Synaptic Transmission

Question 1

What are the differences between electrical and chemical synaptic transmission?

Answer 1

1. Speed; electrical is fast while chemical is slow
2. Electrical neurotransmissions uses gap junctions while chemical has a synaptic cleft (gap)
3. The direction of neurotransmission: electrical is multidirectional and chemical is unidirectional

Question 2

What is the first step of a chemical synapse?

Answer 2

Neuron is going to synthesize neurotransmitters

Question 3

What is the second step of a chemical synapse?

Answer 3

Neurotransmitters stored in axon terminal

Question 4

What is the third step in a chemical synapse?

Answer 4

Action potential will cause the release of neurotransmitters into the synaptic cleft (fusion of vesicle with membrane)

(Action potential triggers a calcium channel to open which causes influx of calcium (going down its concentration gradient), which will cause the release of neurotransmitters due to the new ion imbalance)

Question 5

What is the fourth step of chemical synapse?

Answer 5

Neurotransmitters travel to bind to receptor in post-synaptic

Question 6

What is the fifth step of the chemical synapse?

Answer 6

Post synaptic response = change in membrane potential

Question 7

What is the last step of a chemical synapse?

Answer 7

Neurotransmitters will either be taken up by the presynaptic cell, or diffuse into blood stream or be enzymatically inactivated

Question 8

What are the two precursors for synthesis of neurotransmitters in eapresynaptic neurons?

Answer 8

Amino acids (glutamine, glycine and aspartate) and can be made in soma of neurons

Question 9

What is the quantal hypothesis?

Answer 9

Each time a synaptic vesicle is released, about 5000-10000 molecules of neurotransmitter is released within that synaptic vesicle to be sure that you have an action potential.

Question 10

What two things is neurotransmitter release dependent on?

Answer 10

Neurotransmitter release is equal to the increase in calcium release plus the increase in action potential

Question 11

What are the four criteria of neurotransmitters?

Answer 11

1. Synthesis in pre-synaptic neuron
2. Release in response to pre-synaptic action potential (calcium dependent, quantal hypothesis, NT release)
3. Post synaptic receptors receive signal and respond
4. NTs must somehow be inactivated

Question 12

What are the different classifications of neurotransmitters?

Answer 12

1. Choline esters (mAChR will bind to mAChR or nAChR)
2. Biogenic amines (dopamine, epinephrine, norepinephrine and serotonin)
3. Amino acids (glutamate, glycine, GABA)
4. Neuropeptides (ACTH, glucagon, endorphins)

Question 13

What are the three post synaptic responses?

Answer 13

Action potential (all or none)

EPSP

IPSP

Question 14

What’s an EPSP? What moves in and out of the cell?

Answer 14

Depolarizations, which will get the cell closer threshold in order to action potential

Potassium moves out and sodium moves in (net gain positive charge)

Question 15

What’s an IPSP? What moves in and out of the cell?

Answer 15

Repolarizations, which will get the cell farther away from the threshold and action potential

Potassium moves out of the cell or a negative charge (chloride) will move into the cell (net negative gain)

Question 16

What is summation?

Answer 16

The addition of EPSPs and IPSPs

Question 17

What is spatial summation?

Answer 17

EPSP only; there are many pre-synaptic neurons firing onto one post-synaptic neuron, and it happens all at the same time.

Question 18

What is temporal summation?

Answer 18

EPSP only; theres is only one presynaptic neuron firing at a postsynaptic neuron over a period of time

Question 19

What are the acetylcholine receptors?

Answer 19

Nicotine AChR and muscarinic AChR

Question 20

What is the nicotinic AChR?

Answer 20

Ionotropic receptor (involves ions)

Acetylecholine binds the receptor and causes an increase in sodium and potassium permeability across the membrane; this change will cause membrane depolarization, which will then cause an action potential, and could cause skeletal muscle contraction for example

Question 21

What is the muscarinic AChR?

Answer 21

A metabotropic receptor (GCPR)

Acetylcholine binds to this receptor and causes part of the protein to release alpha-GTP subunit from the beta/gamma subunit, which will elicit a variety of responses and thats how the muscarinic receptor will signal (for example, autonomic nervous system, parasympathetic nervous system responses)