Muscular System

The Muscular System Muscles are responsible for all types of body movement Three basic muscle types are found in the body Skeletal muscle Cardiac muscle Smooth muscle

Characteristics of Muscles Muscle cells are elongated (muscle cell = muscle fiber) Contraction of muscles is due to the movement of microfilaments All muscles share some terminology Prefix myo refers to muscle Prefix mys refers to muscle Prefix sarco refers to flesh

Muscular System Functions The main function of the muscular system is to move your bones.

Voluntary Muscle Voluntary muscles are under your conscious control for things like running, grabbing, and other activities. Video Notes Anatomy Muscular System Voluntary

Skeletal Muscle Skeletal muscles are voluntary, connected to bones, and are responsible for your movement.

Skeletal Muscle Characteristics Most are attached by tendons to bones

Skeletal Muscle Characteristics Cells are multinucleate Striated – have visible banding Voluntary – subject to conscious control Cells are surrounded and bundled by connective tissue

Function of Muscles Produce movement Maintain posture Stabilize joints Generate heat

Nerve Stimulus to Muscles Skeletal muscles must be stimulated by a nerve to contract Motor unit One neuron Muscle cells stimulated by that neuron

Muscles and Body Movements Movement is attained due to a muscle moving an attached bone

Muscles and Body Movements Muscles are attached to at least two points Origin – attachment to a moveable bone Insertion – attachment to an immovable bone

Muscles work in pairs. Muscles can only contract or pull, not push and are controlled by electrical impulses from the brain.

Muscles work in pairs. Because muscle cells can only contract, not extend, skeletal muscles must work in pairs.

Muscles work in pairs. While one muscle contracts, the other muscle in the pair returns to its original length.

Muscles work in pairs. Flexors bend parts of your body. Extensors straighten parts of your body.

Levers In Your Body Bones and muscles make levers which are machines that make it easier to lift and move things.

Lever Systems and Leverage bones act as levers joints are the fulcrums levers can operate at a mechanical advantage when a smaller effort can move a heavier load mechanical disadvantage when a larger effort moves lighter load position of effort, load, and fulcrum on lever determine mechanical advantage or disadvantage

Levers In Your Body Levers achieve mechanical advantage: a measure of how much easier it is to lift or move something.

Naming Skeletal Muscles Most skeletal muscle names contain combinations of word roots for their features 1.size 2.shape 3.action 4.number of origins 5.location of muscle 6.sites of origin and insertion

Involuntary Muscle Involuntary muscles are not under your conscious control and are responsible for things like breathing and digesting food. Video Notes Anatomy Muscular System Involuntary

Muscular System Functions The muscular system is responsible for the beating of your heart.

Cardiac Muscle Cardiac muscle is involuntary and only found in the heart. Video Notes Anatomy Muscular System Smooth and Cardiac Muscle

Cardiac Muscle Characteristics Has striations Usually has a single nucleus Joined to another muscle cell at an intercalated disc Involuntary Found only in the heart

Muscular System Functions The muscular system pushes food and other materials through your body.

Smooth Muscle Smooth muscle is involuntary, found in the digestive tract, and helps to move food and materials through your body.

Smooth Muscle Characteristics Has no striations Spindle-shaped cells Single nucleus Involuntary – no conscious control Found mainly in the walls of hollow organs

Effects of Exercise on Muscle Aerobics result in stronger muscles due to increase blood supply Muscle fibers increase mitochondria and oxygen storage Muscle becomes more fatigue resistant Heart enlarges to pump more blood to body Does not increase skeletal muscle size

Results of increased muscle use from resistance training Individual muscle cells make more contractile filaments & connective tissue increases Increase in muscle size Increase in muscle strength Effects of Exercise on Muscle

Types of Ordinary Body Movements Flexion Extension Rotation Abduction Circumduction

Body Movements

Muscular Dystrophy Congenital muscle-destroying disease affect specific muscle groups Muscle fibers degenerate & atrophy due to an absence of dystrophin, a protein that helps keep muscle cells intact Most common & serious—Duchenne’s M.D. Mostly in males (diagnosed between2-6 yrs) Survival is rare beyond early 30’s X-linked recessive

Myasthenia gravis Rare adult disease caused by antibodies to acetylcholine receptors at the neuromuscular junction which prevents the muscle contraction from occurring Drooping upper eyelids, difficulty swallowing & talking, muscle weakness & fatigue Death occurs when respiratory muscles cease to function

Aging Connective Tissue increases Amount of Muscle tissue decreases Muscles become stringier (sinewy) Body weight declines due to loss of muscle mass By age 80, muscle strength usually decrease by 50% without weight training exercises