Electrical Neuro Communication

Question 1

hyperpolarization

Answer 1

increasing negativity of membrane potential (more neg inside cell than out)

Question 2

depolarization

Answer 2

decreases membrane potential
- less negative on inside of cell

triggers action potential

Question 3

Excitatory (EPSP)

Answer 3

positive ions enter the cell and produce depolarization
- helps get cell closer to action potential threshold

Question 4

Inhibitory (IPSP)

Answer 4

negative ions enter cell and produce hyperpolarization
- cells get further from reaching AP threshold

Question 5

How does depolarization lead to AP

Answer 5

at rest, activation gate is closed; ions don’t flow through

when depolarization reaches threshold, sodium (Na+) ions flow in through the open gate
- when another threshold is hit, they close again

Question 6

Are Na+ channels located all over the cell?

Answer 6

No, they are concentrated at points where AP will be initiated (axon hillock and along axon)

Question 7

Refractory period (and types)

Answer 7

when another AP cannot occur

• absolute refractory period
• relative refractory period

Question 8

Absolute refractory period

Answer 8

another AP cannot occur no matter how large stimulus is bc Na+ channels are closed

Question 9

relative refractory period

Answer 9

stronger stimulus needed to cause AP bc K+ efflux hyperpolarizes neuron

Question 10

what is the significance of a refractory period?

Answer 10

since it can’t generate another AP for a period of time, the signal is one way

Question 11

Action Potential Characteristics

Answer 11

APs are regenerated along the axon

• each adjacent section is depolarized and new AP occurs

-size and shape are the same regardless of where it is generated along the neuron

• all or nothing property
• AP is coded by frequency not shape

Question 12

what keeps communication btw neurons efficient and fast?

Answer 12

• myelin sheath: helps keep depolarization straight through node of ronvier
• nodes of Ronvier: small gaps in myelin sheath; don’t have to regenerate AP along each section of axon, only at nodes

Question 13

Saltatory Conduction

Answer 13

axon potential travels inside axon and regenerates from node to node

Question 14

How does diameter of axon affect action potential?

Answer 14

larger diameter axon has faster conductance bc of less resistance

• slowest propagation of AP are from unmyelinated, small diameter axons

Question 15

Otto Loewi’s Key Experiment

Answer 15

• vagus nerve was stimulated in heart 1
• heart 2 was stimulated by solution transferred from heart 1
• provided evidence that there was more than electrical info being transmitted (chemical signaling)

Question 16

Synaptic Transmission

Answer 16

neurotransmitter transmitted from presynaptic to postsynaptic

Question 17

Synaptic Transmission sequence

Answer 17

1. AP gets to axon terminal
2. change in voltage opens voltage-gated Ca2+ channels and Ca2+ ion enter
3. Ca2+ ions go into channel and cue vesicle to fuse with membrane and release NT into synapse
4. NT binds to postsynaptic receptor in postsynaptic membrane which opens ion channels
5. ion flows create EPSP or IPSP in postsynaptic neuron

Question 18

Exocytosis

Answer 18

the process by which cells move materials from within the cell into the extracellular fluid.
occurs when a vesicle fuses with the plasma membrane, allowing its contents to be released outside the cell

Question 19

SNARES

Answer 19

proteins that mediate the neurotransmitter release of synaptic vesicles in neurons

Question 20

V-SNARES vs T-SNARES

Answer 20

v on vesicles
t on target membrane

Question 21

ionotropic receptors

Answer 21

ligand gated ion channels
- direct alteration to ion channels

Question 22

metabotropic receptors

Answer 22

indirect method of communication
indirect alteration of ion channels

Question 23

why might it be useful to have 2 diff types of receptors

Answer 23

metabotropic: helps have more control and allows amplification or tweak signal (allow sustained gradient)

ionotropic: quicker and consistent signaling

Question 24

up-regulation

Answer 24

increased number of receptors

Question 25

down-regulation

Answer 25

decreases number of receptors

Question 26

docking

Answer 26

v-SNAREs and t-SNAREs attach -> trans-SNARE complx

Question 27

what is Ca2+ influx effect on SNAREs

Answer 27

triggers zippering of SNAREs to drive bilayer fusion

Question 28

How does botox work?

Answer 28

botulinum toxin cuts SNAREs

Question 29

How do strong stimulus get expressed?

Answer 29

more frequency

a stronger stimulus -> more Ca2+ channels are open -> more NT are released

Question 30

Post-synaptic receptors

Answer 30

• recognize NT
• alter ion channels in postsynaptic membrane