There are three main types of muscle tissue: skeletal, cardiac, and smooth muscle. Skeletal muscle is voluntarily controlled and attached to bones, cardiac muscle is only found in the heart, and smooth muscle is found in internal organs and blood vessels. All muscle tissues contract through a mechanism involving calcium, ATP, and the protein myosin interacting with actin fibers, though the details vary between tissue types.

1. Excitable tissues
muscles

2. Types of muscle:
1. Skeletal muscle.
2. Cardiac muscle.
3. Smooth muscle.

3. Skeletal muscle:

4. Skeletal muscle:

5. Cardiac muscle:

6. Cardiac muscle:

7. Smooth muscle:

8. Smooth muscle

9. Skeletal muscle:

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11. .

13. Sarcotubular system:
• Membranous structure in the muscle fibers
• Consist of:
- T tubules.
- Sarcoplasmic reticulum.

14. Mechanism of muscle contraction

15. Muscle contraction:

16. .

18. Smooth muscle:
- Smooth muscle is composed of
small fibers 1-5 μm in diameter.
- The internal physical arrangement
of smooth muscle fibers is different
from skeletal muscle.
Types of smooth muscle
Two major types:
1. Multi-unit smooth muscle
2. Single-unit (visceral) smooth muscle

19. multi-unit smooth muscle
- composed of discrete, separate, smooth muscle fibers.
- Each fiber operates independently of the others
- Examples: ciliary muscle, the iris muscle of the eye
single-unit (unitary, visceral) smooth muscle
- fibers are arranged in sheets or bundles
- joined by many gap junctions
- joined by many gap junctions
- contract together as a single unit
- found in the walls of most viscera
the GIT, bile ducts, ureters, uterus,
and many blood vessels.

20. Contraction of smooth muscle:
The mechanism for controlling contraction is different
- does not contain the troponin complex
- In place, contain a large amount of another regulatory
protein called calmodulin.

21. - Contract as much as 80% of their length
- Slow of onset of contraction and relaxation
- Contraction is prolonged
- Low energy requirement to sustain smooth muscle
contraction.

22. Types of contraction
- Isotonic contraction
- Isometric contraction

23. Single muscle twitch
A single sufficient stimulation of a muscle fiber results in a
single action potential that results in a single contraction
followed by relaxation.
Summation of contractions
- Repeated stimulation of a muscle fiber results in repeated
- Repeated stimulation of a muscle fiber results in repeated
action potentials that are followed by successive
contractions.
- Summation of contractions into one continuous
contraction is called tetanus.

24. Types of muscle fibers
Type one fibers (red muscles):
- Respond slowly to stimulation
- Have high oxidative capacity
- Contract to maintain posture
- E.g. muscles of the back
Type two fibers (white muscles):
- Have short twitch duration
- Respond rapidly
- Have high glycolytic capacity
- Specialized for fine skilled movement
- E.g. muscles of the hand

25. The oxygen debt mechanism: