L18 & 19: Cardiovascular System III & IV Flashcards
major arteries
divide into smaller and smaller arteries, the character of the wall changes, becoming less elastic and more muscular
the walls of arterioles
contain several layers of smooth muscles that contract and relax under the influence of chemical signals
systemic veins serve as
expandable volume reservoir
elastic systemic arteries serve as
pressure reservoir that maintains blood flow during ventricular relaxation
capillaries
small, extremely thin, have nucleus, basement membranes, endothelial cells inside
veins have ___ than arteries
less muscle tissue
veins do not have __
elastic tissue
pulse
the pressure increase generated by the left ventricles ejecting blood into the aorta, transmitted through the arteries
pulse pressure
pulse pressure = systolic pressure - diastolic pressure
venous blood flow
steady and it’s not pulsatile
mean arterial pressure
represents driving pressure because arterial pressure is pulsatile
MAP formula
MAP = Diastolic pressure + 1/3 pulse pressure
hypotension
blood pressure falls too low and blood flow is unable to overcome opposition by gravity
hypertension
blood pressure is chronically elevated
the elevated pressure in the arteries during diastole is due to
elastic recoil property of arteries
arterial blood pressure is measured by
sphygmomanometer and stethoscope
when the cuff is inflated above the systolic pressure
arterial blood flow is stopped, no sound
when the cuff pressure is below diastolic pressure
the artery is no longer compressed, no sound
when the cuff pressure is between systolic and diastolic pressures
turbulent blood flow produces Korotkoff sounds due to compressed artery
cardiac output
the amount of blood pumped out of each ventricle in one minute
cardiac output formula
CO = Heart rate x Stroke volume
total blood volume
around 5 liters
normally, cardiac output is
the same for each side of the heart
autonomic input to the heart can
raise or lower heart rate and affect cardiac output
heart rate is initiated by
autorhythmic cells in the SA node at a rate of 100 bpm in the absence of any nervous or hormonal influence
at the resting state
there is more parasympathetic activity to the heart than sympathetic
normal resting heart rate
lower, closer to 70 bpm
what sympathetic receptors are there in SA node
beta-adrenergic
what channels do protein kinases in heart cells trigger to open
F-type Na+ and T-type Ca2+ channels
what parasympathetic receptors are there in SA node?
muscarininc cholinergic receptors
what channels and how do G-proteins trigger in a parasympathetic pathway?
open K+ and close T-type Ca2+ channels
sympathetic NS activity can also
increase the force of contraction and stroke volume
when can the sympathetic activity increase the strength of contraction?
at any given end-diastolic ventricular volume
Frank-Starling principle
the heart will pump all the blood that returns to it
the strength of contraction increases as
the end-diastolic ventricular volume increases
mean arterial pressure formula
MAP = Cardiac Output x Total Peripheral Resistance
total peripheral resistance
the sum of resistances to flow offered by all the systemic blood vessels
the homeostatic regulation of systemic MAP is important because
MAP influences blood flow to all organs in the systemic circuit
the primary short-term reflex pathway for control of MAP
baroreceptor reflex
sensory receptors of the barareceptor reflex are located
in the walls of carotid arteries (high in the neck) and aorta
carotid baroreceptors measure
pressure of blood flowing to the brain
aortic baroreceptors measure
pressure of blood flowing to the body
___ with changes in blood pressure
baroreceptor firing frequency
if increased blood pressure in the arteries stretches the baroreceptor membranes,
the firing rate of the receptor increases
if the blood pressure in the arteries falls
the firing rate of the receptors decreases
the primary integrating center for the baroreceptor reflex is
medullary cardiovascular control center located in medulla oblongata
medullary cardiovascular control center
integrates sensory input and initiates a rapid response
in how many minutes are changes in CO and TPR initiated?
in two heartbeats of the stimulus
output signals from the cardiovascular control center are carried by
both sympathetic and parasympathetic neurons
peripheral resistance is under
tonic sympathetic control
increased sympathetic discharge causes
vasoconstriction
the heart is regulated by
antagonistic control
increased sympathetic activity
increases heart rate at the SA node, shortens conduction time through the AV node, and enhances the force of myocardial contractions
increased parasympathetic activity
slows heart rate but has only a small effect on ventricular contraction
arterial baroreceptor reflex functions as
short-term regulator of arterial blood pressure
if arterial pressure deviates from its normal set point for ___, the arterial baroreceptors ___
more than a few days, adapt to this new pressure
arterial baroreceptors cannot
set long-term arterial pressure
in individuals who have chronically elevated blood pressure
the arterial baroreceptors continue to oppose minute-to-minute changes, but at a higher set point
___ are the single most important long-term determinant of blood pressure
changes in steady-state blood volume
if blood volume increases
blood pressure increases
an increase in blood volume due to increased fluid ingestion induces
an increase in arterial pressure
events that can lead to change in blood volume
dehydration, hemorrhage, ingestion of a large quantity of fluid
___ restores blood volume to the original value
increase in excretion of fluid in the urine by the kidneys
compensation for decreased blood volume
is more difficult because kidneys cannot restore lost fluid
kidneys can
conserve blood volume
rapid response to elevated blood pressure
by cardiovascular system: vasodilation and decreased cardiac output
slow response to elevated blood pressure
by kidneys: excretion of fluid in urine blood volume
