Muscle tissue Flashcards
Types of Muscle Tissue
Skeletal muscle
Cardiac muscle
Smooth muscle
Main characteristics of skeletal muscle
- Striated (contains sarcomeres)
- Voluntary control
- Connected to bones and allow movement.
- Connected to bones through tendons.
- Long fibers.
Functions of skeletal muscles
- Move skeleton and support.
- Maintenance of body temperature.
- Movement of fluids in the cardiovascular and lymphatic system.
- Protection of internal organs.
- Stabilization of joints.
Structure of skeletal muscle
-Endomysium: loose connective tissue surrounding muscle fibers
- Perimysium: divide muscles in fascicles
- Epimysium: dense connective tissue surrounding entire muscle. In
continuity with the tendons.
Structure of sarcomere in skeletal muscle
Myofilaments: Thick filaments: - myosin Thin filaments - actin - tropomyosin: covers myosin binding site on actin - troponin: binds to actin, tropomyosin and calcium Contractile elements of striated muscle.
Mechanism of contraction: sliding filament theory (Skeletal muscle)
Protein filaments slides on top of each other, and the overlap of the thick and thin
filaments increases.
- Trigger: Nerve impulse from motor neuron = stimulus to a single fiber
- Depolarization of the sarcolemma (plasma membrane) (Na+ goes inside) and T tubule system: Brings signal inside to the sarcoplasmic reticulum in order to:
- Release Ca2+ from sarcoplasmic reticulum
- Ca2+ binds to troponin
- Troponin displaces tropomyosin
- Actin and myosin can interact
- Z lines pull together.
- Actin and myosin slide on top of each other. Filaments do not shorten.
Relaxation: removal of intracellular calcium
Differences between red (type 1) and white (type 2b) muscle
Type 1 Type 2b ↑Mitochondria ↓Mitochondria Aerobic metab. Anaerobic metab. Small Big ↑Capillaries ↓Capillaries Slow contraction Fast contraction Oxidative Glycolytic Resistant to fatigue Prone to fatigue ↑ Myoglobin ↓ Myoglobin
Main characteristics of Cardiac muscle
- Striated (contains sarcomeres).
- Unvoluntary control.
- Nerve impulse modulate frequency.
-Individual cells, 1 nucleus
Two types of cells (short, branched) - Pacemaker cells
- Cardiomyocytes
Connected by intercalated discs: - Desmosomes: keep cells physically together
Cardiac muscle cells
Individual cells, tightly connected through intercalated discs, mechanically and through gap junctions that help the synchronization of the contractions.
- Pacemaker cells: Spontaneous depolarization. Synchronize the cardiac activity, establish a rhythm.
- Cardiomyocytes: Form contractile walls of the heart. force generating cells
Gap junctions in cardiac muscle cells
Allow passage of Ca2+ between cells
Create functional syncytium
Coordinated, sequential contraction
Mechanism of contraction: sliding filament theory (Cardiac muscle)
Identical to skeletal muscle: only Ca2+ entry in cells is different
- Trigger: Spontaneous depolarization of pacemaker cells (rhythm can be
modified by autonomic nervous system)
- Ca2+ spreads to neighboring cells through gap junctions, and from the outside with calcium triggered calcium release
- Depolarization of the sarcolemma and T tubule system
- Release of Ca2+ from sarcoplasmic reticulum/Ca2+ enter from extracellular
environment
- Ca2+ binds to troponin
- Troponin displaces tropomyosin
- Actin and myosin can interact
Relaxation: removal of intracellular calcium
Characteristics of smooth muscle
- Not striated, No sarcomere.
- Unvoluntary control.
- Individual cells, 1 nucleus
- Spindle shape
Location: - G.I. tract, airway, blood vessels, uterus, bladder.
Triggers for contraction of smooth muscle
Triggers:
- Nerve impulse from autonomic nervous system.
- Mechanical reflex.
- Local chemical signals (e.g. levels of CO2 & O2).
- Ca2+ spreads to neighboring cells through gap junctions.
Mechanism of contraction (smooth muscle)
- Depolarization of the sarcolemma
- Release of Ca2+ from sarcoplasmic reticulum/ Ca2+ enter from extracellular environment.
- Ca2+ binds to calmodulin
- Ca2+/calmodulin activates a kinase: phosphorylation of myosin
- Interact with actin
Relaxation: Removal of intracellular calcium
Removal of phosphate group from myosin
