1. Muscular System

2. Outline
Types and Functions of Muscles
Smooth
Cardiac
Skeletal
Muscle Innervation
Whole Muscle Contraction
Oxygen Deficit
Athletics and Muscle Contraction
Slow and Fast Twitch Fibers
Muscle Disorders

3. Types and Functions of Muscles
Smooth muscle is located in the walls of hollow internal organs and contracts involuntarily.
Cardiac muscle forms the heart wall and contracts involuntarily.
Skeletal muscle runs the entire length of the muscle and contracts voluntarily.
Cells are muscle fibers

5. Functions of Skeletal Muscles
Body support.
Bone movement.
Maintenance of body temperature.
Assist movement in cardiovascular and lymphatic vessels.
Protect internal organs.
Stabilize joints.

6. Skeletal Muscles of the Body
A whole muscle contains bundles of skeletal muscle fibers, fascicles.
Muscles are covered with fascia that becomes tendons.
Muscles originate on the stationary bone, and insert on the bone that moves.

8. Names and Actions of Skeletal Muscles
Skeletal muscles are named based on characteristics.
Size. Gluteus maximus
Shape. Deltoid
Direction of muscle fibers. Rectus abdominus
Number of attachments. Biceps brachii
Action. Extensor digitorum

10. Skeletal Muscle Fiber Contraction
Overview of Muscular Contraction.
Nerve impulses originate in the brain, travel down motor neurons, and stimulate muscle fibers at neuromuscular junctions.
When muscle fibers are stimulated to contract, myofilaments slide past one another, causing sarcomeres to shorten.

11. Skeletal Muscle Fiber Contraction
Sarcolemma (plasma membrane)
Sarcoplasm
Myofibrils
T Tubule
Sarcoplasmic reticulum
Contain Ca2+

13. light and dark bands (striations) sarcomeres
thin filaments – actin
thick filaments - myosin
Z line, A band, I band, H zone
Sliding Filament Theory – actin and myosin
filaments moving. Myosin does work. ATP

16. Muscle Innervation
Muscle fibers are stimulated to contract by motor nerve fibers.
Signaled when nerve impulses bring about release of neurotransmitter molecules at a neuromuscular junction.

18. Muscle Innervation
Released Calcium gets to troponin
Troponin causes a shift in tropomyosin
Myosin head attaches (ATP=ADP + P)
Stroke (ADP + P released)
Contraction continues until nerve impulses cease.

21. Whole Muscle Contraction
Muscle Twitch - Single muscle contraction.
Divided into three stages.
Stimulation.
Contraction.
Relaxation.
If a muscle is given a rapid series of threshold stimuli, muscle contraction summates in a sustained contraction, tetanus.

23. Whole Muscle Contraction
A motor neuron, together with all of the muscle fibers that it innervates, is a motor unit.
As the intensity of nervous stimulation increases, more motor units are activated.
(recruitment)

24. Energy for Muscle Contraction
ATP produced previous to strenuous exercise lasts a few seconds, and then muscles acquire new ATP in three ways.
Phosphate breakdown. (anaerobic)
Fermentation. (anaerobic)
Cellular respiration. (aerobic)

28. Oxygen Deficit
When a muscle uses the anaerobic means of supplying energy, it incurs an oxygen deficit.
Repaying an oxygen deficit requires replenishing creatine phosphate supplies and disposing of lactic acid.

29. Athletics and Muscle Contraction
Muscles that are not used, or are used in only weak contractions can atrophy.
Can cause muscle fibers to progressively shorten, leaving body parts contracted in contorted positions.
forceful exercise can cause muscle size to increase or hypertrophy.

30. Athletics and Muscle Contraction
Slow-twitch fibers produce most of their energy aerobically and tire only when their fuel supply is gone.
Fast-twitch fibers tend to be anaerobic and seem to be designed for strength as their motor units contain many fibers.
Can develop greater, and more rapid, maximum tension than slow-twitch fibers.

32. Homeostasis
Cardiac muscle contraction accounts for the heartbeat, delivering blood to the tissues.
Smooth muscle contraction accounts for peristalsis and urination.
Skeletal muscle contraction returns blood to the heart and moves bones, allowing for body movement.