Heart functioning Flashcards
Receptors present in the heart vessels
B1, M2
Action of M2 receptors and the PNS in the heart
Decrease heart rate
Action of B1 receptors and the SNS in the heart
Increase heart rate, Increase contractility
State the factors determining BP
Cardiac output and TPR
State the factors determining cardiac output
Stroke volume and heart rate
State the factors determining stroke volume
Difference between end diastolic volume and end sytolic volume
State how end diastolic volume is set
Venous pressure
State how end systolic volume is set
Higher force of contraction decreases ESV, Higher arterial pressure decreases ESV
Describe preload
Stress on the myocardium, set by stretch of the myocardium (determined by the EDV)
Describe how blood pressure is controlled
Detected in baroreceptors, If low increase SNS input raising HR and contractility, If high increase PNS input lowering HR
How is cardiac output increased during exercise
Muscle pump increases venous return, On initiation of exercise HR is increased
Describe how postural hypotension is avoided
TPR is increased
Describe the bodies response to blood loss
Venoconstriction and auto-transfusion
Describe how depolarisations occur in pace maker cells
Spontaneous influx of Na brings the membrane to threshold, Causes Ca channels to open causing depolarisation
Describe how depolarisations occur in ventricular cells
Action potential opens Na channels, Ca enters maintaining depolarisation
