13 Flashcards
How does the knee jerk reflex work?
Patellar tendon stretches and stimulates a reflex arc which causing the extensor muscle in top of the thigh to stretch
Relay neuron inhibits flexor muscle’s motor neuron so it relaxes
Antagonistic flexor hamstring muscle relaxes
Knee kicks
Describe a myosin molecule’s structure
Head has a binding site for actin and ATP
Tail is aligned with others to form a myosin (thick) filament
How does adrenaline act once it reaches the plasma membrane?
Binds to complementary receptor
Activates adrenal cyclase which converts ATP to Cyclic AMP (cAMP)
cAMP activates protein kinases which phosphorylase
Then other enzymes activated, e.g. for glycogenolysis (glycogen to glucose)
Structure and function of skeletal muscle?
Multinucleated fibres
Cross striations
Cell’s regularly arranged (contract in 1D)
Move bones/joints
Structure and function of cardiac muscle?
Fibres branch and interconnect allowing simultaneous contractions
Uninucleated cells
Specially striated
Pump blood
Involuntary/smooth muscle structure?
Fibres are uninucleated and not regularly arranged
Can contract for a long time
Control blood vessel and bronchioles diameter, peristalsis, and pupil size
Describe the structure of actin (thin filament)
Have actin-myosin binding sites for myosin
Binding sites blocked by tropomyosin to prevent filaments sliding
Describe what happens at the sarcolemma during muscle contraction (up until cross-bridges)
Depolarisation spreads down T-tubules causing calcium ions channels to open
Ca2+ diffuses into sarcoplasm
Ions bind to troponin so tropomyosin pulls away from the binding sites
Myosin heads bind to form actin-myosin cross-bridges
Describe what happens at the sarcolemma during muscle contraction (after cross-bridges)
Myosin head flexes to pull filament along
ADP bound to myosin head releases
ATP molecule binds to myosin head so it detached from actin filament and is hydrolysed do energy can be used to return myosin head
