Unit 3- Chapter 9- Muscular system

3 types of muscle tissue

• Skeletal muscle

• smooth muscle

• cardiac muscle

Skeletal muscle

• Location - attached to bones

• Function- locomotion, facial expressions, posture, respiratory movements

Smooth muscle

• Location - walls of hollow organs, blood vessels, eyes, glands, skin

• Function- propel urine in urinary tract, mechanical churn food in digestive tract, dilation of pupils, regulation of blood flow

Cardiac muscle

• Location- heart

• Function- movement of blood throughout the body (pumping)

Contractility

Ability of a muscle to shorten → generating force

Excitability

Ability of muscle to respond to electrical stimuli

Extensibility

Capacity to be stretched beyond its normal resting length without being destroyed

Elasticity

Ability to recoil to original resting length after being stretched

G actin

contain active site= location where myosin can bind

Tropomyosin

• long strand of protein that wraps around actin strand

• Important - in a relaxed muscle the tropomyosin is purposely blocking the G actin site→ prevents myosin from bonding

Troponin

• has receptor for calcium ions

• Important- when calcium ions bind to troponin, troponin causes tropomyosin to move→ exposing the G actin sites

Myosin myofilaments (thick)

• contain myosin heads that binds to G actin to cause muscle contraction

• Heads are ATPase enzymes break down ATP molecules into ADP to release energy

Sarcomere

Basic functional unit of a muscle fiber

Z disk

• other end of sarcomere

• dark, protein-rich boundary structures that mark the ends of each sarcomere in striated (skeletal and cardiac) muscle

M line

• In the center of the sarcomere

• a dark, fine vertical line in the exact center of a sarcomere that anchors thick myosin filaments and keeps them aligned during muscle contraction

H zone

• found in the center of the sarcomere → contains M line and myosin filaments only

A band

• Contains both actin and myosin filaments, area of sarcomere where filaments are overlapping

• dark stained region

I band

• found at the end of sarcomere → contains Z disk and actin filaments only

• light stained region