Test 3: lecture 5 Flashcards
what structures are the primary determinants of resistance?
arterioles
•In the ____organs: intrinsic mechanisms predominate
critical
•In ___ organs: extrinsic mechanisms predominate
non-critical
•In ___: both extrinsic and intrinsic influences are strong
skin
intrinsic control of blood flow
- Local factors control flow in response to changes in metabolic activity
- Increased metabolic activity generally causes vasodilation
- Decreased metabolic activity generally causes vasoconstriction
___metabolic activity generally causes vasodilation
•Increased
___ metabolic activity generally causes vasoconstriction
•Decreased
active hyperemia
if you work harder you will get more blood flow to that area (causes vasodilation)
trys to keep the amount of O2 used and CO2 produced even
reactive hyperemia
occurs in response to a temporary physical restriction to blood flow
think capillary refill time - when you restrict blood flow and then restart blood to that area, more blood then usual will go to the area to try to collect the excess waste products that were just sitting there
when you press on gums, then remove is white then becomes even more pink then normal
what are some things that increased metabolic rate will lead to
metabolic autoregulation
in response to increased perfusion pressure
explain what happens to blood flow through metabolic autoregulation in response to increased perfusion pressure
increase in pressure causes the washout of vasodilators which causes vasoconstriction which will decrease blood flow→ fixing the problem
myogenic autoregulation
stretch receptors
(happen in kidneys)
increased flow = causes pressure on stretch receptors, this will cause constriction and decreased overall flow
what are some mechanisms of intrinsic control of blood flow
active hyperemia- give more blood to area that is more active
reactive hyperemia- give more blood to area that had lost blood supply
metabolic autoregulation: increase BP causes washout of vasodilators which leads to vasoconstriction and overall decrease in Blood flow and decrease in BP
myogenic autoregulation: increase in blood flow cause stretch receptors which will cause vasoconstriction and decrease overall flow
sympathetic control will cause blood vessels to ___
constrict
norepinephrine binds to alpha adrenergic receptors
this activates phosphatidylinositol bisphosphate second messenger system → vasoconsrtiction → increased TPR → increased MAP
what does epinephrine bind to and what does it cause
can bind to alpha or Beta 2 adrenergic receptor
likes Beta 2 more
if it binds to alpha receptor → activation of PIP2 second messenger → vasoconstriction→ increased TPR
if bind to beta 2 → cAMP second messenger system → vasodilation→ decreased TPR
epinephrine binding to beta 2 adrenergic receptors cause
beta 2 → cAMP second messenger system → vasodilation→ decreased TPR
epinephrine binding to alpha adrenergic receptors cause
alpha receptor → activation of PIP2 second messenger → vasoconstriction→ increased TPR
where do you find beta 2 adrenergic receptors
arterioles (coronary and skeletal muscle)
(skeletal muscle, and coronary arteries will have increased blood flow during sympathetic control in response to epinephrine binding to beta2 receptors)
fight or flight response- sympathetic response
when epinephrine binds to beta 2 it will cause vasodilation= more blood supply
where do you find alpha receptors
arterioles (all organs)
veins (abdominal organs)
when these receptors bind to norepinephrine or EPI it will cause vasoconstriction
explain sympathetic response on arterioles
alpha receptors in veins( abdominal organs) and arterioles (all organs) will bind to norepinephrine and cause vasoconstriction and venoconstriction
beta receptors in arterioles of coronary and skeletal muscle will bind to epinephrine and cause vasodilation
fight or flight- heart and muscles get more blood, GI tract gets less blood
norepinephrine response on veins(abdominal organs)
norepinephrine binds to alpha receptors and causes venoconstriction which causes more venous blood toward the heart
parasympathetic response on arterioles happens where? and what does it cause
M2 receptors in the arterioles of the coronary, genitals, skeletal muscle and other organs
ACh will bind and cause vasodilation
how does MAP associate with SV
if you decrease HR what happens to MAP
decreases
parasympathetic nerves to SA can decrease HR and cause decrease in MAP
•Arterial baroreceptor reflex
stretch receptors in the carotid sinus and the aortic arch send impulses to the CNS when stretched
if BP drops less AP will be sent by the stretch receptors, this will trigger the CNS to stimulate the sympathetic nervous system and increase BP
- Reflex results in increase in TPR and CO
- Useful for moment to moment regulation, but not for long term regulation
what helps maintain blood pressure from laying down to standing up quickly
baroreceptor reflex
how will drop in MAP influence veins to increase MAP again
increase in venomotor tone (increase steel pipe)
decrease compliance
increase venous pressure
what happens to GI blood supply during hemorage
will decrease at first to continue to supply brain
but over time toxins would accumulate and that would cause vasodilation to the GI, stealing blood from the brain and shock and death
Atrial Volume Receptor Reflex
•Stretch receptors located in the atria and large systemic veins
- Act to quickly compensate for changes in blood pressure (like arterial baroreceptors)
- In addition, long-term regulation occurs through regulation of blood volume
how do atrial volume receptors react to low blood volume
will increase sympathetic activity to increase water intake, decrease urine and decrease Na excretion → this will lead to increase in blood volume
sympathetic will also increase TPR and increase CO which will increase BP (same way arterial baroreceptor reflex works)
___ are also called low pressure baroreceptors
arterial volume receptor
stretch receptors in the atria and large systemic veins that control BP and regulate blood volume
will increase sympathetic activity to increase water intake, decrease urine and decrease Na excretion → this will lead to increase in blood volume
sympathetic will also increase TPR and increase CO which will increase BP (same way arterial baroreceptor reflex works)
two psychogenic effects on blood pressure
fight or flight
vasovagal syncope
vasovagal syncope
•Decreased sympathetic activity and increased parasympathetic activity leads to vasodilation in noncritical organs and decreased TPR
in heart failure
- What would be the immediate change in:
- Stroke volume?•Cardiac output?•Arterial blood pressure?•Venous blood pressure?
Stroke volume? decreases
- Cardiac output? decreases
- Arterial blood pressure? decreases
- Venous blood pressure? increases
during acute heart failure
Name two compensatory mechanisms that come into play here?
…. Hint 1: think about how a heart responds to increased venous return
…. Hint 2: think about the role of arterial blood pressure here
heart will try to pump harder→ increase contractility→ increase preload → trying to increase end-diastolic volume
vasoconstriction - baroreceptor reflex → increase MAP
how are kidneys effected during chronic heart failure
short term, kidneys will work harder to try to increase BP by absorbing water and Na
over time, kidneys will start to receive less blood because they are “non critical” organ and they will start to fail
effects of heart failure
left sided heart failure
pulmonary edema
right sided heart failure lead to ___
peripheral edema
ascites(abdominal edema)
how can we increase contractility through a different mechanism other than increasing preload?
influence calcium channels
(vetformin, digitalis)
preserved calcium in the body
