptic cell, in the process opening channels that allow small _ to move through them

A

cations (sodium and potassium ions)

135
Q

In EPSPs, the neurotransmitter binds to a receptor and activates a G protein, the G protein then activates the enzyme adenylate cyclase; which in turn catalyzes the reaction converting ATP to cAMP which activates the protein _ A which catalyzes the addition of a phosphate group to the potassium channel

A

kinase A

136
Q

_s, a type of voltmeter, is used to measure electrical activity in the cell when measuring excitatory synapses

A

oscilloscopes

137
Q

In fast EPSPs, the series of steps results in the phosphorylation and closure of the potassium channel, resulting in…

A

depolarization, decreasing potassium permeability and maintaining sodium permeability, the same effect as if sodium permeability increased

138
Q

Slow EPSPs last seconds to _

A

hours

139
Q

What takes slow EPSPs so long to return to resting level is waiting for the potassium channels to be _, which will not occur until enough cAMP has been degraded by phosphodiesterase to return the cAMP concentration to its resting level

A

phosphorylated

140
Q

At inhibitory synapses, the binding of a neurotransmitter to its receptors opens channels for either potassium or _ ions

A

chloride

141
Q

When a neurotransmitter causes potassium channels to open, potassium will move out of the cell, hyperpolarizing it, known as a _ postsynaptic potential

A

inhibitory postsynaptic potential (IPSP)

142
Q

Both IPSPs and EPSPs are _ potentials

A

graded

143
Q

Because the chloride ion has a negative charge (it is an anion), the membrane potential at rest is an electrical force that acts to move chloride … the cell

A

out of the cell

144
Q

During an IPSP, if a neurotransmitter is present at an inhibitory synapse while a second neurotransmitter is present at an excitatory synapse, chloride will move … the cell at the same time that positive charges enter the channel opened by NT2, opposing any change in membrane potential

A

into

145
Q

During an IPSP, depolarization of the membrane means that chloride is no longer at _. The more positive potential inside the cell pulls the negative chloride ions into the cell, stabilizing the membrane potential by countering the influence of positive charge moving into the cell. This effect is considered an inhibitory action because it decreases the likelihood that the neuron will reach threshold for an action potential

A

EQUILIBRIUM

146
Q

During an IPSP, the more positive potential inside the cell pulls the negative chloride ions into the cell, stabilizing the membrane potential by countering the influence of positive charge moving into the cell. This effect is considered an inhibitory action because it decreases the likelihood that …

A

the neuron will reach threshold for an action potential

147
Q

_l _n is the process that determines whether the particular combination of synaptic inputs arriving at a given time at a postsynaptic cell will produce an action potential

A

neural integration

148
Q

The _ _ rule: an action potential is triggered if the membrane potential at the axon hillock is depo- larized to threshold; if the potential is below threshold; no action potential will occur

A

neural integration

149
Q

In _e, a single neuron communicates to several other neurons, whereas In _e, a single neuron receives communication from several other neurons.

A

divergence; convergence

150
Q

What is the degree of hyperpolarization from temporal IPSPs limited by?

A

the equilibrium potential for the ion causing the hyperpolarization

When, for example, the opening of potassium channels produces a hyperpolarization, the more potassium channels that are open, the greater the hyperpolarization will be, until the membrane potential approaches -94 mV (the potassium equilibrium po- tential). The membrane potential can never exceed this value; in fact, it will never reach —94 mV because even when all potassium channels in a membrane are open, sodium leak channels will al- low some sodium to leak into the cell, counteracting the move- ment of potassium

151
Q

The synapse of neuron A with the postsynaptic cell is closer to the axon hillock than is the synapse of neuron B. If a single action potential in each presynaptic neuron results in an 8-mV depolarization at the axon hillock, which presynaptic neuron had to produce the larger depolarization at the site of the synapse?

