THE MUSCULAR SYSTEM

C14L2

How do bones, muscles, and skin help maintain the body’s homeostasis?

The Muscular System

• What does the muscular system do?

• How do types of muscle differ?

• How does the muscular system interact with other body systems?

Muscular System StatsThere are approximately 600 muscles.Of all the many different kinds of cells in the human body, only muscle cells have the ability to shorten (contract) and return to their original length (relax).

Functions of muscles movement stability protection maintain body temperature helps digestion and respiration

Movement Bones move when muscles contract.Tendons attach muscles to bones and help keep joints in place when your body moves. The two key words that describe the muscular system are contraction and movement. Contraction refers to the ability of a muscle tissue to shorten and thereby cause movement. Your muscles can move your body only by pulling, never by pushing.

Stability

Your muscles pull in different directions to help you keep your balance.

Protection

Muscles protect your body by covering most of your skeleton and most of the organs inside your body like a layer of padding.

Maintain Body Temperature

• Shivering occurs when muscles contract rapidly and change chemical energy to thermal energy, thereby raising your body’s temperature.

• Muscles also change chemical energy to thermalenergy during exercise.

Helps Digestion & Respiration

There are many muscles in your body that are not attached to bones.

The contraction of these muscles cause blood and food to move throughout your body.

Muscle Nervous ControlSome muscles you consciously control, and others you can't.

voluntary - a muscle that can be controlled at will (you consciously control)

involuntary - muscles controlled automatically by the brain; controlled without conscious effort

Types of muscle tissue

Skeletal Muscle Visceral Muscle Cardiac Muscle

(distinguished by their location, microscopic appearance, and type of

nervous control)

Skeletal Muscle

named for its location (usually attached to skeleton)striated (dark and light stripes in its cells)-appearancevoluntary (controlled by conscious thought)

Skeletal MuscleSkeletal muscles move bones by pulling them and working in pairs.

Skeletal MuscleSkeletal muscles move bones by pulling them and working in pairs.

Skeletal Muscle• Your skeletal muscles can change

throughout your lifetime.

• Exercise allows muscle cells to increase in size, making the entire muscle larger and stronger.

Visceral Musclelocation: walls of internal organs, iris of the eye, sphinctersappearance: nonstriated or smooth (shorter, one nucleus, arranged loosely)nervous control: involuntary (not directly controlled by conscious thought)

Visceral Musclethe term visceral refers to internal organs

the name fits well because visceral muscles is located in the walls of internal organs such as the stomach, intestines, blood vessels, and urinary bladder

visceral muscle is also located in the iris of the eye

most of the sphincters (circular bundles of muscles that regulate the diameter of various tubular organs and openings) are visceral muscles; the muscular valves at both ends of the stomach are examples of sphincters

Visceral Muscle

Contraction of smooth muscles helps move material through the body, such as food in the stomach and blood through the vessels

Cardiac Musclelocation: only in heartappearance: striated (striations are not as regular and distinct as skeletal; muscle fibers are branched and joined together)nervous control: involuntary

Cardiac Muscle• When cardiac muscles contract and

relax, they pump blood through your heart and through vessels throughout your body.

• Cardiac cells send signals to other cardiac cells so that they all contract at the same time.

The Muscular System and Homeostasis

Muscle contractions convert chemical energy to thermal energy and keep your body warm.

When you exercise, the cardiac muscles of your heart help maintain homeostasis by contracting more often.

When it contracts faster, the heart pumps more blood and more oxygen is carried to the cells.

Muscles Disorders & Diseases

atrophya great reduction in muscle fibers

and possible replacement by fibrous tissue; commonly occurs when limbs are in casts or when nerve cells that supply muscles

are destroyed by injury or disease

convulsionsviolent, involuntary

contractions of an entire group of muscles;

characteristic of epileptic seizures and drug

withdrawals

crampspainful, involuntary

contractions in those muscles that have been used heavily

and have suffered from fatigue

muscular dystrophy

a progressively crippling disease of unknown cause in which the muscles gradually

weaken and atrophy

paralysis

inability to move a muscle or muscles; usually because of

some nervous system failure

shin splints

a soreness on the front of the lower leg due to straining a muscle; often as a result of walking up and down hills

spasm

an involuntary contraction of shorter duration than a

cramp and usually not as painful