Muscular System Flashcards
Function of muscular system
-movement
- maintains posture
-Stabilize joints
- respiration
-communication (verbal and facial expressions)
-contrcitions of vessels amd organs
-generates heat
-heartbeat
Briefly explain the structure of muscles
Single mucles is composed of fibers
Fiber are composed of myofibrils surrounded by endomysiom
Fibers are bundled to fascicles surrounded by perimysioum
Fascicles are bundle to form muscle surrounded by epimysium and fascia
Explain the sliding-filament model of contraction
Skeletal muscles are bundles of myofibrils which are also composed of myofilaments that forms the sarcomere
Thick myofilmanets are myosin and thin myofilmanaent are compoosed of actin which are attached to z-discs
During contractions, myosin heads sticks to actin myofilaments and propel towards the center of sarcomere along with the z-discs. Which shortens the sarcomere
Anatomy of a sarcomere
Z discs
- protein backbones that attaches actin to sarcomere
- end boundaries of sarcomere
Actin
-thin myofilaments attached to z-discs
Myosin
- thick filaments which are attched to actin to form cross-bridge
Titin
- protein that achords myosin to z-discs
Tropojin and tropomyosin
- inhibitory proteins that prevent contraction when muscles are relaxed
Explain mechanism behind muscle contraction
skeletal muscles are triggered by motor neurons or neuromuscular junction
When impulse reaches ends of motor neurons, chemical messengers called acetylcholine are released which diffuses across the synaptic cleft and stimulate sarcolemma
Whene electrical impulse are received, sarcoplamic reticulums releases calciums wich binds to troponin. And the myosin heads of myosin filament latches to actin and contraction occurs
What happens during muscle relaxation
Nerve impulses stops arriving at neuromusclar junction and no more release of acetylcholine.
Calcium are no longer released and troponin and tropomyosin prevents myosin heads from sticking to actin and muscle fiber relaxes
