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Neuroscience 1 Section 2 > Chapter 3 #2 > Flashcards

Chapter 3 #2 Flashcards

0
Q

What is the cause of action potential?

A

The sudden movement of sodium ions into the cell

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1
Q

Voltage gated Na+ channel

A

A Na+ selective channel that opens or closes in response to changes in the voltage of the local membrane potential.

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2
Q

Refractory

A

Temporarily unresponsive or inactivated

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3
Q

Absolute refractory phase

A

A brief period of complete insensitivity to a second stimulus righty after action potential has been produced

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4
Q

Relative refractory phase

A

Period of reduced sensitivity during which only strong stimulation produces an action potential, immediately follows the absolute refractory phase

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5
Q

What determines a neurons maximal rate of firing?

A

The overall duration of refractory phase

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6
Q

What are the 3 properties of the voltage gated Na+ channel that make it responsible for the characteristics of the action potential?

A
  1. Monitoring the axons polarity
  2. At threshold the channel changes shape to open and closes again a millisecond later
  3. Remembers it was just open and refuses to open again for a short time
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7
Q

How does the action potential travel along the axon?

A

Begins at the axon hillock. The action potential is spike of depolarizing electrical activity that in turn depolarizes the adjacent axon segment covered in voltage gated Na+ channels which creates a new action potential and this continues down the axon.

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8
Q

Why is the action potential propagated primarily in only one direction?

A

Because the cell body and dendrites are covered in far fewer voltage gated Na+ channels so they can’t produce action potential and the refractory period

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9
Q

Conduction velocity

A

The speed at which an action potential is propagated along the length of an axon

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10
Q

What variables affects the conduction velocity?

A

Axon diameter. Larger axons can propagate action potential faster. As well as amount of myelin

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11
Q

How fast can neural conduction be done?

A

Over 300 miles per hour. Not the speed of light.

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12
Q

Saltatory conduction

A

The form of conduction that is characteristic of myelinated axons, in which the action potential jumps from one node of Ranvier to the next.

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13
Q

What advantage do vertebrates have over invertebrates?

A

Myelinated axons that have much faster neural conduction

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14
Q

Effects of multiple sclerosis

A

Interference with action potential conduction by destruction if myelin

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15
Q

Post synaptic potentials

A

Brief changes in membrane potential of the post synaptic cell in response to neurotransmitters

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16
Q

What’s the difference between an excitatory and an inhibitory synapse?

A

Excitatory brings the post synaptic membrane closer to firing an action potential while an inhibitory lowers the potential away from threshold

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17
Q

Excitatory postsynaptic potential (EPSP)

A

A depolarizing potential in the postsynaptic neuron that is cause by excitatory presynaptic potentials. EPSP’s increase the probability that the postsynaptic neuron will fire an action potential

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18
Q

Synaptic delay

A

The brief delay between the arrival of an action potential at the axon terminal and the creation of a post synaptic potential. About a half a millisecond.

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19
Q

What is accounted for during the synaptic delay?

A

Neurotransmitter is released, diffuse across the synaptic cleft, and affect the postsynaptic cell.

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20
Q

Inhibitory postsynaptic potential (IPSP)

A

A hyper polarizing potential in the postsynaptic neuron that is caused by inhibitory connections. IPSP’s decrease the probability that the postsynaptic neuron will fire an action potential.

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21
Q

Chloride ions (Cl-)

A

A chlorine atom that carries a negative charge because it has gained one electron

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22
Q

What do IPSP’s usually result from?

A

Opening of channels that permit chloride ions to rush into the cell making the membrane potential more negative.

23
Q

What determines whether a synapse excites or inhibits the presynaptic cell?

A

Which neurotransmitter is being released, some inhibit some excite. So whether a neuron fires an action potential is decided by the balance between excitatory and inhibitory signals that it receives.

24
Q

Where is the trigger zone for action potentials?

A

Axon hillock

25
Q

EPSP’s - IPSP’s = ?

A

The net affect. Calculated to decide whether membrane has reached threshold for firing an action potential.

