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BI211 > Action Potentials > Flashcards

Action Potentials Flashcards

1
Q

If an ion flows down a concentration gradient through a channel, what kind of transport is this?

A

Mediated diffusion

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2
Q

If you place a cell in a concentrated Mg solution, what will happen?

A

The cell volume will decrease (Mg is non pentrarint

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3
Q

Neuron

A

a single nerve cell
Can only send one type of signal in one direction
send electrical signals within the cell, and NT to signal between cells

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4
Q

Nerve

A

a collection of axons outside the brain/spinal cord

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5
Q

General overview of neuron communication

A

Dendrites ad the cell body receive information/stimuli.
They transmit an electrical signal along the axon
The electrical signal reachers the end of the axon
This triggers the release of a chemical neurotransmitter
The neurotransmitter then communicates with a neighboring cell

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6
Q

Afferent neuron

A

brings sensory information in

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7
Q

Efferent neuron

A

Tells muscles what to do

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8
Q

What compromises the CNS

A

spinal cord and brain

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9
Q

Microtubules

A

transport neurotransmitter to the axon terminal of the neuron

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10
Q

dynein

A

protein that moves NT from the axon terminal back to the cell body

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11
Q

kinesin

A

protein that moves NT to the synaptic terminal from the cell body

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12
Q

Resting membrane potential

A

Always more negative INSIDE than outside
In non-excitable cells=-5mV
in Excitable cells=-70mV

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13
Q

What kinds of cells are excitable?

A

only neurons and muscle cells

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14
Q

Why is the inside of a membrane negative?

A

Ion, but a large part is negatively charged proteins inside the cell

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15
Q

Na/K Pump

A 
Active transport of ions
3Na out
2K in
1ATP used
results in a build up of + ions outside the cell- the cell is polarized and at disequilibrium.
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16
Q

If a cell is at -70mV and the Na channels open, which way does Na go?

A

Into the cell

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17
Q

At rest, what where is there more Na? K? + charge?

A

There is more Na outside the cell
There is more K inside the cell
There is overall more + charge outside the cell

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18
Q

When is an ion said to be at equilibrium potential?

A

When the electrical gradient is equal and opposite the chemical gradient

19
Q

What is the equiibrium potential for K?

A

-90mV

20
Q

What is the equilibrium potential of Na?

A

+60mV

21
Q

Will a cell ever be in equilibrium for both Na and K?

A

No, since EP for K is -90, and EP for Na is +60. Since it can never be both of these, ions are always in flux.

22
Q

Action Potential

A

an impulse or signal transmitted along the membrane of an excitable cell by a transient change in the membrane potential. The cell will have an influx of + ions and become temporarily more + inside than outside.

23
Q

All or None law

A

sn individual neuron either fires or doesnt. If the stimulus doesnt depolarize the membrane to threshold, no action potential will occur

24
Q

What is threshold for an action potential?

A

-55mV

25
Q

Mechanically gated ion channels

A

are found in sensory neurons, open in response to stretch of the membrane

26
Q

chemically gated ion channels

A

open in response to ligand binding to a receptor. Channels open, +ions flow in, if enough flow in then they will trigger voltage gated ions to open

27
Q

voltage gated ion channels

A

open in response to a change in voltage away from RMP. Specifically, they will open at -55mV. + ions will then rush into the cell, and it will rapidly depolarize to +30mC

28
Q

Which types of channels start action potentials by creating small, local depolarizing events?

A

Mechanically gated and chemically cgated ion channels

29
Q

Which type of channel causes a massive depolarization of the membrarne?

A

Voltage gated ion channels, will open when the membrane voltage reaches -55mV

30
Q

What are some ways of making a graded potential into an action potential?

A
  • Leave NT in the synapse for a long time, which will lead to repeated binding and opening of chemically gated channels
  • Fire AP of the presynaptic neuron over and over again, continuing to release NT over and over again
  • Have more than one presynaptic neuron release NT into the synapse
31
Q

What gradients are present in a neuron?

A

There is more Na outside the cell, and more K inside the cell.

32
Q

What Equilibrium potentials are relevent for action potentials?

A

Na will want to flow until the cell is at +60mV

K will want to flow until the cell is at -90mV

33
Q

How do local anesthetics like lidocaine and novocaine work?

A

They block voltage gated ion channels
Pain receptors have numerous graded potentials i response to tissue damage, but no action potential will be reached, so the message of pain will not go to the brain.

34
Q

Why do Na channels have inactivation gates?

A

because they have a positive feedback loop and can not resolve it on its own, while K has a negative feedback

35
Q

refractory period

A

The period between action potentials where no action potential can be fired

36
Q

Absolute refractory period

A

all voltage gated Na channels are either already open or inactivated. This means no more Na channels can open and the action potential can not occur.

37
Q

relative refractory period

A

some voltage gated Na channels have returned to resting, but some are still inactivated. K channels may still be open, and the cell may be hyperpolarized. The AP could occur, it the stimulus was greater than normal

38
Q

continual conduction

A

for unmylenated cells, the axon must be covered in Na/K pumps and voltage gated channels to maintain the signal (otherwise the leakage willl degrade the signal over distance)

39
Q

What tyypes of cells are in the nervous system?

A

Neurons and Glial cells

40
Q

Schwann cells

A

Glial cells that modify their plasma membranes to wrap axons, these insulate and prevent leakage.

41
Q

Nodes of Ranvier

A

spaces between Schwann cells where pumps and channels still exist

42
Q

Saltatory conduction

A

channels only exist at the nodes of ranvier, so the signal “jumps” from node-to node.

43
Q

demyelination

A

removal of the myelin sheath/ the death of schwann cells

44
Q

Multiple sclerosis

A

Immune attack of myelin sheath and killing of schwann cells
Is an autoimmune disease
sporadic/periodic attacks (flare ups)

BI211 (11 decks)

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