Module 9 (The Finale) Flashcards
Venous Return driving force amoutn
15 mmHg (0-30 range)
Venous Return hydrostatic pressure
1.2m column of blood
- 100 mmHg
How much BV lies below heart level?
70%
Venous Valves
- one way flow
- break up column into smaller sections
Varicose veins
cause circulatory failure
Why wear tights
stiffens the veins and assists venous return
Muscle pump
- generates 90 mmHg pressure
- need 100 mmHg to drive blood back to right atrium
- contraction squeezes veins (increase in pressure)
Why cool downs are good
- prevents peripheral pooling
- faint, BP needs to return to resting levels due to increased pressure
- e.g. lie down and elevate legs after prolonged exercise
What happens with respiratory pump?
- increased pressure from exhalation
- blood pumped back to heart via pump
what happens with respiratory pump
think about pressure
- Inhalation = decreased intrathoracic pressure where increased pressure in IVC where blood enters back into heart
- Exhalation = IVC reduces allowing liver to send more blood to heart
More inhalation = more blood back to heart
- Exhalation = IVC reduces allowing liver to send more blood to heart
where are baroreceptors located
aortic and carotid bodies (LV, RA and large veins)
stimulated from BP changes
afferent signals –> medulla –>autonomic NS modification
how can BP be modified
(HR x SV) x TPR
Can be solved either
- PNS inhibition (HR and SV decrease)
SNS activation (increase HR and SV/Q) and increase TPR
where are chemoreceptors located?
in aortic arch, carotid sinus and ventrolateral medulla (monitor CSF)
before and during exercise
summarise
BEFORE EXERCISE = Reduced SNS, causing vasodilation while metabolites as by-product of muscular contractions cause override of SNS stimulation = localised vasodilation and increased BF to active muscles
EXERCISE = precapillary sphincters and autoregulation causing dilation for increased BF to working muscles