A

synapse of neuron B because graded potentials diminish along the axon, resulting in less than the initial 8-mV depolarization

152
Q

Temporal summation can occur because postsynaptic poten- tials … than action potentials

A

last considerably longer

153
Q

T or F: when metabotropic receptors are involved in a spatial summation neural integration, a postsynaptic potential cannot persist, even after the neurotransmitter that initiated it has been cleared from the synaptic cleft

A

false - they are so slow to respond that the postsynaptic potential may persist

154
Q

spatial summation occurs as postsynaptic potentials originat- ing at different synapses spread to the _ _, overlapping along the way.

A

axon hillock

155
Q

once a depolarizing stimulus exceeds thresh- old, the degree of depolarization does not affect the size of action potentials, but rather their _

A

frequency

increases in the strength of supratheshold stimuli cause the frequency of action potentials to increase

156
Q

increases in the strength of supratheshold stimuli cause the frequency of action potentials to increase in the postsynaptic neuron, an effected called frequency _

A

coding

157
Q

EPSPs and IPSPs typically occur at axodendritic and axo_ synapses

A

axosomatic (to the body of the cell)

158
Q

In axoaxonic synapses, neurotransmitter from the presynaptic neuron does/not generate electrical signals in the postsynaptic neuron

A

DOES NOT - it is about a change in the amount of calcium that enters the axon terminal in response to an action potential, rather than neurotransmitter to a postsynaptic neuron

159
Q

By binding to receptors on the membrane of the axon terminal of the postsynaptic neuron [i.e., an axoaxonic synapse], the neurotransmitter induces a change in the amount of calcium that enters the axon terminal in response to an action potential, in turn altering the amount of neurotransmitter…

A

released from the post- synaptic neuron

160
Q

In axoaxonic synapses, the enhancement of release of neurotransmitter based on increased amount of calcium that enters the axon terminal in response to an action potential is considered presynaptic _, whereas in cases the neurotransmitter is decreased, it is referred to as presynaptic _

A

facilitation; inhibition

161
Q

In axoaxonic synapses, presynaptic modula- tion affects transmission to the postsynaptic neuron at …

A

one specific synapse, thereby altering the ability of that one synapse to excite or inhibit the postsynaptic neuron,

axodendritic and -somatic synapses don’t care which presynaptic neurons excite or inhibit, but that it happens

162
Q

Enkephalins are morphinelike substances produced in the body. They presynaptically inhibit the release of neurotransmitter from neurons that convey signals from pain receptors (called nociceptors) in the skin to the spinal cord. Based on this information, explain what effect, if any, enkephalins would have on the perception of pain, which occurs at the level of the brain, and thereby acting as an _PSP

A

would reduce the effect of pain, perhaps when it is at its extreme because they inhibit those neurotransmitters (therefore acting as an IPSP)
For a person to perceive pain, information must be transmitted from the sensory receptor in the skin to the primary somatosensory cortex. Disruption of the communication at any level in between the skin and the cortex will decrease the perception. Thus, by decreasing commu- nication from the afferent to the second- order neuron in the spinal cord, less signal is trans- mitted to the cortex and the perception of pain is diminished

163
Q

Neurotransmitters belong to a variety of chemical classes, includ- ing acetylcholine, biogenic amines, amino acids, purines, and neuropeptides. Most are small molecules, with the notable excep- tion of _

A

the neuropeptides

164
Q

_ is released from neurons in both the central and peripheral nervous systems. The most abundant neurotrans- mitter in the peripheral nervous system, it is found in efferent neu- rons of both the somatic and autonomic branches

A

Acetylcholine (ACh)

165
Q

Acetylcholine (ACh) is synthesized in the _ _ of neurons from two substrates, acetyl CoA and choline, and catalyzed by CAT (choline acetyl transferase)

A

axon terminal

166
Q

Acetyl CoA is found in almost all cells of the body, including those neurons that synthesize and release acetylcoline (i.e., _ neurons)

A

cholinergic

167
Q

T or F: choline (NOT acetylcholine) cannot be synthesized by neurons

A

true

although it can be synthesized in the liver, most is obtained from the diet and delivered by the bloodstream to cholinergic neurons

168
Q

Acetyl CoA is a two-carbon molecule produced during the catabolism of lipids, carbohydrates and proteins, and is the initial substrate for the _ cycle

A

Krebs cycle - the citric acid cycle that is used by organisms to respire to generate energy through aerobic respiration. it is also a precursor of certain amino acids, and is integral to metabolism

169
Q

What triggers the release of acetylcholine by exocytosis?

