1. Human Physiology Neuromuscular Transmission
by Talib F. Abbas

2. Excitation of Muscle
Motility is a widespread biological phenomenon that reaches its highest manifestation in the specialized tissue of muscle.
skeletal muscle is the major executive arm of the nervous.
we could have no knowledge if they were not communicated by muscle which express our mental activities by speech, song , and cries , by writing, by gestures and facial expressions, and by morte complex forms of behavior, both sessile or locomotory, individual or social.

4. Excitation of Muscle
Muscle cells, like neurons, can be excited chemically, electrically, and mechanically to produce an action potential that is transmitted along their cell membranes.
The contract proteins : Myosin & Actins.
Smooth muscle contract involuntary .
Heart muscle have their own autonomic conducting system.
Skeletal muscle need nervous stimulation.

5. Skeletal Muscle Organization

6. Neuromuscular junction and T tubules
Sarcotubular system: T system and a sarcoplasmic reticulum.
The sarcoplasmic reticulum, which forms an irregular curtain around each of the fibrils, has enlarged terminal cisterns in close contact with the T system at the junctions between the A and I bands.
T system with a cistern of the sarcoplasmic reticulum on either side has led to the use of the term triads.

8. Motor Unite Action potential
The nerve fiber forms a complex of branching nerve terminals that invaginate into the surface of the muscle fiber but lie outside the muscle fiber plasma membrane. The entire structure is called the motor end plate.
synaptic gutter or synaptic trough.
synaptic space or synaptic cleft.
synaptic transmitter ( Acetylcholine ).
adenosine triphosphate (ATP).
Acetylcholinesterase.
Curare & botulinum toxin.

10. General Mechanism of Muscle Contraction
1. An action potential trigger in fibers.
2. the nerve secretes a neurotransmitter substance.
3. The acetylcholine acts to open “acetylcholinegated”
4. Allows large quantities of sodium ions to diffuse .
5. The action potential travels along nerve fiber.
6. The action potential depolarizes the muscle.
7. The calcium ions initiate attractive forces between the actin and myosin filaments, contractile process.
removal of calcium ions from the myofibrils causes the muscle contraction to cease.

13. molecular machinery of the muscle contractile
sliding of the thin filaments over the thick filaments.
The width of the A bands is constant.
Z lines move closer together.
This “power stroke” depends on the simultaneous hydrolysis of ATP.
Troponin I is bound to actin and tropomyosin and covers the sites where myosin heads interact with actin.
Excitation–contraction coupling.
Depolarization of the T tubule by dihydropyridine receptors (DHPR).
In cardiac muscle, influx of Ca2+ via ryanodine receptor (RyR).

14. THE MUSCLE TWITCH
A single action potential causes a brief contraction followed by relaxation. This response is called a muscle twitch.
The twitch starts about 2 ms after the start of depolarization.
“Fast” muscle fibers 7.5 ms.
. “Slow” muscle fibers 100 ms.

15. Thank you