synaptic communication 2

Question 1

What is the End Plate Potential (EPP)?

Answer 1

EPP is a graded potential that gives rise to an action potential (AP)

EPP occurs at the neuromuscular junction (NMJ) and has an in-built safety factor.

Question 2

What type of receptors are present at vertebrate NMJs?

Answer 2

Cholinergic receptors

These receptors are activated by acetylcholine (ACh).

Question 3

What is the role of curare in neuromuscular transmission?

Answer 3

Curare is a competitive inhibitor of ACh

It does not block Na+ or K+ voltage-gated channels.

Question 4

How can EPPs be generated?

Answer 4

EPPs can be generated by:
* Nerve stimulation
* Iontophoresis

Question 5

What initiates neurotransmitter release at the NMJ?

Answer 5

Ca2+ entry through Ca2+ channels

Ca2+ binds to synaptotagmin, a Ca2+ sensor.

Question 6

What happens after Ca2+ binds to synaptotagmin?

Answer 6

Vesicles are brought close to the membrane to form a fusion pore

The SNARE complex facilitates this process.

Question 7

What is the sequence of events during neuromuscular transmission?

Answer 7

1. Action potential arrives at motor neuron terminal
2. Voltage-gated Ca2+ channels open
3. Ca2+ entry initiates exocytosis of ACh vesicles
4. ACh binds to nicotinic ACh receptors
5. End-plate potential (EPP) is generated

Question 8

What is the synaptic (ACh) reversal potential (EACh)?

Answer 8

0 mV

The driving force is the difference between the postsynaptic membrane potential (Vm) and the reversal potential (Erev).

Question 9

What are Miniature End-Plate Potentials (MEPPs)?

Answer 9

Small depolarizations caused by the spontaneous release of ACh

MEPPs are crucial for understanding synaptic transmission efficiency.

Question 10

What is synaptic plasticity?

Answer 10

The process by which synapses alter their transmission efficiency

It can be short-term (seconds to minutes) or long-term (minutes to days/months).

Question 11

What are the two types of short-term synaptic plasticity?

Answer 11

• Depression
• Facilitation

Question 12

What is the cellular basis for learning and memory?

Answer 12

Long-term potentiation (LTP) and long-term depression (LTD)

These processes involve changes in gene expression and protein synthesis.

Question 13

What is non-synaptic transmission?

Answer 13

Volume transmission via extracellular fluid

It activates extra-synaptic receptors and can occur over short or long distances.

Question 14

What are skeletal muscle relaxants used for?

Answer 14

To relax muscle during surgery and for painful muscle spasms

They are often used with general anesthetics.

Question 15

What are the two types of blockers of nicotinic ACh receptors?

Answer 15

• Competitive blockers (e.g., d-tubocurarine)
• Depolarizing blockers (e.g., succinylcholine)

Question 16

What is the effect of succinylcholine on neuromuscular transmission?

Answer 16

Initial depolarization followed by persistent depolarization and AChR desensitization

This blocks action potential propagation and excitation-contraction coupling.

Question 17

What is Myasthenia Gravis?

Answer 17

An autoimmune disease targeting nACh receptors

It leads to muscle weakness that increases with exercise due to loss of functional nAChRs.

Question 18

What is retrograde (chemical) transmission?

Answer 18

Postsynaptic-to-presynaptic signaling

It involves ‘retro-neurotransmitters’ synthesized in the postsynaptic cell.

Question 19

What happens to ACh release in myasthenic NMJs?

Answer 19

There is upregulation of ACh release

This compensates for the reduced function of nAChRs.