Flashcards in Test 1, Deck 4 Deck (56):
what determines coronary blood flow? what regulates it?
- determines: aortic pressure
- regulates: metabolic activity/changes in arteriolar resistance
when do you see a reversal in the blood flow of the left- but not right- coronary artery?
during max systolic pressure (isovolumetric contraction- rapid ejection) aka early systole
60-65% of coronary blood perfusion to LV muscle occurs during ______
Vessels in the endocardium or epicardium are more compressible?
Which vessels are more dilated?
Which is more at risk for ischemia?
- endo to ALL
What compress endo/epicardium vessles?
Diastolic pressure and contraction
what is the relationship between blood flow and metabolic activity?
* increased metabolism, decreased resistance, increased blood flow
what are the metabolic substrates for the heart, and what is the largest consumer of O2?
fatty acids (LARGEST O2), carbs, ketones/lactate/proteins
how does the heart get more oxygen?
it is flow limited- must vasodilate
what is the equation for cardiac work, and which factor matters more?
cardiac work= MAP x systolic stroke volume
- pressure is more important
which factors affect myocardial oxygen supply?
- diastolic perfusion pressure
- coronary vascular resistance (external vs intrinsic (metabolites))
- O2 carrying capacity
which factors create largest O2 demand?
- heart rate
what is ischemia, considering O2?
imbalance in the ratio of oxygen supply to oxygen demand; creates a relative lack in blood flow
- excessive O2 demand is NEVER the primary cause (always too little supply)
what is coronary steal?
an increase in blood flow to one region can cause a decrease in flow to another-
* problematic with vasodilation if there is a stenosis *
when would coronary steal present clinically?
- exercise-induced ischemia
- stress testing
- peripheral arterial disease
What happens to skeletal muscle circulation during exercise?
- the flow oscillates
- overall, there is a significant reduction in resistance to blood flow to vasodilation
Skeletal flow can increase ___ time during exercise, which is called _____. It constitutes the ____ vascular bed in the body. Which type of muscle has more vascular supply- tonic or phasic?
What is the main vasodilator- working against sympathetics- in skeletal muscle?
Skeletal muscle vasculature is primarily innervated by _____ fibers
Ach causes ___ by acting on ___ coupled to ___
muscarinic (on endothelials)
Epinephrine from ____ causes ____ at low concentrations through activating _____, but _____ at high concentrations through activating ____
- adrenal medulla
- beta-2 adrenergic receptors
- alpha adrenergic receptors
The brain primarily uses _____ metabolism of _____. How metabolically active is it?
aerobic metabolism of glucose
most metabolically active tissue in the body
What is the BBB due to? What can cross?
- endothelial tight junctions
- basement membrane
- neuroglial processes
- metabolic enzymes
- lipid soluble substances- O2, CO2, ethanol, steroids, glucose
What is CPP? If CPP falls, what happens? What reduces CPP?
- cerebral perfusion pressure
- CPP= MAP- intracranial venous pressure
- reduced by decrease in MAP or increase in intracranial pressure
what is the monroe-kellie doctrine?
brain volume + cerebral vascular volume + CSF volume= constant
What happens as CSF pressure rises?
- increase CSF pressure
- cerebral blood flow decreases (veins compressed)
- metabolic autoregulation dilates the arteries
- this only works up until a certain pressure, where the arteries become compressed
Cerebral blood flow is very sensitive to which metabolite?
An increase in pH (hyperventilation) causes what? This helps with what clinical scenario?
- vasoconstriction & decreased blood flow
- cerebral edema (high intracranial pressures)
mechanism for nitric oxide
- causes vasodilation of smooth muscle
- increases cGMP and PKG
- increases phosphorylation of MLCK
- decreases phosphorylation of myosin light chain
what is the cushing response?
with elevated intracranial pressure, you see
- high blood pressure (medulla sympathetics)
- low heart rate (parasympathetics)
when does the cushing response occur?
when CSP (cerebral spinal pressure) is greater than the mean arterial pressure
Pulmonary circulation is a ____ pressure, ____ volume system, ___ resistance; mean pressure gradient= ____
low pressure, high volume, low resistance
mean pressure gradient 6 mm Hg
Pulmonary arteries are ___ compliant than regular arteries because____
7x more; they lack smooth muscle
Pulmonary capillaries represent ___ of the vascular resistance
T/F Pulmonary vessels autoregulate
During inspiration, negative pressure ______'s extra-alveolar vessels and _____ resistance in alveolar vessels - net effect on resistance = ?
net effect- no change!
intravascular (hydrostatic) pressure is greatest at which part of the lung? what does this cause?
what happens in zone 1?
alveolar pressure exceeds arterial and veous pressures, causing capillaries to collapse
- exists w/ hypotension or positive pressure mechanical ventilation
what happens in zone 2?
alveolar pressure exceeds venous pressure but does not exceed arterial pressure; capillaries are partially collapsed, is the upper 1/3rd of lung
what happens in zone 3?
arterial and venous pressures exceed alveolar pressure; flow depends on AV pressure gradient
primary function of cutaneous circulation
maintain a constant body temperature
- provides transport of heat to the body surface for exchange with the environment
what is apical skin?
- high surface-volume ratio that favors heat loss
- has lots of AV anastomoses called glomus bodies
what is nonapical skin?
- lacks AV anastomoses
- innervated by sympathetic fibers- postganglionics release Ach; vasodilation
neural control of apical skin
sympathetic adrenergic nerves that produce vasoconstriction of cutaneous vessels (withdrawal produce passive vasodilation)
neural control of nonapical skin
- sympathetic vasoconstriction (NE)
- active vasodilation via cholinergic fibers via bradykinin
temperature regulation (what kind?) is primarily controlled by major sensory sites in the ______ and less by receptors in the spinal cord
core body temperature; hypothalamus
fetal circulation pathway
fetal branch villi- umbilical vein- ductus venosus- IVC- RA- foramen ovale- LA-LV- aorta
some blood goes RA- RV-pulm artery- ductus arteriosis- systemic circulation
valves close, pressure changes, pipes shut
valves close- foramen ovale
pressure changes- atria
pipes shut- ductus venosus & ductus arteriosus
difference between HbF and HbA and why?
HbF has greater affinity for O2 due to DpG shifting O2 dissociation curve left- more saturation at lower pressures
umbilical artery- medial umbilical ligament
umbilical vein- ligamentum teres
ductus venosus- legamentum venosus
ductus arteriosus- ligamentum arteriosum
what happens with skin circulation and exercise?
sympathetics want to vasoconstrict
internal metabolic heat stimulates cutaneous vasodilation
what does the arrangement of vessels within the intestinal villus form?
contercurrent flow system; arteries and venules run parallel to each other- solutes such as sodium dissolve from the arteries back to the venules to increase osmolarity/blood flow
What ist he portal system?
1- portal vein- blood from intestine/stomach/pancreas (only a few mmHg higher than IVC)
2- liver capillaries- blood from portal vein
3- hepatic vein- liver capillaries
metabolic control of splanchnic circulation
metabolites (CO2, H+, adenosine) increase
hormonal control of splanchnic circulation
cholecystokinin & neurotensin increase vasodilation
neural control of splanchnic circulation
- sympathetic vasoconstriction via NE acting on alpha adrenergic receptors on vascular smooth muscle (also have beta receptors)
- parasympathetics act indirectly by contacting sympathetics in intestinal wall & stimulates motility