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Individual Histology > L1 > Flashcards

L1 Flashcards

1
Q

The visceral motor division is also known as what part of the nervous system?

A

The autonomic division

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2
Q

What two subdivisions is the visceral motor division divided into?

A

Sympathetic (fight or flight) and Parasympathetic (rest and digest)

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3
Q

Which type of neurons make up 90% of all human neurons?

A

Interneurons

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4
Q

T/F Interneurons are only located in the CNS?

A

True

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5
Q

Where are interneurons positioned relative to sensory and motor neurons?

A

In between them

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6
Q

Which type of neurons process, store and retrieve information?

A

Interneurons

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7
Q

What is the longevity of individual neurons that differentiate during fetal development?

A

They can function the entire life of an individual

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8
Q

T/F Most neurons stop dividing after fetal development.

A

True. The few exceptions include olfactory neurons and neurons in some areas of the brain

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9
Q

T/F It is a truism that axon are generally covered by glial cells

A

True

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10
Q

What percentage of cells in the CNS are glial cells? How much volume do all these glial cells make up?

A

90%. 50%

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11
Q

What are the four glial cells of the CNS?

A

Astrocytes, Oligodendrocytes, Microglia, and Ependymal cells.Mnemonic: Another One May Enter

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12
Q

What is the sole glial cell type in the PNS?

A

Schwann cell

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13
Q

What is the cell that acts like a macrophage in the CNS?

A

Microglia

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14
Q

Which is the most abundant glial cell in the CNS?

A

Astrocyte

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15
Q

Which glial cells form an important part of the blood-brain barrier by separating neurons from capillaries?

A

Astrocytes

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16
Q

Which glial cells help to regulate the composition of brain tissue intercellular fluid by selectively absorbing ions and nutrients from blood and removing waste?

A

Astrocytes

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17
Q

What does each dendritic process of an oligodendrocyte do in the CNS?

A

Myelinates part of an axon

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18
Q

Which glial cells form a ciliated simple columnar epithelium that lines ventricles and circulates CSF in the CNS?

A

Ependymal cells

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19
Q

When does myelination start and how long does it continue?

A

Starts during embryonic and fetal development of the nervous system and continues into adulthood

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20
Q

What is the composition of the glial cell plasma membrane?

A

About 20% protein and 80% lipid

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21
Q

True/False Axons can be covered by oligodendrocytes but not myelinated?

A

True

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22
Q

How many axons can one schwann cell cover? How many can one oligodendrocyte cover?

A

Only one region of one axon..Oligodendrocytes can cover regions of axons of more than one axon

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23
Q

What is neuronal communication based on?

A

Mechanisms for producing electrical potentials and currents

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24
Q

What is the electrical potential in neuronal communication? What units is it measured in?

A

The difference in charge (mostly due to ion concentration) across a membrane. Millivolts (mV)

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25
Q

What is the electrical current in neuronal communication? What units is it measured in?

A

Movement of charge (carried by ions) across a membrane. Milliamps (mA)

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26
Q

What is the electric potential of living cells measured with?

A

A sensitive voltmeter with two glass microelectrodes

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27
Q

Where must the microelectrodes be placed to measure the membrane potential of cells?

A

One microelectrode must be placed inside the cell and the other one outside the cell as a reference

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28
Q

What is the instrument used to make thin electrodes from glass tubes?

A

Microforge

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29
Q

What is the ratio of ion transport by the Na+/K+ pump?

A

3 Na+ : 2 K+

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30
Q

How many ATP are needed for each cycle of the Na+/K+ pump?

A

one ATP per cycle

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31
Q

High use of ATP requires which two molecules to be continuously supplied to the nerve tissue?

A

Glucose and oxygen

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32
Q

In which direction to K+ leak channels allow K+ ions to move? Na+ leak channels?

A

Out of the cell. Inside the cell.

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33
Q

Which leak channels are more numerous, K+ or Na+?

