Skeletal Muscles are under voluntary control. Contra of these muscles is initiated by electrical impulses the brain. This is a five step process:
1) Electrical impulse from the brain.
2) Passing electrical impulse to muscle fibers at Neuro muscular junction.
3) Passing electrical impulse inside the muscle fiber.
4) Excitation Contraction Coupling-release of calcium in response to electrical impulse.
5) Cross bridge cycle-contraction by sliding filament theory. . . . 4) Explain the 5 steps in voluntary control of skeletal muscles.
The Correct Answer and Explanation is :
Voluntary control of skeletal muscles involves a complex series of events that allow us to consciously control our movements. Here’s a detailed explanation of the five steps involved:
1) Electrical Impulse from the Brain
The process begins in the brain, where motor neurons are activated. The brain sends an electrical signal through the central nervous system, which travels along a motor neuron toward the specific muscle group that is being targeted for movement. This electrical signal is known as an action potential.
2) Passing Electrical Impulse to Muscle Fibers at the Neuromuscular Junction
When the action potential reaches the end of the motor neuron, it arrives at the neuromuscular junction, which is the synapse between the motor neuron and the muscle fiber. At this junction, the electrical signal is converted into a chemical signal. The neuron releases acetylcholine (ACh), a neurotransmitter, into the synaptic cleft. Acetylcholine binds to receptors on the muscle fiber’s membrane (sarcolemma), leading to depolarization of the muscle cell membrane.
3) Passing Electrical Impulse Inside the Muscle Fiber
The electrical signal spreads along the sarcolemma and into the muscle fiber through structures called T-tubules (transverse tubules). These tubules conduct the action potential deep into the muscle fiber, ensuring the signal reaches all parts of the muscle simultaneously.
4) Excitation-Contraction Coupling
Once the action potential travels down the T-tubules, it reaches the sarcoplasmic reticulum, a specialized organelle that stores calcium ions. The action potential triggers the release of calcium ions from the sarcoplasmic reticulum into the muscle fiber’s cytoplasm. The calcium ions are crucial for muscle contraction as they bind to the protein troponin on the actin filaments, which causes a conformational change, exposing binding sites on actin for myosin.
5) Cross-Bridge Cycle
The final step involves the interaction between myosin (a thick filament) and actin (a thin filament). Myosin heads, energized by ATP, bind to the exposed sites on actin, forming cross-bridges. These cross-bridges then pivot, pulling the actin filaments toward the center of the sarcomere, which leads to muscle contraction. This process is repeated, causing the muscle fibers to shorten, which results in muscle contraction and movement.
In summary, these five steps—initiated by an electrical impulse from the brain—lead to muscle contraction and voluntary movement.