Lesson Overview 32.2 The Muscular System PowerPoint Modified by Mrs. Lagreca

Lesson Overview Lesson Overview The Muscular System THINK ABOUT IT How much of your body do you think is muscle? As surprising at it might seem, about one third of the mass of an average person ’ s body is muscle. What ’ s all that muscle doing? Some of the answers might surprise you.

Lesson Overview Lesson Overview The Muscular System Muscle Tissue What are the principal types of muscle tissue?

Lesson Overview Lesson Overview The Muscular System Muscle Tissue What are the principal types of muscle tissue? There are three different types of muscle tissue: Skeletal Smooth Cardiac.

Lesson Overview Lesson Overview The Muscular System Muscle Tissue Muscle tissue is found everywhere in the body. Each of the 3 different types of muscle tissue are specialized for a specific function in the body.

Lesson Overview Lesson Overview The Muscular System Skeletal Muscles Skeletal muscles are usually attached to bones. Most skeletal muscle movements are consciously controlled by the central nervous system (the brain and spinal cord) – Voluntary muscles.

Lesson Overview Lesson Overview The Muscular System Skeletal Muscles When viewed under a microscope, skeletal muscle appears to have alternating light and dark bands called “striations.” For this reason, it is said to be striated.

Lesson Overview Lesson Overview The Muscular System Skeletal Muscles Skeletal muscle cells are large, have many nuclei, and vary in length. The smallest skeletal muscle, which is about 1 millimeter long is found in the middle ear. The longest skeletal muscle, which may be as long as 30 centimeters, runs from the hip to the knee. Because skeletal muscle cells are long and slender, they are often called muscle fibers.

Lesson Overview Lesson Overview The Muscular System Smooth Muscles Smooth muscle cells don’t have striations and therefore look “smooth” under the microscope. Smooth muscle cells are spindle-shaped and usually have a single nucleus.

Lesson Overview Lesson Overview The Muscular System Smooth Muscles Smooth muscle cells are found throughout the body, and form part of the walls of hollow structures such as the stomach, blood vessels, and intestines. Smooth muscles’ movements are usually involuntary and perform functions such as moving food through the digestive tract, controlling the flow of blood through the circulatory system, and even decreasing pupil size in bright light.

Lesson Overview Lesson Overview The Muscular System Cardiac Muscle Cardiac muscle is found in the heart. It is striated like skeletal muscle, although its cells are smaller and usually have just one or two nuclei.

Classification of Muscle Skeletal- found in limbs Cardiac- found in heart Smooth- Found in organs Striated, multi- nuclei Striated, 1 nucleus Not striated, 1 nucleus voluntaryinvoluntary

Lesson Overview Lesson Overview The Muscular System Muscle Morphology What is the structure and function of muscle components?

Muscles and Muscle Fibers Muscles are composed of many fibers that are arranged in bundles called FASCICLES Individual muscles are separated by FASCIA, a connective tissue that surrounds muscles

Compartment Syndrome

ENERGY Fibers contain multiple mitochondria for energy Mitochondria produce energy in the form of ATP through the process of cellular respiration. Most fibers have multiple nuclei

Lesson Overview Lesson Overview The Muscular System Muscle Contraction How do muscles contract?

Lesson Overview Lesson Overview The Muscular System Control of Muscle Contraction Skeletal muscles are useful only if they contract in a controlled fashion. Impulses from motor neurons control the contraction of muscle fibers.

Lesson Overview Lesson Overview The Muscular System G3HGBrBw Video Break!

Lesson Overview Lesson Overview The Muscular System Control of Muscle Contraction When you lift something light, such as a sheet of paper, your brain stimulates only a few cells to contract. As you exert maximum effort, like this pole vaulter, almost all the muscle cells in your arm are stimulated to contract.

Lesson Overview Lesson Overview The Muscular System Muscles and Movement How do muscle contractions produce movement?

Lesson Overview Lesson Overview The Muscular System Muscles and Movement How do muscle contractions produce movement? Skeletal muscles generate force and produce movement by pulling on body parts as they contract.

Lesson Overview Lesson Overview The Muscular System How Muscles and Bones Interact Skeletal muscles are joined to bones by tough connective tissues called tendons. Tendons pull on the bones and make them work like levers. The joint functions as a fulcrum—the fixed point around which the lever moves. The muscles provide the force to move the lever.

Lesson Overview Lesson Overview The Muscular System How Muscles and Bones Interact Most skeletal muscles work in opposing pairs—when one muscle contracts, the other relaxes.

Lesson Overview Lesson Overview The Muscular System How Muscles and Bones Interact For example, when the biceps muscle contracts, it bends the elbow joint.

Lesson Overview Lesson Overview The Muscular System How Muscles and Bones Interact When the triceps muscle contracts, it opens the elbow joint.

Lesson Overview Lesson Overview The Muscular System Types of Muscle Fibers There are two principal types of skeletal muscle fibers—red and white. Red muscle, or slow twitch muscle, contains many mitochondria. The abundant mitochondria and oxygen allow these fibers to derive their energy through aerobic respiration and work for long periods of time. Red muscle is useful for endurance activities like long- distance running.

Lesson Overview Lesson Overview The Muscular System Types of Muscle Fibers White muscle, or fast-twitch muscle, contracts more rapidly and generates more force than red muscle, but its cells contain few mitochondria and tire quickly. White fibers are useful for activities that require great strength or quick bursts of speed like sprinting.

Lesson Overview Lesson Overview The Muscular System Exercise and Health Skeletal muscles remain in a state of partial contraction called resting muscle tone. Muscle tone is responsible for keeping the back and legs straight and the head upright, even when you are relaxed.

Lesson Overview Lesson Overview The Muscular System Exercise and Health Muscles that are exercised regularly stay firm and increase in size and strength. Muscles that are not used become weak and can visibly decrease in size. Without gravity, many muscles go unused. An astronaut in space may lose up to 5 percent of muscle mass a week.

Lesson Overview Lesson Overview The Muscular System Exercise and Health Aerobic exercises—such as running—place strong demands on the heart and lungs, helping these systems to become more efficient. Regular exercise also strengthens your bones, making them thicker and stronger and less likely to become injured. Resistance exercises increase muscle size and strength and will help you to maintain coordination and flexibility over time.