Regulation of Arterial Pressure Flashcards
What is MAP?
Measure of our blood pressure
How do we calculate MAP?
MAP= CO * TPR
CO= cardiac output
TPR= total peripheral resistance
CO= HR * SV
MAP= HR * SV * TPR
What is our normal MAP?
93.3 mmHg (around 100 mmHg)
How do we regulate our blood pressure?
There are two main mechanisms to regulate our blood pressure
- Baroreceptor reflex- regulates our BP on a minute-to-minute basis.
- RAAS- fixes chronic problems by altering our blood volume
What are our baroreceptors and where are they located?
Where do they then, convey signals to?
Baroreceptors are stretch receptors that respond to RATE of change in our MAP.
They are located in our carotid sinus and our aortic sinus.
They convey signals to our NTS (nucleus tractus solitarius)
What detectors are involved in the baroreceptor reflex? (2)
- Mechanorecptors (stretch receptors) that respond to changes in blood pressure
- Chemoreceptors that respond to pO2, pCO2 and pH.
Low BP–> decreased stretch on the walls of the carotid sinus.
How do the baroreceptors respond?
Decrease of firing rate of of the carotid sinus nerve (herings nerve and the CN IX)
What are the brain regions involved in the baroreceptor reflex?
- NTS (nucleus tractus solitarius)– receives and coordinates the peripheral signals
- Dorsal motor nucleus of the vagus and nucleus ambigiquus–> alters parasympathetic activity
- Rostral ventrolateral medulla- alters sympthetic activity
What is the control center of the baroreceptor reflex?
The NTS (vasomotor center in the medulla).
How do we increase and decrease TPR?
Sympathetically stimulate our arterioles.
How do we alter our stroke volume?
Sympathetic stimulation
and
Preload
HR is dependent on what?
1. Parasympathetic NS
2. Sympathetic NS.
What is the mechanism baroreceptor initiates when there is a decrease in BP?
***Not activating our parasympathetics would increase HR
What is the mechanism baroreceptor initiates when there is a increase in BP?
How does the baroreceptor adapt with people who have chronic high blood pressure?
Hypertension will reset the baroreceptors to regulate BP at a higher set point.
Thus, they can adjust to different conditions.
Activation of what receptors causes renin to be released from juxtaglomerular cells in the kidney?
B-1 adrenergic.
Describe the RAAS complex to increase our BP.
What causes the release of ADH (vasopressin)
- Angiotensin II
- Atrial receptors that detect a low preload
- Increase osmolarity of the blood
What are the purposes our our natriuretic peptides (Atrial NP, Brain NP, C-type NP)?
Natriuretic peptides are the opposite of aldosterone. They are secreted when we have too much preload of the atria and the ventricles; thus, they want to get rid of fluid.
1. Dilating the arterioles (decrease TPR)
2. Increase fluid loss
3. Inhibits renin (decreasing both TPR and preload)
What helps to protect against overdilation and overstretching of our heart chambers?
Natriuretic peptides
What can cause a decrease in blood volume?
1. Hemorrhage
2. Dehydration
3. Loss of body fluids
What is the result of a decrease in blood volume?
- Decrease venous return
- Decrease preload
- Decrease SV
- Decrease CO
- Decrease MAP
- Vascular function curve shows a shift to the LEFT
What mechanisms are activated to compensate for a hemorrage?
- Baroreceptor reflex (increases sympathetic activatio and decreases parasympathetic)
- RAAS
- Decrease in capillary hydrostatic pressure–> increase fluid retention–> increase plasma volume
Jerry was found on the floor with a BP of 60. What will his compensatory responses be?
- Carotid sinus nerve (baroreceptor) will decrease firing
- HR, contractility, CO, TPR will increase
- Unstressed volume will increase, to produce an increased venous return
- Renin, angiotensin II, aldosterone EPI and ADH all increase
Increased BV (increased or decreased preload)
What does this cause?
Increased BP means a increased preload
- Increase in ANP secretion
- Decrease in ADH secretion
- Renal vasodilation
- Increase HR
During most aerobic excercise, how do our activators and inhibitors of chemoreceptors change?
They do not change much.
What happens in response to normal aerobic excercise
- Messages sent to cerebral cortex, which will increase our sympathetic response and decrease our parasympathetic response (increase HR only)
- Increase HR, contractility, CO
- Vasoconstriction via B1 of inactive tissue, skin, splanchnic region, kidney
- Increase in VR.
- Vasodilation of active tissue because there is an increase of lactate, K+ and adenosine. Thus, this decreases TPR
–> Increase blood flow to skeletal m (pulse pressure increases, SBP increase, DBP should not change
What happens if we are standing upright too long?
Blood pools to the feet.
Venous return will increase in the limbs, increasing venous return to the feet (decreasing central venous pressure) and capillary hydrostatic pressure, causing edema or hypotension.
-Our baroreceptor reflexes will attempt to work to bring shit back together. RAAS is too slow to have an affect.
