Question

1. Which of the following represents the CORRECT order of events in a motor neuron when I decide that I want to wiggle my finger?

A. An action potential reaches the end of the motor neuron causing the influx of calcium through ligand-gated calcium channels and the fusion of vesicles containing acetylcholine with the presynaptic membrane

B. An action potential reaches the end of the motor neuron causing the influx of calcium through voltage-gated calcium channels and the fusion of vesicles containing acetylcholine with the presynaptic membrane

C. An action potential reaches the end of the motor neuron causing the influx of sodium through ligand-gated sodium channels and the fusion of vesicles containing acetylcholine with the presynaptic membrane

D. An action potential reaches the end of the motor neuron causing the influx of sodium through voltage-gated sodium channels and the fusion of vesicles containing acetylcholine with the presynaptic membrane

2. During endochondral ossification, osteoblast is derived from which cell type?

A. Articular cartilage

B. Fibroblast

C. Chondrocytes

D. Mesenchymal stem cells

3. Which of the following is TRUE about muscle contraction?

A.Hydrolysis of ATP to ADP and Pi “cocks” the myosin head to a high energy state

B.Rigor mortis (continued contraction) occurs when there is an excess of ATP binding to the myosin head.

C.The binding of ATP to the myosin head causes myosin heads to bind to actin.

D.Each cycle of the sliding filament model (Cross-bridge cycle) leads to lengthening of the sarcomere

Answer 1

1. An action potential reaches the end of the motor neuron causing the influx of calcium through voltage-gated calcium channels and the fusion of vesicles containing acetylcholine with the presynaptic membrane. It's the option B.

When an action potential reach the neuromuscular junction the voltage gated calcium channel open which thus leads to the acetyl choline release to the synaptic cleft. The acetylcholine is transported in vesicles. The vesicle gets fused with the presynaptic membrane byo release the acetylcholine to the cleft.

2. Chondrocyte.

The endochrondal ossification is the process by which bone is formed from the cartilage. So the chondrocyes if the cartilage are replaced by the osteoblast and they generate itself from the cartilage.

3. Hydrolysis of ATP to ADP and Pi “cocks” the myosin head to a high energy state.

The ATP hydrolysis leads the myosin to a high energy stage. We know that the ATP hydrolysis gives energy, so when the ATP hydrolysises the myosin head gets the energy.