Unit 3

Question 1

Define what are synapses?

Question 2

Describe the functions of synapse?

Question 3

Identify and describe anatomical arrangements of synapses?

Question 4

Identify the differences between electrical and chemical synapses and be able to draw them?

Question 5

Describe the synaptic events involved in chemical synaptic transmission?

Question 6

What are synapses and what are the functions of synapses?

Answer 6

Synapse: the region of contact (or near contact) where the neuron transfers information to another cell

Functions: transmit and modulate information between cells

Question 7

What are Two main types of synapses?

Answer 7

Electrical synapses (gap junction)
• ioniccurrentspreadstonextcellthroughgap junctions
• faster,two-waytransmission&capableof synchronizing groups of neurons
– Chemical synapses
• chemicalmessage(neurotransmitters)
• synapticdelay,one-waytransmissionfroma presynaptic neuron to a postsynaptic neuron

Question 8

What are the Features of electrical synapses?

Answer 8

Fast transmission (very common in invertebrate for fast withdrawal reflex)
• Vertebrate retina, neocortical interneurons (synchronization signals during early development)
• Nearly always open (specific exceptions such as dark/light modulation in retina), non-selective to ions
• Often bidirectional current flow, but some only pass current in one direction.
• Passage of second messengers, cAMP, Ca2+

Question 9

Synaptic transmission at Chemical synapses

Answer 9

1. Action potential reaches nerve terminals
   • 2. voltage-gated Ca2+ channels open
   • 3. Ca2+ flows inward triggering release of neurotransmitter
   • 4. Neurotransmitter crosses synaptic cleft & binding to ligand-gated receptors 5. which allow ions flow in and
   • 6. induce postsynaptic potential change or even
   • 7. trigger action potential (nerve impulse) in the
   postsynaptic cell
   Synaptic delay is ~0.5 msec and One-way information transfer

Question 10

What is the Synapses?

Answer 10

are functional contact sites between neurons

Question 11

What are the two main types of Synapses?

Answer 11

electrical and chemical synapses

Question 12

What is an Electrical Synapses?

Answer 12

Electrical synapses made of connexin proteins which form two halves of connexon that are non- selective for ions and small molecules to pass bidirectionally

Question 13

What is a Chemical Synapses?

Answer 13

Chemical synapses are composed of presynaptic nerve terminals containing transmitter vesicles, synaptic cleft and postsynaptic receptors

Question 14

Chemical synaptic transmission

Answer 14

a series of events

Question 15

What are neurotransmitters?

Question 16

What are the criteria for being a neurotransmitter?

Question 17

What are the mechanisms of transmitter removal?

Question 18

What are the major types of neurotransmitters?

Question 19

What are the clinical relevance of major transmitters
of Acetylcholine , Serotonin, and Dopamine?

Question 20

What is a neurotransmitter?

Answer 20

A chemical released by a presynaptic element upon
stimulation that activates postsynaptic receptors
–Housed in presynaptic axon terminal
–Packages in little sacks called vesicles
–Released into synapse with arrival of action potential
–Activates postsynaptic cell –Is cleared from synapse

Question 21

What are the criteria for a neurotransmitter?

Answer 21

To be a Neurotransmitter, a substance must have
the following properties:
1. A presynaptic cell must have machinery to synthesize or otherwise neurotransmitter is present in the terminal
2. Must be released in sufficient quantities to produce an effect
3. Receptors must exist on post synaptic cell
4. Action must be mimicked by exogenous application of
substance
5. Mechanism for removal exists to stop the postsynaptic effect

Question 22

Serotonin (5-HT) as a transmitter of clinical relevance
Depression:

Answer 22

Depression: low levels of serotonin in the brain? affect one in 4 to one in 10 people

Question 23

Neurotransmitters are?

Answer 23

chemicals synthesized, stored,
released in presynaptic neurons which act on their postsynaptic receptors and induced postsynaptic effects. The neurotransmitter is removed from the synaptic site after its action is done.

Question 24

What are the three major types of conventional transmitters?

