Excitation COupling

cgeorge's version from 2016-02-27 10:13


Question Answer
Cardiac and skeletal muscle similarities Both striated and contain T tubules
Differences between cardic and skeletal muscle (T tubule, any specialised fibres, connecting junctions, length of AP)1) Cardiac has less developed T tubule system and SER system 2) Heat contains SAN and purkinje fibers 3)Heart contains gap junctins 4)Ventricular AP is 200ms compared with 1-2ms in skeletal
Differences in the SER between cardiac/skeletalCardiac - T tubues larger, but contain fewer t tubules than skeletal. In cardiac, SER more sparse
What is excitation coupling Its the process where an AP triggers myocyte to contract
Where are L type voltage gated Ca channels foundPlasma membrane
What opens the L type voltage gated channels?Depolarisation of the sarcolemma
What does opening of the L type voltage gated Ca channels trigger?Further release of Ca from SER stores via ryanodine receptor
Role of ryandoine receptor Mediates release of Ca ions from SER
Whats the role of the Na/Ca exchangesExhcnages 3 moles of Na for 1 mole of Ca
What does SERCA doSERCA is a Ca-ATPase pump that sits in the SER plasma membrane that pumps Ca from cytosol to lumen of SER
What is phospholambanIts a phosphoprotein component of the SER that helps to regulate cardiac SER calcium uptake
What happens when [Ca] in cytoplasm reaches 10-15M?Ca binds to troponin C and induces conformational change in tropomyosin that releases troponin I. This exposes the myosin binding site on actin and binding of myosin inititates contraction cycle
Explain the beta adrenergic receptor signalling pathway that regulates cytosolic [Ca]1) Norad/Adren binds to B1 adrenergic receptor 2) Activates GTP binding protein 3)Adenylyl cyclase 4)cAMP 5)PKA pathay 6) PKA phosphorylates proteins e.g. PLB/L type Ca channels
Activation of A1-adrenoceptors, angiotensin receptors and endothelin 1 receptors activatesPhospholipase C. PIP2 > IP3. Increased IP3 stimulates Ca release from SER in heart, increasing contractions
What does ionotrophy meanMyocardium contraction
What does lusitrophy meanMyocardium relaxation
In a lusitropic effect what does PKA phosphorylate?Via phosphorylation of PLB and troponin I. This speeds up Ca reuptake and dissociation of Ca from myofilaments
How is the inotrophic effect of PKA activated?Via combination of increased intracellular Ca and greater availability of SER Calcium

Recent badges