Mcb 80 - Lecture 8 Quiz Quest.

Front 1

List three things that can happen to a released neurotransmitter besides binding to a neurotransmitter receptor

Back 1

Degraded in the intercellular space; uptaken by glial cells and degraded; uptaken by presynaptic neuron

Front 2

List three different ways to functionally classify synapses

Back 2

Neurotransmitters that activate them; agonists that activate them; antagonists that activate them

Front 3

What is alpha bungarotoxin and what does it do?

Back 3

Decreases quantal size and therefore response to transmitter

Front 4

Where precisely are AChRs localized on muscle fibers?

Back 4

Aligned with nerve terminal

Front 5

Briefly describe the structure of an AChR

Back 5

Made of 5 subunits; 2 identical alphas, a beta, gamma, and an delta; ACh binds to each alpha-subunit; each unit has 4 membrane-spanning domains (M1-M4); M2 lines the pore

Front 6

What is the main structural similarity of a GABA channel and an AChR channel?

Back 6

5 subunits

Front 7

What is the main difference?

Back 7

AChR has 2 alpha, beta, gamma, delta; GABA has alpha, beta, gamma, delta, and p

Front 8

Briefly describe what a patch clamp is.

Back 8

Entails sealing the tip of an electrode to a very small patch of neuraonl membrane. Can be torn away from the neuron and the ionic currents across it can be measured as the membrane potential is clamped at any value the experimenter selects

Front 9

List three attributes of AChR channel openings that can be concluded from patch clamping membranes that contain AChRs

Back 9

1. They open with little delay
2. They stay open for about 1 msec and then close
3. They cannot be opened again by depolarization until the membrane potential returns to a negative value near threshold

Front 10

What is a reversal potential? What ions are responsible for the reversal potential at neuromuscular synapses?

Back 10

The critical value of membrane potential at which the direction of current flow reverses. Na+ and K+.

Front 11

List 5 differences between the channels associated with action potentials and those associated with neuromuscular transmission

Back 11

- AP Channels require 2 channels (Na+ and K+), whereas AChR needs only 1 channel
- AP is voltage-gated; AChR channel is ligand-gated
- AP: gNa+ then gK+; AChR: simultaneous g’s
- AP channels inhibited by TTX; AChR channels inhibited by alpha-BTX
- APs have some channelpathies; AChR have myasthenia gravis

Front 12

Define desensitization.

Back 12

If AChR or other LGIC is open for long time (such as too much neurotransmitter) then the channel closes analogous to Na inactivation in VGIC

Front 13

How does succinyl choline affect neuromuscular transmission and why is it useful?

Back 13

Not cleaved easily by AChE so causes desensitization; used as a muscle relaxant in surgery

Front 14

Name the main excitatory neurotransmitter in the brain and list its four main receptor types

Back 14

Acetylcholine; agonist: nicotine on nictonic and muscarine on muscarinic; antagonist: curare on nicotinic and atropine on muscarinic

Front 15

Name the main inhibitory neurotransmitters and where they are found in the nervous system. What ionic conductance do they affect?

Back 15

GABA/Glycine; GABA is in the brain; Glycine is in the brainstem and spinal cord; affect conductance for chloride

Front 16

What is meant by “shunting” when talking about synaptic inhibition?

Back 16

Cl- influx counterbalances Na+ influx of excitatory synapses; prevents current from flowing from the some to the axon hillock

Front 17

Why does a low dose of strychnine poisoning resemble the genetic disease hyperekplexia?

Back 17

Strychnine blocks glycine receptors; so resembles hyperekplexia, because lack of inhibition causes exaggerated startle response in situations of distress