Venou return mechanism Flashcards
(15 cards)
why is the body dependent on venous return?
because the heart can only pump out as much blood as it receives, so cardiac output is dependent on it.
what can a rapid increase in venous return do?
enables a significant increase in stroke volume and therefore cardiac output
what are the 3 ways to overcome venous return?
- muscle pump
- respiratory pump
- pocket valves
what is muscle pump?
the muscles surrounding the veins expand and contract, pressing on the veins and causing a pumping effect.
why’s muscle pump important?
it is particularly important in maintaining venous return during exercise
what is respiratory pump?
muscles around the thoracic and abdominal regions cause change in pressure.
what can the change in pressure allow during respiratory pump?
allow the veins in this region to compress, causing blood to be ‘sucked’ through
what do pocket valves do?
they can only move blood in the veins towards the heart; it cannot fall back to where it came from
why don’t pocket valves allow blood to go back?
because at regular intervals there are semi lunar pocket valves situated in large veins.
what does myogenic mean?
it generates its own impulse through it’s own pacemaker, the SA node
Is the heart myogenic?
yes
how can the rate of the impulse be changed?
through mechanisms like the:
Neural control mechanism- NCM
intrinsic control mechanism- ICM
hormonal control mechanism- HCM
NCM: what do chemoreceptors do?
detect an increase in CO2 and blood acidity, they send messages to the CCC
NCM: what do the baroreceptors do?
they’re located in the blood vessel walls and detect increases and decreases in blood pressure and send an impulse to the CC.
NCM: what do the proprioreceptors do?
they’re located in the muscles and detect increases in muscle movement, joint and tendon activity.
