Flashcards in blood pressure Deck (34)
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1
what is mean arterial bp?
driving force for blood flow through organs (-lungs)
maintenance is essential for ensuring adequate blood flow to organ systems (120/80mmHg)
2
what is systolic bp?
pressure in arteries (aorta) during myocardial contraction (systole)
3
what is diastolic bp?
pressure in arteries during myocardial relaxion (diastole)
4
what is pulse pressure?
SBP-DBP
5
what is mean arterial pressure?
DBP + 1/3 pulse pressure
6
what is mean systemic arterial pressure? (MAP)
CO x TPR
7
what is the formula for CO?
SV x HR
8
what is total peripheral resistance?
systemic vascular resistance
-total resistance to flow of blood in systemic vasculature
9
how is bp measured?
sphygmomanometer
-occlude artery of an extremity with and inflatable cuff and by ausculatation for detection of Korotkoff sounds
10
what are the 2 mechanisms for control of bp?
rapid regulation
-nerves
-hormones
long term regulation
-blood volume
11
describe rapid control
pressure gradient exists from arterial system to venous system
pressure highest when blood enters aorta on contraction of LV
baroreceptors
12
what are baroreceptors?
mechanoreceptors that detect the degree of stretch of bv walls
monitor bp
mechanical stretch in arteries occurs due to pulsatile blood flow
-directly related to bp
increases during systole
reduces in diastole
most abundant in aortic arch and carotid sinus
13
what is the carotid sinus?
2 carotid arteries supply the head and neck
each divide into 2 smaller arteries
-artery wall thinner
-large no. nerve endings
baroreceptors innervated by sinus nerve of hering
14
what is the aortic arch?
innervated by aortic nerve
baroreceptors have higher threshold pressure so less sensitive than carotid sinus baroreceptors to changes in stretch
15
how do baroreceptors fire in response to a decrease in arterial pressure?
reduced AP firing from baroreceptors
stimulation travels along afferent neurons
medullary cvs centre
increased stimulation of sympathetic neurons to heart/arterioles/veins
decreased stimulation of Parasympathetic neurons to heart
16
how do baroreceptors fire in response to an increase in arterial pressure?
increased AP firing from baroreceptors
stimulation travels along afferent neurons
medullary cvs centre
decreased stimulation of sympathetic neurons to heart/arterioles/veins
increased stimulation of parasympathetic neurons to heart/arterioles/veins
17
what is the Valsalva manoeuvre?
attempt to expire against a closed glottis
exhaling when mouth & nose are closed
18
what is the physiological response to the Valsalva manoeuvre?
1) Increased intrathoracic pressure 2) Raising blood pressure; normal LV contraction + (1); increased baroreceptor firing 3) Heart rate falls transiently – impeding venous return of blood to heart 4) Fall in CO and MAP 5) As MAP decreases, HR rises and (w/TPR), stabilises blood pressure
19
what happens when the glottis re-opens in the Valsalva manoeuvre?
6) Intrathoracic pressure falls 7) BP falls initially 8) Venous return is rapidly restored 9) EDV & CO increase, raising BP 10) Increased BP is sensed by baroreceptors results in reflex bradycardia (slowing of HR)
20
what is baroreceptor resetting?
when arterial bp elevated for prolonged periods, the threshold for baroreceptor activity rises to a higher value
meaning they are:
ineffective monitors of absolute pressure
short term only
resetting occurs:
-during exercise
-hypertension
21
what does blood volume influence?
venous pressure
venous return
end-driastolic vol.
stroke vol.
cardiac output
increased blood vol. = increased arterial pressure
22
what are arterioles?
small diameter bv
small changes in arteriolar radius control bp in response to locally circulating substances
23
what is the effect of decreased arteriolar radius?
sympathetic nerves
noradrenaline
alpha 1 adrenoreceptors
=constriction
24
what is the effect of increased arteriolar radius?
sympathetic cholinergic nerves
-acetylcholine
-muscarinic receptors
plasma
-adrenaline
beta-2 adrenoreceptors
local controls
-increased K+, adenosine
-decrease in PO2
=dilation
25
what are local controls of bp?
modulated bp and blood flow
ability to override central bp control systems
bp midified by local changes in TPR
occurs in response to factors such as metabolites, blood gases endothelium derived factors
26
what is a capillary fluid shift?
occurs due to venous dilators
caused by reduced proximal capillary hydrostatic pressure
most vasodilators have effects on both arteries and veins
27
what is hypertension?
140/90 and up
bp increases with age
lachs noticeable symptoms until severe
lifestyle changes and/or pharmacological intervention can lower
28
what factors raises risk of hypertension?
age
smoking
high salt intake
lack of exercise
being overweight
drinking a lot
stress
genetic predisposition
family history
29
what health conditions can raise HT risk?
kidney conditions
-CCK
-narrowing of arteries that supply blood to kineys(renal HT)
-long-term infections
-glomerulonephritis
diabetes
obstructive sleep apnea
hormone problems
30
what therapeutics can raise HT risk?
contraceptive pill
NSAIDS
recreational drugs
31
what are the implications of HT?
aneurysms in cerebral arteries
LV hypertrophy
thickening of arteries
atherosclerosis deterioration
these effects can lead to:
renal disease
heart failure
malignant HT
angina
myocardial infarction
stroke
32
what is clonidine?
centrally acting HT drug
alpa-2 adrenoreceotor agonist
stimulated alpha-2 adrenoreceptors in brain stem
reduces sympathetic outflow from CNS
decreases:
-peripheral resistance
-renal vascular resistance
-HR
-bp
33
what is alpha methyldopa?
centrally acting HT drug
alpha-2 adrenoceptor agonist
converted into metabolite-methylnoradrenaline in CNS
stimulates central inhibitory alpha adrenoceptors
reduction in sympathetic tone, TPR, & bp
34
