Muscles Flashcards
What are T-tubules?
T-Tubules are extensions of the sarcolemma (cell membrane) that folds inwards at 90 degree angles and penetrates the cardiac and skeletal muscles.
What are Myofibrils?
Basic rod-like units of the muscle fibre.
Single multinucleate cells.
What is the sarcolemma?
Cell surface membrane of the muscle cells.
What is the sarcoplasmic reticulum?
membrane-bound organelle (similar to the Endoplasmic Reticulum) that absorbs Calcium ions during muscle contraction.
What is the epimysium?
Thin sleeve of fibrous connective tissue that covers the muscle fibres.
What are tendons?
Fibrous connective tissue which joins (skeletal) muscle to bone
What are ligaments?
Fibrous connective tissue which joins bone to bone
What does it mean that skeletal muscle is voluntary nervous control?
Movement controlled by the motor cortex within the cerebral cortex of the brain (movement requires conscious thought)
Why do skeletal muscle contain high concentrations of mitochondria?
During strenuous exercise, the energy demands of the body increase. The rate of respiration of the individual increases (via increased breathing rate and blood flow). This allows greater rate of ATP hydrolysis within the mitochondria which releases energy. The more mitochondria present means the more ATP can be hydrolysed which leads to more energy being released to meet energy demands.
Aerobic respiration is more efficient that anaerobic respiration hence it release more energy making it more desirable for the body to meet energy demands
What are the two types of proteins found in the myofibril?
Myosin- thicker filaments that form more dense striations
Actin- thin filaments which form less dense striations.
How are the myosin filament arranged in the muscle?
Each myosin filament is surrounded by six actin filaments in a hexagonal pattern when myosin and actin filaments overlap at the ends of A-band.
What is the Theory of Sliding Filament Mechanism in Muscle Contraction?
> Action Potential diffuses across the synapse between the conducting motor neurone and the sarcolemma of the muscle fibre and is propagated through the T-tubule system along the sarcoplasmic reticulum.
Ca2+ ion channel proteins in sarcoplasmic reticulum open and Ca2+ ions diffuse down the conc. gradient into the sarcoplasm.
Ca2+ ions cause ancillary protein (tropomyosin) to be displaced, exposing actin filament binding sites to the myosin filament heads
Myosin bulbous heads form actomyosin bridges with the actin filament binding sites before rotating back 45 degrees (pulls actin filament over myosin filament)
ATP molecule attaches to each myosin bulbous head and energy is released from ATP hydrolysis via ATPase.
Energy releases breaks the actomyosin bridges causing the myosin heads to detach from the binding sites
cycle continues provided nervous stimulation and Ca2+ ions are present
Why is muscle contraction powerful?
Power of muscle contraction due to numerous parallel myofibrils bunched within each muscle fibre and numerous parallel muscle fibres within each muscle contracting simultaneously
