Muscles and Muscle Contraction by Doctor-dr

By Microbiology Doctor-dr

Muscles

While bones provide structure and support to the body, they cannot move on their own. Muscles are responsible for movement. Muscles are responsible for walking, lifting, talking, and breathing. Muscles have three primary functions: movement, posture stability, and the generation of body heat. Muscles also contribute to the form of our bodies.

Types of Muscles

Skeletal muscle, smooth muscle, and cardiac muscle are the three forms of muscle tissue present in the human body. Bones are related to skeletal muscles. Because they are under your conscious control, they are also known as voluntary. This implies you have the ability to make these muscles perform whenever you desire. Ion Plates Two and Three depict the body's primary skeletal muscles.

Because it appears striped under a microscope, skeletal muscle is also known as striated muscle [STRY ay tid]. Muscle fibres are individual muscle cells that make up the stripes. Muscle fibres range in length from a quarter of an inch to 16 inches. They are always seen in groupings known as bundles.

Smooth muscle, unlike skeletal muscle, is not consciously regulated. As a result, it is referred to as involuntary. Many internal organs are surrounded by smooth muscle. The digestive system is lined with smooth muscular layers that naturally push food forward during digestion. Smooth muscle can also be found in the walls of blood vessels. This muscle aids in the regulation of blood pressure. Cardiac muscle is an involuntary muscle that can only be found in the heart. Cardiac muscle must operate continuously for the rest of one's life. The heart beats roughly 60 to 70 times per minute at rest. For a minute, try to simulate the heart by opening and closing your hand once per second. What is the rate at which your hand becomes tired?

Muscle Contraction

To move bones, skeletal muscles contract, or shorten. Their cells, or muscle fibres, contract, allowing them to do so. The muscle pulls are stronger when there are a lot of fibres contracting. Raise your hand in the air, for example. Raise this book in the air with the same hand. Lifting the book required more muscle cell contraction than lifting your arm.

Muscles pull bones, which causes all skeletal movement. To bend a joint, one muscle pulls. Another muscle must bring the bone back to its original place to straighten the joint. Muscles join together in this way to provide a range of motion. Flexor muscles are those that bend joints. The joint flexes or bends as a result of their actions. Extensor muscles are those that extend or straighten joints. Figure 11 depicts a well-known muscle pair. The biceps is a flexor muscle. It causes the forearm to flex. The triceps is an extensor muscle. It straightens out the forearm. With your palm up, extend your arm straight out in front of you. Raise your hand to your shoulder's level. Biceps bulge can be seen or felt. The biceps has shrunk and is now firm. The triceps should be felt. It's loose and unstructured. Now straighten your arm. Feel the biceps relax as the triceps works. In muscle pairs, when one muscle contracts the other relaxes.

Tendons can be found at both ends of each muscle. Tendons are the connective tissue that connects muscles to bones. The origin is a fixed connection that connects one end of a muscle to a bone. The origin bone serves simply as a point of reference. The muscular motion has no effect on it. Another tendon connects the muscle's opposite end to the bone that it moves. The insertion is the place where the muscle is attached to the moveable bone. Take another look at Figure 11. Find the biceps-triceps muscle pair's origin and insertion locations.

Muscles seldom lie precisely on the bone they are moving. The muscles that move the lower leg, for example, are mostly located in the thigh, whereas those that move the head are mostly found in the neck. Contract your biceps muscles once more. Although this muscle is located in your upper arm, it is responsible for moving the bones in your lower arm. Are you able to identify the muscles that control your upper arm's movement?

What is the name of the muscle in your back that straightens it? Do you know where it is in your body? To maintain posture, this muscle collaborates with the abdominal muscles. The front of your ribs are flexed to your pelvis by your abdominal muscles. The back-straightening muscle moves the rear of your ribs toward the back of your pelvis.

Figure 11: A muscle pulls the bone of insertion by contracting. When one muscle contracts, the opposing muscle relaxes.

Fuel for Muscles

Your muscles must break down glucose, a kind of sugar transported in the blood, in order to function. For energy, muscles are said to "burn" glucose. This burning, like a real fire, need the presence of oxygen. Energy becomes available for muscular contraction when your muscles utilise glucose.

Only a portion of the energy generated by muscles is utilised for contraction. The remaining energy is converted to heat, which keeps the body warm. A variety of waste items are also produced. It's as though you're burning wood. When wood burns, it produces heat and light, as well as gases and ash. Carbon dioxide and water are the waste products of glucose breakdown. These wastes are taken from muscle cells and transported through the bloodstream until they may be expelled. The lungs expel carbon dioxide and water vapour. Urine is also a kind of water that leaves the body. The quantity of glucose you utilise depends on your activities. Your muscles consume very little glucose when you are seated at your workstation. When you workout hard, your muscles require a lot of energy and use a lot of glucose. During activity, you breathe more deeply and quickly. This increases the amount of oxygen available to break down glucose. It also aids in the elimination of carbon dioxide generated by muscle action. 

During strenuous exercise, your blood may not be able to supply enough oxygen to burn all of the glucose your muscles require. Your muscles then use no oxygen to break down a type of stored glucose. Another waste product is lactic acid, which is produced as a result of this process. Lactic acid buildup can make your muscles hurt and feel fatigued. You may have observed that after a strong workout, you breathe heavily for a little longer. The extra oxygen from this breathing aids in the conversion of lactic acid to glucose stored in the body.

