Exam 2: 11 Feb 25 Regulation of CO and BP During Stress Flashcards
What role does Vasopressin play in the body?
A hormone that helps regulate blood pressure by promoting water retention and vasoconstriction.
What are the two most protected circulatory beds in the body?
- Coronary circuit
- CNS (Brain)
Without bloodflow to these 2 areas, it is impossible to maintain life.
What is Atrial Natriuretic Peptide (ANP)?
A hormone released by the heart that reduces blood volume and pressure by promoting sodium excretion.
Why would a higher circulating blood volume not be advantageous?
Higher blood volume means that there is a slower circulation time. The longerblood takes to circulate, the higher the risk of it clotting.
How does the body signal the kidney in response to volume changes?
- Direct neural signaling via carotid body baroreceptors (signals the glossopharyngeal nerve) and the aortic arch (signals the vagus nerve)
- Hormones (ANP/ANF/BNP) tells the kidney to waste sodium. This sodium waste increases UOP which decreases circulating volume.
Note: ANP is mostly active in the right atria but there is some activity in the left.
What is the CNS Ischemic Response?
The body’s strongest sympathetic nervous system response to low blood pressure, aimed at restoring perfusion to critical organs.
What is the Fick Equation used for? What is the condensed formula?
A method for estimating cardiac output based on oxygen content measurements in blood.
CO=VO2/(Ca-Cv)
- VO2 is the body’s O2 consumption which should equal 250mLO2/min with a CO of 5L
- Ca is the content of O2 in the artery (should be 20mLO2/dL)
- Cv is the content of O2 in the vein (should be 15mLO2/dL)
If all of the math works out 5L/min=250mLO2/min/(20mLO2/dL-15mLO2/dL)
What is the formula for Cardiac Output?
Cardiac Output (CO) = Stroke Volume (SV) x Heart Rate (HR).
What are the normal values for Cardiac Output?
CO ~ 5-6 L/min, Blood Volume ~ 5 L.
Fill in the blank: Atrial Natriuretic Peptide (ANP) and B-type Natriuretic Peptide (BNP) are released in response to _______.
Where are these peptides produced?
ANP is atrial stretch, BNP is ventricular stretch.
ANP=Atria
BNP=Ventricle
Where are Baroreceptors located?
What nerve innervates tham and responsible for the HR responses with their manual stimulation?
In the carotid sinus and aortic arch.
Vagus Nerve (Vagal drop in HR response to physical stimulation)
What is the primary neurotransmitter for sympathetic nervous system responses?
Norepinephrine.
What is stretch-relaxation? How about reverse-stretch relaxation?
- Stretch-relaxation can be thought of like stretching a rubber band. Initially there is less compliance on the band (blood vessel) so increasing tension on it (adding fluid to the CV system) positively increases pressure. Just like a rubber band that has been stretched for too long, eventually (minutes to hours) the stretched vessels relax (compliance increases) and pressure drops again.
- Reverse Stretch-relaxation happens when there is a sudden change in volume (like major hemorrhage). The SNS activates and over time, the walls tighten to increase pressure again. This can happen without initially replacing volume but is not as effective.
- Over time, where volume is increased or decreased, the system attempts to accomodadte.
What is Cardiac Reserve? Can we increase or decrease it? How?
The maximum increase in cardiac output above normal levels.
It can increase up to 600% and go all the way to 0 depending on level of fitness, and cardiopulmonary status.
How does Atrial Natriuretic Peptide (ANP) function?
Reduces blood volume by increasing urine output and sodium excretion.
Natriuretic=Sodium Waste
What do Cardiac Glycosides like Digoxin do?
Increase contractility of the heart by inhibiting sodium-potassium ATPase.
Leads to increased intracellular Ca++ via NCX upregulation
What is the goal of drug therapy in heart failure?
To augment the body’s compensatory mechanisms and buy time for heart recovery.
What happens to the kidneys in response to increased atrial stretch?
Increased urine output, reducing blood volume.
- This is to baroreceptor activation in the atria that send ANP to the system which is an endogenous diuretic.
What happens to blood volume and plasma proteins during hemorrhage?
Blood volume decreases, and fluid is redistributed to maintain plasma volume.
True or False: ANP and BNP have long-lasting effects in the body.
False.
- Primarily regarding ANP, the effects only last a couple of weeks which isn’t enough time for the heart to repair on its own.
What fluid dynamics occur if 20% of blood volume is lost?
Serious but not immediately fatal; fluid redistributes between compartments.
What percentage of blood volume loss can be serious but not immediately fatal?
20%
How much plasma and red blood cells are lost when losing 1 liter of blood?
- 600 cc’s of plasma
- 400 cc’s of red blood cells
What is the best way to replace lost fluids after bleeding?
Replace what’s missing, such as plasma
