Action Potentials

Question 1

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

Answer 1

Mediated diffusion

Question 2

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

Answer 2

The cell volume will decrease (Mg is non pentrarint

Question 3

Neuron

Answer 3

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

Question 4

Nerve

Answer 4

a collection of axons outside the brain/spinal cord

Question 5

General overview of neuron communication

Answer 5

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

Question 6

Afferent neuron

Answer 6

brings sensory information in

Question 7

Efferent neuron

Answer 7

Tells muscles what to do

Question 8

What compromises the CNS

Answer 8

spinal cord and brain

Question 9

Microtubules

Answer 9

transport neurotransmitter to the axon terminal of the neuron

Question 10

dynein

Answer 10

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

Question 11

kinesin

Answer 11

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

Question 12

Resting membrane potential

Answer 12

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

Question 13

What kinds of cells are excitable?

Answer 13

only neurons and muscle cells

Question 14

Why is the inside of a membrane negative?

Answer 14

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

Question 15

Na/K Pump

Answer 15

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.

Question 16

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

Answer 16

Into the cell

Question 17

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

Answer 17

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

Question 18

When is an ion said to be at equilibrium potential?

Answer 18

When the electrical gradient is equal and opposite the chemical gradient

Question 19

What is the equiibrium potential for K?

Answer 19

-90mV

Question 20

What is the equilibrium potential of Na?

Answer 20

+60mV

Question 21

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

Answer 21

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.

Question 22

Action Potential

Answer 22

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.

Question 23

All or None law

Answer 23

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

Question 24

What is threshold for an action potential?

Answer 24

-55mV

Question 25

Mechanically gated ion channels

Answer 25

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

Question 26

chemically gated ion channels

Answer 26

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

Question 27

voltage gated ion channels

Answer 27

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

Question 28

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

Answer 28

Mechanically gated and chemically cgated ion channels

Question 29

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

Answer 29

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

Question 30

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

Answer 30

- 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

Question 31

What gradients are present in a neuron?

Answer 31

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

Question 32

What Equilibrium potentials are relevent for action potentials?

Answer 32

Na will want to flow until the cell is at +60mV | K will want to flow until the cell is at -90mV

Question 33

How do local anesthetics like lidocaine and novocaine work?

Answer 33

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.

Question 34

Why do Na channels have inactivation gates?

Answer 34

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

Question 35

refractory period

Answer 35

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

Question 36

Absolute refractory period

Answer 36

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.

Question 37

relative refractory period

Answer 37

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

Question 38

continual conduction

Answer 38

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)

Question 39

What tyypes of cells are in the nervous system?

Answer 39

Neurons and Glial cells

Question 40

Schwann cells

Answer 40

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

Question 41

Nodes of Ranvier

Answer 41

spaces between Schwann cells where pumps and channels still exist

Question 42

Saltatory conduction

Answer 42

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

Question 43

demyelination

Answer 43

removal of the myelin sheath/ the death of schwann cells

Question 44

Multiple sclerosis

Answer 44

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