Overview

Question 1

What are the two basic forms of synaptic transmission?

Answer 1

Electrical and Chemical

Question 2

During excitatory synaptic transmission at an electrical synapse, what effect do voltage-gated ion channels in the presynaptic cell have on the postsynaptic cell?

Answer 2

The voltage-gated ion channels in the presynaptic cell generate a current that depolarizes the postsynaptic cell.

Question 3

What are gap-junction channels?

Answer 3

Specialized protein structures that conduct ionic current from the presynaptic to the postsynaptic cell

Question 4

What is the role of hemichannels?

Answer 4

The role of hemichannels is to form a continuous bridge that provides a direct communication path between two cells

Question 5

How many connexins are in each hemichannel?

Answer 5

6

Question 6

What is the intracellular structure of connexin sub-units that span the cell membrane?

Answer 6

An intracellular N- and C-terminus with four interposed alpha-helixes

Question 7

What are the two chemical changes which trigger most gap-junction channels to close?

Answer 7

Lowered cytoplasmic pH or elevated cytoplasmic Ca2+

Question 8

What is a neurotransmitter?

Answer 8

A neurotransmitter is a chemical substance that binds receptors in the postsynaptic membrane of the target cell.

Question 9

What are active zones?

Answer 9

Synaptic vesicles which are clustered at specialized regions of the presynaptic membrane

Question 10

What is the process of a presynaptic action potential?

Answer 10

Voltage-gated Ca2+ channels at the active zone open, allowing Ca2+ to enter the presynaptic terminal

Question 11

What does a rise in intracellular Ca2+ concentration trigger?

Answer 11

A rise in intracellular Ca2+ concentration triggers a biochemical reaction that causes the vesicles to fuse with the presynaptic membrane and release neurotransmitter into the synaptic cleft, a process termed exocytosis.

Question 12

What are the effects of a rise in intracellular Ca2+ concentration on the activity of transmitter molecules?

Answer 12

After a rise in intracellular Ca2+ concentration, the transmitter molecules diffuse across the synaptic cleft and bind their receptors on the postsynaptic cell membrane. This in turn activates the receptors, leading to the opening or closing of ion channels

Question 13

What is the main functional difference between ionotropic receptors and metabotropic receptors?

Answer 13

Ionotropic receptors produce fast synaptic action lasting only milliseconds, which metabolic receptors produce slow synaptic actions lasting seconds to minutes