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BIOL 103 > Neurons > Flashcards

Neurons Flashcards

1
Q

What does it mean when a cell is excitable? And what are two examples of excitable cells?

A

To be excitable means that they can experience rapid changes in membrane potential as part of a signalling process to trigger something.

Neurons and myocytes are examples of these cells.

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2
Q

What is the general structure of a neuron?

A

cell body with a nucleus, has extensions called dendrites, axon, axon termini.

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3
Q

What is the function of dendrites?

A

they sample the environment around them, and look for ligands.

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4
Q

What are ligands?

A

they are chemicals that open and close ion channels in the dendrite cell membrane.

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5
Q

What happens when dendrites receive information?

A

once they receive info from a ligand, the dendrites send the signal to the cell body in the form of a change in membrane potential, then the cell body takes this information and decides what to do.

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6
Q

What happens if the cell body decides to send a signal?

A

The signal moves down through the axon in the form of an electrical impulse. This causes the axon termini to trigger exocytosis of a storage vesicles, which releases neurotransmitters from the cell.

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7
Q

What is exocytosis?

A

process by which cells move materials from within the cell into the extracellular fluid.

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8
Q

What is the difference between a neuron and a nerve?

A

a neuron is a single cell and a nerve is a collection of many neurons, usually in combo with other cells that support neural function.

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9
Q

What do neurons play an important role in?

A

in the most of the control of our physiological systems. it plays an important role in regulating virtually every physiological system, and therefore is essential for homeostasis.

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10
Q

What is synaptic transmission?

A

It is sending a signal from a neuron to another cell.

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11
Q

What is an action potential?

A

it is a temporary shift (from negative to positive) in the neuron’s membrane potential caused by ions suddenly flowing in and out of the neuron.

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12
Q

What do cells use membrane potential for?

A

use as energy to drive transport in and out of the cell

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13
Q

What is inside of the cell?

A

lots of negatively charged proteins, which cause for a negatively charged cytoplasm (no matter what always neg)

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14
Q

Is sodium levels high or low outside of the cell membrane?

A

Na levels are high outside of the cell membrane.

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15
Q

Are potassium levels (K) high or low outside of the cell membrane?

A

K is high inside of the cell membrane, low outside of the cell membrane.

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16
Q

What are the 2 aspects of the electrochemical gradient?

A

A chemical gradient, and the electrical gradient. and the main players are channels and pumps that regulate this.

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17
Q

What is the chemical gradient?

A

the concentration differences across the cell membrane.

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18
Q

What is the electrical gradient?

A

it is the membrane potential

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19
Q

What happens when channels open?

A

select ions can move down their electrochemical gradients.

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20
Q

What are the roles of pumps in electrochemical gradients?

A

pumps move ions against their electrochemical gradients.

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21
Q

What do the sodium-potassium pumps use the energy of ATP hydrolysis for?

A

they use it to pump sodium out and potassium in, usually to re-establish the gradients that we dissipated when the channels opened.

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22
Q

What is the membrane potential?

A

it is the difference in electrical charge between the inside and outside of the cell.

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23
Q

What is any cell with a membrane potential considered?

A

polarized. just means the membrane potential is not zero.

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24
Q

What is the resting membrane potential?

A

it is the normal conditions of the cell.

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25
Q

What is a neurons membrane potential?

A

70 mV. this means that the inside is 70 mV more negative to the outside.

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26
Q

How do you report the direction of the gradient?

A

the membrane potential is reported as inside relative to the outside.

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27
Q

What is depolarization?

A

the magnitude of the potential decreases relative to the resting potential

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28
Q

What is hyper-polarization?

A

where the gradient grows greater than the resting potential

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29
Q

What is repolarization?

A

it is the cell returning to its resting membrane potential?

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30
Q

What are the changes that occur due to the movement of ions in or out of the cell?

A

depolarization, hyper-polarization, repolarization.

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31
Q

What type of chemical gradient is there for sodium?

A

inward

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32
Q

What type of chemical gradient is there for potassium?

A

outward

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33
Q

What determines if K moves in or out?

A

depends on which of the two forces is greater, the electrical or chemical gradient.

