CV response to exercise Flashcards
define physical activity
any body movement
define exercise
body movement that is planned, structured, repetitive; has goal to improve physical fitness
define physical fitness
a set of attributes related to the ability to perform a skill
what is VO2
oxygen consumption (ml/min)
3 determinants of VO2
HR
SV
oxygen diff. between arterial & venous sides
equation for VO2
VO2 = HR x SV x (aO2 - vO2)
increase in exercise = _____ VO2
increases
what is VO2 max (literal definition)
maximal oxygen consumption
(maximum of all 3 components of equation)
what is VO2 max (overall definition)
maximal / optimal rate at which heart, lungs, & muscles can effectively use oxygen during exercise
_____ can improve VO2 max
training
3 factors that change VO2 (impact all determinants of VO2)
-CO
-sympathetic activity
-redistribution of blood flow to exercising muscle
equation for CO
CO = HR x SV
pathway symp/parasymp response to increase in exercise
exercise
->
increase symp / decrease parasymp
->
increase HR & SV
->
increase CO, increase VO2
does HR or SV have a larger impact on CO
HR
CO _____ with exercise in order to _____
CO increases
to deliver O2 to exercising muscle
_____ SNS, _____ PNS = increase HR
increase SNS
decrease PNS
2 reasons SV increases during exercise
-positive inotropic effect
(increased contractility = increased SV)
-increased EDV (bc of increased venous return)
why does ESV decrease during exercise
less blood in chamber after each contraction (bc increased contractility- Frank Starling)
increase venous return = _____ EDV = _____ SV = _____ CO
increase venous return
increase EDV
=
increase SV
=
increase CO
3 reasons venous return increases during exercise
-skeletal muscle pump activity
-respiratory pump activity
-SNS-induced vasoconstriction (decreased compliance)
normally:
increase SNS = _____ vasoconstriction, _____ TPR
increases vasoconstriction
increases TPR
exercise:
increase SNS = _____ vasodilation, _____ TPR
induces vasodilation
unchanged TPR
5 mechanisms of vasodilation / smooth muscle relaxation
-sheer stress
-prostacyclin / nitric oxide pathways
-increase [H+] (lower pH, increase CO2)
-functional sympatholysis
-epinephrine (stimulates beta2 receptors- induces vasodilation)
what is functional sympatholysis
local vasodilators can ALSO block alpha1-adrenergic receptors (which normally constrict)
increase in MAP during exercise is attributed to _____ & _____
increase in SBP
increase in CO
equation for MAP
MAP = CO x TPR
_____ relay changes in MAP during exercise
arterial baroreceptor afferents
increase in MAP =
activity of baroreceptor firing normally
vs
activity of baroreceptor firing during exercise
normally: increase in MAP = increases baroreceptor firing
exercise: increase in MAP = decreases baroreceptor firing
increase in MAP pathway normally
increase in MAP pathway during exercise
why does exercise result in a decrease in baroreceptor activity even though MAP increases
exercise “resets” the baroreceptor reflex
normal mechanism of MAP increase
MAP increases
->
aortic baroreflex afferents increase firing / excite NTS
->
suppresses RVLM
->
suppresses SNS activity / outflow
exercise mechanism of MAP increase
MAP increases
->
aortic baroreflex afferents INHIBITED by muscle mechano- & metaboreflex afferents
->
NTS inhibited
->
RVLM no longer inhibited
->
increases SNS activity / outflow
during exercise, TPR _____
is unchanged (or slightly decreases)
