LP #107 Factors Affecting BP Flashcards
- increase P in aorta just after ventricular systole
- aorta resists stretch, which maintains increase P
- in BP readings: top value
Systolic P
- decrease P in aorta- as it recoils
- in BP reading: bottom value
Diastolic P
In healthy adults:
- peak P (systolic P): ~___ _ Hg
- diastolic P: ~ __- __ _ Hg
- 120mm
- 70-80mm
*the rhythmical expansion or dilation of the heart and arteries correlative to systole or contraction=
Diastole
*contraction of the heart=
Systole
Pre-capillary sphincters control=
Smooth m contracts; pre-capillary sphincters close=
Smooth m relaxes; pre-capillary sphincters open=
Capillary BP:~ ___ __ Hg
- BF into capillaries
- Decrease BF into capillary bed (sympathetic)
- increase BF into capillary bed
- 40mm
Capillaries have tunica intima only (1 cell thick)=
Decrease BF allows for adequate time for=
From venues, BP is ___ __ Hg
- increase P would rupture capillary
- substance exchange (nutrients & waste)
- 28mm
- 10 mm Hg
- no blood pressure
- venous BP changes little during cardiac cycle
- venous BF: very decrease P & opposes gravity
Venous pressure
Venous return is driven by alternative means:
- One-way venous valves
- Skeletal m pump
- Respiratory pump
- extensions of endothelium
- ensure minimal back flow
One-way venous valves
- skeletal mm surround deep vv
- when mm contract: compress vv & moves blood towards heart
- valves prevent backflow when mm relax
Skeletal m pump
- inspiration: diaphragm pushes on abdominal viscera
- leads to increase abdominal P & decrease thoracic P
- increase P gradient b/w abdominal & thoracic vv: pushes blood from abdomen to thoracic vv
- as blood returns to heart via vv: pick up metabolic waste (disposed of by lungs & kidneys)
Respiratory pump
- volume (ml) of blood pumped out by 1 ventricle w/ each heartbeat
- correlates w/force of ventricular contraction (increase force= increase SV)
Stroke volume (SV)
- amount of blood pumped out by both ventricles in 1 minute
* CO is influenced by HR & SV (CO= HR x SV)
Cardiac output (CO)
Cardiac output:
- N adults total BVol is=
- an adults total BVol passes through heart each ___
- 5L
- Min
- difference in CO at rest & during intense activity
- increase reserve= increase ability to engage in intense physical activity
Cardiac reserve
- arterial pulsation- felt at various points in the body
- d/t increase arterial BP
- force of blood ejection from heart & ability of aa to dilate/ recoil
- increase HR & increase CO= faster & stronger pulse
- decrease CO= weak, thready pulse
Pulse pressure
Variables affecting BF:
- CO
- PR
- BVol
CO= ___ x ___
HR x SV
BP is a fxn of?
CO & PR
BP is monitored/ maintained at constant levels, ensured by:
- heart (CO)
- bv’s (PR)
- kidneys (vasoconstriction)
- brain (Vasomotor centres)
Normally:
- increase CO=
- increase PR=
- decrease PR
- decrease CO
Short-term & long-term mechanisms medicate?
BP maintenance
Affects distribution- responds to tissue needs by altering bv lumen to maintain arterial P=
Neural control
Maintaining BP short-term mechanisms (2)?
Baroreceptor reflexes
Chemoreceptors reflexes
- respond to changes in arterial BP
- mediated by stretch receptors in aortic arch & carotid sinuses
- effectively mediate quick changes in BP,ex. D/t postural changes, emotional changes etc.
- do not mediate long-term BP changes
Baroreceptor reflexes
- respond to changes in blood pH & other chemicals
- mediated by receptors in aortic arch & carotid sinus
- sensitive to decrease O2 levels, changing pH levels, & increase CO2
Chemoreceptor reflexes
Chemoreceptor reflexes role in regulating ventilation (hypothalamus):
- mediate changes in blood distribution
- modify BP (via Vasomotor centre)
- emotional situations (higher brain fxns)
Maintaining BP long-term regulation:
- mediated by renal & endocrine mechanisms
- kidneys
- important in maintaining BP
- regulate fluid & electrolyte balance
- affects distribution (vasoconstriction)
