Muscles & Joints
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In this video you will get a fun introduction that teaches young students all about the muscular system and highlights the various muscles of the body. In this video we highlight Cardiac, Skeletal and Smooth muscles with examples in each category and their purposes. We also learn about Voluntary and Involuntary muscles with examples and teach about their purposes as well!
What Are Muscles and What Do They Do?
What Are Muscles and What Do They Do?
Muscles pull on the joints, allowing us to move. They also help the body do such things as chewing food and then moving it through the digestive system.
Even when we sit perfectly still, muscles throughout the body are constantly moving. Muscles help the heart beat, the chest rise and fall during breathing, and blood vessels regulate the pressure and flow of blood. When we smile and talk, muscles help us communicate, and when we exercise, they help us stay physically fit and healthy.
Humans have three different kinds of muscle:
Skeletal muscle is attached by cord-like tendons to bone, such as in the legs, arms, and face. Skeletal muscles are called striated (STRY-ay-ted) because they are made up of fibers that have horizontal stripes when viewed under a microscope. These muscles help hold the skeleton together, give the body shape, and help it with everyday movements (known as voluntary muscles because you can control them). They can contract (shorten or tighten) quickly and powerfully, but they tire easily.These are the muscles we use to move around. They cover our skeleton and move our bones. Sometimes they are called striped muscles because they come in long dark and light bands of fibers and look striped. These muscles are voluntary because we control them directly with signals from our brains.
3. Cardiac muscle is found in the heart. The walls of the heart's chambers are composed almost entirely of muscle fibers. Cardiac muscle is also an involuntary type of muscle. Its rhythmic, powerful contractions force blood out of the heart as it beats. This is a special muscle that pumps our heart and blood through our body.
2. Smooth, or involuntary, muscle is also made of fibers, but this type of muscle looks smooth, not striated. We can't consciously control our smooth muscles; rather, they're controlled by the nervous system automatically (which is why they're also called involuntary). Examples of smooth muscles are the walls of the stomach and intestines, which help break up food and move it through the digestive system. Smooth muscle is also found in the walls of blood vessels, where it squeezes the stream of blood flowing through the vessels to help maintain blood pressure. Smooth muscles take longer to contract than skeletal muscles do, but they can stay contracted for a long time because they don't tire easily.
Five Important Muscles in Your Back and What They Do:
How Do Muscles Work?
How Do Muscles Work?
The movements that muscles make are coordinated and controlled by the brain and nervous system. The involuntary muscles are controlled by structures deep within the brain and the upper part of the spinal cord called the brain stem. The voluntary muscles are regulated by the parts of the brain known as the cerebral motor cortex and the cerebellum (ser-uh-BEL-um).
When you decide to move, the motor cortex sends an electrical signal through the spinal cord and peripheral nerves to the muscles, making them contract. The motor cortex on the right side of the brain controls the muscles on the left side of the body and vice versa.
The cerebellum coordinates the muscle movements ordered by the motor cortex. Sensors in the muscles and joints send messages back through peripheral nerves to tell the cerebellum and other parts of the brain where and how the arm or leg is moving and what position it's in. This feedback results in smooth, coordinated motion. If you want to lift your arm, your brain sends a message to the muscles in your arm and you move it. When you run, the messages to the brain are more involved, because many muscles have to work in rhythm.
Muscles move body parts by contracting and then relaxing. Muscles can pull bones, but they can't push them back to the original position. So they work in pairs of flexors and extensors. The flexor contracts to bend a limb at a joint. Then, when the movement is completed, the flexor relaxes and the extensor contracts to extend or straighten the limb at the same joint. For example, the biceps muscle, in the front of the upper arm, is a flexor, and the triceps, at the back of the upper arm, is an extensor. When you bend at your elbow, the biceps contracts. Then the biceps relaxes and the triceps contracts to straighten the elbow.
IN OTHER WORDS
Muscles work by getting shorter. We say that they contract.
Muscles are attached to bones by strong tendons. When a muscle contracts, it pulls on the bone, and the bone can move if it is part of a joint.
Muscles can only pull, but not push. This would be a problem if a joint was controlled by just one muscle. As soon as the muscle had contracted and pulled on a bone, that would be it, with no way to move the bone back again. The problem is solved by having muscles in pairs, called antagonistic pairs.
To move the bone back the second muscle of the antagonistic pair contracts. Examples of antagonistic pairs are biceps and triceps.
Main functions of the muscular system
Main functions of the muscular system
Main functions of the muscular system
Mobility
The muscular system’s main function is to allow movement. When muscles contract, they contribute to gross and fine movement.
Gross movement refers to large, coordinated motions and includes:
walking
running
swimming
Fine movement involves smaller movements, such as:
writing
speaking
facial expressions
The smaller skeletal muscles are usually responsible for this type of action.
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.
Stability
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.
Posture
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.
Circulation
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.
Smooth muscle in the arteries and veins plays a further role in the circulation of blood around the body. These muscles maintain blood pressure and circulation in the event of blood loss or dehydration.
They expand to increase blood flow during times of intense exercise when the body requires more oxygen.
