lecture 8 - skeletal muscle Flashcards
What are the cells that make up muscles?
Muscle fibres
What are the three levels of muscle structures?
Muscle fibres, fascicles, muscle
What is a fascicle?
A bundle of muscle fibres, surrounded by a layer of perimysium connective tissue.
Why do muscle fibres have lots of nuclei?
When muscle is developing, proto cells / pre cells fuse together together to form the final muscle fibres.
Why do muscle fibres and fascicles have a blood supply?
The blood supply provides nutrients and fuel to the muscles and removes waste.
Why are fascicles coated in connective tissue?
To prevent friction during contraction.
What are the components of a muscle fibre?
Made up of myofibrils made up of repeating units called sarcomeres
What are the repeating units in muscle fibres?
Sarcomeres
What are the myofilaments found in a sarcomere?
Actin and Myosin.
Which myofilament is thin and which is thick?
Actin is thin, Myosin is thick
What are transverse tubules (T-tubules)?
Tube-like extensions of the sarcolemma that extend deep into the muscle fibres.
What is the outer membrane of a muscle fibre?
Sarcolemma
What is the membrane bound network of a muscle fibre?
Sarcoplasmic Reticulum (SR)
What is the role of the sarcoplasmic reticulum?
Takes up and stores Ca2+ ions while the muscle is relaxed and then release them into the cytoplasm when the muscle contracts.
What is the full name of EC-coupling?
Excitation-contraction coupling
What are the three key proteins of EC-coupling?
Voltage-gated sensor (DHPR), ryanodine receptor (RyR), SR Ca2+ -ATPase (SERCA)
What is the voltage-gated sensor (DHPR)?
Sits in the transverse tubule and receives electrical signals/action potentials from nerves, allowing it to change shape and trigger the ryanodine receptor.
What is the ryanodine receptor (RyR)?
A passive Ca2+ channel which allows Ca2+ to flow out of the SR, which activates myofilaments causing contraction.
What is the process of muscle relaxation?
The SR Calcium-ATPase pump (SERCA) senses the rise in Ca2+ and then burns ATP to provide the energy to move Ca2+ back into the SR against their concentration gradient. This ends the signalling event and the muscle is able to relax.
What is the connective tissue that surrounds muscle fibres?
Endomysium
What is the connective tissue that surrounds muscle fascicles?
Perimysium
What is the connective tissue that surrounds muscle?
Epimysium
What are the functions of muscle? (5)
Movement/posture, protection, passages in/out of body, shivering thermogenesis, develop force