Muscles	Origin	Insertion	Action	Function
Sternocleidomastoid	Clavicle and top of sternum	Side of cranium	Flexor	Pulls head to shoulder; together pull head to chest
Splenius	Upper vertebrae	Back of cranium	Extensor	Pulls head dup and to the side, together raise the head
Rectus abdominis	Front of pelvis	Front of ribs	Flexor	Pulls ribs to pelvis; important for posture
Erector spinae	Lower vertebrae and top of pelvis	Back of ribs and thoracic vertebrae	Extensor	Straightens back
Trapezius	Back of cranium and upper vertebrae	Clavicle and scapula	Flexor	Raises shoulder
Serratus anterior	Side of ribs	Scapula	Extensor	Pulls shoulder down
Biceps	Side of scapula	Upper radius	Flexor	Flexes forearm
Triceps	Side of scapula and back of humerus	Upper ulna	Extensor	Straightens forearm
Flexor carpi	Lower humerus	Metacarpals	Flexors	Close hand and fingers
Extensor carpi	Lower humerus	Metacarpals	Extensors	Open hand and fingers
Hamstring	Pelvis and upper femur	Upper tibia and fibula	Flexor	Pulls lower legback
Quadriceps femoris	Femur and top of pelvis	Upper front of tibia	Extensor	Straightens lower leg
Tibialis anterior	Upper side of tibia	Metatarsal	Flexor	Raises foot
Gastrocnemius	Lower back of femur	Heel bone	Extensor	Points foot down

Figure 12: Find some of these muscles in your body. can you trace them from origin to insertion and identify their actions?

Posture and Muscle Tone

The components of your body are in equilibrium with one another when you have good posture. Your neck, shoulders, lower back, pelvis, and hip joints should all be in a straight line as you stand. Your hips and back of thighs should support your weight as you sit, and your feet should be flat on the floor. Your lower back should be supported by the chair's back. Because the body is out of equilibrium, poor posture causes the muscles to work harder. Over time, bones, ligaments, and joints must carry a higher weight. This might result in discomfort in the lower back.

Muscle tone is important for good posture. Muscle tone refers to the small but continual contraction that all muscles sustain. At any given time, just a few muscle fibres in a single muscle contract. The fibres contract and relax in a cycle. While one group contracts, the other relaxes. Internal organs are also kept in place by muscle tone. The abdominal muscles' muscular tone aids in the sustaining of body weight. Weak abdominal muscles put more tension on the lower back vertebrae, which increases the risk of lower back discomfort and disc rupture. Muscle tone is maintained by exercise and stretching.

Muscle Disorders and Injuries Muscle injuries are a typical occurrence. Your muscles have most likely been overused or overstretched at times. Muscles can be damaged, although they normally heal on their own. Cramping is a frequent muscle issue. A cramp is a painful muscular spasm that lasts for a long time. When muscles are overused, they might cramp. The cramp may be relieved by massaging and gently stretching against the muscle's pull.

Muscle strain, often known as a pulled muscle, can occur when a muscle is overworked. Muscle tension can be caused by lifting too much weight. A strain, which is a muscle injury, should not be confused with a sprain, which is an injury to the ligaments and tendons of a joint. A strain usually does not cause permanent harm, however the muscle may be painful for some time. Large muscles, such as the thigh and calf muscles, are frequently strained. Ice packs can help reduce swelling and lessen some of the discomfort associated with muscular strains. Heat can be administered after 48 hours. Resting the muscle helps it recover faster. A torn muscle is a more serious injury. A ripped muscle fibre is referred to as a torn muscle.

Heavy lifting or a sudden push or pull might cause it. Tendons can rupture or be pushed away from the bone. Torn muscles are treated in the same way that muscular tension is treated. Some of the discomfort may be relieved by ice, followed by heat and relaxation. Because this is a serious injury, the muscle may take a long time to heal. Tendon damage can also occur as a result of overuse or injury. When a tendon gets inflamed and swollen, it is referred as as. Tendonitis (ten duh NY tis) is a kind of tendonitis. One example of this injury is tennis elbow, which causes a distinct ache in the region of the elbow. Tendonitis is a bothersome ailment since it might reoccur. It also takes a long time to recover. Rest appears to be the only option.

When a part of the intestine pushes through the layer of skeletal muscle in the belly or groyne, it is called a hernia [HUR nee uh]. Hernias are most common in this layer of muscle when there are naturally occurring weak places. Hernias are most commonly caused by lifting too much weight, however they can also be caused by coughing or sneezing excessively. Hernias are most common in people who lack power and muscular tone. The intestine may move back into place with the use of a sup port, enabling the muscle to recover on its own. Surgical correction of the problem, on the other hand, is frequently required.

Some muscle illnesses have unclear aetiology. Muscular dystrophy [MUHS kyuh lur DIS truh fee] is one such ailment. a genetic illness that causes muscle fibres to deteriorate over time. Its victims lose control of their muscles over time, eventually being unable to move. The paralysis of the muscles that govern respiration or the failure of the heart muscle are both causes of death. This illness has no recognised treatment.

Review of the Lesson

Muscles assist in the movement of the body, the maintenance of posture, and the production of heat. Some muscles can be intentionally controlled. Other muscles operate on their own. Skeletal muscles function in pairs to move bones by contracting. Glucose, a kind of sugar in the body, provides the energy for muscles to contract. It is important to exercise in order to maintain muscular tone. Muscular tone promotes proper posture and aids in the prevention of muscle ailments such as cramps, strains, and tears.