Neurobiology

Question 1

What happens if the APs causes K+ to increase in Normal Muscle?

Answer 1

Increased [K+] exerts depolarizing effect on membrane potential –> High permeability to Cl-, so Cl- moves into cell to resist depolarization.

Question 2

What happens if the APs causes K+ to increase in Myotonic Muscle?

Answer 2

Increased [K+] exerts depolarizing effect on membrane potential –> In myotonia congenita the depolarization sustained discharge of action potentials.

Question 3

What does Resting Potential reflect?

Answer 3

Resting membrane potentials reflect the weighted average of equilibrium potentials of the ions that can across the membrane.

Question 4

True or False: Is action potential threshold typically close to the resting potential.

Answer 4

True.

Question 5

Conditions that after resting potential often cause aberrant neural signaling.

Answer 5

• Alteration of equilibrium potential (alterations in extracellular K+)
• Altered channel activity.

Question 6

What happens to [K+] in Hyperkalemia?

Answer 6

elevated extracellular k+

Question 7

What is the concentration of [K+] in normal conditions?

Answer 7

• Resting potential dominated by k+

- Low extracellular K+

Question 8

Where the neurotransmitters are stored?

Answer 8

In vesicles

Question 9

What is the sequence of events in transmission from nerve to muscle?

Answer 9

1. Action potential depolarizes nerve terminal, leading to the opening of Ca2+channels and Ca2+entry
2. Resulting increase in intracellular Ca2+concentration causes ACh filled vesicles to fuse with nerve terminal membrane Released ACh diffuses across the synaptic cleft, binds to and activates postsynaptic ACh receptors. Activation of ACh receptors produces a non-selective cation current, which is mostly an inward movement of Na+at normal membrane voltages
3. Inward movement of Na+depolarizes muscle fiber, leading to action potential
4. Released ACh is degraded by acetylcholinesterase

Question 10

What is the function of the Botulinum toxins?

Answer 10

Botulinum toxin disrupts proteins involved in ACh release and hence renders the nerve unable or less able to elicit contraction in the muscle.

Question 11

Important properties of synaptic transmission at NMJ

Answer 11

• Transmitter (ACh) stored in vesicles.
• Depolarization –> calcium influx –> release
• ACh activates receptor/Channel complexes
• ACh removed by enzymatic degradation
• Presynaptic AP –> muscle AP (one to one)
• One directional