Week 3: Chemical Synapsis, Pharmacodynamics & Neurotransmitters

Question 1

What is a synapse?

Answer 1

The site where a neuron contacts another cell to transmit information.

Question 2

What is the synaptic cleft?

Answer 2

The small gap between pre- and post-synaptic cells where neurotransmitters diffuse.

Question 3

What is a discrete synapse?

Answer 3

A type of synapse where neurotransmitters are released from terminal boutons at defined active zones.

Question 4

What is a diffuse synapse?

Answer 4

A synapse where neurotransmitter is released from swellings called varicosities along the axon.

Question 5

What determines neurotransmitter synthesis location?

Answer 5

Non-peptide transmitters are synthesized in terminals; peptides in the cell body.

Question 6

How are neurotransmitters transported to terminals?

Answer 6

Via microtubules using kinesin-mediated anterograde transport.

Question 7

What triggers neurotransmitter release at terminals?

Answer 7

Voltage-gated Ca2+ influx upon action potential arrival.

Question 8

What proteins mediate vesicle fusion?

Answer 8

SNARE proteins facilitate docking and fusion of vesicles with the membrane.

Question 9

What is synaptotagmin?

Answer 9

A calcium sensor that completes the SNARE complex to trigger fusion.

Question 10

What causes synaptic delay?

Answer 10

Time needed for vesicle fusion and neurotransmitter diffusion and receptor binding (~0.5–1 ms).

Question 11

Why are peptide synapses less efficient?

Answer 11

Require repetitive stimulation and have lower vesicle docking readiness.

Question 12

What types of post-synaptic receptors exist?

Answer 12

Ionotropic (ion channels) and metabotropic (G-protein coupled).

Question 13

What happens after neurotransmitter release?

Answer 13

It binds receptors, induces a response, and is then removed or degraded.

Question 14

What ends neurotransmitter action?

Answer 14

Reuptake, enzymatic breakdown, or diffusion away from the cleft.

Question 15

What is the difference between excitatory and inhibitory postsynaptic potentials?

Answer 15

Excitatory depolarizes the cell; inhibitory hyperpolarizes it.

Question 17

What is pharmacodynamics?

Answer 17

The study of drug effects on the body.

Question 18

What is efficacy in pharmacology?

Answer 18

The maximum effect a drug can produce (Emax).

Question 19

What is drug potency?

Answer 19

The amount of drug needed to produce a specified effect (measured by EC50 or ED50).

Question 20

What is binding affinity?

Answer 20

The strength with which a drug binds to its receptor (inverse of Kd).

Question 21

What is a full agonist?

Answer 21

A drug that fully activates a receptor to produce maximum effect.

Question 22

What is a partial agonist?

Answer 22

A drug that binds to and activates a receptor, but produces less than the maximal effect.

Question 23

What is an inverse agonist?

Answer 23

A drug that reduces receptor activity below basal levels.

Question 24

What is a competitive antagonist?

Answer 24

Binds to the same site as the agonist, blocking activation without triggering a response.

Question 25

What is a non-competitive antagonist?

Answer 25

Binds elsewhere or irreversibly blocks receptor, reducing max response regardless of agonist concentration.

Question 26

What is an allosteric modulator?

Answer 26

A molecule that binds at a site other than the active site and alters receptor activity.

Question 27

What is the therapeutic index?

Answer 27

Ratio of TD50 (toxic dose) to ED50 (effective dose), indicating drug safety margin.

Question 29

What is a graded dose-response curve?

Answer 29

A plot showing the range of drug effects across increasing concentrations.

Question 30

What does EC50 indicate?

Answer 30

The concentration of a drug that produces 50% of its maximal effect.

Question 31

What is Bmax?

Answer 31

Maximum receptor binding capacity.

Question 32

What is Kd?

Answer 32

Dissociation constant; concentration at which 50% of receptors are bound.

Question 33

What are spare receptors?

Answer 33

Receptors not required to achieve maximal response, indicating amplification.

Question 34

What is a quantal dose-response curve?

Answer 34

A graph showing all-or-none responses across a population.

Question 35

What does ED50 mean in a quantal curve?

Answer 35

The dose at which 50% of the population shows a defined effect.

Question 36

What is TD50 or LD50?

Answer 36

The dose at which 50% experience toxicity (TD50) or lethality (LD50).

Question 37

What is a therapeutic window?

Answer 37

Range of drug doses that are effective without being toxic.

Question 38

How is drug safety evaluated?

Answer 38

By calculating therapeutic index (TI = TD50 / ED50).

Question 39

Why is EC50 useful in dosing?

Answer 39

Helps determine effective and safe dosage levels.

Question 40

What is the relationship between EC50 and potency?

Answer 40

Lower EC50 indicates higher potency.

Question 41

What happens if EC50 < Kd?

Answer 41

Indicates presence of spare receptors in the system.

Question 42

Why do partial agonists reduce full agonist effects?

Answer 42

They compete for receptors but yield smaller responses.

Question 43

What is neutral antagonism?

Answer 43

A drug that binds without activating or altering baseline receptor activity.

Question 45

What are the 3 main neurotransmitter classes?

Answer 45

Amino acids, amines, and peptides.

Question 46

What qualifies a chemical as a neurotransmitter?

Answer 46

Synthesized and stored presynaptically, released on stimulation, and mimics synaptic effects when applied experimentally.

Question 47

What is the main excitatory neurotransmitter in the CNS?

Answer 47

Glutamate.

Question 48

What is the main inhibitory neurotransmitter in the CNS?

Answer 48

GABA.

Question 49

What are the two glutamate receptor types?

Answer 49

Ionotropic (iGluRs) and metabotropic (mGluRs).

Question 50

What are examples of ionotropic glutamate receptors?

Answer 50

NMDA, AMPA, and kainate receptors.

Question 51

What are the two types of GABA receptors?

Answer 51

GABA_A (ionotropic) and GABA_B (metabotropic).

Question 52

What neurotransmitter do cholinergic neurons release?

Answer 52

Acetylcholine (ACh).

Question 53

What enzyme synthesizes acetylcholine?

Answer 53

Choline acetyltransferase (ChAT).

Question 54

What breaks down acetylcholine?

Answer 54

Acetylcholinesterase (AChE).

Question 55

What are the two cholinergic receptor types?

Answer 55

Nicotinic (ionotropic) and muscarinic (metabotropic).

Question 56

What is serotonin also known as?

Answer 56

5-hydroxytryptamine or 5-HT.

Question 57

How is serotonin synthesis regulated?

Answer 57

By availability of tryptophan, its dietary precursor.

Question 58

What are serotonin receptor types?

Answer 58

Seven families (5-HT1 to 5-HT7) with diverse functions.

Question 59

How is serotonin action terminated?

Answer 59

By reuptake into the presynaptic terminal via a specific transporter.