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

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

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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: ______________

This sarcomere is: ______________