Action potentials

Question 1

role of graded potentials?

Answer 1

integrate incoming inputs at a local area. info comes from diff parts of nervous system

Question 2

role of action potential?

Answer 2

used for communication. all or nothing

Question 3

T/F if threshold is reached communication does not occur?

Answer 3

False, communication does not occur if threshold is not reached in graded potential

Question 4

Local synaptic potentials occur at synapse. caused by what?

Answer 4

chemical agent that opens chemically gated channels

Question 5

what is the response of synaptic potential if both potassium and sodium channels open?

Answer 5

excitatory

Question 6

What type of potentials are generator potentials?

Answer 6

mechanically gated

Question 7

what happens at an electronic potential

Answer 7

opens electric voltage gated channels in response to current change

Question 8

how is size related to strength of local potential?

Answer 8

larger size larger stimulus strength

Question 9

where are local potentials generated?

Answer 9

axon hillock

Question 10

what is spatial summation?

Answer 10

same time different location on dendrite

Question 11

what is temporal summation?

Answer 11

same location different times

Question 12

where is an action potential initiated?

Answer 12

axon hillock then propagated down axon

Question 13

what is the RMP?

Answer 13

-65

Question 14

what is the voltage in order to reach threshold?

Answer 14

-55

Question 15

what occurs during depolarization phase?

Answer 15

sodium channels open membrane potential becomes more positive

Question 16

what happens after the peak of an action potential?

Answer 16

sodium channels close, potassium channels open

Question 17

why does hyperpolarization occur??

Answer 17

gated potassium channels are open as well as already high permeability of potassium so it will polarize below RMP

Question 18

what is an absolute refractory period?

Answer 18

start of an action potential when the sodium channels are open, a second AP cannot be stimulated

Question 19

what is a relative refractory period?

Answer 19

hyperpolarization phase when potential is lower than resting so it takes an even bigger AP to trigger a reaction

Question 20

during an action potential why is homeostasis not affected?

Answer 20

astrocytes buffer away extra potassium leaving the cell, sodium potassium pump removes sodium from inside the cell

Question 21

where are the most sodium channels located?

Answer 21

at axon hillock and nodes of ranvier

Question 22

where are the most potassium channels located?

Answer 22

along unmyelinated neurons, under the myelin

Question 23

where are the most calcium channels?

Answer 23

dendrites, soma, terminal site of an axon

Question 24

where are the more chloride channels?

Answer 24

dendrites and soma

Question 25

does strength of action potential decrease along the axon?

Answer 25

no, the strength stays the same

Question 26

calculate the conduction velocity given diameter of unmyelinated? myelinated?

Answer 26

Velocity = diameter (.5) | diameter (5.5)

Question 27

T/F myelinated axons do not have an after hyperpolarization

Answer 27

True

Question 28

if the membrane potential remains depolarized above threshold, another action potential can not be stimulated. T/F

Answer 28

true

Question 29

Explain why someone suffering from MS can sometimes recover? (CNS)

Answer 29

with demyelination more potassium will leave the cell than normal, in order to create an action potential there needs to be more sodium channels to balance. over time there is a migration of electrically gated sodium channels. neuron will take on the appearance of unmyelinated nerve

Question 30

how is recovery possible for people with Guillian Barre syndrome (PNS)?

Answer 30

In PNS schwann cells can replace the myelin

Question 31

what is the time course difference between Guillian Barre syndrome and MS?

Answer 31

MS gets worse over time with periods of remission. Barre is an acute one time event

Question 32

what is the incidence rate of MS?

Answer 32

60 to 100 / 100,000 people

Question 33

typical age onset of MS?

Answer 33

20-40

Question 34

if a neuron dies can it be replaced?

Answer 34

No, mature neurons withdraw from division cycle

Question 35

what occurs in a neuron after a neuronal trauma?

Answer 35

the axon is severed, distal segment degenerates. Glial cells come in and remove degenerated parts, astrocytes remove incoming inputs

Question 36

what happens in PNS neuron if trauma occurs?

Answer 36

schwann cells will increase and form a pathway. neurons will regenerate and send branches to replace the damaged segment. the neuron will return to normal with smalled diameter

Question 37

what kind of transport is used in PNS neuronal damage reparation?

Answer 37

slow anterograde transport. 3mm/day