Synaptic Transmissions

Question 1

Major difference between chemical and electrical synapses

Answer 1

In a chemical synapse, the nerve impulse is transmitted chemically via neurotransmitters, whereas in an electrical synapse, the nerve impulse is transmitted electrically via channel proteins.

Question 2

How does communication occur in an electrical synapse?

Answer 2

Communication occurs via the (fast), passive flow of current through gap junctions.

Question 3

How does communication occur in a chemical synapse?

Answer 3

Presynaptic neurons produce secondary current flow in postsynaptic neurons via the slow release of neurotransmitters

Question 4

Gap Junction

Answer 4

specialized membrane channels that connect two cells at electrical synapses?

Question 5

An important characteristic of electrical synpases

Answer 5

They are bidirectional; current can flow in either direction of the gap junction

Question 6

Connexin

Answer 6

Assembly of six proteins that form the pore for a gap junction

Question 7

Explain how electrical synapses allow synchronization of electrical activity in hippocampal interneurons

Answer 7

In a pair of interneurons connected by electrical synapses, generation of an action potential in one neuron often results in the synchronized firing of an action potential in another neuron

Question 8

Describe the process of how neurons receive glucose

Answer 8

1) Glucose has to be transported across the BBB by a very specific system of proteins
2) Taken up by astrocytes (a type of gilal cell) which distribute glucose over wide distances and supply glucose to neurons

Question 9

Gilal Cells

Answer 9

Play an active role in regulating synaptic transmission and important for cognitive processes

Question 10

Correctly order the sequence of events involved in transmission at a typical chemical synapse, beginning with neurotransmitter synthesis and ending with membrane recycling.

Answer 10

a) Transmitter is synthesized and then stored in vesicles
b) An action potential invades the presynaptic terminal.
c) Depolarization of presynaptic terminal causes opening of voltage-gated Ca²⁺ channels.
d) Influx of Ca²⁺ through channels.
e) Influx of Ca²⁺ through channels.
f) Transmitter is released into synaptic cleft via exocytosis.
g) Transmitter binds to receptor molecules in postsynaptic membrane.
h) Opening or closing of postsynaptic channels.
i)Postsynaptic current causes excitatory or inhibitory postsynaptic potential that changes the excitability of the postsynaptic cell.
j) Removal of neurotransmitter by glial uptake or enzymatic degradation.
k)Retrieval of vesicular membrane from plasma membrane.

Question 11

What did loewi’s experiment discover?

Answer 11

Discovered that there are molecules that allow chemical transmission

Question 12

Correctly order the sequence of events involved in the metabolism of small-molecule transmitters.

Answer 12

a) Synthesis of enzymes
b) Slow axonal transport
c) Synthesis of neurotransmitter
d) Release and diffusion of neurotransmitters
e) Transport of precursor into terminal

Question 13

Correctly order the sequence of events involved in the metabolism of peptide transmitters.

Answer 13

a) Synthesis of neurotransmitter precursors and enzymes
b) Fast axonal transport
c)Enzymes modify precursors to produce peptide
d) Neurotransmitter diffuses away and is degraded by proteolytic enzymes

Question 14

Where does the synthesis of small-molecule neurotransmitters take place? What about the enzymes needed to synthesize these transmitters?

Answer 14

Presynaptic terminal; cell body of a neuron

Question 15

Where does the synthesis of peptide transmitters take place? What about the enzymes needed to synthesize these transmitters?

Answer 15

Cell body; cell body

Question 16

What type of transmitters are released in response to low-frequency activity?

Answer 16

small molecules

Question 17

What type of transmitters are released in response to high-frequency activity?

Answer 17

neuropeptides

Question 18

What three criteria define a neurotransmitter?

Answer 18

(1) Presence in the presynaptic terminal, (2) Release at the synaptic cleft, (3) Presence of postsynaptic receptors

Question 19

Agonists vs. Antagonists

Answer 19

Agonists are substances that bind to synaptic receptors and increase the effect of the neurotransmitter. Antagonists also bind to synaptic receptors but they decrease the effect of the neurotransmitter

Question 20

What type of chemical synapse is formed by the contact between a motor neuron and a muscle fiber?

Answer 20

Neuromuscular Junction

Question 21

End Plate Potential

Answer 21

change in electrical property of the muscle cell

Question 22

Miniature End Plate Potential

Answer 22

Spontaneous changes in muscle cell membrane potential occur even in the absence of stimulation from the presynaptic motor neuron

Question 23

What was the purpose of stimulating the presynaptic terminal with a train of action potentials?

Answer 23

activate endocytosis of HRP

Question 24

What does the fusion of synaptic vesicles cause?

Answer 24

New membranes to be added to the plasma membrane of the pre-synaptic terminal

Question 25

Synaptic vesicle cycle

Answer 25

Process that describes the retrieval of vesicular membrane where it eventually is used to make new synaptic vesicles?

Question 26

What special endocytotic organelles was HRP found in immediately following stimulation?

Answer 26

Coated pits and vesicles

Question 27

What intracellular organelle was HRP found in ~5 minutes following stimulation?

Answer 27

Endosome

Question 28

What intracellular compartment was HRP found in ~ 1 hour following stimulation?

Answer 28

Synaptic vesicle

Question 29

Correctly order the sequence of events involved in exocytosis during neurotransmitter release.

Answer 29

1)Vesicle docks.
2) SNARE complexes form to pull membranes together.
3) Entering Ca²⁺ binds to synaptotagmin.
4) Ca²⁺-bound synaptotagmin catalyzes membrane fusion by binding to SNAREs and the plasma membrane.

Question 30

What are the two different types of neurotransmitter receptor?

Answer 30

Ligand-gated ion channels (ionotropic receptors), G-protein-coupled receptors (metabotropic receptors)

Question 31

Ligand Gate Channel

Answer 31

Involve the direct opening of ion channels with the binding of a neurotransmitter,

Question 32

G-coupled Protein Receptors

Answer 32

Involved in the indirect binding of ion channels with metabolic activation of G-protein