Muscles are arranged in groups of fibres that contract when triggered by nerves. They need oxygen, and a lot of energy, supplied by food. Regular, vigorous exercise increases a muscle’s size and improves its circulation of blood.
Types of Muscles
You have three different types of muscles in your body: voluntary muscles, involuntary muscles, and cardiac muscles.
Voluntary Muscles
These are your skeletal muscles. They are attached to the bones and are used to move the body. This sort of muscle only works when you want it to. Your leg won’t bend to kick the ball unless you want it to. So it is called a voluntary muscle.
Voluntary muscles come in many different sizes and shapes to allow them to do many types of jobs. Some of your biggest and most powerful muscles are in your back, near your spine. These muscles help keep you upright and standing tall.
Involuntary Muscles
Involuntary Muscles - sometimes also called ‘smooth muscles’ - are usually in sheets, or layers, with one layer of muscle behind the other. You can’t control this type of muscle. Your brain and body tell these muscles what to do without you even thinking about it. An example is muscle around the gut which pushes food along it.
Cardiac Muscles
The muscle that makes up the heart is called cardiac muscle. The thick muscles of the heart contract to pump blood out and then relax to let blood back in after it has circulated through the body. Just like involuntary muscle, cardiac muscle works all by itself with no help from you.
Face Muscles
You may not think of it as a muscular body part, but your face has plenty of muscles. You can check them out next time you look in the mirror. Facial muscles don’t all attach directly to bone like they do in the rest of the body. Instead, many of them attach under the skin. This allows you to contract your facial muscles just a tiny bit and make dozens of different kinds of faces. Even the smallest movement can turn a smile into a frown. You can raise your eyebrow to look surprised or wiggle your nose. And while you’re looking at your face, don’t pass over your tongue - a muscle that’s attached only at one end! Your tongue is actually made of a group of muscles that work together to allow you to talk and help you chew food. Stick out your tongue and wiggle it around to see those muscles at work.Muscles warm up when used, providing about four fifths of the body’s heat. Many organs have muscles, such as the heart, intestines and bladder. Most voluntary muscles (muscles under conscious control) are anchored to bones at two or more points by strong cords called tendons.
Contraction
Muscle fibre contains tiny strands called myofibrils. A myofibril contains overlapping layers of two proteins: actin and myosin. When triggered by an electrical nerve signal, the actin and myosin attract each other, and their layers slide closer together. The myofibril shortens; the muscle contracts.
Muscle Functions
* Move bones at joints.
* Force food through intestines.
* Blink the eyelids.
* Smile or make other facial expressions.
* Make breathing movements of chest and diaphragm.
* Contract walls of blood vessels.
Muscle Action
Muscles can only pull, not push. So, they often work in opposing pairs called antagonists; one muscle in the pair contracts while the other relaxes.
Muscle Facts
* Muscle cells can contract by up to one-third of their length.
* The muscles that work a gnat’s wings can beat at over 1000 times a second.
* Humans have more than 600 muscles, but an average sized caterpillar has over 2,000.
* The muscles that hold shellfish shells together remain contracted for hours on end without using up much energy or getting tired.
* It takes the interaction of 72 different muscles to produce human speech.
Muscle Records
* Longest muscle is the sartorius, which runs from the pelvis to just below the knee.
* Biggest muscle is the gluteus maximus (buttock).
* Smallest muscle is the stapedius in the middle ear less than 1.27mm long.
* Relative to size, the strongest muscle in the body is the tongue.
* Fastest muscle blinks the eyelids up to five times every second.
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