Complete each sentence with the correct word Then click and

Complete each sentence with the correct word. Then click and drag the sentences to arrange them in a logical order.

Solution

1. When the membrane potential reaches threshold an action potential spreads across the sarcolemma due to the opening of voltage gated Na+ channels.

Explanation- Sodium and potassium ions contribute to the membranbe potential. A higher concentration of sodium ions on the outside than the inside and a higher concentration of potassium ions on the inside than the outside results in the propagation of action potential. In Resting membrane potential, all the sodium gates are closed and some of the potassium gates are open. Thus, sodium cannot diffuse through the membrane & largely remains outside the membrane. An action potential is a very rapid change in membrane potential that occurs when a nerve cell membrane is stimulated. Specifically, the membrane potential raises from the resting potential (normally -70 mV) to some positive value ( about +30 mV) in a very short period of time. The stimulus causes the sodium channels to open.

2. Sodium ions enter the axon terminal leading to the release of acetylcholine via synaptic cleft.

Explanation- Afer depolarization sodium ions enter the axon terminal. The presynaptic terminals have active zones that contain vesicles, also called quanta, full of acetylcholine molecules. These vesicles can fuse with the presynaptic membrane and release ACh molecules into the synaptic cleft via exocytosis after depolarization.

3. Acetylcholine diffuses across the synaptic cleft before binding to its receptor located on the motor end plate.

Explanation- The motor neuron receives a nerve impulse and releases acetylcholine from the synaptic vesicles to the synaptic cleft.The motor end plate of the muscle fibre contains protein receptors that bind to the neurotransmitter and impulse spreads over sarcolemma.

4. Acetylcholine receptors function as ligand gated ion channels.

Explanation- nAchRs are ligand-gated ion channels composed of five protein sub units.

5. An action potential reaches the axon terminal causing voltage-gated Ca2+ channels to open.

Explanation- When action potential reaches synaptic terminal calcium channels open and calcium ions enter synaptic teminal.

6. In response to acetylcholine binding, Calcium ions move into the muscle fibre causing the membrane potential to rise.

Explanation-After acetylcholine binding, contraction occurs which is due to the movement of calcium ions into the muscle fibre causing membrane potential to rise.