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MCAT > MCAT biology Nervous system > Flashcards

MCAT biology Nervous system Flashcards

1
Q

___is localized area of depolarization of the plasma membrane that travels in a wave-like manner along an axon

A

Action potential

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2
Q

Where does an action potential transform from an electrical to a chemical signal?

A

At the end of an axon at a synapse

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3
Q

The basic functional and structural unit of the nervous system is the __

A

neuron

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4
Q

Neurons have a central cell body called the __

A

soma

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5
Q

Neurons have only one ___

A

axon

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6
Q

___of a neuron receive signals

A

Dendrites

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7
Q

____carry action potentials away from the cell body

A

Axons

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8
Q

A ___ is a large bundle of many different axons from different neurons

A

Nerve

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9
Q

The resting membrane potential is an electric potential across the plasma membrane of approximately ___

A

-70 millivolts

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10
Q

The interior of a neuron is ___ with respect to the exterior of the cell

A

negatively charged

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11
Q

What two proteins are required to establish the resting membrane potential of a neuron?

A

Na+/K+ ATPase and the Potassium leak channels

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12
Q

The Na+/K+ ATPase pumps ___ out of the cell and __ into the cell with the hydrolysis of one ATP molecule

A

three sodium ions out of the cell

two potassium ions into the cell

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13
Q

The Na+/K+ ATPase uses ATP to drive transport against a gradient this is___

A

primary active transport

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14
Q

Potassium leak channels allow potassium to flow _

A

down their gradient OUT of the cell

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15
Q

What is the ratio of Na+/K+ ATPAse and potassium leak channels

A

there are 100:1 potassium channels to Na+/K+ ATPase, the cell is virtually impermeable to SODIUM

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16
Q

Key proteins in the propagation of action potentials are the ___ located in the plasma membrane of the axon

A

voltage-gated sodium channels

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17
Q

____ open to allow sodium ions to flow down their gradient INTO the cell and depolarize that section of the membrane

A

Voltage-gated sodium channels

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18
Q

The threshold potential is __

A

-50 mV

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19
Q

Opening of the ___ can cause the interior of the neuron to have a momentary positive charge

A

Opening of the voltage-gated sodium channel

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20
Q

___form myelin within the PNS which increases the speed of conduction of AP’s along the axon

A

Schwann cell

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21
Q

____form myelin in the CNS which increases the speed of conduction of AP’s along the axon

A

Oligodendrocytes

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22
Q

___guide neuronal development

-Regulate synaptic communication via regulation of neurotransmitter levels in the CNS

A

Astrocytes

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23
Q

_____remove dead cells and debris from the CNS

A

microglia

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24
Q

___ produce and circulate CSF in the CNS

A

Ependymal cells

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25
Q

What is true concerning myelinated and unmyelinated axons

A

The amount of energy consumed by the Na+/K+ ATPase is much less in myelinated axons than in unmyelinated axons.

-Na+/K+ ATPase works to maintain the resting potential in the nodes of Ranvier only, in unmyelinated cells it has to maintain the resting potential across the entire membrane

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26
Q

___are specialized, non-neuronal cells that typically provide structural and metabolic support to neurons

A

Glial Cells

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27
Q

The movment of Na+ and K+ ions across the membrane during APs through voltage-gated channels is ___

A

Passive transport, driven by gradients

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28
Q

The ____ is the membrane potential at which this driving force or gradient does not exist, no net movement of ions across the membrane

A

Equilibrium potential

29
Q

During the ___ a neuron will NOT fire another AP no matter how strong a membran depolarization is induced

A

Absolute refractory period

30
Q

During absolute refractory period the __ have been inactivated after depolarization

A

voltage gated sodium channels

31
Q

During ___ a neuron can be induced to transmit an action potential but the depolarization required is greater than normal because the membrane is HYPERPOLARIZED

A

Relative refractory period

32
Q

If a fruit fly mutant is found that has voltage-gated potassium channels that shut more quickly after repolarization, how would this affect the refractory period in the fly?

A

The absolute refractory period would not be altered, since this is due to the inability of voltage-gated sodium channels to open. The relative refractory period would be decreased

33
Q

A __ is a junction between the axon terminus of a neuron and the dendrites, soma, or axon of a second neuron

34
Q

__ occur when the cytoplasms of two cells are joined by gap junctions

A

Electrical synapse

35
Q

If two cells are joined by an ___ an AP will spread directly from one cell to another

A

Electrical synapse

36
Q

___are quite important in propagating action potentials in smooth muscle and cardiac muscle

A

Electrical synapses

37
Q

___are found at the ends of axons where they meet their target cell, here an action potential is converted to a chemical signal

A

Chemical synapse

38
Q

Give the 8 steps of transmission of a signal across a chemical synapse in the nervous system

