1. The Muscular System

2. Do you remember what
muscle tissue
looks like?

3. Group of Skeletal Muscle Fibers

4. Cardiac Muscle

5. Smooth Muscle

6. 2) Cardiac - heart; striations; NOT voluntary; STEADY contraction
Muscle Types
1) Skeletal - longest; striations (bands); voluntary control; FAST contraction
2) Cardiac - heart; striations; NOT voluntary; STEADY contraction
3) Smooth - visceral; NO striations; NOT voluntary; SLOW contraction

7. Muscle Function 1) Movement - locomotion; blood pressure; propulsion
2) Support Soft Tissues - support the weight of visceral organs; shield internal tissues
3) Maintain Posture & Body Position
4) Maintain Body Temperature - energy is used, converted to heat, heat is released
5) Guard Entrances & Exits - digestive/urinary openings provide voluntary control

8. Muscle Characteristics
1) Excitability - receive & respond to a stimulus
2) Contractility - shortening
3) Extensibility - stretch or extend
4) Elasticity - resume resting length

9. Muscle Movement
Flexion - the angle between the two bones
Extension - the angle between the two bones

10. Abduction - a bone is moved away from the midline of the body
Adduction - a bone is moved toward the midline of the body.

11. Rotation - a body part partially revolves on its axis

12. Levels of Structure

13. Anatomy of a Muscle Fiber
Collagen fibers
aponeurosis
(Attach muscle to bone)
Anatomy of a Muscle Fiber

17. A sarcomere is the smallest organized functional unit of the myofibril
A sarcomere is the smallest organized functional unit of the myofibril. It contains thick and thin filaments (actin and myosin).
A myofibril consists of about 10,000 sarcomeres.

18. Single Muscle Fiber

20. Two Important Proteins
Involved in
Muscle Contraction

21. Myosin
Myosin heads are also called cross-bridges. The heads pivots at the base, a key step in muscle contraction.

22. Each thick filament consists of about 500 myosin molecules.

23. Actin
F actin is a twisted strand composed of 300+ G actin molecules. Each G actin contains an active site that binds to a thick filament (myosin). Tropomyosin covers the active sites. Troponin binds tropomyosin and G actin.

24. (cross bridges)
Actin and Myosin

28. How do muscles contract?
The Sliding Filament Theory
The thin actin filaments slide past the thick myosin filaments
The I bands shrink
The H zone disappears
The A bands move closer

31. Look where it overlaps

32. What happens at the
cellular level?

33. Acetylcholine
Axon
Action potential
ACh
T-tubules
Sarcoplasmic reticulum
Actin
Myosin

34. Action Potential is generated & travels along sarcolemma down T-tubules
Neurotransmitter is released, diffuses across synapse
Action Potential triggers calcium release from SR
ACh - acetylcholine 1 2
Contraction ends, muscle fiber relaxes 3 SR 7 6
Calcium inside SR binds to troponin - changes shape - actin active sites exposed 4 5
Removal of calcium by re-uptake into SR after action potential ends A
Contraction - myosin cross bridges attach, detach from actin. Cross bridges split ATP & store energy. T P

35. Types of Skeletal Muscle Fibers
Fast Fibers - most muscle fibers in the body; contract in 0.01 second or less; powerful contractions
Slow Fibers - smaller than fast; take 3 times as long to contract; continue contracting after fast muscles are fatigued
Intermediate Fibers - properties between fast and slow fibers
MORE

36. White Muscles - dominated by fast fibers
White Muscles - dominated by fast fibers. Example - chicken breast contain “white meat” because chickens use their wings only for brief intervals.
Red Muscles - dominated by slow fibers; extensive blood vessels. Example - chickens walk around all day moving their slow muscle fibers, the “dark meat” in their legs.

37. Muscle Hypertophy Athletes & Muscle Builders - Muscle Enlargement
Occurs in muscles that are repeatedly stimulated to produce near-maximal tension.
Muscles develop more mitochondria, more enzymes, larger glycogen reserves.
Fibers have more myofibrils containing more thick and thin filaments.
Number of fibers does not change, but the muscle diameter increases.

38. Muscle mass of men exceeds that of women because muscle fibers are stimulated by testosterone.

39. The Muscles!