Integrated Control of the Cardiovascular System

Question 1

What is the ultimate goal of the cardiovascular system?

Answer 1

To maintain blood flow!

Question 2

What is preload?

Answer 2

venous pressure that results in the filling of the heart in diastole. depends on venous return
OR
the degree to which the ventricles are stretched prior to ejection.

Question 3

What is afterload?

Answer 3

Pressure against which the heart must work to eject blood. depends on aortic pressure.

Question 4

What is stroke volume?

Answer 4

The volume of blood ejected with each heart beat.

SV=EDV-ESV

Question 5

What is the main regulator of TPR?

Answer 5

The resistance of the arterioles.

Note: this appears to only apply to the systemic circulation, not the pulmonic.

Question 6

What does an increase in preload do to SV?

Answer 6

This implies an increase in venous return & therefore an increased stretching in the ventricles.
This increase the SV. This increase CO.

Question 7

What do an increase in afterload do to SV?

Answer 7

This decreases SV.

It decreases it b/c it has to eject against a greater pressure.

Question 8

If the venous return doesn’t equal the cardiac output–>then where does the extra blood go?

Answer 8

It is stored in the central venous pool. This is comprsied of the great veins in the thorax & the RA.

Question 9

If heart rate is greatly increased…how does this affect diastolic pressure?

Answer 9

It increases it b/c there’s not enough time for relaxation b/w contractions/ejections.

Question 10

Review: What is the equation for tissue perfusion/blood flow?

Answer 10

Q=P/R

Question 11

What are the factors that determine systolic pressure?

Answer 11

stroke volume
aortic distensibility
ejecting velocity

Question 12

What are the factors that determine diastolic pressure?

Answer 12

systolic pressure
heart rate
aortic distensibility
peripheral resistance

Question 13

What is the main determinant of stroke volume? What are its 3 main determinants?

Answer 13

Venous Return.–>
Blood Volume
Skeletal Muscle Pump
Respiratory Pump

Question 14

How does gravity affect the pressure of various blood vessels in the body?

Answer 14

Blood vessels that are below the level of the heart have higher pressure.
Blood vessels that are above the level of the heart have lower pressure.
*There is actually a negative intracranial pressure.

Question 15

What’s the deal w/ orthostatic redistribution of blood?

Answer 15

So basically if there were increased compliance of our veins…more blood could pool in our lower extremities & maybe never make it back to our heart to be pumped out.
The only way we can stand up is that we have a proper amount of compliance of our veins & valves that prevent backflow.
Still…going from supine to standing decrease intrathoracic blood volume & decreases CO & Pulse pressure.

Question 16

So when you move from supine to standing…you can experience this sudden drop in BP as blood moves to your lower extremities….but the body fights this. How does the body fight this mechanically? There are 3 ways.

Answer 16

Muscle Pump.
Respiratory Pump
Venous Valves

Question 17

What is another thing that happens with venous pooling in the lower extremities?

Answer 17

This increases local venous pressure & fluid is filtered into the interstitium.

Question 18

What is the neural response to postural change?

Answer 18

Blood pressure decreases.
Baroreceptors decrease frequency of firing.
Vasomotor Control Center increases sympathetic activity & decreases parasympathetic activity.
This increases HR, arterial constriction, venous constriction. This increases CO & BP.
RAAS also plays a long term role in this regulation.

Question 19

Why do people sometimes faint when they stand up too quickly?

Answer 19

B/c w/ venous pooling in lower extremities, BP decreases. If it gets low enough…then cerebral pressure will be low enough that you’ll faint.

Question 20

Why could prolonged standing theoretically lead to syncope?

Answer 20

B/c prolonged standing causes increased capillary hydrostatic pressure & therefore increased filtration & interstitial fluid volume buildup. This decreases venous return, CO & BP.
Low cerebral BP–>syncope.
But we have compensatory mechanisms…mainly baroreceptors that counteract this so we are usu good.

