Venus return
Cards (12)
- What is the equation for blood pressure ?Cardiac output x resistance
- what are the three Venus return mechanisms used at rest ?pocket valvessmooth musclesuction pump of the heart
- what are the Venus return mechanisms used during exercise ?muscular pumprespiratory pump
- pocket valves -
- found in the veins
- prevent backflow
- smooth muscle-
- vasomotor tone - the walls of the veins are in a constant state of construction
- this helps to increase resistance
- aid flow of blood
- help push blood along
- suction pump of the heart-
- during systole the walls squeeze in then during diastole they relax ,expand and draw blood into the atria
- muscular pump -
- veins lay between muscles
- when muscles contract they squeeze the walls of the veins inwards
- this squeezes blood through the vein towards the heart
- respiratory pump -
- veins travel through the chest area
- increased breathing rate increase the pressure in the thoracic cavity
- the pressure squeezes the walls of the veins
- this squeezes blood through the vein towards the heart
- Starlings law -stroke volume is determined by venous return ,if venous return increases ,stroke volume increases .If venous return decreases stroke volume decreases
- increased venous return
- greater diastolic filling
- greater stretch of the heart wall
- greater recoil of the heart wall
- increased force of contraction
- increased stroke volume
- increased ejection fraction
- Decreased venous return
- reduced diastolic filling
- reduced stretch of the heart wall
- reduced recoil of the heart wall
- reduced force of contraction
- decreased stroke volume
- decreased ejection fraction
- cardio vascular drift
- after 10 mins we begin to sweat ,we sweat out blood plasma causing an increase in blood viscosity
- this causes a decrease in venous return
- starlings law occurs
- decrease in stroke volume
- decrease in ejection fraction
- increase it heart rate in order to maintain cardiac output