A

an action potential!

170
Q

Acetylcholine can be degraded by an enzyme on the pre-, postsynaptic neuron, or either, is known as _

A

acetylcholinesterase (AChE)

171
Q

The following are biogenic amines, including:
catecholamines (which include dopamine, epinephrine and norepinephrine)
serotonin
_

A

histamine

172
Q

Amino acid class of neurotransmitters include:
glutamate
aspartate
glycine
_

A

GABA

173
Q

The purine class of neurotransmitters includes:
ATP
ADP
_

A

adenosine

174
Q

Neuropeptides are larger neurotransmitters that include:
TRH
_
Oxytocin
Substance P
Cholecystokinin
Endogenous opioids (enkephalins, endorphins)
Orexin

A

Vasopressin

175
Q

Unique molecules that act as neurotransmitters are:
nitric oxide
_

A

endocannabinoids

176
Q

Receptors for acetylcholine are of two types:
muscarinic cholinergic receptors and
_ cholinergic receptors

A

nicotinic

177
Q

Nicotinic cholinergic receptors are _tropic, and have TWO binding sites for acetylcholine and trigger the opening of channels that allow both sodium and potassium to move through, causing an EPSP in the postsynaptic cell (mostly in the PNS, although some in the CNS)

A

ionotropic (meaning, they are fast responses of synaptic transmission, compared to slower metabotropic ones)

178
Q

Muscarinic cholinergic receptors are _ receptors…Their binding with acetylcholine can open or close ion channels and activate enzymes,

A

slow receptors / metabotropic receptors that operate through the action of G protein

179
Q

Muscarinic cholinergic receptors are found on some _ organs of the autonomic nervous system and are the dominant cholinergic receptor type in the CNS

A

effector

180
Q

The action of any chemical messenger ultimately depends not on the nature of the messenger, but rather on the signal trans- duction mechanism activated by the _ once the messenger binds to it.

A

receptor

181
Q

Biogenic amines are a class of neurotransmitters derived from _ _s

A

amino acids

182
Q

The biogenic amines (neurotransmitters) are both released primarily by neurons in the _NS [including epinephrine, but it’s generally considered a hormone released from the adrenal medulla, i.e., the sympathetic nervous system], but neuroepinephrine is also released from neurons in the _NS

A

CNS; PNS

183
Q

Epinephrine and norepinephrine are a_ receptors, with subclasses designated by numerical subscripts, such as alpha 1, alpha 2, beta 1, beta 2, and beta 3.

A

adrenergic (i.e., alpha adrenergic and beta adrenergic)
- think of them as adrenaline and noradrenaline, respectively

184
Q

Adrenergic receptors (i.e., adrenaline and noradreline, i.e., epinephrine and norepinephrine) are found in the _NS and in the effector organs for the sympathetic branch of the _ nervous system

A

CNS; autonomic

185
Q

Which cholinergic receptor type (nicotinic or muscarinic) produces the faster response?

