acute cardiovascular response to exercise Flashcards
three factors regulating venous return during exercise
- constriction of the veins (venoconstriction)
-pumping action of contracting skeletal muscle (muscle pump) - pumping action for the respiratory system (respiratory pump)
what is Cardiac output (Q)
- the amount of blood pumped by the heart each minute
at rest CO should be at?
during exercise?
- 5L per/min at rest
- 20-35 L/min during exercising
Components of CO
- product of HR and SV
stroke volume is the volume of
blood ejected with each heartbeat
another variable that affects SV is
aortic pressure (MAP)
if you have an increase of mean arterial pressure, what happens to stroke volume?
decrease
final factor that influxes stroke volume is the effect of circulating
- catecholamine (N/NE)
- direct sympathetic stimulation of the heart by cardiac accelerator nerves
overall, what three factors affect CO
- EDV
- Cardiac contractility
- cardiac after load (aortic blood pressure)
increase of CA influx into the myocardial cell would cause?
cardiac contractility
increase in cardiac afterload results in a
decrease in stroke volume
Factos affecting cardiac rate
- parasympathetic
- sympathetic nerves
factors affecting stroke volume
- sympathetic nerves
- frank starling
- EDV
- MAP
blood flow is
the change of pressure over resistance
what happens to blood flow when vascular resistance increase
blood flow decrease
blood flow can be increased by
- increase in blood pressure
- decrease in resistance
regulation of HR - PSNS
- via vagus nerve
- slows HR
- decreases contractility of the myocardium indirectly by inhibiting SNS
regulation of HR - SNS
- via cardiac accelerator nerves
- increases HR by stimulation SA and AV node
- increases contractility of the myocardium directly
Cardiovascular control center is in the
medulla oblongata
medulla oblongata consists of 4 areas
- pressor area (vasoconstrictor)
- depressor area (vasodilator)
- cardiac acceleration
- cardiac inhibitory center
increased oxygen delivery to exercising skeletal muscle is accomplished via two mechanism
- increase in CO
- redistribution of blood flow form inactive organs to the working skeletal muscle
Fick Equation
VO2 = Q x (a-VO2diff)
during exercise, blood flow to contracting muscle is increased, and blood flow to less active tissues is
reduced
auto regulation refers to
intrinsic control of blood flow by increases in local metabolites
these factors work together to promote vasodilation to increase blood flow to the working muscles?
NO, prostaglandins, ATP, adenosine, and endothelium derived
what does NTS stand for
nucleus tractus solitarius - receiving inputs from afferent
vagal stimulation only goes
to the heart
sympathetic stimulation goes to the
heart and the blood vessels
glossopharyngeal nerve
carotid sinus
vagus nerve
aortic baroreceptors
a decrease in action potential frequency from the barorecepotros, should elicit
an increase in SNS activity
SNS response to decrease in bp effects on SA node
increase heart rate
SNS response to decrease in bp effects on myocardium
heart rate contractile
SNS response to decrease in bp effects on arteries
vasoconstrict
SNS response to decrease in bp effects on veins
stiffen
chemoreceptor reflex
- sensitive to decrease O2, increase CO2, increase hydrogen ion
- signals excite the vasomotor center
volume reflex
- atrial stretch = dilation of afferent arterioles in the kidney
- signals hypothalamus to decrease ADH
- atria release atrial natriuretic peptide (ANP)
abdominal compression reflex
baroreceptor and chemoreceptor reflexes also excite motor nerves to the abdomen
respiratory
- inspiration: decrease in BP
- early expiation: increase in BP
bainbridge reflex
- increase atrial stretch = increase HR and strength of contraction
increase in HR at onset of exercise
- initial increase due to parasympathetic withdrawal
- later increase due to increased SNS firing (outflow)
intrinsic rate of the heart is
90 to 100 bpm