THE MUSCULAR SYSTEM

I. Overview of muscle tissues.

A. Muscle types- skeletal, cardiac and smooth

B. Muscle functions

1. Producing movement

2. Maintaining posture

3. Stabilizing joints

4. Generating heat

C. Functional characteristics of muscle

1. Excitability

2. Contractility

3. Extensibility

4. Elasticity

II. Skeletal muscle

A. Gross anatomy of a skeletal muscle

B. Microscopic anatomy of a skeletal muscle fiber

1. Myofibrils- sarcomeres, myofilaments

2. Sarcoplasmic reticulum

C. Contraction of a skeletal muscle fiber

1. Sliding filament mechanism of contraction

2. Physiology of a skeletal muscle fiber-- Regulation of contraction

a. The neuromuscular junction and the nerve stimulus

b. Generation of an action potential across the sarcolemma

c. Destruction of acetylcholine

d. Excitation-contraction coupling

e. Summary of roles of ionic calcium in muscle contraction

D. Contraction of a skeletal muscle

1. Motor unit

2. Muscle twitch and development of muscle tension

3. Graded muscle responses- summation, tetanus

4. Treppe- the staircase effect

5. Muscle tone

6. Isometric and isotonic contractions

E. Muscle metabolism

1. Providing energy for contraction

a. Stored ATP

b. Direct phosphorylation of ADP by creatine phosphate

c. Aerobic respiration

d. Anaerobic respiration

2. Muscle fatigue

3. Oxygen debt

4. Heat production during muscle activity

F. Force of muscle contraction

1. Force of contraction increases when number of muscle fibers stimulation increases

2. Large muscle fibers generate more force

3. When stimulation increases, contractions sum up, producing tetanus—more force

4. Optimal length-tension relationship when the muscle is slightly stretched

G. Velocity, and duration of muscle contraction

1. 3 muscle fiber types: slow oxidative, fast oxidative, and fast glycolytic

2. Muscle fiber type—genetically determined trait

3. As load increases, the slower the velocity and shorter the duration of contraction

4. Recruitment of motor units increases velocity and duration of contraction

H. Effect of exercise on muscles

1. Aerobic or endurance exercise- increase in capillary penetration, mitochondria,

myoglobin, more efficient metabolism—no hypertrophy

2. Resistance exercise (weight lifting or isometric exercise) increase number of

Mitochondria, myofilaments and myofibrils, glycogen storage—cells hypertrophied

3. Training smart to prevent overuse injuries

III. Smooth muscle

A. Microscopic structure and arrangement of smooth muscle fibers

B. Contraction of smooth muscle

C. Types of smooth muscle- single unit; multiunit