PHYSIOLOGY
MUSCLE CONTRACTION
|
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
|
|
|
An electrical charge from a neuron
|
|
|
Neurotransmitters released by a neuron
|
|
|
Sodium influx
|
|
|
A nerve signal
|
Detailed explanation-1: -This gradual depolarization mainly occurs via a depolarization current or pacemaker current (If). Pacemaker current occurs due to the slow influx of Na+ ions through the hyperpolarization-activated cyclic nucleotide-gated channel (HCN channel).
Detailed explanation-2: -Depolarization is caused when positively charged sodium ions rush into a neuron with the opening of voltage-gated sodium channels. Repolarization is caused by the closing of sodium ion channels and the opening of potassium ion channels.
Detailed explanation-3: -Activation of the nAChR leads to an influx of cations (sodium and calcium) that causes depolarization of the muscle cell membrane. This depolarization in turn activates a high density of voltage-gated sodium channels on the muscle membrane, eliciting an action potential.
Detailed explanation-4: -The correct answer is (b): Depolarization occurs when sodium ions enter into the muscle fiber cell causing the membrane potential to move towards +30 mV.
Detailed explanation-5: -During depolarisation, the magnitude of negative membrane potential is reduced due to influx of sodium ions.