Synaptic transmission

Question 1

Where do electrical synapses occur?

Answer 1

Gap junctions

Question 2

How many connexins form a connexon?

Answer 2

6

Question 3

How many connexons form a gap junction?

Answer 3

2

Question 4

What does PSP stand for?

Answer 4

Post synaptic potential

A PSP is formed when current flows in through a gap junction.

Question 5

Active zones

Answer 5

Pyramid like protein accumulations on the presynaptic side of the membrane.

Question 6

Postsynaptic density

Answer 6

Proteins accumulated under the postsynaptic membrane

Question 7

Axodendritic

Answer 7

A synapse that is attached to the dendrite of the postsynaptic cell

Question 8

Axoaxonic

Answer 8

A synapse attached to the axon of the postsynaptic cell

Question 9

Axosomatic

Answer 9

A synapse attached to the soma of a postsynaptic cell

Question 10

Dendrodentric

Answer 10

A synapse formed between two dendrites

Question 11

What are two types of synapses?

Answer 11

Gray’s type 1 and type 2. Type 1 are typically excitatory and 2 inhibitory.

Question 12

synaptic vesicles

Answer 12

vesicles containing neurotransmitters in chemical synapses

Question 13

What are the main types of neurotransmitters?

Answer 13

amino acids, peptides, amines

Question 14

What are the amino acids used in fast synaptic transmission?

Answer 14

glutamate(GLU), gamma-aminobutyric (GABA), glycine (Gly). The amine acetylcholine (Ach) mediates fast synaptic transmission

Question 15

Exocytosis

Answer 15

Is the process of releasing neurotransmitters from vesicles inside the cell to the synaptic cleft. Exocytosis is triggered by Ca2+ inflow into the cell through voltage gated calcium channels.

Question 16

Excitatory post synaptic potential

Answer 16

A transient postsynaptic membrane depolarization caused by presynaptic release of neurotransmitter

Question 17

inhibitory postsynaptic potential

Answer 17

A transient hyperpolarization of the postsynaptic membrane potential caused by the presynaptic release of neurotransmitter

Question 18

Autoreceptors

Answer 18

Presynaptic receptors that are sensitive to the neurotransmitters released by the presynaptic terminal

Question 19

Neuropharmacology

Answer 19

the study of the effect of drugs on nervous system tissue

Question 20

What are the two types of EPSP summation?

Answer 20

Spatial and temporal

Question 21

voltage-gated calcium channel

Answer 21

a channel on the presynaptic membrane which opens as the result of a depolarization. It enables ca2+ ions to flow into the cell from the synaptic cleft.

Question 22

What are secretory granules?

Answer 22

Large synaptic vesicles about 100nm in diameter.

Question 23

How wide is the synaptic cleft?

Answer 23

20-50nm

Question 24

What are the different types of chemical synapses?

Answer 24

Axodendritic (postsynaptic membrane on the dendrite), axosomatic (on the soma), axoaxonic.

Question 25

What are the three categories of neurotransmitters?

Answer 25

Amino acids, amines, peptides

Question 26

How is the post synaptic potential formed?

Answer 26

Neurotransmitters bind to ion channels near the synaptic cleft which causes an ion influx.

Question 27

What modulation of EPSP's?

Answer 27

The modification of the effectiveness of the EPSPs

Question 28

Describe the gap junction channel.

Answer 28

The gap junction channel allows ions to pass directly from the cytoplasm of one cell to the cytoplasm of the other. The pore of most gap junction channels is relatively large, about 1-2 nm in diameter, big enough for all the major cellular ions and many small organic molecules to pass through.

Question 29

What are asymmetrical (or Gray's type I) synapses? What are symmetrical (or Gray's type II) synapses?

Answer 29

Asymmetrical, Gray's type 1 are synapses in which the membrane differentiation on the postsynaptic side is thicker than that on the presynaptic side. These are often excitatory synapses. Symmetrical Gray's type 2 synapses are synapses in which the membrane differentatiation are of similar thickness on the post- and presynaptic sides. There are often inhibitory.

Question 30

What is a neuromuscular junction?

Answer 30

Chemical syanpses that occur between the axons of motor neurons of the spinal cord and skeletal muscle. It has many of the structural features of the chemical syanpses in the CNS.

Question 31

What is a motor endplate?

Answer 31

The postsynaptic membrane at a muscular junction.

Question 32

What are some of the properties of amino acid and amine neurotransmitters?

Answer 32

They are all small organic molecules containing at least one nitrogen atom, and they are stored in and released from synaptic vesicles.

Question 33

What happens after the amino acids and amine neurotransmitters are synthesized in the axon terminal?

Answer 33

They must be taken up by the synaptic vesicles. Concentrating the neurotransmitters inside the vesicle is the job of transportes, special proteins embeded in the vesicle membrane.

Question 34

What mechanisms are used to synthesize and store peptides in secretory granules?

Answer 34

Peptides are formed when amino acids are strung together by the ribosomes of the cell body. In the case of peptide neurotransmitters, it happens in the rough endoplasmic reticulum. Generally, a long peptide synthesized in the rough ER is split in the Golgi apparatus, and one of the smaller peptide fragments is the active neurotransmitter. Secretory granules containing the peptide neurotransmitter bud off from the Golgi apparatus and are carried to the axon terminal by axoplasmic transport.

Question 35

What is exocytosis? Describe the process of exocytosis.

Answer 35

Exocytosis is the release of neurotransmitters from the synaptic vesicles. The membrane of the synaptic vesicle fuses to the presynaptic membrane at the active zone, allowing the contents of the vesicle to spill out into the synaptic cleft. Exocytosis can occur very rapidly, within 0.2 msec of the Ca2+ influx into the terminal in a squid. Synapses in mammals are even faster. Ca2+ enters the active zone precisely where synaptic vesicles are ready and waiting to release their contents.

Question 36

What two classes of receptors are neurotransmitter receptors classified into?

Answer 36

Transmitter-gated ion channels and G-protein-coupled receptors.

Question 37

When are transmitter-gated ion channels excitatory and when are they inhibitory?

Answer 37

They are excitatory when they are permeable to Na+ -> this depolarizes the postsynaptic cell, and brings it toward the threshold for generating action potentials. They are inhibitory when they are permeable to Cl-, since they hyperpolarize the postsynaptic cell -> bring it away from the action potential threshold.

Question 38

What are second messengers and metabotropic receptors?

Answer 38

Second messengers = Molecules that diffuse away in the cytosol. Metabotropic receptors = G-protein-coupled receptors, since they can trigger widespread metabolic effects.

Question 39

What are inhibitors and receptor agonists/antagonists in neuropharmacology?

Answer 39

Inhibitors = Drugs that inhibit the normal function of specific proteins in synaptic transmission. Receptor antagonists = Inhibitors of neurotransmitter receptors: they block (antagonize) the normal action of the transmitter. Receptor agonists = Drugs that mimic the actions of the naturally occurring neurotransmitter.