A stretched or torn ligament. Ankle and wrist sprains are common. Symptoms include pain, swelling, bruising, and being unable to move the joint. Strain streyn. A stretched or torn muscle or tendon. Twisting or pulling these tissues can cause a strain. Strains can happen suddenly or develop over time. Back and hamstring muscle strains are common. Many people get strains playing sports. Voluntary VOL-uhn-ter-ee muscles. Muscles that you can control. Many of our publications are available in print.
Would you like to order publications on pain to be mailed to you? Visit our online order form. Sprains and Strains MedlinePlus. Basic facts about muscles Did you know you have more than muscles in your body? Why healthy muscles matter to you Healthy muscles let you move freely and keep your body strong. Different kinds of muscles have different jobs Skeletal muscles are connected to your bones by tough cords of tissue called tendons TEN-duhns.
What can go wrong? Injuries Almost everyone has had sore muscles after exercising or working too much. How can I keep my muscles more healthy? Physical activity Muscles that are not used will get smaller and weaker. This is known as atrophy A-truh-fee. Get 60 minutes of physical activity every day. A balanced diet: Emphasizes fruits, vegetables, whole grains, and fat-free or low-fat dairy products like milk, cheese, and yogurt.
Includes protein from lean meats, poultry, seafood, beans, eggs, and nuts. Is low in solid fats, saturated fats, cholesterol, salt sodium , added sugars, and refined grains.
Is as low as possible in trans fats. Balances calories taken in through food with calories burned in physical activity to help maintain a healthy weight.
Prevent injuries To help prevent sprains, strains, and other muscle injuries: Warm up and cool down. They are called warm-up exercises because they make the muscles warmer—and more flexible. Cool-down exercises loosen muscles that have tightened during exercise. Wear the proper protective gear for your sport, for example, pads or helmets. This will help reduce your risk of injuring yourself.
Dehydration can cause many medical problems. You might need to see a doctor, or you might just need to rest for a while.
Increase physical activity gradually over time. Be careful when you lift heavy objects. Keep your back straight and bend your knees to lift the object. This will protect the muscles in your back and put most of the weight on the strong muscles in your legs. Get someone to help you lift something heavy. Because visceral muscle is controlled by the unconscious part of the brain, it is known as involuntary muscle—it cannot be directly controlled by the conscious mind.
This smooth appearance starkly contrasts with the banded appearance of cardiac and skeletal muscles. Found only in the heart , cardiac muscle is responsible for pumping blood throughout the body. Cardiac muscle tissue cannot be controlled consciously, so it is an involuntary muscle. While hormones and signals from the brain adjust the rate of contraction, cardiac muscle stimulates itself to contract. The natural pacemaker of the heart is made of cardiac muscle tissue that stimulates other cardiac muscle cells to contract.
Because of its self-stimulation, cardiac muscle is considered to be autorhythmic or intrinsically controlled. The cells of cardiac muscle tissue are striated—that is, they appear to have light and dark stripes when viewed under a light microscope.
The arrangement of protein fibers inside of the cells causes these light and dark bands. Striations indicate that a muscle cell is very strong, unlike visceral muscles. The cells of cardiac muscle are branched X or Y shaped cells tightly connected together by special junctions called intercalated disks. Intercalated disks are made up of fingerlike projections from two neighboring cells that interlock and provide a strong bond between the cells.
The branched structure and intercalated disks allow the muscle cells to resist high blood pressures and the strain of pumping blood throughout a lifetime. These features also help to spread electrochemical signals quickly from cell to cell so that the heart can beat as a unit.
Skeletal muscle is the only voluntary muscle tissue in the human body—it is controlled consciously. Every physical action that a person consciously performs e. The function of skeletal muscle is to contract to move parts of the body closer to the bone that the muscle is attached to.
Most skeletal muscles are attached to two bones across a joint, so the muscle serves to move parts of those bones closer to each other. Skeletal muscle cells form when many smaller progenitor cells lump themselves together to form long, straight, multinucleated fibers. Striated just like cardiac muscle, these skeletal muscle fibers are very strong.
Skeletal muscle derives its name from the fact that these muscles always connect to the skeleton in at least one place. Most skeletal muscles are attached to two bones through tendons. Tendons are tough bands of dense regular connective tissue whose strong collagen fibers firmly attach muscles to bones.
Tendons are under extreme stress when muscles pull on them, so they are very strong and are woven into the coverings of both muscles and bones. Muscles move by shortening their length, pulling on tendons, and moving bones closer to each other.
One of the bones is pulled towards the other bone, which remains stationary. The place on the stationary bone that is connected via tendons to the muscle is called the origin. The place on the moving bone that is connected to the muscle via tendons is called the insertion. The belly of the muscle is the fleshy part of the muscle in between the tendons that does the actual contraction.
Skeletal muscles are named based on many different factors, including their location, origin and insertion, number of origins, shape, size, direction, and function. Skeletal muscles rarely work by themselves to achieve movements in the body.
More often they work in groups to produce precise movements. The muscle that produces any particular movement of the body is known as an agonist or prime mover. The agonist always pairs with an antagonist muscle that produces the opposite effect on the same bones. For example, the biceps brachii muscle flexes the arm at the elbow.
As the antagonist for this motion, the triceps brachii muscle extends the arm at the elbow. When the triceps is extending the arm, the biceps would be considered the antagonist.
Synergists are muscles that help to stabilize a movement and reduce extraneous movements. They are usually found in regions near the agonist and often connect to the same bones.
Because skeletal muscles move the insertion closer to the immobile origin, fixator muscles assist in movement by holding the origin stable. If you lift something heavy with your arms, fixators in the trunk region hold your body upright and immobile so that you maintain your balance while lifting. Skeletal muscle fibers differ dramatically from other tissues of the body due to their highly specialized functions. Many of the organelles that make up muscle fibers are unique to this type of cell.
The sarcolemma is the cell membrane of muscle fibers. The sarcolemma acts as a conductor for electrochemical signals that stimulate muscle cells. Examples of such activities include running, chewing, and writing. Smooth muscle lines the inside of blood vessels and organs, such as the stomach, and is also known as visceral muscle. It is the weakest type of muscle but has an essential role in moving food along the digestive tract and maintaining blood circulation through the blood vessels.
Located only in the heart, cardiac muscle pumps blood around the body. Cardiac muscle stimulates its own contractions that form our heartbeat. Signals from the nervous system control the rate of contraction. This type of muscle is strong and acts involuntarily. When muscles contract, they contribute to gross and fine movement. Most muscle movement of the body is under conscious control.
However, some movements are reflexive, such as withdrawing a hand from a source of heat. Muscle tendons stretch over joints and contribute to joint stability. Muscle tendons in the knee joint and the shoulder joint are crucial in stabilization. The core muscles are those in the abdomen, back, and pelvis, and they also stabilize the body and assist in tasks, such as lifting weights. Skeletal muscles help keep the body in the correct position when someone is sitting or standing. This is known as posture.
Good posture relies on strong, flexible muscles. Stiff, weak, or tight muscles contribute to poor posture and misalignment of the body. Long-term, bad posture leads to joint and muscle pain in the shoulders, back, neck, and elsewhere.
The heart is a muscle that pumps blood throughout the body. The movement of the heart is outside of conscious control, and it contracts automatically when stimulated by electrical signals.
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