1. Skeletal Muscle Tissue
Ch notes

2. Connective Tissue Components
Fascia (fash-ee-a) – a sheet or broad band of C. T. that supports and surrounds muscles and other organs of the body
2 types
Superficial and deep
deep has 3 layers
Epimysium (most superficial)
Perimysium
Endomysium (most deep)

3. Anatomy of Muscle Fiber
Epimysium – outermost
Perimysium – surrounds bundles of muscle fibers
Endomysium – separates muscle fibers from each other

4. Microscopic Anatomy of a Muscle Fiber
Muscles form from the fusion of myoblasts
Once fusion occurs, the fiber can no longer divide
Number of muscle fibers is set before birth
The size of the muscle fibers is what changes over time

5. Components of a Muscle Fiber
Sarcolemma – covering of muscle fiber that contains the nuclei
Transverse (T) tubules – tunnel from surface toward center of fiber; carry action potential
Sarcoplasm – cytoplasm of muscle fiber
Contains myoglobin (binds oxygen to diffuse into muscle fibers)

6. Components

7. Components
Myofibrils – contractile organelles of muscle fiber, little fibers stuffed into sarcoplasm
Contain filaments
Thin and thick
Sarcoplasmic reticulum (SR) – fluid-filled system of sacs, surround each myofibril, stores Ca2+ for muscle contraction

8. Components Filaments – small structures within myofibrils
Thick
2 thins for every 1 thick
Arranged in sarcomeres
Sarcomeres are separated by Z discs

9. Components Thin and thick filaments overlap
Sarcomere can be divided into zones and bands
A band – darker middle part of sarcomere
Zone of overlap – where thick and thin filaments overlap
I band – lighter, less dense area with thin filaments; Z disc passes through
H zone – center of A bad with thick filaments
M line – proteins hold the thick filaments together at the center of the H zone

10. Components

11. Muscle Proteins Myofibrils are built from 3 proteins
Contractile – generate force during contraction
Regulatory – help switch contraction process on and off
Structural
Keep thick and thin filaments in proper alignment
Give myofibril elasticity and extensibility
Link myofibrils to sarcolemma

12. Muscle Proteins Contractile proteins Myosin Actin Myosin and actin
Form thick filaments
Functions as a motor protein – push or pull structures to achieve movement
300 myosin form a single thick filament
Actin
Form thin filaments
Each actin has a myosin-binding site

13. Muscle Proteins

14. Muscle Proteins Regulatory proteins tropomyosin Troponin
Tropomyosin and troponin
Part of the thin filament
tropomyosin
Covers the myosin-binding sites during the relaxed state
Troponin
Hold tropomyosin in place