Question

The muscle relaxes if no new nerve signal arrives. However the neurotransmitter from the previous stimulation is still present in the synapse. The activity of ________ helps to remove this neurotransmitter. a. myosin b. action potential c. tropomyosin d. acetylcholinesterase

Short answer

a. Myosin b. Action potential c. Tropomyosin d. Acetylcholinesterase Answer: d. Acetylcholinesterase

Step-by-step solution

Read the question carefully

Understand the exercise and focus on the main point which is the removal of neurotransmitter from the synapse.

Analyze the given options

Go through the options one by one and understand their functions in the muscle relaxation process. a. Myosin: A protein that plays a key role in muscle contraction b. Action potential: Electrical impulse that travels along a nerve cell membrane c. Tropomyosin: A protein that helps regulate muscle contraction d. Acetylcholinesterase: An enzyme that breaks down the neurotransmitter acetylcholine

Choose the correct answer

Based on the understanding of the functions of the given options, choose the option which helps remove the neurotransmitter from the synapse. The correct answer is: d. Acetylcholinesterase, since it helps break down the neurotransmitter acetylcholine, clearing it from the synapse and allowing the muscle to relax when no new nerve signal arrives.

Key concepts

Acetylcholinesterase

Acetylcholinesterase is a vital enzyme in the process of muscle relaxation. It acts in the synapse—the gap between nerve cells and muscle cells—by breaking down the neurotransmitter acetylcholine. When a nerve impulse ends, acetylcholine must be removed quickly to prevent continuous muscle contraction. Acetylcholinesterase achieves this by hydrolyzing acetylcholine into acetate and choline, which are then reabsorbed for reuse by the neuron. This breakdown is crucial for the muscle to return to its relaxed state after being stimulated.

Without acetylcholinesterase:

• Acetylcholine would remain in the synaptic cleft longer.
• Muscles might experience prolonged contraction.
• Neuromuscular communication could be disrupted.

This enzyme's role highlights its importance in regulating muscular activity and ensuring efficient nerve-muscle communication.

Neurotransmitter

Neurotransmitters are chemical messengers that transmit signals from one neuron to another across the synapse. In terms of muscle contraction and relaxation, acetylcholine is the primary neurotransmitter involved. When a nerve signal reaches the end of a neuron, acetylcholine is released into the synapse. It binds to receptors on the muscle cell, prompting it to contract.

Key features of neurotransmitters include:

• Rapid action and inactivation.
• Specificity to certain receptors.
• Role in both excitation and inhibition of target cells.

Once the signal needs to be stopped, enzymes like acetylcholinesterase help degrade these neurotransmitters to cease their action, thereby allowing the muscle to relax. This cyclical release and breakdown is essential for the precise control of muscle movements.

Synapse

The synapse is a specialized junction through which neurons communicate with each other or target cells such as muscle cells. It consists of the presynaptic ending containing neurotransmitters, the synaptic cleft where neurotransmitters are released, and the postsynaptic membrane holding receptors.

Several processes occur at the synapse:

• Release of neurotransmitters into the synaptic cleft from the presynaptic neuron.
• Binding of neurotransmitters to receptors on the postsynaptic cell, triggering a response.
• Clearance of neurotransmitters to reset the synapse for the next signal.

For muscle relaxation, the synapse relies heavily on the timely breakdown of neurotransmitters like acetylcholine. Acetylcholinesterase ensures the synaptic cleft is cleared, preventing continuous signal transmission and maintaining normal neuromuscular function. Understanding the synapse is crucial for grasping how neurons efficiently communicate and orchestrate complex body movements.