Question

place the steps of muscle relaxation in order starting at the top.

tropomyosin covers the myosin binding sites

ache breaks ach down

calcium releases from troponin

active transport pumps in the sarcoplasmic reticulum begin to pump calcium back into the cisternae

the nerve signal ceases

Explanation:

Cessation of nerve signal

Using the Skeletal Muscle Relaxation knowledge point
The process of muscle relaxation begins when nerve impulses stop arriving at the neuromuscular junction. Without action potentials, the motor neuron stops releasing acetylcholine (ACh) into the synaptic cleft.

Breakdown of acetylcholine

Using the Acetylcholinesterase Function knowledge point
Acetylcholinesterase (AChE) quickly degrades the remaining ACh in the synaptic cleft. This stops the stimulation of the sarcolemma, allowing the muscle fiber to return to its resting membrane potential.

Active transport of calcium

Using the Calcium Reuptake knowledge point
Active transport pumps (SERCA) in the sarcoplasmic reticulum membrane pump calcium ions (\(\text{Ca}^{2+}\)) back into the terminal cisternae, removing them from the sarcoplasm.

Dissociation of calcium from troponin

Using the Muscle Relaxation Mechanism knowledge point
As sarcoplasmic calcium levels drop, calcium ions dissociate from troponin, which initiates the conformational shift of the thin filament regulatory proteins.

Covering of myosin binding sites

Using the Muscle Relaxation Mechanism knowledge point
Without calcium bound to troponin, tropomyosin shifts back into its resting position, covering the active myosin-binding sites on the actin filaments and preventing cross-bridge formation.

Answer:

1. The nerve signal ceases
2. AChE breaks ACh down
3. Active transport pumps in the sarcoplasmic reticulum begin to pump calcium back into the cisternae
4. Calcium releases from troponin
5. Tropomyosin covers the myosin binding sites