Muscular System

Skeletal

voluntary control (movement of skeleton), striated (alternating bands- sarcomeres), connected by tendons to bones, multinucleated

Cardiac

involuntary control, heart muscle, striated (not like skeletal)

Smooth

not striated, lining of the blood vessels/inner organs (intestines)

Functions of Muscles

1. Movement of the skeletal/bones (skeletal)

2. Movement of food/blood (smooth)

3. Posture- stabilize/maintain position

4. Muscle contractions generate 85% of body heat

5. Pump blood (cardiac)

Contractibility

ability for muscle to contract/shorten to generate force when stimulated by nerve

Extensibility

ability to lengthen beyond normal resting length (ex: stretching)

Elasticity

ability to return to normal resting length

Atrophy

decrease in # of myofibrils, decrease in muscle mass due to inactivity

Hypertrophy

muscle increase in size due to the increase in # of myofibrils (ex: weight training)

Trained

Hypertrophy (Increase in myofibrils)

Untrained

Atrophy (Decrease in myofibrils); Inactivity/injury, age, space flight leads to atrophy

Digestive

smooth muscle, peristalsis

Circulatory

cardiac muscle (heart), smooth muscle (blood vessels)

Nervous

Neuromuscular junctions: nerves send an impulse to muscle, causing it to contract

Endocrine

hormonal control (ex: adrenaline) of the muscular system

Origin

muscle attaches to stationery bone

Insertion

muscle attaches to moveable bone

Rectus femoris

Origin: Hip (pelvis)

Insertion: Patella

Vastus Intermedias

Origin: Femur

Insertion: Patella

Fascia

outer layer/covering

Epimysium

outer fascia covering entire muscle

Perimysium

covering bundles of muscle fibers (fascicle)

Endomysium

deep fascia covering muscle fibers

Sarcomere

striations= bands of myosin/actin

Actin

thinner protein fiber

Myosin

thicker protein fibers