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Psych 115 > Midterm 1 - Neurotransmission > Flashcards

Midterm 1 - Neurotransmission Flashcards

1
Q

Membrane Potential

A

Electrical charge across a membrane. The difference between the inside and the outside.

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2
Q

Resting Potential

A

The membrane potential when the axon is neither being excited nor inhibited.

  • 70 mV
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3
Q

Depolarization

A
  • Towards 0
  • A rise in the membrane potential from the normal resting potential.
  • EPSP
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4
Q

Hyperpolarization

A
  • In the negative direction
  • A decrease in the membrane potential relative to the resting potential.
  • IPSP
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5
Q

Action Potential

A

A brief electrical impulse that’s responsible for the conduction of information down an axon.

AKA, “spike,” “the neuron fires”

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6
Q

Critical Firing Level

A
  • The threshold of excitation.
  • The value of the membrane potential that must be reached in order to produce an action potential.
  • Change = +15 mV (-55 mV)
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7
Q

Where Do EPSPs and IPSPs Occur?

A

Dendrite

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8
Q

How long is an AP?

A

1 mSec

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9
Q

Summation

A

When 2 EPSPs build on each other.

2 Types.

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10
Q

2 Types of Summation

A
  1. Temporal - Same neuron sends a signal 2x in a row in a very short time period.
  2. Spatial - When 2 different neurons send a NT to a neuron at about the same time.
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11
Q

Does Summation Apply to IPSPs?

A

NO.

2 IPSPs building on each other don’t yield a reverse spike - the most that happens is that the membrane potential just drops to a certain level and stays there.

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12
Q

Concentrations of Ions In and Out of Cell At Rest

A
  • More sodium (Na+) outside than inside
  • More potassium (K+) inside than outside
  • More chloride (Cl-) outside than inside
  • More calcium (Ca2+) outside than inside
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13
Q

Resting Membrane Potential

(Visual)

A
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14
Q

Action Potential Graph

A
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15
Q

Driving Forces on an Ion

(2)

A
  1. Diffusional Force - An ion will want to go from an area of high concentration to an area of low concentration.
  2. Electrostatic Force - Opposites attract.
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16
Q

Which Ion Has The Largest Driving Force Acting On It?

A

Na+

(Both diffusional and electrostatic forces want to push it inside)

17
Q

Driving Force on Cl- inside Cell?

A

Because it’s negative, it wants to leave the cell to go to the positive environment (electrostatic force)

18
Q

Driving Force on K+ inside Cell

A

Because K+ is in high concentration on the inside, the diffusional force wants to push it out of the cell.

19
Q

Driving Force on Na+ Inside Cell

A

Na+ is happy where it is b/c the inside of the cell is negative and it’s positive.

20
Q

Driving Force on Cl- Outside of Cell

A

Diffusional force wants to push inside because it is in higher concentration outside.

21
Q

Driving force on K+ Outside Cell?

A

Electrostatic force wants to push it in to a negative environment because it’s positive (opposites attract).

22
Q

Diffusional Force on Sodium Outside The Cell?

A

Both the diffusional force and the electrostatic force want to push Na+ into the cell b/c

  • There is less concentration of it inside the cell (diffusional force)
  • It is positive and is attracted to a negative environment (electrostatic force)
23
Q

Equilibrium Potential

&

Equation

A

At some point, an ion will reach a balance where the driving force is zero (the diffusional and electrostatic forces are balanced).

Nernst Equation (need to know concentration of ion inside and outside of cell)

E(Na+) = +45 mV

E(K+) = - 80 mV

24
Q

Driving Force on Na+?

A
  • -70 at rest
  • EP = +40
  • Therefore, 110 mV of driving force on Na+ (diffusional + electrostatic)

Na+ will rush in until the diffusional and electrostatic forces balance (driving force = 0). Once its EP is reached, Na+ channels will close.

***All the K+ will leave the cell until it reaches it’s equilibrium potential of -80mV.

25
Q

Permeability of Membrane to K+ vs Na+

A
  • Very permeable to K+ (leak channels), therefore resting membrane potential is closer to K+ equilibrium potential
  • Whereas the membrane is not permeable to Na+ unless the ion channels are open.
26
Q

Na+, K+ Pump

A

Carries 3 Na+ out for every 2 K+ back in

Ensures that Na+ remains in greatest concentration in extracellular fluid despite both the forces of diffusion and electrostatic pressure.

27
Q

All-or-None Law

A
  • An action potential is always the same value (e.g., +45).
  • It either fires or it doesn’t.
  • The only thing that changes is the frequency of firing.
28
Q

Rate Law

A
  • An action potential can vary in frequency
  • Ex. The difference between a small pain and a big pain is the frequency with which a neuron fires.
29
Q

Where do neurons synapse?

A

Dendritic Spine

30
Q

How Is A Message Conveyed From The Dendrite Down the Axon?

A
  • If there are more EPSPs than IPSPs at the initial segment/axon hillock, there will be an AP and the neuron will fire.
  • As AP sweeps down axon and if at NOR the critical firing level is reached, the spike will happen again (nothing happens in the internode space).
  • At the end, there are Ca2+ voltage gated channels and if they open, the NT will be released.

NOT Saltatory Conduction but rather a WAVE OF DEPOLARIZATION. Na+ will leak out as goes along but so long as the charge is +15mV at NOR, the AP will be re-propagated.

31
Q

Speed of Neurocommunication

A

Avg. = 120 meters/second

32
Q

What travels faster to brain: Messages About Temperature or Messages About Pain?

A

Temperature.

Pain fibers are small and unmyelinated, whereas temperature axons are myelinated and wider around.

33
Q

To Make An Axon Faster …

A
  1. Myelinate (provides insulation, AKA decreases resistance)
  2. Make axon giant (the larger it is around, the less resistance = more current)
34
Q

Ohm’s Law

A

Cable Properties

  • Speed of transmission down an axon.
  • Decrease resistance by insulating with myelin and making axon bigger
  • Voltage = Current (Amps) x Resistance (Ohm)
35
Q

Multiple Sclerosis

A

Disease of demyelination. Because myelin is lost, there’s a loss of voltage and a lack of re-propagation at the subsequent NOR.

36
Q

Picture of Forces and Concentrations of Ions Inside and Outside of Cell @ Rest

A

Psych 115 (12 decks)

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