18-3: Regulation and measurement of blood pressure Flashcards
Neural regulation of blood pressure counteracts moment-by-moment fluctuations in BP by altering ___.
peripheral resistance
vasomotor center
clusters of sympathetic neurons in the medulla whose function is to control the diameter of blood vessels, especially arterioles.
The vasomotor center transmits impulses along _ _ neurons into __.
sympathetic motor neurons; smooth muscle in vessel walls
vasomotor tone
VC sends steady rate of impulses resulting in a constant state of mild vasoconstriction
vasoconstriction
VC increases the # of impulses sent, increasing blood pressure
vasodilation
VC decreases the # of impulses sent, lowering blood pressure
In vasoconstriction, a(n) ___ # of impulses are sent, __ blood pressure; in vasodilation, a(n) __ # of impulses are sent, __ blood pressure.
increased; increasing; decreased; lowering
Vasomotor activity is modified by inputs from where?
baroreceptors, chemoreceptors, higher brain centers
baroreceptors
pressure receptors in the wall of the aorta and carotid sinuses that send impulses to the vasomotor center as well as the cardiac center in the medula
What is the affect of increased blood pressure on the baroreceptors?
increased BP > stretches baroreceptors > inhibits VC
less sympathetic stimulation of arterioles > vasodilation > decreased blood pressure
Baroreceptors protect circulation against _ changes in BP.
short-term
chemoreceptors
special cells in the aorta and carotid arteries that are sensitive to blood levels of oxygen, carbon dioxide and pH.
hypoxia, hypercapria, and acidosis have what effect on chemoreceptors?
low blood oxygen, high blood carbon dioxide, or low pH > stimulate chemoreceptors to send impulses to vasomotor center
increased sympathetic stimulation of arterioles > vasoconstriction > causes blood pressure to rise
(increase speed of return of blood to heart and lungs)
What affect do the higher brain centers have on vasomotor activity?
anxious/angry/very emotional > cerebral cortex and hypothalamus stimulate vasomotor center
increase sympathetic impulses to arteriorles > vasoconstriction > increased blood pressure
What chemicals have an effect on blood pressure?
epinephrine and norepinephrine; antidiuretic hormone; histamine; nicotine
all short-term control
epinephrine and norepinephrine
hormones produced by the adrenal gland during periods of stress
Epinephrine/NE cause cardiac output to _, resulting in _ and blood pressure to _
increase; vasoconstriction of all vessels (except skeletal and cardiac muscle); increase
antidiuretic hormone
a hormone made by the hypothalamus that stimulates the kidneys to conserve water
Antidiuretic hormone causes __, causing blood pressure to __.
vasoconstriction (for severe blood loss); increase
histamine
potent vasodilator produced during the inflammatory response and certain allertiges - causes blood pressure to decrease (as in anaphylactic shock)
nicotine
causes intense vasoconstriction - blood pressure goes up
Which chemicals cause vasodilation, and therefore blood pressure to go down?
histamine
Which chemicals cause vasoconstiction, and therefore blood pressure to go up?
epinephrine/norepinephrine, antidiuretic hormone, nicotine
renal regulation of blood pressure
long-term control; the kidneys act directly and indirectly to provide major long term control of blood pressure by altering blood volume
direct renal regulation of blood pressure
pressure diuresis: blood pressure increases > rate of fluid filters through kidneys increases > urine production increases
blood volume decreases > blood pressure decreases
indirect renal regulation of blood pressure
renin-angiotensin mechanism
What are the four classic vital signs?
blood pressure, pulse/heart rate, temperature, respitory rate
(newer: O2 saturation)
Where is blood pressure usually measured?
left brachial artery (closed to the aorta) using a sphygomomanometer
How is blood pressure reported? [x / y]
Systolic Blood Pressure / Diastolic Blood Pressure
When is systolic blood pressure reported?
at the first Korotkoff sound - produced when blood is able to squirt through during ventricular systole (eg. heart contracting)
When is diastolic blood pressure reported?
when the Korotkoff sound disappears - when the vessel is wide open and blood is able to flow through smoothly (eg. heart is between contractions)
What are the steps of measuring blood pressure?
- BP cuff wrapped around arm over brachial artery just superior to the elbow
- cuff inflated until P in cuff > P in artery - wall compresses and no blood flows through, no pulse felt, no sound heard in stethoscope
- cuff gradually deflated - SBP reported at first Korotkoff sound when blood is able to squirt through during ventricular systole
- Korotkoff sound gets louder and then disappears entirely when the vessel is wide open, allowing blood to flow smoothly - DBP reported
systolic BP
force with which blood is pusing against arterial walls when the heart is contracting (in systole)
diastolic BP
force with which blood is pushing against arterial walls when the heart is relaxing (in diastole)
Normal blood pressure varies with what?
age, gender, weight, mood, race, posture, and physical activity
pulse pressure
the difference between systolic and diastolic blood pressure, felt as throbbing in the artery. It decreases as you move farther away from the heart, disappears in arterioles
MAP
mean arterial pressure
MAP = DBP + (PP/3) = DBP + ((SBP-DBP)/3)
