Smooth muscle is found in the walls of hollow organs throughout the body. Smooth muscle contractions are involuntary movements triggered by impulses that travel through the autonomic nervous system to the smooth muscle tissue.
The arrangement of cells within smooth muscle tissue allows for contraction and relaxation with great elasticity. The smooth muscle in the walls of organs like the urinary bladder and the uterus allow those organs to expand and relax as needed. The smooth muscle of the alimentary canal the digestive tract facilitates the peristaltic waves that move swallowed food and nutrients.
In the eye smooth muscle changes the shape of the lens to bring objects into focus. Artery walls include smooth muscle that relaxes and contracts to move blood through the body. The heart wall is composed of three layers.
Cardiac muscle, found only in the myocardium, contracts in response to signals from the cardiac conduction system to make the heart beat. Shapes of skeletal muscle Generally speaking, skeletal muscles come in four main shapes, including: Spindle — wide through the middle and tapering at both ends, such as the biceps on the front of the upper arm. Flat — like a sheet, such as the diaphragm that separates the chest from the abdominal cavity. Triangular — wider at the bottom, tapered at the top, such as the deltoid muscles of the shoulder.
Circular — a ring-shape like a doughnut, such as the muscles that surround the mouth, the pupils and the anus. These are also known as sphincters. Muscle disorders Muscle disorders may cause weakness, pain, loss of movement and even paralysis. The range of problems that affect muscles are collectively known as myopathy. The three main types of muscle include skeletal, smooth and cardiac.
The brain, nerves and skeletal muscles work together to cause movement — this is collectively known as the neuromuscular system.
More information here. Give feedback about this page. Was this page helpful? Yes No. View all bones muscles and joints. Related information. From other websites How Stuff Works. Content disclaimer Content on this website is provided for information purposes only. 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. Because there are so many skeletal muscles in your body, we can't list them all here. But here are a few of the major ones:. Reviewed by: KidsHealth Medical Experts. Larger text size Large text size Regular text size.
Smooth Muscles Smooth muscles — sometimes also called involuntary muscles — are usually in sheets, or layers, with one layer of muscle behind the other. Page 1 A Hearty Muscle The muscle that makes up the heart is called cardiac muscle. Skeletal Muscle. Face Muscles You may not think of it as a muscular body part, but your face has plenty of muscles. Major Muscles Because there are so many skeletal muscles in your body, we can't list them all here.
But here are a few of the major ones: In each of your shoulders is a deltoid say: DEL-toyd muscle. Your deltoid muscles help you move your shoulders every which way — from swinging a softball bat to shrugging your shoulders when you're not sure of an answer.
The pectoralis say: pek-tuh-RAH-lus muscles are found on each side of your upper chest. These are usually called pectorals say: PEK-tuh-rulz , or pecs, for short. When many boys hit puberty, their pectoral muscles become larger. Many athletes and bodybuilders have large pecs, too.
These muscles work automatically without stopping, day and night. They are similar in structure to the skeletal muscles, so doctors sometimes classify them as striated muscles. The cardiac muscles contract so that the heart can squeeze out blood and then relax so that it can fill up with blood again.
Muscle weakness can affect people with upper or lower motor neuron dysfunction or conditions such as myasthenia gravis that affect the area where the nerves join the muscle. Stroke , spinal cord compression, and multiple sclerosis can all also lead to muscle weakness.
They are likely to use the universal scale for testing muscle strength:. If a doctor finds evidence of muscle weakness, they may order tests to identify the underlying problem.
The treatment will depend on the cause. A person can often relieve the symptoms of a muscle injury using the RICE method :. If a person experiences extreme and unexplained muscle pain or muscle weakness, especially if they also have difficulty breathing, they should see a doctor as soon as possible. Developing muscles through exercise can improve balance, bone health, and flexibility, and it can enhance strength and stamina.
People can choose from a wide range of physical activity options, but there are two main types of exercise: aerobic and anaerobic. Aerobic exercise sessions are typically of long duration and require medium-to-low levels of exertion. This type of exercise requires the body to use the muscles at well below their maximum strength capacity.
A marathon is an example of an aerobic activity with a very long duration. They use a higher proportion of the slow-twitch muscle fibers. Energy consumption comes from carbohydrates, fat, and protein, and the body produces high quantities of oxygen and very little lactic acid.
During anaerobic exercise, the muscles contract intensely at a level nearer to their maximum strength. Athletes who aim to improve their strength, speed, and power will focus more on this type of exercise. A single anaerobic activity lasts from a few seconds to a maximum of 2 minutes. Examples include weightlifting, sprinting, climbing, and jumping rope. Anaerobic exercise uses more fast-twitch muscle fibers. The main fuel sources are ATP or glucose, and the body uses less oxygen, fat, and protein.
This type of activity produces high quantities of lactic acid.
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