A

nicotinic, since it’s an ionotropic receptor

186
Q

Catecholamines generally produce fast/slow responses mediated through _ _ and changes in second messenger systems

A

slow; G proteins

187
Q

_ function as autocrines, binding to receptors on the axon terminal of the cell that released them, enabling a neuron to modulate its own release of neurotransmitter mostly by altering the amount of calcium entered during an action potential

A

catecholamines

188
Q

Catecholamines can be degraded by two enzymes:
_
catechol-O-methyltransferase (COMT)

A

monoamine oxidase (MAO)

189
Q

MAO (monoamine oxidase), a type of enzyme that degrades catecholamines, is located in the:
synaptic cleft
_ of the axon terminal of the neurons that release the catecholamines
some glial cells

A

mitochondria

190
Q

catechol-O-methyltransferase (COMT), a type of enzyme that degrades catecholamines, is located in the _ _

A

synaptic cleft

191
Q

Serotonin and histamine are biogenic amines, but they are not _

A

catecholamines

192
Q

Serotonin is found in the CNS, particularly in the _ _

A

brain stem

193
Q

Serotonin, a biogenic amine, regulates sleep and _

A

emotions

194
Q

Histamine, which is better known for its release from non-neuronal cells during allergic and other types of reactions, can also function as a neurotransmitter. It is found in the CNS, primarily in the _

A

hypothalamus

195
Q

_ _ neurotransmitters are the most abundant class in the CNS, where they are widely distributed

A

amino acid

196
Q

Aspartate and glutamate are amino acid neurotransmitters released at _ synapses, whereas glycine and gamma-aminobutryic acid (GABA), are released at _ synapses (also amino acid neurotransmitters)

A

excitatory; inhibitory

197
Q

Glutamate is the most commonly released neurotransmitter at excitatory synapses in the _NS

A

CNS

198
Q

Glutamate inspires a fast EPSP when it binds with receptors to move sodium into the cell, and when it binds with other receptors, _ channels open, which acts as a second messenger

A

calcium

199
Q

_ is the neurotransmitter most commonly released at inhibitory synapses in the CNS

A

GABA

200
Q

T or F: GABA is a type of ionotropic receptor

A

false - there are 2 ionotropic receptors and 1 metabotropic receptor found from GABA

201
Q

GABAc receptors are located in the _ where they play a role in communication of visual information

A

retina - they inhibit certain impulses to the brain, enabling one to see (revisit perception chapter in cognitive psych)

202
Q

GABAa receptors in the CNS can bind to sedatives such as _, thereby depressing neural activity

A

Valium

203
Q

ATP, ADP, GTP and AMP are stored in synaptic vesicles and released by exocytosis. _, however, is generated from ATP released into the extracellular fluid by enzymes located there

A

adenosine

204
Q

T or F: ATP can be in the form of an ionotropic receptor or a metabotropic receptor

A

true - P2X is an ionotropic receptor that allows cations to move through the cell membrane, excitatory; whereas P2Y is coupled to G proteins

205
Q

Adenosine, ADP and ATP are all neurotransmitters that can bind to the P2Y receptor, the _ receptor of ATP

A

metabotropic receptor

206
Q

Drugs that act on GABAergic systems include
_ (such as Valium)
sleeping aids (such as zolpidem)
alcohol

A

benzodiazepines

207
Q

Benzodiazepines treat anxiety by deadening the fight-or-flight response from the sympathetic nervous system, a branch of the _ nervous system

A

autonomic

208
Q

Monoamine oxidase inhibitors prevent the breakdown of biogenic amines, including _ and _ by inhibiting their degradation, acting as though these neurotransmitters are increased

A

norepinephrine and serotonin

209
Q

selective serotonin reuptake inhibitors _ the amount of serotonin that remains in the synaptic cleft

A

increase

210
Q

Nucleotidases break down _ and _ wherease adenosine deaminase breaks down adenosine

A

ADP and ATP

211
Q

_s are short chains of amino acids that are synthesized in the same manner as proteins, and more than 50 of them are found in neurons which function as neurotransmitters

A

neuropeptides

212
Q

Much like _ that are to be secreted from cells, neuropeptides are synthesized in the rough endoplasmic reticulum and packaged into secretory vesicles by the Golgi apparatus

A

proteins

213
Q

Neuropeptides occur in the _

A

soma/cell body

214
Q

Neuropeptides are more commonly known as _s

A

hormones
e.g., vasopressin, oxytocin, enkephalins, etc.

