The molecular and ionic basis of cardiovascular control Flashcards
Describe the intrinsic regulation of the force of contraction of cardiac muscle
Frank-Starling relationship Increased contractility Increased preload Longer and stronger “More cross bridges means more of everything”
Describe the extrinsic regulation of the force of contraction of cardiac muscle
Sympathetic stimulation
Faster and stronger
NOT longer duration
“Extant cross bridges work harder and faster”
How does increased EDV (more stretch) cause an increase in the force of Contraction?
Increased Overlap of thin + thick filaments
Increased Overlap causes an increase in force generators
What is the isolated or denervated heart rate in beats per minute?
~100 beats per minute
What is the normal resting heart rate?
60 bpm
What is normal resting heart rate caused by?
Tonic (on all the time) parasympathetic (vagal) stimulation
What is heart rate mostly determined by?
The slope of the pacemaker potential
Which nervous supply is noradrenaline released in?
Sympathetic nervous system
What does noradrenaline do?
Noradrenaline Increases If (Net inward current)
- increases slope of pacemaker potential
- Via Beta 1 receptor
Also in nodal & ventricular:
Noradrenaline increases inflow of calcium which increases the force of contraction
Noradrenaline increases current of repolarizing potassium
-IK = delayed rectifier
-shortens AP duration
-Allows faster HR
Which direction is the net current in the funny current?
Inward
Which channel is involved in the funny current and when do they open?
HCN Channel opens when membrane gets more negative
What does an increase in sympathetic stimulation do to the funny current?
Increases
List the different types of adrenergic receptors
Alpha 1 - Gq, works using phospholipase C- responsible for vasoconstriction
Alpha 2- Gi, works using adenylyl cyklase- less insulin and more glucagon
Beta- Gs, stimulates adenylyl cyclase- heart contraction increases, increases heart rate, an increase in skeletal muscle perfusion and an increase in lipolysis in adipose tissue
Describe the parasympathetic supply to the heart
Acetylcholine leads to an increase in potassium current which hyperpolarizes the membrane and decreases the slope pacemaker potential
Describe the ACh activated potassium channel
Muscarinic
G protein coupled
What does atropine do?
Blocks the muscarinic receptor therefore blocks vagal slowing of heart rate and causes heart rate to increase. Useful in asystole