Muscles

Muscle Tissue Contains many mitochondria to power contractions Muscles are longer than they are wide Muscles are divided into fibers Muscle fibers contract (or shorten) when stimulated by the nervous system Muscle fibers do not elongate

Skeletal Muscle Helps you move your body Under voluntary (conscious) control Tendon – band of connective tissue that attaches muscle to bones The Achilles tendon attaches the calf muscle (Gastrocnemius) to the heel / ankle bone

Skeletal Muscle Functions Moves bones at joints Pushes substances such as blood, food and fluids throughout the body Helps regulate body temperature, providing heat through contractions and causing you to shiver when you are cold

Features of Skeletal Muscle Cell is rectangular and has multiple nuclei Striations = alternating light and dark bands/stripes created by the arrangement of the two types of proteins that make up the muscle fiber

Structure of Skeletal Muscle Muscle fiber is made up of long strands of protein called myofibrils Myofibril is divided into multiple sarcomeres Sarcomere is the “functional unit” of the muscle

The Sarcomere The sarcomere contains two types of filaments, both made up of protein.  Actin = thin filament  Myosin = thick filament

Skeletal Muscle Contraction These protein filaments - actin and myosin - cause muscle contraction The thick myosin filaments anchor the thin actin filaments as they “slide” or contract Animation – skip to section 6: Muscle Contraction Animation

The Role of the Nervous System Muscle contraction is controlled by the nervous system. The nervous system causes calcium ions to be released, which stimulates the protein filaments to pull. Muscle contraction is all or nothing. It requires the shortening of millions of sarcomeres.

Smooth Muscle Not striped Cells only have one nucleus Completely involuntary

Smooth Muscle Function Moves food through digestive system Empties the bladder Controls blood flow

Cardiac Muscle Found only in heart Looks like a combination of skeletal and smooth muscle types Adjacent cells are separated by intercalated disks - Striated - Oval-shaped - Many nuclei

Cardiac Muscle Function Have more mitochondria and ATP energy than other muscle cells (even skeletal) Involuntary  Impulse from the pacemaker causes cardiac muscle contraction  Brainstem can modify rate of contractions

Make sure you can label these parts of skeletal muscle

Practice labeling these parts of a sarcomere

____________ muscle.. ____________ muscle ____________ muscle Make sure you can tell the three types of muscle apart

Which diagram shows a sarcomere (functional unit of muscle) that is contracted? Which diagram shows a sacromere that is relaxed? Label above. This sarcomere is: ______________