Correct order of stages of muscle contraction is

Options

A. Stimuli `to` Neurotransmitter secretion `to` Relase of calcium `to` Cross-bridges formation `to` Excitation of T-system `to` Sliding of actin filament
B. Stimuli `to` Neurotransmitter secretion `to` Excitation of T-system `to` Release of `Ca^(2+)to` Cross-bridges formation `to` Sliding of actin filamemts `to` 'H' band diminishes
C. Stimuli `to` Excitation of T-system `to` Neurotransmitter secretion `to` Cross-bridges `to` 'H' band diminishes
D. `Stimuli `to` Excitation of T-system `to` Neurotranmitter secretion `to` Cross-Neurotransmitter secretion `to` Sliding of actin filaments `to` 'H' band diminishes.

Answer

To determine the correct order of stages of muscle contraction, we can break down the process into a series of steps. Here’s a step-by-step explanation of the muscle contraction process:

### Step-by-Step Solution:

1. **Action Potential Generation**: The process begins with the generation of an action potential in the motor neuron, which is triggered by a stimulus.

2. **Neurotransmitter Secretion**: The action potential travels down the neuron and leads to the secretion of neurotransmitters (such as acetylcholine) into the synaptic cleft.

3. **Excitation of T-System**: The neurotransmitters bind to receptors on the muscle cell membrane, causing depolarization and excitation of the transverse (T) tubules.

4. **Release of Calcium Ions**: The excitation of the T-system leads to the release of calcium ions from the sarcoplasmic reticulum into the cytoplasm of the muscle cell.

5. **Binding of Calcium to Troponin**: The released calcium ions bind to troponin, a regulatory protein on the actin filaments. This binding causes a conformational change in troponin.

6. **Exposure of Binding Sites**: The conformational change in troponin shifts tropomyosin, exposing the binding sites on actin filaments for myosin heads.

7. **Cross Bridge Formation**: Myosin heads attach to the exposed binding sites on actin, forming cross bridges.

8. **Sliding of Actin Filaments**: The myosin heads pivot, pulling the actin filaments toward the center of the sarcomere, which results in muscle contraction.

9. **Muscle Contraction**: The repeated attachment and detachment of myosin heads lead to the sliding of actin filaments, resulting in overall muscle contraction.

10. **Calcium Ion Removal**: After contraction, calcium ions are pumped back into the sarcoplasmic reticulum, causing troponin and tropomyosin to return to their original positions, which blocks the binding sites on actin.

11. **Muscle Relaxation**: The muscle relaxes as the actin and myosin filaments slide back to their resting positions.

### Correct Order of Stages:
1. Action Potential Generation
2. Neurotransmitter Secretion
3. Excitation of T-System
4. Release of Calcium Ions
5. Binding of Calcium to Troponin
6. Exposure of Binding Sites
7. Cross Bridge Formation
8. Sliding of Actin Filaments
9. Muscle Contraction
10. Calcium Ion Removal
11. Muscle Relaxation