A

K+ leak channels are more numerous

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34
Q

How does the leaking out of K+ affect the membrane potential? Leaking in of Na+?

A

Makes the membrane potential more negative. Leaking in of Na+ makes the membrane potential only slightly more positive since there are very few Na+ leak channels

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35
Q

Which areas of a neuron have ligand-gated receptors?

A

The soma membrane and dendrites

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36
Q

Which area of the neuron has a high density of Na+ and K+ channels?

A

The axon hillock.

37
Q

What is the area of the neuron known as the “trigger zone” for initiating an action potential?

A

Axon hillock

38
Q

Where are the voltage gated Na+ and K+ channels located on an axon?

A

They are clustered at the Nodes of Ranvier

39
Q

What kind of channels does the terminal bouton have?

A

Voltage-gated Ca++ channel and a Ca++ pump

40
Q

What are the four segments of a neuron containing various channels and pumps?

A

Receptive, Initial, Conductive, and Transmissive segments.Mnemonic: Run In Circles and Trip

41
Q

Are ligand channels open or closed at rest?

A

Closed

42
Q

What are the three characteristics of local potentials?

A

The are graded, decremental, and reversible?

43
Q

T/F Local potentials vary in magnitude with stimulus strength.

A

True. This is how they are “graded”

44
Q

How does the decremental quality of local potentials affect the spread of depolarization?

A

The local depolarization of the membrane gets weaker as it spreads

45
Q

What do the excitatory postsynaptic potentials (EPSP) do to membrane potential? Inhibitory postysynaptic potential (IPSP)?

A

Depolarizes it because they make the membrane potential more positive. IPSP hyperpolarize the membrane potential becaue it makes it more negative.

46
Q

What are two examples of excitatory neurotransmitters? How do they affect the flow of Na+?

A

Noradrenaline and glutamate. They cause it to flow into the cell

47
Q

What are two examples of inhibitory neurotransmitters?

A

Glycine and GABA

48
Q

IPSP results from the flow of which to ions and in which direction?

A

Cl- flowing in or K+ flowing out depending on the type of channel stimulated

49
Q

Which neurotransmitters (nt) can be both excitatory or inhibitory? What factor decides how the nt will affect the membrane potential?

A

ACh and Norepinephrine. The receptor decides if it will be excitatory or inhibitory.

50
Q

What are the two types of local membrane potentials?

A

EPSP and IPSP

51
Q

What are the two summations of the EPSP?

A

Temporal summation and spatial summation

52
Q

What is temporal summation? What is Spatial summation?

A
  1. Temporal summation is the reception of many EPSPs from a single presynaptic cell in a short period of time enough to reach the threshold for an action potential.2. Spatial summation is the reception of EPSPs from multiple presynaptic cells, enough to reach the threshold for an action potential
53
Q

What are two defining characteristics of an action potential?

A

It is all-or-none and irreversible

54
Q

What is the charge of the threshold potential? What is the peak potential?

A

-55mV+35mV

55
Q

What is the first step of an action potential at the Axon Hillock? Second step?

A
  1. Na+ influx leads to depolarization.2. The threshold potential of -55mV is reached
56
Q

What happens when the threshold potential is reached?

A

Many voltage-gated Na+ channels open

57
Q

Which voltage-gated channels are open quickly? Which ones open and close slowly?

A

Na+ open quickly. K+ slowly

58
Q

What is the positive feedback in the depolarization stage?

A

Voltage-gated Na+ channels open quickly and cause more voltage-gated Na+ channels to open.

59
Q

At what stage of the action potential do K+ channels begin to slowly open?

A

At the end of the depolarization stage

60
Q

What happens to Na+ channels at the peak of depolarization?

A

They become inactivated as the membrane potential becomes positive on the inside

61
Q

What is the position of voltage-gated K+ channels during repolarization?

