Muscle Tissue Flashcards
Functions of the muscular system
Locomotion (movement)
Posture maintenance and muscle tone
Heat generation
Joint Stability
Vasoconstriction and vasodilatation
Peristalsis
Cardiac motion/contractility
Striations
- Only present in skeletal and cardiac muscles (absent in smooth muscle)
- Created by I (light) and A (dark) bands
Nucleus
Smooth and cardiac muscles are uni-nucleated (one nucleus per cell), skeletal muscle is multinucleated (several nuclei per cell)
Transverse (T) tubule
Well developed in skeletal and cardiac muscles to transport calcium (absent in smooth muscle)
Intercalated disk
- Specialized intercellular junction that is only present in cardiac muscle
- Synchronous electrical activity
- Contains gap junctions to allow transport of ions
- Contains adherens junction to bind cells together
Control (voluntary and involuntary)
Skeletal muscle is under voluntary control‚ smooth and cardiac muscles are under involuntary control
Types of skeletal muscle
Skeletal muscle structure
Epimysium- An “overcoat” of dense irregular connective tissue that surrounds the whole muscle.
Perimysium and Fascicles- Within each skeletal muscle, the muscle fibers are grouped into fascicles (bundles) that resemble bundles of sticks. Surrounding each fascicle is a layer of dense irregular connective tissue called perimysium (around the muscle).
Endomysium- The endomysium is a sheath of connective tissue that surrounds each individual muscle fiber and is connective tissue in nature.
Cross-section skeletal muscle
skeletal muscle cells have a roughly hexagonal profile with individual cells moulded together. Nuclei (N) are arranged beneath the cell membrane. Fibrocollagenous septa (S) contain blood vessels
Longitudinal-section skeletal muscle
Motor endplate
The sarcoplasmic membrane in the region of the motor endplate contains specialized receptors which, when activated by acetylcholine, permit muscle cell membrane depolarization. Activation of the motor axon causes the release of acetylcholine from its storage granules by exocytosis. Acetylcholine then diffuses across the gap between the axon and muscle fibre and interacts with specific membrane receptors to cause depolarization of the muscle fibre, which initiates contraction. The activity of secreted acetylcholine is rapidly curtailed by the activity of an enzyme called ‘acetylcholinesterase’, which is bound to the basement membrane investing the junctional folds. It immediately breaks down or hydrolyzes acetylcholine (Ach) into acetic acid and choline.
In addition to nerve fibres controlling voluntary movement, specialized motor axons (γ efferent fibres) innervate fibres in the muscle spindle.
Duchenne muscular dystrophy histology
Cardiac muscle histology
Smooth muscle histology
Skeletal, cardiac and smooth muscle summary
