Muscle Physiology and Neuromuscular Function

Many different factors are involved in the subjective sensation of fatigue and there is growing evidence that events occurring within the brain may be just as important. These involve a variety of neurotransmitters. Administration of drugs that affect dopamine and serotonin activity in the brain has been shown to affect exercise performance.

The hydrolysis of Adenosine Triphosphate (ATP) provides the energy required by cells for normal function and the intracellular ATP concentration must be maintained for normal function to continue. If the ATP concentration falls, the actin-myosin interactions that generate force within the muscle will not occur effectively. 

Skeletal muscle cells do not contain myosin filaments. Smooth muscle cells have no repeating sarcomeres, but a loose array of actin and myosin filaments.

The above statement is true. The action potential propagates by muscle fibre's plexus of T-tubules, depolarizing the inner portion of the muscle fibre.

This statement is incorrect. The neurotransmitter acetylcholine diffuses across the synapse and binds to nicotinic acetylcholine receptors on the myocyte, opening them. An influx of Na⁺ and an efflux of K⁺ results, depolarising the cell and generating an end-plate potential.

This statement is incorrect as cytoplasmic calcium binds to troponin C instead of troponin T making the troponin complex to move off the actin binding site allowing the myosin head to bind to the actin filament.

The calcium for skeletal muscle contraction is derived from sarcoplasmic reticulum. The increase in intracellular calcium permits the interaction between actin and myosin head groups.

It gets transformed into melanocytes, cartilage, connective tissue and neurons of some pharyngeal arches. It also leads to the formation of some regions of the heart such as musculoconnective tissue of the large arteries.

Epinephrine is a catecholamine hormone secreted by adrenal medulla. It is a potent stimulator of the sympathetic nervous system stimulating the heart muscle, accelerating the heart rate and increasing cardiac output. In a cardiac muscle, the force of contraction is enhanced by propogating epinephrine.

Smooth muscle fibers have a fusiform shape and, like striated muscle, can tense and relax. Some smooth muscles have the ability to contract spontaneously, i.e., it contracts without any external stimulation.

As power = force x velocity, the maximum power depends on the load moved by the muscle. Too high a load and the muscle cannot shorten effectively; too light a load requires little power to move it.

The above option is correct as the velocity of conduction action potential propagation is the fastest in large diameter myelinated axons.

It is correct statement there is an unequal distribution of ions on the two sides of a nerve cell membrane and therefore, neurons can respond to stimuli and conduct impulses because a membrane potential is established across the cell membrane.

In the central nervous system, the neurons are conserved from changes in plasma composition. The blood-brain barrier isolates central neurons from alterations to plasma composition.

 The motor nerve endings secrete acetylcholine, which activates nicotinic receptors of the muscle fibre membrane.