Question 21

T/F Abdominal & Limb resistance increases when standing up & therefore abdominal & limb blood flow decreases.

Answer 21

True.

Question 22

When you give blood why don’t you experience the symptoms of hemorrhage?

Answer 22

B/c they don’t take a detrimental volume of blood & they take it over a long period of time.
Also, they give you nutrients like chocolate or something afterwards to replenish you.

Question 23

Why does a patient with a hemorrhage present w/ tachycardia?

Answer 23

Their heart rate is increased b/c of increased sympathetic activity as a part of the compensatory mechanism signaled for by the baroreceptor reflex.

Question 24

What would you think happened w/ a patient who presents w/ hemorrhage & bradycardia?

Answer 24

Head trauma.
B/c a lower heart rate (increased parasympathetic tone) is a characteristic of the ischemic brain response, not the normal baroreceptor reflex.

Question 25

What is the order & the 3 compensatory mechanisms that seek to reestablish a healthy BP after hemorrhage?

Answer 25

1. Fastest–Baroreceptor Reflex.
2. Fluid reabsorption from the interstitial compartment b/c the capillary hydrostatic pressure is so low.
3. Decreased renal excretion & increased ingestion of salt & water.

Question 26

How much of a blood loss can your body’s compensatory mechanisms counteract?

Answer 26

1-1.5 L of blood lost.

Question 27

What happens if you lose more blood than your body can handle?

Answer 27

Circulatory Shock.

Basically, tissue death.

Question 28

T/F Athletes & non-athletes can surprisingly achieve the same high HR & CO.

Answer 28

False.
Athletes & non-athletes can achieve the same HR. like 200 bpm.
However, athletes achieve a much higher CO (like 40L/min).

Question 29

What is the approx HR when you just remove vagal tone?

Answer 29

100 bpm.

Question 30

If athletes & non-athletes & cardiac patients can all achieve the same high HR…why are athletes so awesome?

Answer 30

B/c athletes can perform more activity @ a lower heart. Like at rest athletes may have a HR of significantly less than 50bpm.

Question 31

How is cardiac output increased during exercise?

Answer 31

Thru increase in HR (SNS)
But mainly thru an increase in SV.
SV is increased by:
Increasing Preload/EDV:
muscle pump
respiratory pump
splanchnic venoconstriction (b/c this shifts more blood to the heart)-->done by SNS
Decreased ESV:
Increased Contractility (done by SNS)

Question 32

Where does the cardiac output during exercise mainly redistribute to?

Answer 32

The muscle that is working
Skin (to get rid of extra heat)
Lungs (need to get that O2 & deliver that CO2)

Question 33

How can the blood flow to muscle cells increase SO much during exercise.

Answer 33

Almost entirely b/c of local control by massive metabolic vasodilation.
Low pO2, High pCO2, low pH
Adenosine, Potassium, Lactate
**also b/c of capillary recruitment.

Question 34

BP raises somewhat during exercise.

What happens to CO & TPR?

Answer 34

CO always raises during exercise.
TPR always decreases during exercise.
**This is so that the BP won’t get dangerously high & so that blood flow can get to the skeletal muscle.

Question 35

What happens to the systolic & diastolic BP during exercise?

Answer 35

Systolic increases significantly b/c of increased CO & SV & vasoconstriction to inactive tissues.
Diastolic may be relatively constant b/c of the reduced TPR b/c of the release of metabolic vasodilators to skeletal muscle.

Question 36

Why do people who are lifting super heavy weights or something w/ static exercise have a higher BP than ppl on the treadmill for a period of time?

Answer 36

B/c they have all of the same forces increasing their BP…
But they don’t have the vasodilation & increased blood flow to their muscles decreasing their BP b/c the tonic muscle contraction is obstructing this blood flow.

Question 37

What is the major determinant of pulse pressure (something that increases it)?

Answer 37

Decreased Arterial compliance.