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PHGY 209 RME > nerve/synapse 1-3 > Flashcards

nerve/synapse 1-3 Flashcards

1
Q

Who is the founder of modern neuroanatomy?

A

Santiago Ramoon y Cajal

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2
Q

How many neurons does the nervous system comprise?

A

Around 100 billion neurons

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3
Q

The 2 fundamental properties of neurons

A

-Neurons are electric cells
-Neurons communicate each other

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4
Q

What differentiates the 2 fundamental properties of neurons from the basic units of the rest of the body systems?

A

Complexity and number of neurons

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5
Q

Why is it that computers are faster than the brain but still less competent?

A

Amount of connections possible in the brain

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6
Q

Despite their morphological diversity, what characteristic structures do neurons share?

A

Cell body (soma)
Dendrites antons (receive info)
Axon cables (sending info to other neurons)

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7
Q

Why are dendrites so extensive & numerous?

A

Large amount of surface to allow neuron to make many synapses (receive info)

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8
Q

What is the general direction of information through neurons?

A

From dendrites
Through cell body
To axones

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9
Q

What are the electrical properties of neurons?

A

-resting membrane potential
-action potential

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10
Q

What is a voltage?

A

Measure of electrical potential energy
*measure of electric pressure
*E needed to move a unit charge from a reference point to a specific point against an electric field

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11
Q

What is the difference in electrical potential energy inside and outside a typical neuron?

A

0,7 volts

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12
Q

What determines resting membrane potential? equilibrium potential

A

small excess of negatively charged ions inside the cell:

-Concentration gradients
-Relative permeability
*equilibrium potential for K+ (EK)

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13
Q

How are sodium & potassium gradients maintained?

A

Sodium-potassium pump

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14
Q

How does the sodium-potassium pump maintain gradients?

A

Uses the energy of hydrolysis of ATP in ADP to pump 3 sodium out for every 2 potassium in

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15
Q

To which ion is the membrane permeable at rest?

A

Potassium ion (K+)

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16
Q

What causes the resting permeability to K+?

A

Leak channels
proteins that form selective pores

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17
Q

What does the resting permeability to K+ allow?

A

K+ leak out of the cell down their concentration gradient

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18
Q

How is the electrical (electrostatic) gradient created?

A

-K+ leak out of the cell, leaving negatively charged ions (impermeant)
-This accumulation of unpaired negative ions inside the cell creates electrical gradient that tends to pull K+ ions back into the cell

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19
Q

What does the Nernst equation describe?

A

The membrane potential at equilibrium
chemical gradient = electrical gradient

20
Q

Chemical gradient VS Electrical gradient
at resting membrane potential

A

Chemical gradient : K+ concentration gradient Electrical gradient: K+ attracted by Anions

21
Q

True or false?
The inside of the neurone has more negative ions then the outside

A

True
The inside of the neuron has more negative ions then the outside but it is a significantly small amount and therefore can sometimes be disregarded

22
Q

Why isn’t the voltage difference (Erest) across the membrane at rest -90mV?

A

The membrane is not exclusievly permeable to K+ (occasional leaks of Na+) therefore Erest=-70mV

*If membrane were Ek would be of -90mV

23
Q

How do neurons communicate with each other?

A

With the action potentials

24
Q

Define an Action potential

A

Brief electrical impulses

25
Q

What is the usual trajectory of the action potentials?

A

APs usually start at the initial segment of the axon an propagate down the length of the axon to the presynaptic terminals

26
Q

How long is the depolarizing spike (AP) take to move down the axon?

A

Within 1 milisecond

27
Q

At the action potential peak, which ions potential does the membrane approach?

A

Ena : Sodium electrical potential

28
Q

When is the AP initiated?

A

When the membrane depolarizes to a threshold level

29
Q

What is the value of the threshold level?

A

-50mV

30
Q

What properties determine the threshold level?

A

Properties of of ion channels in the axon membrane

31
Q

Which class of ion channels has an important role on the threshold level?

A

Voltage-gated sodium channels

32
Q

Hyperpolarize VS Depolarize

A

Hyperpolarize: make axon more negative than at rest

Depolarize: make the axon more positive than at rest

33
Q

True or false
Voltage-gated sodium channels < Na+/K+ pump in axon membrane

A

False
Voltage-gated sodium channels > Na+/K+ pump

*Voltage-gated sodium channels : mostly around axon
*Na+/K+ pump: all over neuron

34
Q

What causes the rising phase of the AP (depolarization)

A

Sodium ions flowing into the cell through voltage gated sodium channels

35
Q

Name the 3 critical properties of voltage gated sodium channels

A

1) They are closed at the resting membrane
potential, but open when the membrane depolarizes 2) They are selective for Na+
3) The open channel rapidly inactivates, stopping the flow of Na+ ions

36
Q

Is the rising phase of the AP a positive or negative feedback?

A

Positive feedback (regenerative process)
*the more the membrane depolarizes the more voltage gated sodium channels open

37
Q

What contributes to the falling phase of the AP?

A

-Sodium channel inactivation that terminates the sodium influx

-K+ ions flow back out through K+ leak channels & voltage gated K+ channels

38
Q

What contributes to the rapid falling phase of the AP?

A

Delayed activation of voltage gated K+ channels

39
Q

Na+ VS K+ current at depolarization

A

Na+ current increases
K+ current decreases

40
Q

Na+ VS K+ current at refractory period

A

Na+ current decreases
K+ current increases

41
Q

Why does the Na+ permeability flood the resting permeability for K+?

A

Density of voltage-gated sodium channels > Na+/K+ pump in axon membrane

42
Q

Where are found voltage-gated potassium channels?

A

On the axons

43
Q

When do voltage gated potassium & sodium channels open?

A

When the membrane depolarizes

44
Q

Why would we want the AP to be as short as possible?

A

A single neuron can send multiple AP in a short period of time

45
Q

Why doesn’t AP backtrack in the neuron?

A

Sodium channel rapid inactivation

46
Q

What is the only way for voltage-gated sodium channels to open?

A

Membrane goes back to -70mV

47
Q

How long does it take for membrane to be excitable?

A

It takes a few milliseconds for voltage-gated sodium channels to open

PHGY 209 RME (11 decks)

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