Let 15 Blood Volume , BP Flashcards
CO is what?
Cardiac Output (CO), is the volume of blood pumped/min by each ventricle -(SV)(HR)
Define stroke volume
SV is blood pumped/beat by each ventricle
- CO=SVxHR thus at rest, CO= about 5500ml/min=5.5L
What is about the total blood volume in the body
about 5.5L
what is the main controller of HR
the Autonomic innervation of SA node b/c nerve fibers modify rate of spontaneous depolarization
- symp (increases HR)
- parasymp (decreases HR)
what stimulates the opening of pacemaker HCN channels
NE & Epi
-this depolarizes SA faster, increasing HR
What promotes opening of K+ channels
ACh, the resultant k+ outflow counters Na+ influx, slowing depolarization & decreasing HR
Cardiac control center of medulla does what
coordinates activity of autonomic innervation
-sympathetic endings in atria &ventricular can stimulate increased strength of contraction
What 3 variables determine SV
- End diastolic volume(EDV)
- Total peripheral resistance(TPR)
- Contractility
Define EDV
volume of blood in ventricles at end of diastole; increase EDV= incr SV; dear EDV=decr SV
define TPR
impedance to blood flow in arteries; increase TPR= decreased SV; decreased TPR= increased SV
define contractility
strength of contraction decreases contractility=decreased SV
what is workload(preload)
EDV is amount of blood in ventricles just before they contract
- SV is directly proportional to preload & contractility
- strength of contraction varies directly with EDV
afterload which impedes ejection from ventricle comes from what
TPR
Frank-Starling Law of the Heart says what
states that strength of ventricular contraction varies directly with EDV
- when EDV increases, strength of ventricular contraction increases, thus SV increases
at any given EDV, strength of contraction depends upon level of what activity?
sympathoadrenal activity= positive inotropic effect; NE & Epi produce an increase in HR & contraction
Effect on SV is what effect
inotropic (positive)
what are the 2 ways CO is affected by sympathoadrenal activity
- positive inotropic effect on contractility
2. positive chronotropic effect on HR
effect on HR is what effect
positive chronotropic effect
what is venous return
return of blood to heart via veins
- controls EDV & thus SV & CO
- dependent upon total blood volume & venous pressure
what percentage of blood do veins hold
about 70% & are called capacitance vessels
describe capacitance vessels
they have thin walls & stretch easily to accommodate more blood w/o increased pressure (higher compliance)
-have only 0-10 mmHg pressure vs. arteriole pressure of 90-100mmHg
venous return is aided by what ?
- vasoconstriction caused by symp(smooth muscle contraction)
- skeletal muscle pumps (squeezes veins)
- pressure to drop during inhalation; promotes flow of venous blood to heart
urine formation begins with what
filtration of plasma in renal capillaries=glomeruli; filtrate passes thru & is modified by nephron
-volume of urine excreted can be varied by changes in reabsorption of filtrate
ADH is released by what
posterior pituitary when osmoreceptors in hypothalamus detect high osmolality
Aldoesterone
steroid hormone secreted by adrenal cortex
what does aldosterone do
helps maintain blood volume & pressure thru reabsorption & retention of salt &water
release stimulated by salt deprivation, low blood volume, and low bp
when there is a salt deficiency, low blood volume or pressure what is produced
angiotensin 2
ANP is what
Atrial Natriuretic peptide
- increase blood volume is detected by stretch receptors in left atrium
- causes release of ANP hormone
- inhibits aldosterone, promoting Na+ excretion & water excretion to lower blood volume, also promotes vasodilation
- WORKS TO DECR. BP
vascular resistance to blood flow determines what
how much blood flows through a tissue or organ
vasodilation=
decrease resistance= increase blood flow
vasoconstriction =
increase resistance = decrease blood flow
how is bp regulated
by mainly controlling HR, SV, and TPR
-NOTE: CO=HRxSV thus BP=HRxSVxTPR
What is the baroreceptor reflex
it is activated by changes in BP; which is detected by baroreceptors located in aortic arch & carotid sinuses
no sound is heard during what flow
laminar flow= normal, quiet, smooth blood flow
Korotkoff sounds are heard when?
when the sphygmomanometer cuff pressure is greater than diastolic (lowest BP) but lower than systolic (highest bp) pressure
explain Korotkoff sounds
1st korotkoff sound is heard at pressure that blood is 1st able to pass thru cuff; represents systolic pressure
-last sound occurs when cuff pressure=diastolic pressure
when do the korotkoff sounds disappear
sounds are heard until cuff pressure equals diastolic pressure
define pulse pressure
systolic pressure- diastolic pressure
- rise in pressure from diastolic to systolic levels=reflects SV
define mean arteriole pressure (MAP)
represents average arterial pressure during cardia cycle
- has to be approx b/c period of diastolic is longer than period of systole
- MAP = pulse pressure/3 + diastolic pressure
what is hypertension
abnormally high bp
what causes primary/essential hypertension
caused by complex & poorly understood mechanisms
what causes secondary hypertension
caused by unknown disease processes
primary/ essential hypertension is what
about 95% of high bp cases; CO & HR are elevated in many
- kidneys appear to be unable to properly excrete Na+ & H20
Dangers of hypertension
- patients usually asymptomatic until vascular damage occurs
-contributes to atherosclerosis, increases workload of the heart leading to ventricular hypertrophy & congestive heart failure, often damages cerebral blood vessels leading to stroke.
“silent killer”
treatment of hypertension
- lifestyle changes, ex; cessation of smoking, decrease in alcohol intake, weight reduction..etc
- drug treatments: diuretics to reduce fluid volume, beta blockers to decrease HR, calcium blockers…etc
what is circulatory shock
occurs when there is inadequate blood flow to & or 02 usage by tissues
- cardiovascular system undergoes compensatory changes
- sometimes shock becomes irreversible & death ensues
other causes of circulatory shock
- severe allergic rxn= rapid fall in bp called anaphylactic shock
- rapid fall in bp called neurogenic shock can result from decrease in simp tone following spinal cord damage or anesthesia
- cariogenic shock; is common following cardiac failure
what is septic shock
refers to dangerously low bp resulting from sepsis(infection); mortality rate (50-70%)
- often occurs as a result of endotoxin release from bacteria
what does endotoxin do
induces NO production causing vasodilation & resultant low bp
- treatment:drugs inhibiting production of NO
what is hypovolemic shock
circulatory shock caused by low blood volume
- ex; hemorrhage, dehydration, or burns
- decreased BP and CO
- results in low bp, rapid pulse, cold clammy skin, low urine output
what is congestive heart failure
occurs when CO is insufficient to maintain blood flow
- caused by myocardial infraction, congenital defects, hypertension, aortic valves stenosis, disturbance in electrolyte levels
