L23: Cardiac reserve and heart response to physiological stress

Question 1

how is CO determined

Answer 1

CO= HR x SV

Question 2

What is SV and how is it determined

Answer 2

SV= EDV= ESV or EDV x EF

it is the volume of blood at the end of the filling phase- the volume of blood at the end of the systolic phase

Question 3

EDV is also termed

Answer 3

preload

Question 4

How can you enhance EF

Answer 4

increase heart contractility w/ inc sympathetic tone

Decrease afterload

Question 5

How can horses increase their cardiac output during exercise??

Answer 5

increasing their HR due to inc sympathetic tone and dec para tone

increasing their SV due to INC preload, DEC after load and INC contractility

Question 6

When horses contract their spleen, how much can they increase their Hct by?

Answer 6

from 35-60

Question 7

CO is very important for O2 delivery, how do we measure O2 consumption by tissues?

Answer 7

= CO (O2 in arterial blood - O2 in venous blood)

Question 8

How does systemic arterial pressure change during intense exercise?

Answer 8

Dec vascular resistance in important beds (E.g. muscle) due to vasodilation in response to local factors (e.g. K+, adenosine, H+ from working muscle).

Vasoconstriction in some beds.. e.g. splanchnic

Question 9

what effect does intense exercise have on ventricular filling pressures?

Answer 9

Inc pressure > inc venous return > in at RA, RV, lungs, LA, LV