Exam II: 3C Regulation of Arterial Blood Pressure Flashcards
What is the long term regulation for Mean Arterial Pressure (MAP)
- Occurs within hours to days
- Occurs primarily via endocrine pathways
- Targets the kidneys & blood vessels
What is the short term regulation for Mean Arterial Pressure (MAP)
- Occurs within seconds to minutes
- Occurs primarily via neural pathways
- Targets the heart & blood vessels
What are the short term regulation baroreceptors?
Neutral receptors located in the CAROTID SINUS & AORTIC ARCH
*** They participate in BARORECEPTOR REFLEXES
What cranial nerves carry signals from the baroreceptors to the MEDULLARU CARDIOVASCULAR (or CARDIOREFULATORY CENTER) of the brainstem
CN 9 and CN 10
What does the Medullary Cardiovascular Center consist of ?
Consists of individual “mini-centers” such as vasomotor area & cardioinhibitory area
What does the Medullary cardiovascular center do?
Makes decisions about what to do about hypertension or hypotension and then employs the serves of the SNS and ParaNS to send those orders to various target tissues.
What occurs if the BP increases with baroreceptor reflexes
Detection by barorecpetors in the carotids & aortic arch–>Cardio regulatory center informed–> SNS cardiac nerve activity & vasoconstrictor nerve active decreases. ParaNS cardiac nerve activity increases–> HR & SV Decreases (Vasodilation)–> CO and TPR decreases–> BP decreases to normal
What occurs if BP decreases in barorecpetor reflexes?
Detection by barorecpetors in the carotids & aortic arch–>Cardio regulatory center informed–> SNS cardiac nerve activity & vasoconstrictor nerve active increases. ParaNS cardiac nerve activity decreases–> (Vasoconstriction) HR & SV increases–> CO and TPR increases–> BP increases to normal
What is the pathway response to a hemorrhage in the parasympathetic system?
Acute hemorrhage–> Decreased Mean arterial pressure –> Decreased carotid sinus baroreceptors–>Decreased firing rate of carotid sinus nerve (Hering’s nerve)–> Decreased PARASYM outflow to heart –> Increased HR–> Increased arterial pressure toward normal
What is the pathway response to a hemorrhage in the sympathetic system?
Acute hemorrhage–> Decreased Mean arterial pressure –> Decreased carotid sinus baroreceptors–>Decreased firing rate of carotid sinus nerve (Hering’s nerve)–> Increased SYMPATHETIC outflow to heart & Blood vessels –> Increased HR, Inc.. Contractility, Inc. Constriction of Arterioles (Inc TPR), Inc. Constriction of veins, inc. venous return, and Inc. mean systemic pressure –> Increased arterial pressure toward normal
How can the sensitivity of the baroreceptors be altered?
By disease
For example in hypertension how do the baroreceptors respond?
The baroreceptors do not see the elevated blood pressure as abnormal. The hypertension will be maintained rather than corrected by baroreceptor reflex.
What is Long-term regulation–> RAA pathway ?
A decrease in renal perfusion pressure (blood pressure) causes kidneys to secrete the enzyme RENIN.
What catalyzes the conversion of Angiotensinogen to Angiotensin I in the plasma ?
How does this affect the kidnet?
Renin
Kidney decreases Na+ excretion and decreases water excretion
What does the ANGIOTENSIN CONVERTING ENZYME (ACE) ?
**Catalyzes the conversion of angiotensin I into Angiotensin II, the primarily in the LUNGS **
How does the RAA pathway respond to a hemorrhage?
Arterial pressure is decreased–>Decreased Renal
perfusion pressure–>Renin–> Inc. Conv of Angiotensinogen to angiotensin I via ACE–>Increase conv. of angiotensin I to angiotensin II–> Increase Angiotensin II–> Increases Thirst, TPR, Na+-H+ exchange & resorption–>Increases Arterial pressure toward normal.
What are other hormonal long term pathways–> ADH
Anti-diuretic hormone (ADH ) is also known as VASOPRESSIN
What is the most important physiologic stimulus for increasing ADH secretion?
Increased plasma osmolarity
What is another potent stimulus for ADH secretion?
Hypovolemia, or volume contraction (due to hemorrhage)
What does decreases in extracellular fluid (ECF) volume of 10% (hypovolemic state) or more cause ?
A decrease in arterial blood pressure that is sensed by the baroreceptors in the left atrium, carotid artery, and aortic arch.
What are the 4 things the primary effects of Angiotensin II ?
1) Affects the adrenals to secrete aldosterone (inc. BP, water retention, and conservation of salt)
2) Angiotensin directly affects the kidneys (decrease salt + H2O)
3) Goes straight to the blood vessels (vasoconstrictor)
4) Goes to the Blood Brain Barrier to activate ADH (retain water & increases BP)
What are the 2 effects that tend to increase BP toward normal?
1) Increases water reabsorption via the kidneys by activation V2 receptors
2) It is a potent vasoconstrictor that increases TPR by activating V1 receptors on the Arterioles
What is ANP? (Atrial Natriuretic peptide)
-Is a powerful vasodilator secreted by the Atria to help regulate & respond to high blood volume (decreases BP)
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What are the 2 responses a increase in blood volume ?
1) Increased section of ANP (inc Na+ and H2O)
2) Decreased secretion of ADH \
What effects do ANP have?
1) Causes relaxation of smooth muscle resulting in vasodilation and decreased TPR
2) In the kidney, this vasodilation leads to increased Na+ & water excretion –> decreasing total body Na+_ content, ECF volume, and blood volume.
What else can effect venous return?
Skeletal muscle pump
Note: when skeletal muscle contracts they force blood back to the heart
What do the venous valves do?
**Prevent the back flow of blood away from the heart.
How does the skeletal muscle pump work?
When muscle contracts, upper valve opens, but lower closes, so that contraction muscle pushes blood up. After muscle relaxation, upper valve closes, preventing black flow and lower valve opens, allowing veins to fill.