A

They are fully open and rapidly diffusing K+ out of the cell to reduce the positive charge of the membrane potential on the inside of the cell

62
Q

How does the slow closing of the voltage-gated K+ channels affect the membrane voltage?

A

The membrane voltage actually gets below the resting potential (hyperpolarizes) because a lot of K+ escapes while the slow gate closes

63
Q

How is the resting membrane potential restored?

A

Restored through the action of the Na+/K+ pump and the K+ leak channels that mitigate the super negativity of hyperpolarization

64
Q

What is the refractory period?

A

A short period of time when a neuron is resistant to stimulation because voltage-gated Na+ channels are temporarily deactivated

65
Q

What is the benefit of the refractory period?

A

Assures one way conduction of the impulse

66
Q

In which direction does the action potential travel?

A

From the soma to the bouton, one way only

67
Q

What are the two refractory period types?

A

Absolute and relative

68
Q

What is the absolute refractory period?

A

No stimulus can start an action potential since all (or the vast majority) of the voltage-gated Na+ channels are closed

69
Q

What is the relative refractory period?

A

When some voltage-gated Na+ channels have become reactivated, but it still requires a stronger than normal stimulus because of hyperpolarization

70
Q

What temporarily inactivates the voltage-gated Na+ channel during the refractory period?

A

By a part of channels protein that blocks the channel much like an old style sink plug on a chain

71
Q

During the resting membrane potential (RMP) which ion is primarily responsible for the membrane voltage?

A

K+ (out)

72
Q

What kind of gate opens Na+ channels during the graded local potential? (ligand or voltage)

A

a ligand-gate (by binding an excitatory nt)

73
Q

During depolarization which ion is primarily responsible for the membrane voltage? Repolarization?

A

Na+ (in)

74
Q

Which ion is responsible for hyperpolarization of the membrane potential?

A

K+ keeps flowing out of the slowly closing voltage-gated K+ channel longer than necessary to reach the RMP

75
Q

The membrane of which part of the neuron must reach the threshold voltage for an action potential to start moving towards the terminal bouton?

A

Axon hillock

76
Q

What is a nerve signal or impulse along an axon?

A

A chain reaction of action potentials caused by the activation and deactivation of voltage-gated Na+ and K+ channels along the axon

77
Q

What significantly affects the speed of action potential conduction along an axon?

A

Myelination

78
Q

T/F All healthy axons are covered by glial cells

A

True (Fernandez said he will test us on this)

79
Q

What is the difference between an unmyelinated and myelinated axon?

A

Unmyelinated is covered with only one layer of glial cell membrane, while myelinated is covered with many layers

80
Q

What two things affect the speed of nerve signals?

A

Diameter of the axon and myelination

81
Q

What is the affect of axon diameter on the speed of nerve signals?

A

A larger diameter results in faster signal conduction because of increased membrane surface area for signal conduction

82
Q

What kind of pain sensations travel through slow unmyelinated fibers?

A

Burning, aching, and throbbing pain from a sprain, sun burn or stubbing a toe

83
Q

T/F Unmyelinated fibers take a long time to reach the CNS and last a long time

A

True

84
Q

What kind of pain sensations travel through fast myelinated fibers?

A

Sharp pricking pain like stepping on a thorn that are conducted quickly to help prevent further injury

85
Q

Where do fast myelinated signals travel?

A

To the CNS from sensory organs and to skeletal muscles

86
Q

Which type of axon myelination has continuous conduction? Which type has saltatory conduction?

A

Unmyelinated axon fibers. Myelinated axons.

87
Q

What must unmyelinated axons along the entire length of the axon?

A

Uninterrupted sequence of voltage-gated Na+ and K+ channels

88
Q

How many more times are voltage-gated channels concentrated at the Nodes of Ranvier than in myelin covered regions?

A

almost 500 times

89
Q

How do the nodes conduct their signals to the next nodes?

A

By generating a local current flow

Individual Histology (10 decks)

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