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Lecture 19 Flashcards

(44 cards)

1
Q

What is the absolute refractory period?

A

Period during which no action potential is possible due to the inactivation gate of voltage-gated Na+ channels being closed

Occurs after depolarization to +30mV

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2
Q

What is the relative refractory period?

A

Period during which a large stimulus can generate an action potential, but the membrane potential is more negative due to K+ efflux

Inactivation gates are in the process of opening

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3
Q

Describe the movement of an action potential down the axon of a neuron.

A

An action potential activates adjacent segments of the axon by opening voltage-gated Na+ channels, propagating the signal along the axon

This process is known as active propagation

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4
Q

What is synaptic transmission?

A

The process where neurotransmitters are released from the presynaptic neuron and bind to receptors on the postsynaptic neuron, causing local potentials

This process occurs at the axon terminal

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5
Q

Fill in the blank: Na+ = _______

A

Sodium

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6
Q

Fill in the blank: K+ = _______

A

Potassium

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7
Q

Fill in the blank: Cl- = _______

A

Chloride

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8
Q

Fill in the blank: Ca2+ = _______

A

Calcium

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9
Q

What types of channels are found on dendrites of some sensory neurons?

A

Mechanically-gated ion channels

More detail is provided in Lecture 23

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10
Q

What are chemically gated channels?

A

Channels that open when a chemical molecule, such as a neurotransmitter, binds to a receptor, allowing ions to flow down their electrochemical gradient

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11
Q

Define excitatory post-synaptic potential (EPSP).

A

A local potential that results in depolarization, making the membrane potential more positive, often due to Na+ influx

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12
Q

Define inhibitory post-synaptic potential (IPSP).

A

A local potential that results in hyperpolarization, making the membrane potential more negative, often due to K+ efflux or Cl- influx

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13
Q

What is temporal summation?

A

The process where local potentials arrive close together in time, allowing their effects to add together

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14
Q

What is spatial summation?

A

The process where local potentials occur close together spatially, allowing their effects to combine

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15
Q

At resting membrane potential (RMP), what is the state of the activation and inactivation gates of voltage-gated Na+ channels?

A

Activation gate closed, inactivation gate open

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16
Q

What occurs during depolarization to threshold?

A

Activation gates of voltage-gated Na+ channels open, allowing Na+ to flow into the cell

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17
Q

Describe the rapid depolarization phase of an action potential.

A

Na+ flows into the cell, causing a rapid increase in membrane potential to +30mV

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18
Q

What happens during the inactivation phase of voltage-gated Na+ channels?

A

The inactivation gate closes, preventing further Na+ flow into the cell

19
Q

What initiates the repolarization phase of an action potential?

A

Opening of voltage-gated K+ channels, allowing K+ to leave the cell

20
Q

What causes hyperpolarization during an action potential?

A

Efflux of K+ as voltage-gated K+ channels close slowly

21
Q

What is the role of myelination in action potential propagation?

A

Myelin acts as insulation, preventing ion movement across the membrane except at Nodes of Ranvier, speeding up signal propagation

22
Q

What is the function of Nodes of Ranvier?

A

Gaps in the myelin sheath that contain concentrated numbers of voltage-gated Na+ and K+ channels, facilitating rapid regeneration of action potentials

23
Q

What is the unidirectional flow of information in synaptic transmission?

A

The flow of information is from the presynaptic neuron to the postsynaptic neuron

24
Q

What is the role of calcium ions (Ca2+) in synaptic transmission?

A

Ca2+ influx triggers the release of neurotransmitters from synaptic vesicles into the synaptic cleft

25
What happens to neurotransmitters after they bind to receptors on the postsynaptic membrane?
They cause local potentials, such as EPSPs or IPSPs, depending on the type of neurotransmitter
26
How is synaptic transmission turned off?
Neurotransmitters are removed from the synaptic cleft, often by enzymatic breakdown or reuptake
27
What enzyme breaks down acetylcholine (ACh) in the synaptic cleft?
Acetylcholinesterase (AChE)
28
What happens to choline after ACh is broken down?
Choline is taken back up by the presynaptic terminal and recycled to produce new ACh
29
What are the main types of synaptic potentials?
* Excitatory Post-Synaptic Potentials (EPSPs) * Inhibitory Post-Synaptic Potentials (IPSPs)
30
What is the threshold potential needed to trigger an action potential?
-60mV at the axon hillock
31
What is the primary neurotransmitter involved in cholinergic synapses?
Acetylcholine (ACh)
32
Which type of synapse uses GABA as a neurotransmitter?
Inhibitory synapses
33
What is the effect of EPSPs on the postsynaptic neuron?
They can bring the neuron to threshold, initiating an action potential if sufficient in number
34
What is the effect of IPSPs on the postsynaptic neuron?
They move the membrane potential further from threshold, preventing action potential firing
35
What is the significance of action potential propagation in unmyelinated axons?
Each segment of the axon must generate an action potential, leading to slower propagation speed
36
What is the significance of action potential propagation in myelinated axons?
Action potentials jump from node to node, increasing conduction speed due to reduced ion leakage
37
The site of initiation of the action potential is the:
C) Initial segment ## Footnote The initial segment of the axon is where the action potential is generated.
38
Which of the following statements regarding action potentials is NOT true?
D) A large stimulus may initiate an action potential during the absolute refractory period ## Footnote During the absolute refractory period, no action potential can be initiated regardless of stimulus size.
39
At a typical nerve-nerve chemical synapse, an action potential in a presynaptic neuron commonly results in a:
A) post synaptic action potential ## Footnote Presynaptic action potentials typically lead to the release of neurotransmitters that can generate postsynaptic action potentials.
40
What causes neurotransmitter release at a synapse?
D) Entry of Ca2+ into the presynaptic terminal ## Footnote The influx of calcium ions triggers the release of neurotransmitters from synaptic vesicles.
41
True or False: EPSPs and IPSPs normally arise at different times.
False ## Footnote EPSPs (excitatory postsynaptic potentials) and IPSPs (inhibitory postsynaptic potentials) can occur simultaneously and affect the postsynaptic neuron.
42
Fill in the blank: Myelin _______ the speed of action potential conductance.
increases ## Footnote Myelin acts as an insulator on axons, facilitating faster signal transmission.
43
The repolarization phase of the action potential is due to _______ exiting from the axon.
potassium ## Footnote The outflow of potassium ions helps restore the resting membrane potential after depolarization.
44
Action potentials normally propagate in only one _______.
direction ## Footnote This unidirectional flow is due to the refractory periods of the axon segments.