Blood Pressure Regulation and Hypertension Flashcards
rate of blood flow through the lungs and why
pulmonary blood flow constitutes the entire right ventricle. PBF is equal to the entire right ventricle volume of 5 L/min
what control mechanisms regulate blood flow to organ or tissue capillary beds
intrinsic control: within that tissue, sympathetic blood flow into caps, auto regulated
extrinsic blood flow SNS hormones
intrinsic- metabolic theory of auto regulation
as local tissue metabolism increases due to increased activity, local factors are produced by the tissue that dilates arterioles that perfuse the tissue resulting in increased blood flow to that tissue. it decreases resistance
O2 and nutrient supply to tissues increases as long as metabolism is increased
O2 decrease
cell metabolism
CO2 increase
cell metabolism
H increase pH decrease
cell metabolism
K+ increase
cell metabolism
adenosine
ATP breakdown
Histamine
mast cells
Nitric Oxide (NO2)
endothelium
Prostacyclin (PGI2)
endothelium
myogenic theory of autoregulation
myogenic- contraction originates in the muscle. true of cardiac and smooth muscle. Ca2+ stretch-activated smooth muscles open when pressure or force distends the cell membrane allowing the muscle to contract in response to stretch - increased perfusion pressure, increase VGCC, increased vasoconstriction, decreased flow - negative feedback
extrinsic blood flow (outside, not local) controls
ANS and Hormones/Neurohormones
which branch of ANS has control of blood vessel tone
sympathetic
alpha 1 receptor
NE, some EPI, constricts
Beta 2
epi only, dialates
muscurinic receptors
controls the bladder, cold medication may cause bladder relaxation
angiotensin regulates blood volume and blood flow
regulation of aldosterone release from adrenal cortex (inc Na+ reabsorption)
regulation of vasopressin release from hypothalamus (anti-diuretic)
increased SNS activity - increased vasopressin (antidiuretic), increases thirst, increases CV response, increases Na+ reabsorption
direct vasoconstriction
effects of angiotensin 2 synthesis inhibitors or receptor blockade
reduction of SNS activity from CV control center in Medulla Oblongata
reduction in vasopressin release from posterior pituitary
- decreased H2O reabsorption in kidney decreased blood volume
- reduction of aldosterone synthesis - decrease Na+ reabsorption in kidney - decreased blood volume
- reduce direct vasoconstriction
epinephrine
produced in response to SNS activation and released from adrenal medulla - allows vessels to dilate while others will constrict ( alpha constricts and beta dialates)
regulation of mean arterial pressure
arterial pressure- driving pressure created by the pumping of the heart. when we measure the brachial artery its an estimate of the total pressure created by ventricular contraction. abnormally high or low blood pressure can be indicative of a problem in the CV.
MAP =
Diastolic Pressure + 1/3 Pulse Pressure
Pulse Pressure =
systolic - diastolic
factors that affect MAP - Blood Volume
drug: diuretics
determined by fluid intake or fluid loss (passive or regulated at kidneys)
describe baroreceptor response to either a rapid drop or increase in blood pressure
control of HR and MAP
stretch receptors in aorta or carotid relay information to the CV control center. the afferent nerves from the baroreceptors fire faster with increased pressure, slower with decreased pressure - aortic pressure inc, inc firing rate
CV control center in medulla oblongata-
- dec symp output (alpha 1 receptor (dilate arteriole, dec peripheral resistance), b1 receptor (dec force of contraction on ventricular myocarium dec CO), B2 (SA node, dec heart rate, dec CO)
- inc para symp- inc more ACh on muscurinic receptor- SA node, dec heart rate- dec CO
Preventable risk factors
smoking (nicotinic receptor: ligand gated dec heart rate, chronic use elevates pressure), untreated hypertension, diabetes, obesity, dylipidemia, sedentary lifestyle, atheroclerosis (inc lipid levels)
describe criteria for stage 1 and stage 2 hypertension. when should pharmacological treatment be initiated
stage 1 pressure: 130-139
stage 2 pressure: above 140
treatment of BP should begin at stage 2. the goal, even those with diabetes, should be between <130/80, patients over 80 years should have <150 systolic
primary hypertension
unknown origin
90% of all hypertension
multiple gene involvement
common theory: baroreceptors reset at higher levels
compensation for increase blood flow
compensation by CV system- vasodilation, CO goes down (fast response)mediated by baroreceptor reflex
compensation by kidneys- excretion of fluid in urine decreases blood volume (slow response)
tissue/organ effects of uncontrolled hypertension
- vascular tissue: acceleration of atherosclerosis, rupture of aortic aneurysms, peripheral arterial disease, erectile dysfunction
- heart: increase IM risk, cardiac hypertrophy, angina
- kidney: renal failure, proteniuria, increase BUN
- eyes: retinopathy and blindness
- brain: hemorrhagic or ischemic stroke, reduced cognition, aneurysm
unpreventable risk factors
age, gender, risk, family history
higher in younger men, older women, African Americans
older women more at risk because of menopause
AA> hispanic > Caucasian
secondary hypertension cause!
cause is known:
- renal disease (renal artery stenosis
- endocrine disorders: hyperthyroidism
- vascular disorders- atherosclerosis, coarctation(smaller in diameter of the aorta)
- neurologic disorders- brain tumors, spinal cord injuries
- tobacco use
- medications or illicit drug abuse- cocaine, amphetamines/stimulants (ritalin, ADHD meds), cold meds (pseudoephedrine), diet pills: ephedrine, sibutramine
treatments for primary hypertension
life style modification, pharmacotherapy, diet, exercise, sodium restriction, beta blockers, direct vasodialators, alpha1 adrenergic antagonists, alpha2 adrenergic agonists, thiazide diuretic, angiotensin 2 synthesis or receptor blockers, calcium channel blockers
