Lecture 7 Flashcards
What regulates cerebral blood flow?
- solely PCO2
- not under the influence of the ANS
- More PCO2 = higher blood flow
ECG anomalies due to hypokalemia:
- globally present (all leads)
- ST depression with flattened T waves
Ischemia due to angina on ECG:
- ST depression
- usually accompanied by T wave inversion
Renal circulation can accommodate about how much of CO?
20%
Hepatic circulation can accommodate about how much of CO?
25%
What is portal vein venous inflow set by?
splanchnic arteriolar tone (celiac trunk, SMA, IMA)
What gives the splanchnic arterial system a relatively low threshold for VSM activation/vasoconstriction?
- large concentrations of α1 adrenoreceptors
- will vasoconstrict in response to low levels of SNS tone
Pulse pressure equation:
PP = systolic BP - diastolic BP
What determines pulse pressure (3)?
SV, arterial compliance, and ejection force
As SV increases, arterial compliance must coordinately increase to maintain a normal pulse pressure. If arteries become less compliant, what occurs?
- turbulent flow
- systolic arterial BP elevates
- greater work load on LV
Anticipatory phase of exercise:
- SNS becomes activated solely by cognitive output.
- HR increases via beta-1 activation, some inotropy as well.
- Increased TPR due to alpha-1 mediated vasoconstriction.
Cause of cardiac output increase during anticipatory and early stages of exercise:
- mostly increase HR via beta-1 activation; little inotropy
What changes occur during the early phase of exercise?
- SNS increase.
- PSNS decrease.
- HR increase = CO increase.
- TPR increase (no vasodilation yet).
- Skeletal muscle vasodilatory factors increase.
- Skeletal muscle afferents reset high pressure baroreceptors and increase resipiratory drive.
During exercise, skeletal mechanoreceptor afferents cause two changes in the medullary cardio/respiratory centers:
- high pressure baroreceptors are reset so that the SNS can remain active.
- respiration drive increased due to increased PCO2. Chemoreceptors.
How does vasodilation due to vasodilatory metabolites increase heart efficiency during exercise?
- decreases afterload
- occurs in late phase of exercise
Differences in systolic and diastolic blood pressures during exercise:
- systolic increases (dependent on CO) throughout.
- diastolic decreases due to vasodilatory factors (dependent on TPR) in late stage.
What changes during the late stage of vigorous exercise?
- increased HR, EDV, EDP, CO (5X)
- decreased ESV
- increased systolic BP
- diastolic BP stable or drops
What happens to arterial blood gases (ABGs) during the late exercise stage?
- PCO2 increases in the venous blood
- Mild acidemia drives ventilation
Anaerobic threshold:
- level at which lactic acid production exceeds removal. Accumulates.
- Mild acidemia drives ventilation.
Draw cardiac function curve during the initial phase of exercise:
- SNS tone increases.
- Vasoconstriction and inotropy.
Draw cardiac function curve during the late stage of physical exercise:
Vasodilation occurs due to skeletal muscle work metabolites
