humoral and nervous control of circulation (midterm 2) Flashcards
what do tissues control and how
their own blood flow - the greater the metabolic needs of a tissue, the greater the blood flow
what are the two forms of blood flow control and what are their differences
acute - seconds to minutes
long term - days, week, months (better control)
what is a major determinant of control of blood flow
oxygen deficiency (lower oxygen pressure leads to greater blood flow)
what is vasodilator theory
decreased blood flow, decreased oxygen increases the formation of vasodilator compounds (i.e. adenosine), which increases vessel diameter and blood flow increases
what is oxygen demand theory
decreased blood flow leads to decreased oxygen pressure leading to decreased vessel muscle tone/contraction, leading to increased vessel diameter and therefore increased blood flow
how is blood flow autoregulated
blow flow is maintained despite changes in arterial blood pressure
increased arterial pressure leads to increased blood flow, which leads to normal blood flow
what is the metabolic theory of acute blood flow control
arterial pressure increases, blood flow increases, nutrition is too high, blood vessel diameter decreases, blood flow decreases
what is the myogenic theory of acute blood flow control
arterial pressure increases, blood flow increases, smooth muscle cells contract, vessel diameter deceases, blood flow decreases
what is blood flow driven by for kidneys, brain, and skin
kidneys: filtration needs
brain: oxygen delivery and co2 removal
skin: temperature regulation
what is tissue vascularity
if there is decreased blood flow that isn’t meeting the needs to a tissue, the number of vessels perfusing the tissue unit can increase to provide sufficient blood flow
driven by max need, not average
what is angiogenesis
the growth of new blood vessels via vessels sprouting from small venules or capillaries
what is collateral circulation
increased vascular density when an artery or vein is blocked to restore blood flow
what are vasoconstrictors and examples
narrowing of blood vessels
norepinephrine, angiotensin, vasopressin, endothelin
what are vasodilators and examples
open (dilate) blood vessels
bradykinin, serotonin, histamine, prostaglandins
where does nervous regulation occur through
the autonomic nervous system (involuntary), which acts through sympathetic and parasympathetic systems
what is the sympathetic system
impacts vasculature and heart
what is the parasypathetic system (vagal system)
impacts heart
what occurs when sympathetic system is stimulated
increased vascular resistance, decreased vascular diameter, decreased blood flow, increased cardiac output
all maintain blood pressure
what occurs when parasympathetic system is stimulated
decreased SN rate, decreased heart rate
where is the vasomotor system located and what does it act under
bilaterally in the reticular substance of the medulla and lower third of the pons
acts under both sympathetic and parasympathetic stimulation
what does the vasomotor center do under normal conditions
sends signals that act to maintain sympathetic signals that act to maintain sympathetic vasoconstrictor tone
what happens when the vasomotor center is blocked by spinal anesthesia
loss of vessel tone and arterial pressure drops dramatically
what restores vessel tone in the vasomotor center
stimulation by norepinephrine, which increases blood pressure
what does the sympathetic vasoconstrictor system function to do
control cardiac output - increases pressure (cardiac output) with vasoconstriction
- decreases pressure (cardiac output) with vasodilation
what do baroreceptors do
stretch receptors in the corrotid arteries and aorta in response to an increase in pressure in order to decrease arterial pressure again
where are signals transmitted from for baroreceptors to work
from each carotid sinus through Hering’s nerve to the glossopharyngeal nerve and then to the tractus solitarius in the medullary of the brain
- signals from the aortic arch are transmitted through the vagus nerve into the same area of the medulla
what are the specific changes in arterial pressure that impact impulse transmission in Hering’s nerve
little change = < 60 mmHg
change in impulses = 60 - 180 mmHg
big change in impulses = steep slope
increased duration = decreased HR and decreased heart contraction
what do functional baroreceptors look like plotted
steep peak; disrupted is more of a small, jagged curve - system resets after 1 or 2 days
