The human body has more than 650 individual muscles to provide movement for the body. The muscles make up nearly half the weight of the human body. Muscles stretch across joints to link one bone with another and work in groups to respond to nerve impulses. Without muscles we cannot open mouth, speak, shake hands, walk, talk, smile, blink, breathe or move food through digestive system. Muscles are all made of a type of elastic tissue. Thousands or even tens of thousands, of small fibers make up each muscle.
The muscular system consist of three different types of muscle tissues: skeletal, cardiac, smooth. Each of these different tissues has the ability to contract, which then allows body movements and functions. There are two types of muscles in the system: the involuntary muscles, and the voluntary muscles. The muscle in which we are allow to control by ourselves are called the voluntary muscles and the ones we cannot control are the involuntary muscles. The cardiac muscle is an example of involuntary muscle.
Skeletal Muscle
Skeletal muscles are attached to the skeleton. Skeletal muscles are voluntary muscles – we think about what movements we want to make and send messages via our nervous system to tell the appropriate muscle(s) to contract. Together, the skeletal muscles work with your bones to give your body power and strength. In most cases, a skeletal muscle is attached to one end of a bone. It stretches all the way across a joint (the place where two bones meet) and then attaches again to another bone. Skeletal muscles are held to the bones with the help of tendons (cords made of tough tissue which work as special connector pieces between bone and muscle.). Some of your biggest and most powerful muscles are in your back, near your spine. These muscles help keep you upright and standing tall.
Cardiac Muscle
Cardiac muscles are involuntary muscles found only in the heart and are controlled by the lower section of the brain called the medulla oblongata. The cardiac muscle is the tissue that makes up the wall of the heart called the mydocardium. The cardiac muscle is attached together instead of been attach to a bone. It is a twitch muscle – it only does short single contractions.
Smooth Muscle
Smooth muscle is found in our internal organs: urinary bladder, gallbladder, arteries, digestive system and veins. Smooth muscle can stretch and maintain tension over extended periods. These are involuntary muscles, we cannot consciously control them. The smooth muscles are controlled by the nervous system and hormones. Smooth muscles are usually in sheets, or layers, with one layer of muscle behind the other. Smooth muscles are generally spherical, as most other human cells are, and each contains one nucleus.
Image source: https://www.nsbri.org/humanphysspace/focus5/f5-190.jpg
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