CBG 31

Question 1

where is action potential initiated in neuron?

Answer 1

spike initiation/ near axon hollcock

Question 2

neuroglial cells?

Answer 2

modulating the rate of nerve signal propagation, modulating synaptic action by controlling the uptake of neurotransmitters, providing a scaffold for some aspects of neural development. Also recovery help

Question 3

what is the mylein sheath an outgrowth of?

Answer 3

type of glial cell

Question 4

schwann cells

Answer 4

Supply the myelin for the peripheral nervous system.

Question 5

what do dendrites receive?

Answer 5

presynaptic terminal signals and dendrites determine if action potential arises

Question 6

what is multiple sclerosis?

Answer 6

loss of co ordinated muscle activity due to myelin sheath loss

Question 7

are there voltage gated ion channels along myelinated fibers?

Answer 7

NO. Myelinated fibers lack voltage-gated ion channels (approximately 25 μm/m2) along the myelinated internodes, exposing them only at the nodes of Ranvier.

Question 8

is it easier for vertebrates to repair neurones than low vertebrates such as salamanders?

Answer 8

no. vice-versa

Question 9

what carries information?

Answer 9

electrical action potentials alternating with chemical synaptic signals

Question 10

what are relay neurones also known as?

Answer 10

interneurones

Question 11

what are examples of external and internal stimuli?

Answer 11

light and limb position

Question 12

soma?

Answer 12

cell body of neurones

Question 13

where is neurotransmitter secretion?

Answer 13

axon terminals

Question 14

what are 2 main effector organs?

Answer 14

muscles (contraction)

Glands (secretion)

Question 15

what needs to be recahed for an action potential to be generated?

Answer 15

threshold potential

Question 16

depolarisation?

Answer 16

more positive, inward current of Na+

Question 17

what channels are always open at rest?

Answer 17

leaky potassium K+ out

Question 18

are there 2 types of potassium channels?

Answer 18

yes leaky and voltage-gated that open in response to depolarisation

Question 19

what is reploarizing?

Answer 19

membrane potential is rapidly returning to the resting potential, activation of voltage gated potassium channels are at max and number of open Na+ channels is dramatically reduced

Question 20

what is the repolaristation beyong the resting membrane voltage called?

Answer 20

hyperpolariastion. occurs because most v-g potassium channels are still open.

Question 21

what happens during the recovery phase?

Answer 21

membrane potential returns to steady state and occurs as the delayed voltage gated potassium channels that were opened during the action potential now close. Membrane potential is determined by other channels normally open at resting potential

Question 22

what is the threshold?

Answer 22

-40mV = activation

Question 23

conductance?

Answer 23

how much charge is generated

Question 24

is it positive or negative feedback in neurones?

Answer 24

POSITIVE.usually i biological systems this is a negative thing but here it is advantageous as allows system to work as quickly as possible

if threshold reached,Na+ channels open, Na+ enters, bigger membrane depolarisation.

Positive feedback of Na+ entry

Question 25

Vm

Answer 25

voltage of membrane

Question 26

ENa

Answer 26

equilibrium of Na so +40

Question 27

Erev

Answer 27

resting voltage of membrane -70

Question 28

Ek

Answer 28

equlibrium of potassium | -100

Question 29

ECl

Answer 29

equilib Cl -60

Question 30

what are gNa and gK ?

Answer 30

gNa and gK are both functions of time and membrane potential.

Question 31

when gNa is hig hwhat does the membrane potential approach?

Answer 31

Na equilibrium of +40

Question 32

what 3 things define things as voltage gated ion channels?

Answer 32

sensitive to membrane voltage selective to ions inactivation

Question 33

what 4 different classes of VGIC can you name?

Answer 33

Na+,K+,Ca2+,Cl-

Question 34

what are vgic made up of domain wise? which one is modulatory?

Answer 34

several Beta subunits VGSCB involved in modulatory roles Alpha subunit VGSCa 4 transmembrane domain 240 kda and family of 9 gene products in vertebrates Nav1.1,Nav1.9 expressed in variety of cell types-cardiac muscle, neurones (Brain and PNS), skeletal muscle, smooth muscle). (ii) Called Nav1.1, Nav1.2 etc

Question 35

where are alphas subunits thought to be arranged around?

Answer 35

central pole

Question 36

where is the voltage sensor thought to be?

Answer 36

segment 4

Question 37

how are Voltage-gated Na+ and Ca2+ channels similar

Answer 37

both are composed of alpha-subunits containing four-transmembrane domains (I-IV) each domain with six transmembrane segments. -several smaller proteins associated with the a-subunit (beta-subunits only for Na+ channels) whilst Ca2+ channels have b, g, and d subunits).

Question 38

how many nm across is the lipid bilayer?

Answer 38

5NM

Question 39

how many v per cm for a 50mV pd?

Answer 39

100,00V per cm

Question 40

what direction does AP travel in?

Answer 40

left to right

Question 41

why is transmission unidirectional?

Answer 41

a patch of newly depolarized membrane cannot initially be reactivated

Question 42

what amino acids are in segment 4?

Answer 42

Positively charged amino acids (arginine + lysine)

Question 43

how does the

Answer 43

The action potential generated at the axon hillock propagates as a wave along the axon.The currents flowing inwards at a point on the axon during an action potential spread out along the axon, and depolarize the adjacent sections of its membrane. If sufficiently strong, this depolarization provokes an action potential at the neighboring membrane patches. Once an action potential has occurred at a patch of membrane, the membrane patch needs time to recover( refractory period - time required for the voltage-activated sodium channels to recover from inactivation). There are many types of voltage-activated potassium channels in neurons, some of them inactivate fast and some of them inactivate slowly or don't. Variability guarantees that there will be always an available source of current for repolarization, even if some of the potassium channels are inactivated. However all activated sodium channels inactivate within several millisecond during strong depolarization, thus making following depolarization impossible until a substantial fraction of sodium channels have returned to their closed state. Although it limits the frequency of firing,the absolute refractory period ensures that the action potential moves in only one direction along an axon.The currents flowing in due to an action potential spread out in both directions along the axon.

Question 44

what is antidromic conduction?

Answer 44

opposite way of conduction. Very rare. However, if a laboratory axon is stimulated in its middle, both halves of the axon are "fresh", i.e., unfired; then two action potentials will be generated, one traveling towards the axon hillock and the other traveling towards the synaptic knobs.