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BIO 2 > NERVOUS SYSTEM (LECTURE 14) > Flashcards

NERVOUS SYSTEM (LECTURE 14) Flashcards

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1
Q

How many functions does the nervous system have?

A

3

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2
Q

Name the 3 functions of the nervous system.

A

Sensory input, integration, motor output.

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3
Q

Sensory input is the response to…

A

external and internal stimuli, made possible by sensory neurons.

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4
Q

Describe integration.

A

It is the interpretation of sensory input - decides the appropriate response.

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5
Q

Describe motor output.

A

It is the conduction of signals from the central nervous system to the effector cells, made possible by motor neurons.

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6
Q

Neurons are cells specialized for…

A

transmitting electrical and chemical signals.

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7
Q

Neurons are comprised of what 2 structural components?

A

The cell body and fiber-like extensions.

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8
Q

What are the 2 classes of fiber-like extensions found on neurons?

A

Dendrites and axons.

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9
Q

Describe dendrites.

A

These convey signals towards the cell body - they are short and numerous.

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10
Q

Describe axons.

A

These conduct impulse away from the cell as long, single processes. Some are insulated by a myelin sheath and they all end in an axon terminal.

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11
Q

What do axon terminals do?

A

They relay signals to other cells by releasing neurotransmitters.

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12
Q

Neurons communicate via…

A

synapses.

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13
Q

Neurotransmitters are released from a ____ neuron and act on a ____ neuron.

A

Neurotransmitters are released from a pre-synaptic neuron and act on a post-synaptic neuron.

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14
Q

Nerve signals/impulses are changes in…

A

voltage across the plasma membrane.

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15
Q

Nerve signals/impulses (changes in voltage) are caused by…

A

the movement of ions across the membrane.

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16
Q

What (positively charged) ions move across a neuron’s membrane to cause changes in voltage?

A

Na+ and K+.

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17
Q

What is the membrane potential of a resting neuron?

A

About -70 mV.

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18
Q

Is the inside or outside of a resting neuron more negative?

A

The inside is more negative than the outside.

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19
Q

What determines membrane potential?

A

The ion distribution across the membrane.

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20
Q

What negatively charged molecules (anions) can cause a change in membrane potential? (5)

A

Negatively charged proteins, amino acids, sulfate and phosphate, Cl-.

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21
Q

Charged molecules can cross a neuron membrane using what 2 ways?

A

Either through passive ion channels or gated ion channels.

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22
Q

What are passive ion channels important for? When do they close?

A

These are important for maintaining -70mV membrane potential. They are open all the time.

23
Q

Describe gated ion channels.

A

These require a stimulus to open.

24
Q

Give an example of a stimulus that can open a gated ion channel.

A

A change in voltage.

25
Q

What does the Na+/K+ ATPase pump do?

A

These maintain concentration gradients of Na+ and K+ across the membrane (High [Na+] outside and high [K+] inside).

26
Q

For every 1 ATP used, how many Na+ / K+ are pumped into / out of the neuron?

A

3 Na+ pumped out. 2 K+ pumped in.

27
Q

There are many passive ____ ____ channels that are always ____.

A

There are many passive K+ channels that are always open.

28
Q

What does K+ do with the help of the many passive K+ channels?

A

K+ diffuses down its concentration gradient out of the cell (gradient created by the Na+/K+ ATPase pump).

29
Q

Stimuli can cause changes in ____ ____.

A

Stimuli can cause changes in membrane potential.

30
Q

Stimuli opens ____ ____ ____, changing the ____ ____ across the membrane.

A

Stimuli opens gated ion channels, changing the charge distribution across the membrane.

31
Q

Hyperpolarization is occurring when…

A

the inside of the neuron becomes more negative due to gated K+ channels opening, allowing K+ to diffuse out of the cell.

32
Q

Depolarization is occurring when…

A

the inside of the neuron becomes more positive due to Na+ channels opening, allowing Na+ into the cell.

33
Q

When is an action potential generated?

A

When a depolarizing stimulus is strong enough to pass the threshold potential.

34
Q

What does an action potential do if it is generated?

A

Action potential moves along the entire length of the axon and stimulates the release of neurotransmitters from the axon terminal.

35
Q

Name the steps to generate (propagate) an action potential. (5)

A

(1) Resting state. (2) Threshold. (3) Depolarization. (4) Repolarization. (5) Undershoot.

36
Q

Describe the resting state. (2)

A

No gated channels are open; -70mV resting potential.

37
Q

Describe threshold - what occurs at threshold?

A

Stimuli causes gated Na+ channels to open ; Na+ flows in causing depolarization.

38
Q

Describe depolarization.

A

If depolarization reaches threshold, an action potential will begin. At threshold, voltage-gated Na+ channels open causing a large depolarization.

39
Q

Describe repolarization.

A

Na+ channels close AND K+ channels open - K+ moves out of the cell.

40
Q

Describe undershoot.

A

K+ channels are slow to close allowing more K+ to leave. Membrane potential is more negative than resting potential.

41
Q

Why is the neuron’s membrane insensitive to stimuli during repolarization and undershoot?

A

Na+ channels are closed and thus membrane is insensitive to stimuli.

42
Q

An action potential is a ____ ____ event.

A

An action potential is a localized electrical event.

43
Q

Describe the propagation (path) of the action potential.

A

If stimulation is strong enough to reach threshold, an action potential will be initiated and move along the length of the axon to the axon terminal.

44
Q

How does the action potential propagate along the axon?

A

Depolarization in one part of the axon causes depolarization in the region right next to it by opening voltage gated Na+ channels.

45
Q

Why can an action potential only move in one direction?

A

Since during repolarization and undershoot (processes directly following depolarization), a membrane cannot be depolarized - so action potential can only move in one direction.

46
Q

What is a synapse?

A

It is a space between presynaptic (transmitting) cell and a postsynaptic (receiving) cell.

47
Q

What occurs at chemical synapses?

A

Neurotransmitters are released from the axon terminal of a presynaptic cell and act on a postsynaptic cell.

48
Q

Describe what happens at a synapse in 4 steps.

A

(1) Action potential arrives at the axon terminal. (2) Ca2+ stimulates the fusion of synaptic vesicles containing neurotransmitters with the presynaptic membrane. (3) Neurotransmitters bind to ligand-gated ion channels on the postsynaptic membrane. (4) Neurotransmitters are quickly degraded or taken back up by the presynaptic cell.

49
Q

How does the arrival of the action potential at the axon terminal result in the introduction of Ca2+?

A

Depolarization of the presynaptic membrane causes voltage-gated Ca2+ channels to open and Ca2+ to move into the axon terminal.

50
Q

How does the fusion of synaptic vesicles containing neurotransmitters with the presynaptic membrane lead to the release of neurotransmitters in to the synapse?

A

Neurotransmitters are released into the synaptic cleft via exocytosis.

51
Q

A postsynaptic neuron will form ____ (____ to ____) with many ____ ____.

A

A postsynaptic neuron will form synapses (hundreds to thousands) with many presynaptic neurons.

52
Q

What is excitatory postsynaptic potential (EPSP)?

A

Where Na+ and K+ channels are involved in depolarization.

53
Q

What is inhibitory postsynaptic potential (IPSP)?

A

When K+ and Cl- channels are involved in hyperpolarization.

BIO 2 (14 decks)

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