Respiration
Breathing involves the use of the diaphragm muscle.
The diaphragm is a dome-shaped muscle located below the lungs. When the diaphragm contracts, it pushes downward, causing the chest cavity to get bigger. The lungs then fill with air. When the diaphragm muscle relaxes, it pushes air out of the lungs.
When someone wants to breath more deeply, it requires help from other muscles, including those in the abdomen, back, and neck.
Urination
The urinary system comprises both smooth and skeletal muscles, including those in the:
bladder prostate
kidneys ureters
penis or vagina urethra
The muscles and nerves must work together to hold and release urine from the bladder.
Urinary problems, such as poor bladder control or retention of urine, are caused by damage to the nerves that carry signals to the muscles.
Digestion
The muscular system allows for movement within the body, for example, during digestion or urination.
Smooth muscles in the gastrointestinal or GI tract control digestion. The GI tract stretches from the mouth to the anus.
Food moves through the digestive system with a wave-like motion called peristalsis. Muscles in the walls of the hollow organs contract and relax to cause this movement, which pushes food through the esophagus into the stomach.
The upper muscle in the stomach relaxes to allow food to enter, while the lower muscles mix food particles with stomach acid and enzymes.
The digested food moves from the stomach to the intestines by peristalsis. From here, more muscles contract to pass the food out of the body as stool.
Childbirth
Smooth muscles in the uterus expand and contract during childbirth. These movements push the baby. Also, the pelvic floor muscles help to guide the baby’s head down the birth canal.
Vision
Six skeletal muscles around the eye control its movements. These muscles work quickly and precisely, and allow the eye to:
maintain a stable image
scan the surrounding area
track moving objects
If someone experiences damage to their eye muscles, it can impair their vision.
Organ protection
Muscles in the torso protect the internal organs at the front, sides, and back of the body. The bones of the spine and the ribs provide further protection. Muscles also protect the bones and organs by absorbing shock and reducing friction in the joints.
Temperature regulation
Maintaining normal body temperature is an important function of the muscular system. Almost 85 percent of the heat a person generates in their body comes from contracting muscles.
When body heat falls below optimal levels, the skeletal muscles increase their activity to make heat. Shivering is one example of this mechanism. Muscles in the blood vessels also contract to maintain body heat.
Body temperature can be brought back within normal range through the relaxation of smooth muscle in the blood vessels. This action increases blood flow and releases excess heat through the skin.
In Other Words
Imagine your muscles are tiny furnaces!
They burn fuel (sugar) to give you energy to move and play. But guess what? Burning fuel also creates heat, just like a fire.
That heat from your muscles helps keep your body warm! Here's how it works:
Making Heat: When you move around, your muscles work hard. This "work" makes them heat up, like tiny engines.
Sharing the Warmth: This heat travels in two ways:
Blood Stream: Warm blood from your muscles flows throughout your body, carrying heat like a river.
Direct Touch: The heat also spreads directly from your muscles to your skin, like warming your hands on a hot mug.
Keeping You Cozy: This heat from your muscles helps your body stay at a comfortable temperature, no matter if it's a chilly day outside or you're running around playing.
Bonus Fun Fact: When you feel cold and start shivering, that's your body actually making your muscles work extra hard to generate even more heat!
Remember: Muscles are like tiny furnaces, keeping you warm from the inside out!
What are Muscles?
Brief Summary
What Are Joints and What Do They Do?
What Are Joints and What Do They Do?
What Are Joints and What Do They Do?
Joints are where two bones meet. They make the skeleton flexible — without them, movement would be impossible.
Joints allow our bodies to move in many ways. Some joints open and close like a hinge (such as knees and elbows), whereas others allow for more complicated movement a shoulder or hip joint, for example, allows for backward, forward, sideways, and rotating movement.
Functional Classification of Joints
Functional Classification of Joints
Joints are classified by their range of movement
Immovable, or fibrous joints don't move. The dome of the skull, for example, is made of bony plates, which move slightly during birth and then fuse together as the skull finishes growing. Between the edges of these plates are links, or joints, of fibrous tissue. Fibrous joints also hold the teeth in the jawbone.
Partially movable, or cartilaginous joints move a little. They are linked by cartilage, as in the spine. Each of the vertebrae in the spine moves in relation to the one above and below it, and together these movements give the spine its flexibility.
Freely movable, or synovial joints move in many directions. The main joints of the body — such as those found at the hip, shoulders, elbows, knees, wrists, and ankles — are freely movable. They are filled with synovial fluid, which acts as a lubricant to help the joints move easily.
Four kinds of freely movable joints play a big part in voluntary movement
Hinge joints allow movement in one direction, as seen in the knees and elbows.
Ball-and-socket joints allow the greatest freedom of movement. The hips and shoulders have this type of joint, in which the round end of a long bone fits into the hollow of another bone.
Pivot joints allow a rotating or twisting motion, like that of the head moving from side to side.
Ellipsoidal joints. Ellipsoidal joints, such as the wrist joint, allow all types of movement except pivotal movements
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