1. Muscle Physiology .

2. Muscles Skeletal Muscle Cardiac Muscle Smooth Muscle
There are three types of muscle tissue in the body. Skeletal muscle is the type that attaches to our bones and is used for movement and maintaining posture. Cardiac muscle is only found in the heart. It pumps blood. Smooth muscle is found in organs of the body such as the GI tract. Smooth muscle in the GI tract moves food and its digested products.

3. Microanatomy of Skeletal Muscle
In this unit we will primarily study skeletal muscle. Each muscle cell is called a muscle fiber. Within each muscle fiber are many myofibrils.

4. Each muscle cell (fiber) is micrometer ln diameter & is covered by a cell-membrane called Sarcolemma.
Each cell contains between a few hundreds to a few thousands Myofibrils.
Each Myofibril contains 3000 Actin filaments & 1500 Myosin filaments .
Each myofibril is striated: consisting of dark bands (called A-bands) and
light (I-bands).

5. Z line
A small section of a myofibril is illustrated here. Note the thick myosin filaments are arranged between overlapping actin filaments. *The two Z lines mark the boundary of a sarcomere. The sarcomere is the functional unit of a muscle cell .We will examine how sarcomeres function to help us better understand how muscles work.

6. EXCITATION –CONTRACTION COUPLING
MECHANISIM OF CONTRACTION

7. The influx of sodium will create an action potential in the sarcolemma
The influx of sodium will create an action potential in the sarcolemma. Note: This is the same mechanism for generating action potentials for the nerve impulse. The action potential travels down a T tubule. As the action potential passes through the sarcoplamic reticulum it stimulates the release of calcium ions. Calcium binds with troponin to move tropomyosin and expose the binding sites. Myosin heads attach to the binding sites of the actin filament and create a power stroke. ATP detaches the myosin heads and energizes them for another contraction. The process will continue until the action potentials cease. Without action potentials the calcium ions will return to the sarcoplasmic reticulum.

8. Muscle Contraction Summary
Nerve impulse reaches myoneural junction
Acetylcholine is released from motor neuron
Ach binds with receptors in the muscle membrane to allow sodium to enter
Sodium influx will generate an action potential in the sarcolemma

9. Muscle Contraction Continued
Action potential travels down T tubule
Sarcoplamic reticulum releases calcium
Calcium binds with troponin to move the troponin, tropomyosin complex
Binding sites in the actin filament are exposed

10. Muscle Contraction Continued
Myosin head attach to binding sites and create a power stroke
Attachment of ATP, detaches myosin heads and energizes them for another contaction
When action potentials cease the muscle stop contracting