215
Q

_n, a type of neuropeptide, regulates urine output by the kidney

A

vasopressin

216
Q

_n, a type of neuropeptide, regulates contractions of the uterus and the flow of milk from the breasts

A

oxytocin

217
Q

Endogenous _ are types of neuropeptides that exert effects similar to morphine, which include enkephalins and endorphins

A

Opioids

218
Q

S_, a type of neuropeptide, decreases gastointestinal motility

A

substance P

219
Q

c_n, a type of neuropeptide, regulates gallbladder contraction

A

cholecystokinin

220
Q

_n, a type of neuropeptide, is a hypothalamic neurotransmitter that regulates the sleep-wake cycle, inducing arousal or wakefulness (potentially a treatment for narcolepsy)

A

orexin

221
Q

Although neuropeptides are colocalized with other small neurotransmitters (i.e., released from the axon terminal as non-neuropeptides at the same time), neuropeptides are packaged in larger vesicles, called d_ c_ vesicles

A

dense core vesicles

222
Q

Neuropeptides often act on _ receptors and modulate the response of the postsynaptic neuron to the colocalized small neurotransmitter

A

metabotropic receptors (the small neurotransmitter acting as the second messenger)

223
Q

What makes gas nitric oxide and endocannabinoids unique as neurotransmitters?

A

they are not stores in synaptic vesicles or released by exocytosis

224
Q

Nitric oxide (one nitrogen atom and one oxygen atom)is released as soon as it’s _, because it easily crosses the plasma membrane

A

synthesized

225
Q

Controlling nitric oxide synthesization and release is the catalyzation by the enzyme nitric oxide _

A

synthetase

226
Q

_ are a family of chemicals manufactured in neurons from membrane phospholipids; they include anandamide and 2-arachidonylglycerol, which are produced to increase cytosolic calcium levels

A

endocannabinoids

227
Q

THC, a drug that targets CB1 _c receptors, which are the most common type of cannabinoid receptor in the brain

A

metabotropic

228
Q

THC’s influence on cannabinoid receptors have led its widespread use for diseases such as:
Parkinson’s
anxiety disorders
- _ disorder

A

post-traumatic stress disorder

229
Q

Suppose that the electrochemical force for anion X (X~) acts to move the anion out of the cell. If a neurotransmitter bind- ing to its receptor opened channels for X~ on the postsynaptic cell, then the response would
a) Be an EPSP.
b) Be an IPSE
c) Be stabilization of the membrane.
d) Not occur.

A

a) Be an EPSP.

230
Q

Suppose that all the calcium could be removed from the extracellular fluid sur- rounding a neuron. Such removal would inhibit the ability of a neuron to
a) Produce action potentials.
b) Release neurotransmitter.
c) Respond to the binding of a neuro- transmitter to its receptor.
d) Degrade neurotransmitters

A

b) Release neurotransmitter.

231
Q

Synaptic vesicles
a) Store calcium.
b) Release neurotransmitters by exocytosis.
c) Degrade neurotransmitters.
d) Form gap junctions.
e) Synthesize neurotransmitters

A

b) Release neurotransmitters by exocytosis.

232
Q

If sodium channels closed in response to a stimulus, then
a) The neuron would be depolarized.
b) The neuron would be hyperpolarized.
c) The membrane potential would be stabilized.
d) A second messenger would be produced.
e) The neuron would remain at rest

A

b) The neuron would be hyperpolarized.

Assumes that potassium would rush in instead, creating a hyperpolarization

233
Q

A fast EPSP is most commonly produced by
a) The opening of sodium-selective channels.
b) The opening of potassium-selective channels.
c) The opening of chloride channels.
d) The opening of channels selective for both sodium and potassium.
e) The opening of calcium-selective channels

A

d) The opening of channels selective for both sodium and potassium.

