Muscle Flashcards
Which types of muscle are striated?
Skeletal and cardiac.
Explain the arrangement and number of nuclei found in the three types of muscle.
Skeletal- peripheral, multiple nuclei.
Cardiac- central, 1 or 2 nuclei.
Smooth- central, single nucleus.
What kind of control are the three muscle types under?
Skeletal- voluntary, somatic motor neurones.
Cardiac- myogenic
Smooth- involuntary, autonomic
Where are white and red cells found and what do they indicate?
Found in skeletal muscle. Red, white and intermediate stained cells are proportional to function and role of the muscle. Red = slow, white = fast.
What is each fibre in skeletal muscle surrounded by?
A layer of connective tissue which bears capillaries and nerves.
What is the name given to the plasmalemma of muscle cells?
Sarcolemma
What is the name of the thick filament and the thin filament found in muscles?
Thick filament is myosin, thin filament is actin.
Why does skeletal muscle contain many mitochondria and where are they found?
For muscle contraction. Lies between myofibrils.
What 3 things make up the thin filament in muscle? Describe the arrangement.
Actin, troponin and tropomyosin.
Actin is twisted in a helix. Tropomyosin coils around actin. A troponin complex is attached to each tropomyosin molecule.
Explain how ionic calcium enables muscle contractions to occur, i.e. its binding.
It binds to Tnc in the troponin complex. This causes a conformational change which moves tropomyosin away from actin’s binding sites. This displacement allows myosin heads to bind to actin, so contraction begins.
Explain how muscle contraction occurs.
Myosin cross bridge attaches to the actin myofilament. The myosin head pivots, pulling on the actin, sliding it towards the M line by 5nm. ADP + pI are released. New ATP attaches to the myosin head, detaching the cross bridge. As ATP splits into ADP + pI, cocking of the myosin head occurs.
Where precisely is the triad located in skeletal muscle, and what is it made up of?
Located on top of where the A and I band meet. Made up of T tubule with terminal cisternae of the sarcoplasmic reticulum either side.
What are the functions of skeletal muscle?
Movement, posture, stability of joints and heat generation.
Explain how depolarisation of the T tubule occurs in skeletal muscle.
A nerve impulse along the motor neurone arrives at neuromuscular junction. The impulse releases Ach into synaptic cleft causing local depolarisation of the sarcolemma. Voltage gated Na+ channels in the muscle open, so Na+ enter. General depolarisation then spreads over the sarcolemma and into the T tubule.
Explain the steps involved to get from depolarisation of the T tubule to muscle contraction.
Due to depolarisation, the voltage sensor proteins of T tubule membranes change their conformation. This activates gated calcium channels of adjacent terminal cisternae. Calcium is rapidly released into the sarcoplasm and binds to Tnc subunits of troponin. This enables the contraction of muscle.
