Venous Return and its Control Flashcards
if we increase the EDV through increased VR we ____ the SV
increase
the heart is not working at optimum fibre length at rest . what does this mean for the heart?
it has potential to do more work
what are 4 examples of factors that increase venous return?
- increased venomotor tone
- increased skeletal muscle ‘pump’
- increased respiratory pump
- increased blood volume
what does an increase in VR do?
increases atrial pressure which ^ EDV which ^ SV
what is the venomotor tone?
Venous smooth muscles are supplied with sympathetic nerve fibres.
Stimulation gives venous constriction
On account of venous valves, blood driven to right atrium
what does increased VENOmotor tone do?
INCREASES VENOUS RETURN, SV & MAP
what does increased VASOmotor tone do?
INCREASES TPR & MAP
what is the skeletal muscle pump?
Large veins in limbs lie between skeletal muscles
Contraction of muscles aids venous return
One-way venous valves allow blood to move forward towards the heart
Muscle Activity increases VENOUS RETURN to heart
what happens to the sympathetic nerve activity during exercise
increases
what happens to HR and SV during exercise
increase. this increases CO
what happens to sympathetic vasomotor nerve flow to kidneys and gut during exercise
they vasoconstrict - mainly due to the effect of adrenaline and hormones which are orga specific. These organs have more alpha recepors
what happens to skeletal and cardiac muscle during exercise?
metabolic hyperaemia overcomes vasomotor drive - vasodilatation. have more beta receptors
what happens to blood flow to skeletal and cardiac muscle during exercise?
increases in proportion to metabolic activity
what does te increase in CO do to the BP?
increases systolic BP
what does the metabolic hyperaemia do to TPR and DBP?
decreases both (i.e. the pulse pressure increases) stong vasodilator effect of metabolites
what may happen post exercise?
may get a hypotensive response
what is the effect of sympathetic stimulation on pacemaker cells?
Slope of Pacemaker Potential INCREASES
Pacemaker potential reaches threshold quicker
Frequency of action potentials increases - Positive chronotropic Effect
what is the Effect of sympathetic nerve stimulation on ventricular contraction?
Peak ventricular pressure rises - contractility of heart at a given EDV rises
Frank-Starling Curve is shifted to the left
what is the effect of EDV on SV?
increases SV
what are examples of the chronic CV responses to regular exercise
- Reduction in sympathetic tone and noradrenalile levels
- Increased parasympathetic tone to the heart
- Cardiac remodeling
- Reduction in plasma renin levels - therefore reducing BP
- Improved endothelial function: vasodilators vasoconstrictors
Arterial stiffening