A
  1. An action potential reaches the end of an axon, the synaptic knob
  2. Depolarization of the presynaptic membrane opens voltage-gated calcium channels
  3. Calcium influx into the presynaptic cell causes exocytosis of neurotransmitter stored in secretory vesicles
  4. Neurotransmitter molecules diffuse across the narrow synaptic cleft
  5. Neurotransmitter binds to receptor porteins in the post-synaptic membrane. These receptors are ligand-gated ion channels
  6. The opening of these ion channels in the post-synaptic cell alters the membrane polarization
  7. If the membrane depolarization of the postsynaptic cell reaches the threshold of voltage-gated sodium channels, an action potential is initiated
  8. Neurotransmitter in the synaptic cleft is degraded and/or removed to terminate the signal
39
Q

What 4 things are happening in a presynaptic neuron during synapse?

A
  1. Voltage-gated Calcium channels open
  2. Influx of calcium
  3. Exocytosis of secretory vesicle
  4. Release of neurotransmitter into synaptic cleft
40
Q

What 3 things occur in the postsynaptic neuron during a synapse

A
  1. Neurotransmitter binds to ligand-gated ion channel
  2. Ions enter postsynaptic cell
  3. Membrane polarization is increased or decreased
41
Q

The neurotransmitter released at the neuromuscular junction between neurons and skeletal muscle is

A

Acetylcholine (ACh)

42
Q

Acetylcholine in the synapti cleft is degraded by the enzyme___

A

acetylcholinesterase (AChE)

43
Q

If a neurotransmitter such as acetylcholine,opens a channel that depolarizes the postsynaptic membrane, the neurotransmitter is termed __

A

excitatory

44
Q

Neurotransmitters that induce hyperpolarization of the postsynaptic membrane are termed__

A

inhibitory

45
Q

Ultimately it is not the neurotransmitter that determiens the effect on the postsynaptic cell it is the__

A

receptor for that neurotransmitter and its associated ion channel

46
Q

If a neurotransmitter causes the entry of chloride into the postsynaptic cell, is the neurotransmitter excitatory or inhibitory?

A

Chloride ions are negatively charge. The entry of chloride into the cell will make the postsynaptic potential more negative, or hyperpolarized, it would be INHIBITORY

47
Q

If an inhibitor of acetylcholinesterase is added to a neuromuscular junction, then the postsynaptic membrane will___

A

be depolarized longer with each action potential

-Acetylcholine will remain in the synaptic cleft longer, and acetylcholine-gated sodium channels will remain open longer with reach AP that reaches the synapse

48
Q

What is the best explanation for unidirectionality of signaling at synapses between neurons?

A

Only the presynaptic cell has vesicles of neurotransmitters.

49
Q

Action potentials are initiated when the postsynaptic membrane reaches the threshold depolarization of ___ required to open voltage-gated sodium channels

50
Q

___ is when a presynaptic neuron fires action potentials so rapidly that the EPSP’s or IPSP’s pile up on top of one another

A

Temporal summation

51
Q

How can a presynaptic neuron increase the intensity of signal it transmits?

A

Increase the frequency of action potentials

52
Q

Receiving information is the sensory function of the nervous system carried out by the ___

A

Peripheral nervous system (PNS)

53
Q

Processing the information received is the integrative function carried out by the __

A

Central nervous system (CNS)

54
Q

The motor function is carried out by the __

A

Peripheral nervous system (PNS)

55
Q

Motor neurons carry information from the nervous system toward organs which can act upon that information known as ___

56
Q

What are the two types of effectors?

A

Muscles

Glands

57
Q

Motor neurons which carry information away from the central nervous system and innervate effectors (muscles and glands) are called__

A

efferent neurons

58
Q

Sensory neurons which carry information toward the central nervous system are called __

A

afferent neurons

59
Q

What are the two branches of the PNS?

A

Somatic: voluntary control of skeletal muscle
Autonomic: Involuntary control of glands and smooth muscle

60
Q

What are the two branches of the Autonomic nervous system?

A

Sympathetic division: “fight or flight

Parasympathetic: “rest and digest”

61
Q

Myelinated axons in both the CNS and PNS is referred to as __

A

white matter

62
Q

White matter in the brain is called a __

63
Q

White matter in the spinal cord is called __

A

a tract or column

64
Q

White matter in the PNS is called __

65
Q

Unmyelinated neuronal cell bodies in both the CNS and PNS are referred to as __

A

grey matter

66
Q

Grey matter deep in the brain is referred to as ____

67
Q

Grey matter on the surface of the brain is called__

68
Q

Grey matter in the spinal cord is called a __

69
Q

Grey matter in the PNS is a __

MCAT (45 decks)

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