Synaptic Transmission

Question 1

What are the four primary regions of a neuron?

Answer 1

Dendrites, cell soma, axon (covered with a myelin sheath), synaptic terminals

Question 2

In a neuron, what is the primary area for receiving and integrating complex information?

Answer 2

dendrites

Question 3

What is the name for the region where the axon emerges from cell body?

Answer 3

axon hillox

Question 4

What is the function of the presynaptic terminal?

Answer 4

convert electrical signal that was propagated down the axon into chemical signals (neurotransmitter

Question 5

Describe postsynaptic potentials?

Answer 5

small graded changes

Question 6

What does the axoplasm contain?

Answer 6

parallel arrays of microtubules and neurofilaments that give stability and means of transport

Question 7

Which direction does kinesin move?

Answer 7

Anterograde (from cell body to presynaptic terminal)

Question 8

Which direction does dynein move?

Answer 8

Retrograde (from presynaptic terminal to cell body)

Question 9

Describe the speed and directionality of electrical synapses?

Answer 9

Extremely fast and usually bidirectional

Question 10

How are electrical synapses transmitted?

Answer 10

Allow direct passive flow of electrotonic current between cells by gap junctions

Question 11

What are gap junctions composed of?

Answer 11

6 connexins form connexons. Then 2 connexons in adjacent cells form a hemi- channel which results in a gap junction

Question 12

Benefit of chemical synapses?

Answer 12

Provide directionality, amplification, potential for excitation and inhibition, plasticity, and integration in space and time

Question 13

What are the criteria for chemical neurotransmitters?

Answer 13

1- present in the presynaptic terminal
2- released in a voltage and calcium dependent manner
3- specific receptors present in the postsynaptic target cell
4- means to inactivate the neurotransmitter

Question 14

What are the 7 steps in synaptic transmission?

Answer 14

1- Transmitter molecules are synthesized and packaged in vesicles

2- an action potential arrives at the terminal

3- depolarization of terminal opens volt gated calcium channels

4- increased calcium in terminals triggers vesicle fusion

5- transmitter diffuses across cleft & binds to postsynaptic receptors

6- a postsynaptic response occurs

7- transmitter molecules are cleared/ inactivated by enzymatic degradation, uptake, or diffusion

Question 15

What are active zone in presynaptic terminals?

Answer 15

regions where a subset of vesicles are “docked”

Question 16

What is the the electron dense region in the postsynaptic cell?

Answer 16

Postsynaptic density (they are alighed with the active zones of presynaptic cells)

Question 17

How are neurotransmitters released from presynaptic cells?

Answer 17

exocytosis

Question 18

What are the V-snares involved in neurotransmitter release?

Answer 18

synaptobrevin and synaptotagmin (Calcium sensor)

Question 19

What are the T-snares involved in neurotransmitter release?

Answer 19

SNAP-25 and syntaxin

Question 20

How is vesicle membrane recycled?

Answer 20

endocytosis

Question 21

What are the two classifications of postsynaptic receptors?

Answer 21

ionotropic and metabotropic

Question 22

What are the properties of an ionotropic receptor?

Answer 22

Contains an ion channel as part of its structure and transmitter binding triggers a rapid response

Question 23

What are the properties of a metabotropic receptor?

Answer 23

Linked to G-proteins that transduce a slower biochemical signal

Question 24

What type of receptors does acetylchole bind to?

Answer 24

Both ionotropic (fast response) and etabotropic (slow response)

Question 25

How are postsynaptic potentials produced?

Answer 25

Conductance changes due to ion channel openings lead to ionic current flow through the channels that lead to changes in the membrane potential

Question 26

What do excitatory PSPs do?

Answer 26

Increase the probability that an action potential will be triggered

Question 27

What do inhibitory PSPs do?

Answer 27

Decrease the probability that an action potential will be triggered

Question 28

What type of NT is glutamate?

Answer 28

Major excitatory NT that binds to ionotropic and metabotropic receptors

Question 29

What is the fast/ ionotropic receptor for glutamate?

Answer 29

AMPA. Allow for flow of Na+ and K+ down their electrochemical gradient

Question 30

What is the slow/ ionotropic glutamate receptor?

Answer 30

NMDA. Allow for flow of Na+, K+, and Ca2+ ions

Question 31

What type of NT is GABA?

Answer 31

Major inhibitory transmitter that binds to ionotropic and metabotropic receptors

Question 32

The binding of GABA to ligand gated channels causes?

Answer 32

Hyperpolarization of the target cell

Question 33

What is decremental conduction?

Answer 33

the large amount of potential that is lost by leakage through the membrane of the dendrite before EPSPs can reach the cell soma

Question 34

What are synaptic potential changes?

Answer 34

Local passive events that become progressively smaller at greater distances from the stimulus

Question 35

What is temporal stimulation?

Answer 35

Involves EPSPs produced at one synapse by two sequential action potentials. The membrane time constant plays a role in how fast the first synapse dissipation (with a longer time constant the first EPSP is still present)

Question 36

What is spacial summination?

Answer 36

When action potentials in two neurons produce EPSPs at their synapses, which propagate by passive conduction to the soma and axon hillox The membrane time constant plays a role if the synapses summate (happens when the time constant is longer)

Question 37

When does temporal stimulation occur?

Answer 37

When EPSPs from the same cell arrives in rapid succession

Question 38

When does spatial summation occur?

Answer 38

When EPSPs are received simultaneous from multiple cells.