Answer 24

Amino acids (Glutamate, GABA, Glycine), Amines (ACh, 5-HT, DA, NE etc.), and Peptides (Substance P, CCK, Dynorphin etc.)

Question 25

Clinical medicines target to synaptic transmission at all kinds of levels:

Answer 25

precursors, transporters, synthesis, degradation, receptors etc.

Question 26

Describe several ionotropic and metabotropic receptors and identify key distinctions between them

Question 27

Know which neurotransmitters activate ionotropic and/or metabotropic receptors

Question 28

Describe the key steps in signal transduction for G- protein coupled receptors (GPCRs)

Question 29

What are the Functions of ionotropic receptors?

Answer 29

Mediate Fast synaptic responses
• Essential for rapid communication
• Activation can occur on SUBMILLISECOND time
scale

Question 30

Always INCREASE membrane conductance
• A) depolarize B) hyperpolarize C) either

Question 31

What is Excitotoxicity?

Answer 31

excessive presence of glutamate
(Exciting poisons: too much of a good thing)
Ischemia (stroke)
lack of blood → no oxygen and glucose → no pump activity → depolarization → calcium increase → more glutamate release → depolarization (self-reinforcing and spreading)

Question 32

About metabotropic receptors

Answer 32

They are typically G-protein coupled receptors (GPCRs), or called 7 transmembrane receptors
• Trigger intracellular signaling cascade
• Induce metabolic response
• Mediate slow, wide spread, and long-lasting of responses

Question 33

What is G-protein?

Answer 33

guanine nucleotide-binding proteins

Question 34

What is Heterotrimeric

Answer 34

α, β, γ subunits, βγ form a complex

Question 35

What is Inactive form?

Answer 35

α bound to GDP, no ligand binding to GPCR

Question 36

What is Active form?

Answer 36

α bound to GTP, after ligand binding to GPCR

Question 37

G-protein signaling

Answer 37

1. Ligand binds to GPCR
2. GPCR undergoes conformational change
3. αsubunitexchangesitsboundGDPtoGTP
4. α subunit dissociates from GPCR and βγ complex
5. Both α and βγ regulate target proteins
6. Target proteins relay information via 2nd messenger pathways
7. GTPhydrolyzedtoGDP
8. αsubunitrebindstoβγcomplex

Question 38

Names of G-protein acting via cAMP-PKA pathways

Answer 38

1. Gαs = Gs (stimulatory) increase adenylyl cyclase increase cAMP
   increase PKA
2. Gαi = Gi (inhibitory) decrease adenylyl cyclase decrease cAMP
   decrease in PKA

Question 39

Ligand-gated transmitter receptors:

Answer 39

Ionotropic and metabotropic receptors

Question 40

Ligand binding to ionotropic receptors do what?

Answer 40

change shape allowing ions to flow through the channels.

Question 41

Ligand binding to metabotropic receptors (GPCRs) do not…..
And activate what?

Answer 41

have the ion channels. They activate a G-protein that in turn activates secondary messengers (cAMP, cGMP, IP3, DAG, Ca2+), that in turn will activate downstream targets (ion channels, enzyme, transcription factors etc).

Question 42

The second messengers can do what?

Answer 42

The second messengers can travel throughout the cell and cells in other part of our body and result in a much wider range and long lasting of responses.

Question 43

What is the key structural feature common to all G-protein coupled receptors (GPCRs)?

Question 44

How many subunits in the G-protein that is coupled to an GPCR?

Question 45

Name the enzyme that cleaves a membrane phospholipid to generate IP3 and DAG.

Question 46

Name the enzyme that catalyzes the formation of cAMP.

Question 47

Which of the following is the ligand that opens the ligand-gated Ca2+ channel in the endoplasmic reticulum? [DAG; IP3; cAMP; Gβγ complex; Gα]

Question 48

Name the factor that binds to and activates protein kinase A (PKA).

Question 49

Name the factor that binds to and activates protein kinase C (PKC).

Question 50

Which of the following inactivates the alpha subunit of a trimeric G-
protein? [GTP binding; GTP hydrolysis; phosphodiesterase; cholera toxin;
beta-arrestin].