GENERAL HISTOLOGY

Detailed explanation-1: -(1) A message travels from the nervous system to the muscular system, triggering chemical reactions. (2) The chemical reactions lead to the muscle fibers reorganizing themselves in a way that shortens the muscle–that’s the contraction.

Detailed explanation-2: -The nervous system provides the link between thoughts and actions by relaying messages from the brain to other parts of the body. Nerves and muscles, working together as the neuromuscular system, make the body move as you want it to and also control functions such as breathing.

Detailed explanation-3: -The electrical stimulus excites the axon at some point between the motor neuron and the muscle, and produces pairs of action potentials that travel in both the orthodromic and antidromic directions.

Detailed explanation-4: -Muscles can pull bones, but they can’t push them back to the original position. So they work in pairs of flexors and extensors. The flexor contracts to bend a limb at a joint. Then, when the movement is completed, the flexor relaxes and the extensor contracts to extend or straighten the limb at the same joint.

Detailed explanation-5: -Excitability is the ability to respond to a stimulus, which may be delivered from a motor neuron or a hormone. Extensibility is the ability of a muscle to be stretched.