Question

What are the differences and similarities between phasic and tonic contractions? Where are the two most likely to be found?

Thanks

Answer 1

Postural - it means that muscle is used for keeping straight posture of human body

Tonic - means that muscle contains mostly slow-contraction, long-duralibity fibers. These mucles have tendency to over-tension and to shorten (for example in spasticity).

Phasic - means that muscle contains mostly quick-contraction, hi-power, short-duralibity fibers. These muscles have tendency to under-tension (getting weak), and loose. They also lose their mass very quickly while hypokinesia.

Tonic smooth muscles show continuous contraction as fluids move around them, while phasic smooth muscles show rhythmic motions that cease after a time

tonic muscles as continuously active muscles within the body that are usually filled with fluid. Phasic muscles are active for short periods but spend most of the time in a relaxed state.

For example, phasic muscles in the stomach contract only a few times per hour in between meals. Contractions in the stomach increase to several per minute when someone eats. Muscles that line the bladder and ureter contract only a few times per day when the body eliminates urine.

Tonic muscles are also found in sphincters. Phasic muscles rely on electrical impulses through calcium ions to contract

Phasic contractions work by using action potentials, a process during which the electrical impulses generated by muscle cells briefly reverse to cause a contraction

Tonic muscles do not use electrical impulses or action potentials to work. Both tonic and phasic muscles are known as unitary smooth muscles, or visceral smooth muscles.

Tight Tonic Muscles — Your tonic muscles are responsible for holding your posture. They can constrict and tighten making it more difficult to achieve and maintain correct posture. We need to stretch these muscles to increase our range of motion so that we can improve your posture.

Weak Phasic Muscles — phasic muscles are used for dynamic movement. They can weaken and lengthen, making us more prone to slouching. We need to strengthen them so that oyr neck and back can maintain proper posture all day.