26
Q

Spatial summation

A

The summation of postsynaptic potentials that reach the axon hillock from different locations across the cell body. If this summation reaches threshold, an action potential is triggered.

27
Q

Does distance from the triggering zone matter?

A

Yes. Postsynaptic potentials spread passively and dissipate over the cell membrane.

28
Q

Temporal summation

A

Summation of postsynaptic potentials that reach the axon hillock at different times. The closer in time the potentials occur, the more complete the summation is.

29
Q

How do dendrites effect membrane potential and summation?

A

Expand receptive surface of neuron increase input. The further out on a dendrite the potential occurs, the less affect it will have at the hillock

30
Q

What is the function if the axon hillock?

A

Moment to moment to integration of all the neurons inputs and encodes into action potentials

31
Q

Synaptic vesicles

A

Small structures that contains molecules of neurotransmitter.

32
Q

What happens when an action potential reaches a presynaptic terminal?

A

Hundreds if synaptic vesicles to fuse with presynaptic membrane and six barge their molecules into the synaptic cleft

33
Q

Calcium ion (Ca2+)

A

A calcium atom that carries a double positive charge because it has lost 2 electrons

34
Q

What is the key event in this first part of synaptic transmission?

A

An influx if calcium ions into the axon terminal through a voltage gated channel in response to the arrival of an action potential.

35
Q

What regulates the rate if neurotransmitter creation?

A

Enzymes manufactured in the neuronal cell body and transported actively down the axon to the terminals

36
Q

Ligand

A

“Key” to receptor proteins. Must be correct shape to fit and activate or block it.

37
Q

Acetylcholine (ACh)

A

A neurotransmitter that is produced and released by parasympathetic postganglionic neurons, by motoneurons, and by neurons throughout the brain.

38
Q

Neurotransmitter receptor

A

A protein that captures and reacts to molecules of a neurotransmitter or hormone.

39
Q

What are the chemicals that block ACh receptors?

A

Curare and bungarotixin

40
Q

Curare

A

A neurotoxin that causes paralysis by blocking ACh receptors in muscle. (S. American hunt)

41
Q

Bungarotoxin

A

A neurotoxin, isolated from the venom of the banded krait (snake), that selectively block ACh.

42
Q

Agonist

A

A molecule, usually a drug (nicotine), that binds a receptor molecule and initiates a response like that of another molecule, usually a neurotransmitter.

43
Q

Antagonist

A

A molecule, usually a drug (curare), that interferes with or prevents the action of the neurotransmitter.

44
Q

Cholinergic

A

Refers to cells that use acetylcholine as their synaptic transmitter

45
Q

How many subtypes of Cholinergic receptors does ACh act on?

A

4

46
Q

What are the 2 processes that bring transmitter effects to a prompt halt?

A

Degradation and reuptake

47
Q

Degradation

A

Chemical breakdown of a neurotransmitter into inactive metabolites by special enzymes

48
Q

Acetylcholinesterase (AChaE)

A

Enzyme that inactivates ACh by breaking into parts that are recycled to make more ACh in the axon terminal.

49
Q

Reuptake

A

Process by which released synaptic transmitter molecules are taken up and reused by the presynaptic neuron, thus stopping synaptic activity

50
Q

Transporter

A

Specialized receptor in the presynaptic membrane that recognizes transmitter molecules and returns them to the presynaptic neuron for reuse

51
Q

Axo-dendritic synapse

A

A presynaptic axon terminal synapses onto a dendrite of the post synaptic neuron, either via a dendritic spine or directly onto the dendrite itself

52
Q

Axo-somatic synapse

A

A presynaptic axon terminal synapses onto the cell body of the post synaptic neuron

53
Q

Axo-axonic synapse

A

A presynaptic axon terminal synapses onto the axon terminal of another neuron. Allows the presynaptic neuron to strongly facilitate or inhibit activity of the postsynaptic axon.

54
Q

Dendro-dendritic synapse

A

A synapse at which a synaptic connection forms between the dendrites of 2 neurons. Allows coordination of their activities.

Neuroscience 1 Section 2 (5 decks)

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