03b: The Synapse (Pre/Post)

Question 1

Electrical synapse formed by (X).

Answer 1

X = gap junctions (connexins)

Question 2

(Chemical/electrical) synapses are directional.

Answer 2

Chemical

Question 3

You’d find synaptic delay in (chem/electrical) synapse.

Answer 3

Chemical

Question 4

(Chem/electrical) synapses are more amenable to modulation by controlling factors. Why?

Answer 4

Chemical; multiple biochem steps involved

Question 5

In order to cause muscle response to nerve stimulation, Ca has to be applied where and when?

Answer 5

In immediate vicinity of synaptic region, just before the arrival of AP

Question 6

T/F: NT release from pre-synaptic terminal can occur without AP if Ca is present intracellularly.

Answer 6

True

Question 7

Ca is ideal for role of internal messenger because its (intra/extra)cellular concentration is at such (high/low) values at rest.

Answer 7

Intracellular;

Low

Question 8

T/F: Each MEPP represents response of muscle to single ACh molecule.

Answer 8

False - reponse to quantum of NT

Question 9

EPP are usually (X) times (smaller/larger) than MEPP.

Answer 9

X = 2-3 (or n) times larger

Question 10

(X) proteins are implicated in control of exocytosis.

Answer 10

X = SNARE

Question 11

Synapsin function

Answer 11

Tethers vesicles to cytoskeletal structures

Question 12

Synaptotagmin function

Answer 12

Sensese elevation of Ca and triggers formation of fusion pore

Question 13

Botulinum toxin function

Answer 13

Inhibits transmitter release via proteolysis of SNARE proteins

Question 14

List three mechanisms of NT removal from synaptic cleft.

Answer 14

1. Degradation by enzymes
2. Diffusion away from cleft
3. Reuptake by transporters (use Na gradient)

Question 15

List the types of post-synaptic receptors.

Answer 15

1. Ionotropic

2. Metabotropic

Question 16

T/F: Ionotropic receptor is itself an ionic channel.

Answer 16

True

Question 17

T/F: The machinery that converts electrical impulse to chemical signal and back is all confined to synaptic region.

Answer 17

True

Question 18

The “reversal potential” at NMJ occurs when (product/sum/difference) of (X) equals (Y). What is the value of this potential?

Answer 18

Sum;
X = currents of K and Na
Y = 0

-15 mV

Question 19

NMJ ratio of permeability for ACh-induced current.

Answer 19

Na/K = 1.25

Question 20

NMJ: At potentials more negative than reversal potential, current is (positive/negative), which means net flow of (X) is directed (inward/outward).

Answer 20

Negative;
X = positively-charged ions
Inward

Question 21

At NMJ, the reversal potential is more (positive/negative) than resting potential. Thus, response is (de/hyper)-polarization and synapse is (excitatory/inhibitory).

Answer 21

Positive; depolarization; excitatory (EPSP)

Question 22

By definition, an IPSP response drives the (X) away from (Y) potential.

Answer 22

X = membrane potential;
Y = threshold

Question 23

T/F: Inhibitory synapse can achieve its effect without evoking visible change in membrane voltage.

Answer 23

True - stabilizes membrane at/near resting potential

Question 24

Explain the (EPSP/IPSP) provoked by GABA.

Answer 24

IPSP;

Increases Cl-selective conductance, “clamping” membrane potential around E(Cl), which is at the resting potential

Question 25

T/F: Each CNS bouton produces a very small post-synaptic response.

Answer 25

True