1. Muscles

2. 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

3. 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

4. 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

5. 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

6. 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

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

8. 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

9. 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.

10. Smooth Muscle Not striped Cells only have one nucleus Completely involuntary

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

12. 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

13. 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

14. Make sure you can label these parts of skeletal muscle

15. Practice labeling these parts of a sarcomere

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

17. 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: ______________