 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

 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 ankle bone
) to the heel /

 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

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



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

 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.

 Not striped
 Cells only have one nucleus
 Completely involuntary

 Moves food through digestive system
 Empties the bladder
 Controls blood flow




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

 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

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