Skeletal Muscle Contraction SEM1 Flashcards
How does skeletal and cardiac muscle appear + what are they described as
Appear striped and described as striated
What are the components of the gross skeletal muscle (in order from external to internal)
1)tendon
2)muscle
3)connective tissue
4)nerve and blood vessels
5)connective tissue
6)fascicle
7)muscle fibre
8)nucleus
What are myofibril
Units of muscle cells that contain arrays of thick and thin filaments
Where are thin filaments located
Attached at either end to the Z-disc
Where are thick filaments located
In the centre and overlap with thin filaments on both ends except in the central region- the H-zone
What are thick filaments composed of
Myosin
What are thin filaments composed of
Actin
What is the sliding filament hypothesis of muslce contraction
Sarcomere length shortens but filaments stay same length
What is the overall process of excitation-contraction (EC) coupling process in skeletal muscle
1)neuromuscular transmission
2)action potential propagation
3)calcium release
4)muscle contraction
5)relaxation
What is the process of neuromuscular transmission in excitation-contraction (EC) coupling process in skeletal muscle
Acetylcholine (Ach) released from a motor neuron binds to receptors on muscle cells motor end plate triggering a muscle action potential
What is the process of action potential propagation in excitation-contraction (EC) coupling process in skeletal muscle
Action potential spreads along muscle membrane and into the T-tubules where it activates dihydropyridine (DHP) receptors
What is the process of calcium release in excitation-contraction (EC) coupling process in skeletal muscle
Activation of DHP receptors leads to opening of calcium channels on the sarcoplasmic reticulum causing a release of calcium ions into the muscle cytoplasm
What is the process of muscle contraction in excitation-contraction (EC) coupling process in skeletal muscle
The surge in calcium triggers muscle contraction by facilitating the interaction of actin and myosin within the muscle fibres
What is the process of relaxation in excitation-contraction (EC) coupling process in skeletal muscle
Calcium pumped back into the sarcoplasmic reticulum, lowering cytoplasmic calcium levels causing muscle relaxation
What are L-type Ca2+ channels linked to
Ryanodine receptors on the sarcoplasmic reticulum
What does depolarisation of the L-type channels cause
Causes ryanodine receptors to open and release Ca2+ into the cytoplasm
What is troponin
A regulatory protein attached to thin filaments (actin)
What does calcium bind to to allow myosin to bind to actin
Calcium binds to troponin
What does the binding of calcium induce in troponin
Induces conformational change in troponin and shifts tropomyosin away from these sites and myosin head binds to actin
What occurs following the attachment of the myosin head binding to actin
ADP and Pi are released which triggers the power stroke which pulls the actin filament toward the centre of the sarcomere causing muscle contraction
How does the myosin head detach from actin
A new molecule of ATP binds to myosin head, causing it to detach from actin
What does the hydrolysis of ATP and Pi provide energy for in relation to Ca2+ contraction
Hydrolysis of ATP into ADP and Pi provides energy for myosin head to return to its original angle
What happens when the concentration of calcium decreases
Conc of Ca2+ decreases leads to Ca2+ detaching from troponin and prevents myosin from binding leads to muscle relaxation
What is isometric contraction
Contraction at constant length
