Chapter 7 Lecture Slides

Question 1

why don’t neurons divide?

Answer 1

they lack centrioles, plus new neurons don’t do any good

Question 2

what is the formation of new neurons called?

Answer 2

neurongenesis

Question 3

what is neurongenesis?

Answer 3

formation of new neurons

Question 4

how would you define AP ?

Answer 4

action potential.

a brief change in Vm from (-) to (+)

Question 5

what might a person find in the presynaptic terminal?

Answer 5

lots of mitochondria and vesicles

Question 6

what is the function of dendrites? (2)

Answer 6

1. increase surface area of a neuron
2. provide contact points for neuron to neuron communication

Question 7

what determines the shape of dendritic spines?

Answer 7

shapes correlates with NT receptor density

Question 8

which three pumps are always working in a neuron?

Answer 8

Na+
K+
Na+/K+ ATPases

Question 9

how is neuronal excitation initiated?

Answer 9

opening gated cation channels

Question 10

membrane potential always refers to the voltage inside or outside of a cell?

Answer 10

inside

Question 11

ion influx in post synaptic ligand gated ion channels is __________ as when voltage-gated ion channels open

Answer 11

not as great

Question 12

what happens at +30mV in a voltage-gated Na+ channel?

Answer 12

inactivation gate undergoes a conformational change and gets inserted into the channel

Question 13

inactivation gate has a _____ for the channel and _____ the channel opening

Answer 13

high affinity

blocks

Question 14

what is a “refractive state” ?

Answer 14

inactivation gate blocks the channel opening, Na+ channel cannot be re-opened under this condition

Question 15

what’s the reason for the refractory period during an AP?

Answer 15

1. unidirectional propagation of action potential
2. sets maximum AP frequency

Question 16

what type of stimulus causes depolarization?

Answer 16

excitatory

Question 17

what does an excitatory stimulus cause?

Answer 17

depolarization

Question 18

what does an inhibitory stimulus cause?

Answer 18

hyperpolarization

Question 19

hyperpolarization is caused by?

Answer 19

inhibitory stimulus

Question 20

what happens to Vm in depolarization?

Answer 20

inside becomes less negative, moves towards positive

Question 21

what happens to Vm in hyperpolarization?

Answer 21

inside becomes more negative, harder to depolarize

Question 22

what is resting potential in neurons?

Answer 22

-70 mV

Question 23

what is threshold in neurons?

Answer 23

-55 mV

Question 24

what causes absolute refractory period?

Answer 24

inactivation gate blocks the channel

Question 25

when does relative refractory period occur?

Answer 25

during the delay in the voltage-gated K+ closing

Question 26

how to override relative refractory period?

Answer 26

large graded potential

Question 27

why does a strong stimulus release lots of NT onto the postsynaptic membrane?

Answer 27

ATPases can’t pump out excess Na+ fast enough

so, excess NA+ is still present while K+ is exiting

excess Na+ counters the loss of K+ that occurs from the delay in closing voltage gated K+ channels

this prevents hyperpolarization, so the neuron resets to resting Vm and the next AP can fire

Question 28

why is flow rate faster through a larger conduit?

Answer 28

more space to move around, laminar vs. turbulent

Question 29

why doesn’t depolarization continue to the left in an AP?

Question 30

do APs jump? what happens instead?

Answer 30

NO! flipping from (-) to (+) is completed more rapidly at myelinated regions