34
Q

what is the equilibrium potential?

A

it is the electrical gradient that exactly offsets the energy in the chemical gradient. Therefore, the movements of the ions when you open an ion channel, will cause the membrane potential to move toward the equilibrium potential for that ion.

35
Q

What is the equilibrium for potassium and sodium separately? And what happens when you open the channels for them?

A

Sodium: equilibrium potential is +40 mV, which means when the channel opens, the membrane will depolarize toward +40 mV from 70 mV

Potassium: equilibrium potential is -90 mV, so when you open the channels K will move out of the cell, and will hyperpolarize toward -90 mV from 70 mV

36
Q

At rest is the energu in the electrical gradient less or more than the energy in the concentration gradient?

A

the energy in electrical gradient is a little bit less

37
Q

What is graded depolarization?

A

if more ion channels are open, more ions move, and there is greater depolarization.

38
Q

How can graded depolarization be induced?

A

a chemical that binds a Na channel in the dendrites.

39
Q

What is an agonist?

A

they make it more likely that a neuron will reach its threshold membrane potential.

40
Q

What triggers a massive depolarization?

A

a voltage barrier

41
Q

What is a graded potential?

A

it moves the membrane potential toward or away from the threshold.

42
Q

What is a threshold membrane potential?

A

it is the minimum distance that must be reached in order to fire an action potential.

43
Q

Does potassium moving out of the cell make the membrane more or less polarized?

A

more.

44
Q

How can the effects of a sodium channel be negated?

A

can be negated by an open potassium channel in the same area, and this change can be induced by a chemical that binds a K channel in the dendrites. This ligand would be considered a antagonist.

45
Q

What is a antagonist?

A

it makes it less likely that a neuron will reach its threshold potential.

46
Q

What happens when the combined effects of the dendrites cause the cell body membrane to hit the threshold?

A

an action potential is generated

47
Q

What happens when a dendrite experiences changes in the membrane potential?

A

the signal makes its way toward the cell body. from here it causes a change in the structure of voltage sensitive Na channels, which causes many channels to open. The resulting inflow of Na depolarizes the cell, and at some point Na channels close, and K opens, which returns in the cell to its resting state

48
Q

When the channels are closed is anything leaking out? And if so, how is the membrane potential being held constant?

A

ions are slowly leaking in and out of the cell, but the pumps are keeping pace and holding the membrane potentials constant.

49
Q

What are ligand gated ion channels?

A

it is channels that open in response to a ligand.

50
Q

What happens when voltage change is sensed by the voltage gated Na channels?

A

causes them to open up. when this happens it causes sodium to rush in and cause a massive and rapid depolarization.

51
Q

Why does eating pufferfish sushimi sometimes cause a tingling in the tongue or death?

A

from this toxin it has in it that binds onto these voltage gated sodium channels and prevents them from opening, it is used to discourage predators.

52
Q

What happens when the sodium channels close?

A

the voltage gated potassium channels open, and the open channels permit potassium to rush out of the cell making the inside more negative and driving the membrane potential toward the equilibrium potential for potassium (-90 mV). this is because potassium in response to sodium, was far from its equilibrium potential.

53
Q

What does the recovery of potassium after sodium channels have been open cause?

A

it causes the recovery to make the cell a bit hyperpolarized, since the equilibrium potential for K is greater than the cell. Eventually this evens out and returns to resting state.

54
Q

what does the depolarization in one spot cause in another?

A

it also affects the surrounding area, and as a result the changes also occur over space and time.

55
Q

Describe and detail the propagation of an action potential.

A

first off, it is changes that are happening in a region of that axon. depolarization in one area causes the area downstream from the axon hillock to depolarize as it hits its threshold. This causes the depolarization downstream at the same time as that first region is replarizing. And this causes the second spot to repolarize as the third spot depolarizes. This causes a wave a depolarization, and it is this change in action potentials that triggers the membrane next to it as well.

56
Q

What is the hillock of an axon?

A

acts as an administrator, sums up the total signals received, both inhibitory and excitatory signals. If this sum exceeds the limiting threshold, the action potential is triggered.

57
Q

What is a synapse?

A

it is the point of contact between neurons where information is passed from one neuron to the next.

