Final Cardiac Content; Exam II

Question 1

CV System Reflexes

Answer 1

-Neurological reflexes that kick in almost instantaneously (SNS)

-Baroreceptors in carotid bifurcation (sinus) and aortic arch. Glossopharyngeal nerve transmits information

-Epi/Norepi (main) release from nerves or adrenal glands; regulates SVR & contractility.

-Protected Vascular systems that need to maintain blood flow at all costs: Coronary arteries, CNS, kidneys are somewhat

-Increase HR

-Vasopressin and RAAS

Question 2

Low Pressure System Reflexes

Answer 2

Low pressure parts of circulation; veins and atria contain stretch receptors. Direct neural pathway
-Increase in stretch or pressure in the atria causes an increase in output from the kidney. Reduces risk of clots
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-Decrease in stretch or pressure is inverse
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-ANF/ANP; peptides that are formed predominantly in the R.A. Released in response to an increase in stretch in the atria
-ANP gets rid of Na+ & H2O
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-BNP; formed in ventricles of the heart. BNP is released in response to increased stretch in the ventricles; similar action to ANP

ANP & BNP stop being effective after ~ a week. Need diuretics to achieve similar result

Question 3

Blood/Fluid Shifts During Hemmorrhage

CV System Reflexes

Answer 3

Normal:
5L Blood
3L Plasma
2L Hct

ECF: 14L
1/4-1/5th is plasma
3/4-4/5 is interstitial fluid

If we lose 1L of blood, 600ml will be plasma and 400ml will be RBC’s
Fluid will try to redistribute itself (ratios remain constant)
There will be a decrease in plasma proteins –> decreasing plasma oncotic pressure

Tx by replacing what’s missing
-Plasma
-NS if you have absolutely no other choice. NS will shift into the interstitium

Question 4

Synthetic Colloids

Answer 4

-Dextran
-Hetastarch
Synthetic colloids; large sugar molecules that break down over time but provide an increase in oncotic pressure

Question 5

How does this relate to giving crystalloids?

Streth Relaxation

CV System Reflexes

Answer 5

-Property of large veins
-Response of the smooth muscle that lines the wall of the large veins
-When the smooth muscle becomes distended, or tight, the vessel walls relax–> reducing venous pressure
-This happens when a patient is bolused with fluid

Question 6

Reverse Stretch Relaxation

CV System Reflexes

Answer 6

-Hemmorrhage
-ANS overriding what the smooth muscle & veins are trying to do
-Essentially constricting the walls of the veins

Question 7

CNS Ischemic Response

CV System Reflexes

Answer 7

-Decreased brainstem perfusion
-Most active response that we can get from the SNS
-Maximal levels of all CV system reflexes in order to perfuse the CNS

Question 8

Fick Equation

Answer 8

-Determines CO by looking at O2 levels in the blood and how much O2 needs to be delivered/unloaded as blood moves through the systemic circulation

CO (L/min)=
O2 absorbed per minute by lungs (ml/min)/
arteriovenous O2 difference (ml/L of blood)

Ex:
Arterial: 20ml O2/dL blood
Venous:15ml O2/dL blood
–These numbers reflect the amount of O2 in the dissolved state as well as bound to Hgb

Arteriovenous difference = 5 ml O2/dL blood.
-This means that 5mls of O2 is delivered to each dL of blood moving through the systemic circulation

Avg O2 consumed per minute: 250ml O2/min

250ml O2/min / 5ml O2/dL blood = 50dL/min/blood –> 5L/min

Question 9

Answer 9

-Maximum amount of CO that you can have above and beyond what’s normal (5L/min)

-5L/min can have a maximum CO of 25L/min = 400% cardiac reserve
-An athlete’s cardiac reserve can be up to/over 600%

-This number decreases as we age. Cardiac and valvular diseases can significantly decrease cardiac reserve