# INTRODUCTION ***

Greetings steemians and my special friends @campusconnectng community. Hope your week is running smooth. I hope you have a productive week.

I am a medical student at the University of Nigeria,Enugu Campus and on a particular hot seat involving my 2nd MB professional exams but I've pinched out a little time to leak a secret on the physiology of muscle relaxation.

Hang on, I'm going to take you on a wild ride through the details of the shocking reality of muscle contraction and relaxation I promise to limit my use of medical jargons and terms,in other to make this article reader friendly.

Enjoy!!! *** ### MECHANISM OF MUSCLE CONTRACTION ***

Muscle contraction is a very complex physiological process that involves a lot of tiny details involving a lot of neurotransmitters,enzymes and minerals. You contract your muscles to do work. Hence walking, running, lifting weights, pulling objects all involve muscle contraction.

Therefore, you can easily deduce that muscle contraction and relaxation is integrated in our daily activities. ![images.png](https://cdn.steemitimages.com/DQmYVHuMjkbkDg83mmcDoAmysRvVBS7iWPxTpmsaFrX8hks/images.png) [source](http://leifsaul.com/2019/10/07/how-muscles-work/)

Muscle contraction is kick-started by signal from your nerve( You visit a friend and his dog comes rushing at you,a complex of signals from your brain through your nerves would definitely trigger ur muscles to make you run).

It is a common knowledge that muscle contraction involves energy in the form of ATP, the burning of this energy could even make you sweat during intense muscular actions such as exercises.

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But how exactly is this ATP used?

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The basic smallest unit of muscle as you know it is made up of two filaments, the myosin and actin which pull on each other, like in a tug of war? Nah. More like a mother pulling her child by the ear home. The myosin filaments pull on the actin filaments to cause muscular contraction.

To pull the actin filaments ,the myosin fibres are activated by binding to this source of energy , the ATP. The myosin-ATP complex is hydrolyzed to yield ADP + Pi. This hydrolysis leads to pulling of the actin fibres to form cross bridges with myosin. Binding of this actin to myosin them causes disentanglement of the myosin- ATP complex and the muscle achieves a contracted state. *** ### MECHANISM OF MUSCLE RELAXATION *** Muscle relaxation is an action which immediately comes after muscle contraction. A surprising reality is the fact that muscle relaxation involves ATP too!!! In a contracted state, the two basic units of muscle fibre, myosin and actin are attached to each other by cross bridges. In the absence of ATP,the details of the physiological processes of muscle relaxation are unable to proceed and hence the muscle remain in the contracted state. This can be observed in dead people a state known as ***rigor mortis***. ![images (18).jpeg](https://cdn.steemitimages.com/DQmNW6iA5dgrL1izUGykFZrSq5WJTMoCn19hgeiFNcB9QgM/images%20(18).jpeg) [source](https://www.istockphoto.com/illustrations/muscle-contraction) *** ### HOW IS ENERGY USED IN MUSCLE RELAXATION? ***

Energy in the form of ATP is needed in basically two processes:

A. Energy in the form of ATP is used to activate the Na-ATPase pump that pumps off Calcium ions (Ca²+) from the site of the muscular contraction(the sarcoplasm) to storage sites known as the terminal cisterns. The Calcium ions are very essential in exposing the binding sites of Actin to myosin in a series of processes. Hence when this Calcium ions are pumped off,the exposed sites of binding are covered. Hence unbinding the contraction state by separation of actin and myosin.

B. Energy in the form of ATP also directly inhibits the linkage between the actin and myosin in the myosin-actin complex.The myosin-actin complex which retain the muscle in a contracted state is acted on by ATP.This separates the binding between actin and myosin. ATP now forms a myosin-ATP complex and the cycle of contraction and relaxation is primed. Hence,muscle relaxation is achieved by ATP action via these processes.

*** The illustration below explains the contraction and relaxation cycle of muscles: ![images (19).jpeg](https://cdn.steemitimages.com/DQmVXwv8PB2hXFeaFmJLeQeRjATUzxGumw7JQykei26LcZi/images%20(19).jpeg) [source](http://cecs.wright.edu/~dkender/bme422/musclemenu.htm) *** ## SUMMARY *** Muscle contraction and relaxation is a physiological process which involves a lot of subtle details and is very important component of the excitable nature of muscles. This article attempted to break down these details for easy understanding. I hope you enjoyed reading. Please, feel free to leave a comment or feedback. *** # ACKNOWLEDGMENT *** A loud shout-out to all members of the @campusconnectng family. You are the best. Special thanks to @whitestallion, @alphafx and @swaylee for their support