Skeletal muscles Flashcards
(10 cards)
How do skeletal muscles work?
Skeletal muscles act in antagonistic pairs (when one contracts, the other relaxes). Skeletal muscles work against an incompressible skeleton so bones act as levels for muscles to pull against
What are muscles made of?
Muscles are made of long cells called muscle fibres.
What is the structure of muscle fibre cells?
They contain long organelles called myofibrils. The cytoplasm = sarcoplasm. Cell membrane called sarcolemma. The sarcolemma has many folds called T-tubules which help spread electrical impulses throughout the sarcoplasm and fibre. Contains specialised sarcoplasmic reticulum which stores Ca2+ ions needed for contraction. They contain many mitochondria and are multinucleate as they are formed from the fusion of multiple cells.
What is the structure of a myofibril?
Myofibrils contain bundles of thick and thin myofilaments that move past each other to make muscles contract. There are two types: myosin (thick myofilament), and actin (thin myofilament).
How do myofibrils contract?
Myosin and actin slide over each other to make sarcomeres contract. The simultaneous contraction of the sarcomeres result in the myofibrils and muscles contracting. Then the sarcomeres return to their original length as the muscle relaxes.
What is the role of tropomyosin in muscle contraction?
Tropomyosin blocks the myosin head from binding to the actin-myosin binding site. Since the myosin head can’t bind, the myofilaments can’t slide past each other.
What is the role of ATP in muscle contraction?
Aerobic respiration is a good way of producing ATP for long periods of low-intensity exercise. Anaerobic respiration is good for short periods of high-intensity exercise. However, lactate is then produced which can cause muscle fatigue if it continues to build up.
What is the role of phosphocreatine (PCr) in muscle contraction?
PCr can be used in the ATP-PCr system. PCr is stored inside cells and it phosphorylates ADP to form ATP.
What is the word equation for the phosphorylation of ADP by PCr?
ADP + PCr = ATP + Cr (creatine)
