Action Potential

Question 1

of cell types in the CNS

Answer 1

80-100 billion neurons in the adult brain

Question 2

Each neuron connects to about how many others

Answer 2

1000-thus 100 trillion connections

Question 3

Neurons function

Answer 3

Transmission, storage, and processing of info; communicate mainly via chemical synapses

Question 4

Glia

Answer 4

supporting cells, now known to be involved in processing and signaling

Question 5

Astrocytes

Answer 5

Supply nutrients, buffer substances (pH), communicate, insulation, form CNS scarring

Question 6

Damage repair of brain

Answer 6

Astrocytes

Question 7

Oligodendrocytes

Answer 7

Form myelin sheaths around axons in the CNS

Question 8

Microglia

Answer 8

Macrophage system of CNS

Question 9

Ependymal cells

Answer 9

line ventricles (fluid filled)

Question 10

Gray matter

Answer 10

neuron and glial cell bodies

Question 11

White matter

Answer 11

myelinated axons

Question 12

Soma

Answer 12

Cell body

Question 13

Dendrites

Answer 13

Receive signals to the body

Question 14

dendritic spine

Answer 14

Form synapses/connections-mushroom shaped

Question 15

Axon hillock

Answer 15

important in signaling

Question 16

Axon lenght

Answer 16

very long-can be myelinated too

Question 17

Axon terminal

Answer 17

Vesicles filled with NTs to be sent to the next neuron in the chain

Question 18

Impulse conduction main two categores

Answer 18

graded

Question 19

graded potentials

Answer 19

local changes-change in Amplitude based on distance from the signal

Nearby –> strong effect
Far –> weaker effect (smaller Amplitude)

Question 20

Max distance graded potentials and go and how they move

Answer 20

transduction of these is passive, and can go a max of 5mm

Question 21

Variable Amplitude

Answer 21

Of passive conduction-goes down with distance

Question 22

Action potentials

Answer 22

a way to send a signal very long distances (30ft in a whale :P) without having it decline

ALL OR NOTHING PHENOMONUM`

Question 23

Which cells do APs happen in

Answer 23

Cells which are excitable (neurons, muscles, heart)

Question 24

Threshold potential

Answer 24

Membrane potential at which you would fire an action potential. happens when the sodium conductance is greater than the potassium conduction.

Question 25

Active propagation-

Answer 25

Energy to keep the action potential going is stored along the axon. -Like rows of dominoes.

Potential energy energy stored in dominoes and you are tipping them over and they will keep going.

Energy far from the site is the same as the energy close to the site. AMPLITUDE IS CONSTANT OVER THE DISTANCE!

Question 26

How is action potential energy stored

Answer 26

as resting membrane potential

Question 27

Na+ channel opens when

Answer 27

if the threshold is reached they open –> membrane highly depolarizes

Question 28

Inactivation of Na+ channel? How long?

Answer 28

Seperate from channel opening.

It is like a
flap at the end of the channel and prevents sodium from moving even if channel is open.

Have to reset
it so that it can be activated again. aka REPOLARIZE TO OPEN Open rapidly.

Question 29

K+ delated rectifier-what does that mean

Answer 29

They open slow and close slow (stay open longer)

Question 30

Rate at which Na and K channels open

Answer 30

Na open fast and close fast

Question 31

Resting membrane level is at

Answer 31

-60mV

Question 32

Threshold of AP

Answer 32

All or nothing-Starts here! Sodium is greater than K conductance here

Question 33

Rising phase

Answer 33

Na Channels opening and depolarized up to zero

Question 34

Overshoot

Answer 34

After 0 the potential becomes hyperpolarized to near +25mV

Question 35

Period of Repolarization

Answer 35

K channels open and Na channels inactivate

Question 36

Peak

Answer 36

Na channels maximally opened (not all are open but the most than can be at once are)

Question 37

After hyperpolarization

Answer 37

K conductance returns to the point of normal leak rate

Question 38

Gk vs Gk at rest

Answer 38

gK > Gk at rest

Question 39

What happens to stop depolarization

Answer 39

inactivation flap closes

Question 40

Refractory period

Answer 40

Axon is resistant to firing another action potential, right after one has been fired. Need time to rest

Question 41

Absolute Refractory period

Answer 41

Cannot fire another action potential-system has to reset first and the Na channel is inactive

Question 42

Relative refractory period

Answer 42

Threshold here is higher than at rest-still high levels of K conductance –> threshold you need to reach is more +++ and the amplitude will be less

Question 43

A wave of what follows the action potential (behind it)

Answer 43

in unmyelinated axons—passive depolarization which is very fast and said to be in refractory- this keeps the action potential propagating in one direction.

Question 44

Passive depolarization happens in which kind of neurons

Answer 44

myelinated

Question 45

How AP is propagated in a myelinated axon

Answer 45

oligodendrocytes will insulate more of the cell membrane (CNS)

Question 46

what myelinates axons in the PNS

Answer 46

Schwann cells

Question 47

Nodes of Ranvier

Answer 47

interruptions of myelin on the myelinated axon which the AP jumps across (Saltatory conduction)–high Na channel concentration here

Question 48

Concentration of Na channels at nodes of ranvier

Answer 48

high concentration Na channels here

Question 49

At the nodes what kind of conduction happens?

Answer 49

Passive, thus passive is very fast

Question 50

Myelinated axons conduction V

Answer 50

225mph

Question 51

Unmyelinated axons conduction V

Answer 51

225mph

Question 52

Effect of axon size on speed of conduction

Answer 52

larger the axon the faster it is—–want large myelinated axons