58
Q

Describes what happens once information comes into the first neuron between two axons that are connected together at a synapse.

A
  • information comes to the first neuron at the dendrites
    -cell body decides what to do
    -if stimulation is in order, an action potential that moves down the axon is triggered
    -at the termini, this event causes the cell to release a neurotransmitter
    -the chemical moves across the synapse, and binds onto the dendrites of the target cell
    -the neurotransmitter might inhibit or stimulate the neuron
59
Q

What are interneurons and what are their jobs?

A

lie between sensory and motor neurons. their job is to connect two neurons together, recieve a signal from one, and send a signal to another. They have a great dendrite collection, that allows them to sample lots of different neurons, spaces.

60
Q

Describe the pathway and response of a motor neuron.

A

-dendrites receive info on what to do
-axons send their signal
-the muscle cell (target cell) receive signal
-a response is triggered.

ex. there could be sensory neurons in fingertips, and they could be temp sensitive. if it is too hot, the neurons send a signal down to the cell body, and the body tried to decide what to do about it, and a response is triggered.

61
Q

what is propagation?

A

spreading

62
Q

What are the 2 ways that animals build neurons to have fast propagation of the action potential along the axon?

A

size and insulation.

63
Q

What is the benefit of size to the action potential?

A

the larger the axon, the faster the action potential moves. the rapid response in squid is due to giant axons, and they are also really easy to study.

64
Q

What is the benefit of insulation to the speed of the action potential?

A

it is the way neurons have been able to evolve fast conduction.

the cells have an extracellular matrix that serves as insulation, the sheath is not continous, but has gaps/nodes. The action potential is faster because instead of having to move all the way along the cell membrane,e you can just jump from one node to the next.

65
Q

What is a saltatory conduction?

A

describes the way an electrical impulse skips from node to node down the full length of an axon

66
Q

What do the axon termini contain?

A

has vesicles fulled with a chemical, which is one particular neurotransmitter.

67
Q

What happens when the termini receives a signal?

A

the voltage change causes calcium channels to open, and the inflow of calcium causes the cytoskeletal machinery to push these vesicles to the surface, and dump the contents into the cell and into a small space.

68
Q

what is acetylcholine?

A

the neurotransmitter that tells us to contract.

69
Q

What can other nerve transmitters be?

A

modified amino acids or amino acids

70
Q

why do people get “twitchy” when they have too much MSG in their food?

A

because you ate a neurotransmitter

71
Q

What are some important neurotransmitters important to mental health, and why?

A

dopamine and serotonin because they influence the way your brain perceives the environment.

72
Q

What happens at the synapse?

A

neurotransmitters are released into the gap and affect target cells.

73
Q

What is post synaptic cells?

A

the cell that receives information, since they are also downstream of the synapse.

74
Q

How does a muscle control if it does or does not want to respond to a neurotransmitter?

A

If it does not want to respond, it will stop making the receptor channels for the neurotransmitter. If it wants to be super sensitive, then it will put a lot of the channels in.

75
Q

What would a muscle cells do if it wants it to change in real time?

A

it would maybe cause it to phosphorylate or dephosphorylate the channel to make these channels better or worse, they stay opeen longer they stay open shorter, or they need a different level of neurotransmitter to bind.

76
Q

What is an example of a post synaptic event?

A

stopping the signal, meaning it is either reabsorbing the neurotransmitter or secreting enzymes to degrade it.

77
Q

Why is neuronal function essential for most animals?

A

organisms over the years have evolved in ways to impare function to get food and avoid being eaten.

78
Q

What is the main way to stop the neurotransmitter acetylcholine?

A

by the enzyme acetylcholinesterase.

79
Q

What is snake venom in terms of a neurotransmitter?

A

their toxins enter the interstitial fluid at the bite, make their way into the blood to target tissues where they prevent muscles from relaxing.

80
Q

What is the best way to kill an animal?

A

messing up neuronal transmission. For example, some do this by blocking sodium channels.

81
Q

Why is raid useful but not toxic to us?

A

it contains a potent neurotoxin, but the chemical has a very short half life.

BIOL 103 (12 decks)

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