Cardiovascular system lectures

• Which intracellular structure takes calcium into the mitochondrion?

  MiCa channels
• What is the role of the Na+/K+ ATPase in myocyte relaxation?

  Sets up the sodium gradient for NCX1
• Which channel is an L-type calcium channel?

  Cav1.2
• What exchanges calcium for sodium?

  NCX1
• Which pump exchanges hydrogen for calcium?

  SERCA2a
• What maintains the electrochemical gradient of the mitochondrion?

  -160 mV
• What determines the strength of myocyte contraction at the myocyte level?

  Amount of calcium increase
• What is preload defined as?

  End diastolic volume
• What is afterload defined as?

  Arterial pressure
• What is the relationship between calcium influx/efflux and the strength of myocyte contraction?

  Directly related to strength of contraction
• What is preload determined by in the whole cardiac muscle?

  End diastolic volume
• What pressure do ventricles have to work against to reject blood?

  Arterial pressure
• How are preload and afterload related to myocyte and whole muscle contraction?

  They have an effect at both levels
• What happens to tension in an isometric contraction?

  Tension changes
• What are the proteins involved in passive tension at the fibre level?

  Titin and desmin
• How does titin differ in cardiac muscle compared to skeletal muscle?

  Cardiac titin is shorter
• Why is passive tension evident at lower sarcomere lengths in cardiac muscle?

  Due to shorter titin
• What generates tension in the absence of electrical stimulation?

  Titin and desmin
• What is the reference for cardiac muscle titin length?

  1. 2010;121:2137–2145
• What is active tension in muscle?

  Tension by stimulation @ set length
• What happens to tension if the sarcomere is overstretched?

  Tension decreases to zero
• What causes the difference in active tension between cardiac and skeletal muscle?

  Other mechanisms beyond overlap
• What happens to sarcomere overlap and tension at optimal length?

  More overlap and higher tension
• What is one difference that is due to stretch activate calcium channels?

  Stretch induced calcium release
• What channels are activated when cardiac muscle fibre is stretched?

  Stretch-activated calcium channels (SACs)
• What does increased stretch lead to?

  More calcium entry from ECF
• What is the effect of optimal sarcomere length?

  Increases optimal tension
• What does Starling's law state?

  Contraction depends on fibre length
• According to Starling's law, what is the relationship between sarcomere length and contraction?

  Larger length = greater contraction
• According to Starling's Law what does greater contraction lead to?

  More potential for actin/myosin interaction
• What state is diastole?

  Passive
• What state is systole?

  Active
• What happens during diastole with increased preload (EDV)?

  Increase in pressure
• What happens during systole to pressure as EDV changes?

  Pressure increases faster
• What kind of tension is created by diastole?

  Passive tension
• What happens when more blood enters the ventricles?

  Greater pressure so greater contraction
• What impacts the force required to eject blood?

  Afterload
• What kind of contractions are used to calculate velocity of shortening?

  Isotonic
• What happens to the velocity with increased contraction?

  Velocity speeds up
• What do we need to achieve higher heart rate?

  Increased velocity of contraction