Cardiovascular anatomy & physiology 5 Flashcards
The cardiac cycle influences
how and when blood flows through the coronary circulation
Left ventricular contraction compresses the
endocardial vessels during systole
The ________________ is most vulnerable to ischemia
LV subendocardium
Flow through the __________ is relatively constant throughout the cardiac cycle
right ventricle
Which condition increases myocardial oxygen consumption?
a. decreased diastolic filling time
b. decreased end-diastolic volume
c. decreased P50
d. decreased aortic diastolic blood pressure
a. decreased diastolic filling time
Myocardial oxygen balance requires that oxygen delivery
meets or exceeds oxygen demand
At rest, the myocardium consumes _____ of the oxygen delivered to it.
70%
When oxygen demand increases, ________ and _____________ must increase to satisfy the demand
coronary blood flow and CaO2
Determinants of oxygen delivery include
coronary blood flow
CaO2
oxygen extraction
Determinants of oxygen demand include
preload
afterload
contractility
wall stress
________________ is detrimental to the ischemic heart, because it simultaneously decreases oxygen supply while increasing oxygen demand
Tachycardia
During ischemia, anaerobic metabolism leads to
lactic acid production
Lactic acid contributes to
the perception of chest pain
Most perioperative myocardial infarctions occur
24-48 hours following surgery
Although increased afterload increases myocardial oxygen demand, the benefit of
increased coronary perfusion pressure typically outweighs the risk of increased wall tension
What factors increase oxygen demand?
tachycardia
hypertension
SNS stimulation
increased wall tension
increased LVEDV
increased afterload
increased contractility
What factors decrease oxygen delivery?
decreased CaO2- hypoxemia, anemia
decreased oxygen extraction- decreased P50 (aka left shift)
decreased coronary flow- tachycardia, decreased vessel diameter, increased LVEDP, decreased aortic pressure
Inhaled nitric oxide: (select 2)
a. is inactivated by hemoglobin
b. reduces right ventricular afterload
c. stimulates cAMP production
d. causes hypotension
a. is inactivated by hemoglobin
b. reduces right ventricular afterload
___________ plays a critical role in the regulation of peripheral vessel diameter
Calcium
Increased calcium causes __________ and reduced intracellular Ca2+ leads to _____________
vasoconstriction; vasodilation
Regulation of vascular smooth muscle tone is dependent on the successful integration of the
autonomic nervous system
renin-angiotensin-aldosterone system
local metabolism
myogenic response
Describe 3 second messenger systems that modulate vascular tone by affecting calcium concentrations.
G-proteins cAMP pathway
Nitric oxide cGMP pathway
Phospholipase C Pathway
How does the G-proteins cAMP pathway work.
increased cAMP–> vasodilation
How does the nitric oxide cGMP pathway work?
increased cGMP–> vasodilation
How does the phospholipase C pathway work?
increased IP3 & DAG–> vasoconstriction
What 4 ways does protein kinase A affect excitation-contraction?
- inhibits VGCa2+ channels in the sarcolemma
- inhibits Ca2+ release from the SR
- reduces the sensitivity of the myofilaments to Ca2+
- facilitates Ca2+ reuptake into the SR via the SERCA2 pump
Phenylephrine stimulates what effector to ultimately cause vasoconstriction?
phospholipase C