234
Q

The enzyme that catalyzes the synthesis of acetylcholine is
a) Adenylate cyclase.
b) Choline acetyl transferase.
c) Monoamine oxidase.
d) Acetylcholinesterase.
e) Catechol- 0-methyltransferase.

A

b) Choline acetyl transferase.

235
Q

Which of the following neurotrans- mitters is a biogenic amine but not a catecholamine?
a) Norepinephrine
b) Serotonin
c) Dopamine
d) Epinephrine

A

b) Serotonin

236
Q

Which of the following is most likely to occur at an axoaxonic synapse?
a) An EPSP
b) AnIPSP
c) Stabilization of the membrane potential
d) Temporal summation
e) Presynaptic modulation

A

e) Presynaptic modulation

237
Q

What happens to the concentration of neurotransmitter in the synaptic cleft when the frequency of action potentials increases in the presynaptic neuron?
a) It increases
b) It decreases
c) It remains constant

A

a) It increases

238
Q

The EPSPs from two different synapses occur at the same time and cause a larger depolarization than either one alone can cause. This is an example of
a) Membrane stabilization.
b) Presynaptic inhibition.
c) Presynaptic facilitation.
d) Temporal summation.
e) Spatial summation

A

e) Spatial summation

239
Q

At electrical synapses, which type of junc- tion exists between the two cells?

A

gap junction

240
Q

When the opening of ion channels allows both sodium and potassium ions to move through, no change in membrane poten- tial occurs because sodium moves into the cell and potassium moves out of the cell, (true/false)

A

false - they flow at different rates

241
Q

Neurotransmitter receptors are found at (chemical/electrical) synapses

A

chemical

242
Q

Whether a synapse is excitatory or inhibi- tory is determined by the mechanism of coupling between the neurotransmitter receptor and ion channels in the postsyn- aptic cell, (true/false)

A

true

243
Q

The synaptic delay includes the time it takes for an action potential to travel from the trigger zone of a presynaptic cell to the axon terminal, (true/false)

A

false - it’s from the axon terminal to the synaptic cleft (calcium levels)

244
Q

A given neurotransmitter might be ex- citatory at one synapse and inhibitory at another synapse, (true/false)

A

true

245
Q

Given that release of an inhibitory neu- rotransmitter is altered by presynaptic facilitation, the response in the postsyn- aptic cell will be a (larger/ smaller) degree of hyperpolarization.

A

larger

246
Q

The response to a neurotransmitter is faster at (ionotropic/metabotropic) receptors

A

ionotropic

247
Q

The enzymes that catalyze the degrada- tion of catecholamines are _ and _

A

monoamine oxidase (MAO), catechol- O- methyltransferase (COMT)

248
Q

Adenylate cyclase catalyzes the formation of _

A

cAMP

249
Q

The voltage-gated Na+ channel activation gate is voltage and/or time dependent

A

voltage dependent

250
Q

The voltage-gated Na+ channel activation gate opens during…

A

threshold and depolarization

251
Q

The voltage-gated Na+ channel activation gate is influenced by _ feedback

A

positive feedback -

252
Q

The voltage-gated Na+ channel INactivation gate is voltage and/or time dependent

A

voltage and time dependent

253
Q

The voltage-gated Na+ channel INactivation gate closes during _

A

repolarization

254
Q

The voltage-gated K+ channel gate depends on voltage and/or time

A

voltage and time

255
Q

Action potentials from threshold stimuli has a magnitude that is… supra-threshold stimuli

A

the same as

256
Q

Relative refractory period finds that some of the sodium voltage-gated channel _ gates are closed, but some have opened

A

inactivation gates

257
Q

The absolute refractory period includes the period of depolarization and…

A

most of repolarization

258
Q

Action potential intensity is understood as…

A

a greater number of action potentials in a given time, rather than an action potential being greater than the next (i.e., frequency coding). This would defy the all-or-none principle

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