Integrated Cardiovascular Responses (Middlekauff)

Question 1

What happens when you stand up?

Answer 1

1) Blood pools in lower extremities
2) Decrease in volume
3) Decrease in preload
4) Decrease in contractility
5) Decrease in stroke volume
6) Decrease in CO
7) Decrease in pulse pressure

Question 2

How does our body respond when we stand up?

Answer 2

1) Arterial baroreceptors (acute decrease in BP) increases sympathetic: contractility, vasoconstriction
2) Cardiopulmonary baroreceptors (decline in LVEDP) increases sympathetic: contractility, vasoconstriction
3) Muscle pump: muscle contraction when you stand up pumps blood toward heart and doesn’t allow blood to go backward so increase preload
4) Respiratory pump: breathe in when you stand up, get negative intrathorac pressure, sucks blood back to thorax to increase preload

OVERALL: we are able to MAINTAIN our normal BP when we stand up

Question 3

Valsalva Maneuver

Answer 3

Phase 1/Initiation of forced expiration: BP increases (pressing on aorta) for a few beats

Phase 2/Duration of forced expiration: opposite of inhalation–decrease in venous return, preload, SV, BP –> as a result, baroreceptors (fire less to) increase sympathetic activity –> increased HR, increased contractility, vasoconstriction –> BP stabilizes (also SV is now lower)

Phase 3/Release: Immediate brief decrease in BP (release of pressure on aorta) –> also increase in venous return and increased SV because negative intrathoracic pressure

Phase 4/Rebound: BP increases above normal because of the sustained increased sympathetic tone and recent surge in venous return and SV from phase 3 –> baroreceptors (fire more to) decrease sympathetic –> vagal tone increases –> BP goes back down to normal

Question 4

How does heart rate change during exercise?

Answer 4

HR increases up to 100 bpm due to removing cardiac vagal tone

HR increases past 100 bpm due to increasing sympathetic tone

Question 5

How do you increase EDV during exercise?

Answer 5

1) Muscle pump and respiratory pump increase ventricular filling
2) Sympathetic system (muscle metaboreceptors) venoconstrict to the gut to increase preload

Question 6

How do you decrease ESV during exercise?

Answer 6

Increase contractility (increase sympathetic tone)

Question 7

How does the body know to increase CO during exercise?

Answer 7

Central command (located near motor cortex; engaged throughout exercise and is proportional to effort)

Muscle metaboreflex

Baroreflexes

Question 8

Simple Faint (Swooning)

Answer 8

Response to noxious stimulus (sight of blood)

Get bradycardia, hypotension and collapse to “play dead” and avoid danger

Question 9

Neurocardiogenic (Vasovagal) Syncope

Answer 9

Increase in sympathetic outflow is supposed to increase HR and SV to maintain BP is exaggerated

Heart starts squeezing VERY forcefully, and that is sensed by baroreceptors –> decrease in sympathetic and increase of vagal tone –> HR slow, vasodilation, BP way down –> faint

Question 10

How is static (isometric) exercise different from dynamic exercise?

Answer 10

Muscle contraction opposes muscle blood flow, so NO metaboreceptor response to allow vasodilatation –> increased BP