Flashcards in Cardio Deck (24):
What is the equation for the net filtration
Net filtration pressure = (Pc - Pi) - (Pi c - Pi i)
What is one equation for CO?
CO = HR * SV
What is the relationship between tube (vessel) cross sectional area and fluid velocity through that tube(vessel)?
They are inversely proportional. If the cross sectional area is decreased by four, the velocity of the fluid moving through the tube will increase by four.
What nerves are involved in the baroreceptor reflex?
The glossopharyngeal nerve (IX)
The vagus nerve (X)
What would be the result of stimulating the afferent portions of the glossopharyngeal and vagus nerves?
This would lead to bradycardia and hypotension via the baroreceptor reflex.
What message would be sent (to the brain) if the glossopharyngeal and vagus nerves were severed?
The afferent portions of these nerves carry information to the medulla from the carotid and aortic sinuses, respectively. The rate of firing of these neurons increases with increases in blood pressure. This stimulates the baroreceptor reflex. Severing these nerves sends the false signal to the medulla that the patient has suddenly lost all blood pressure. This elicits the baroreceptor reflex, leading to increased sympathetic outflow, resulting in tachycardia and hypertension. Since the vagus is cut, which is the parasympathetic innervation of the heart, this would also produce tachycardia.
What is the vagus nerve's role in determining basal heart rate?
The vagus provides the parasympathetic innervation of the heart. The dominant basal control of the heart rate is suppression of the intrinsic rate by vagal activity.
What does the pulmonary capillary wedge pressure measure?
The pressure in the left atrium
(When the balloon is inflated, the catheter becomes wedged in a small branch of the pulmonary artery. This stops blood flow in the vessels distal to the catheter. These vessels, in which there is no flow, can be thought of as physical extensions of the catheter, and allow blood pressure to be measure on the other side of the pulmonary circulation, ie, the left atrium.)
This value is usually a little but higher than the true left atrial pressure.
When a balloon-tipped catheter is placed in the pulmonary artery and is deflated, what pressure is being measured?
The pulmonary artery pressure. In this case, the pressure measured should give both a systolic and diastolic reading (e.g., 25/8 mmHg)
Can a catheter placed in the pulmonary artery be used to measure left ventricular peak systolic pressure?
The left ventricular peak systolic pressure occurs when the mitral valve is closed, making it impossible to approximate this pressure using a catheter in the pulmonary artery: The lumen in which the catheter is placed, and the lumen in which we want to measure the pressure, must be physically continuous.
Can the right atrial pressure be measured or approximated by a catheter placed in the pulmonary artery?
What happens to total peripheral resistance when an organ is removed?
Total resistance decreases when additional resistances are added in parallel to a circuit. Conversely, total resistance increases when additional resistances are added in series to a circuit. Because the various organs of the body are arranged in parallel, the total peripheral resistance increases when an organ is removed.
Describe the Fick equation for calculation of CO in words
CO can be found by dividing oxygen consumption by the difference between the arterial and venous oxygen content. Lets say that oxygen consumption is 300mL O2/min, and that the difference between the arterial and venous oxygen contents is 50mL O2/ L of blood. We then must ask ourselves, if this amount of oxygen is being picked up in the lungs (or dropped off in the tissues) each minute, and each liter of blood is picking up (or dropping off) 50mL of O2, how many liters of blood would be required to pick up/consume this amount (300mL) of 02? This is the CO, and in this case would be 6L/min.
Which segment of the systemic resistance has the greatest resistance? What is the correlation to blood pressure?
The arterioles. This "greatest" resistance is reflected in the fact that the greatest drop in blood pressure is also observed across the arterioles.
When is the sarcomere length of the left ventricular muscle fibers the greatest?
At the end of diastole, when the left ventricular volume is the greatest/filled to the greatest extent with blood. The volume of blood in the left ventricle at this point as call the end diastolic volume.
When is the sarcomere length of the left ventricular muscle fibers the shortest?
At the end of systole, when the left ventricular volume is the lowest.
Which vascular compartment contains the greatest proportion of the total blood volume? Roughly what proportion does it contain? Is the proportion altered by posture?
The venules and veins.
The systemic veins contain approximately 2/3 of the total blood volume.
The proportions can be altered to a limited extent by posture or exercise.
This large volume contained within the venous vasculature explains why venous return to the heart can be a powerful influence on CO
Rank the velocity of blood flow from highest to lowest by vessel type.
aorta and large vessels > vena cavae > large veins > small arteries > arterioles > small veins > venules > capillaries
V is proportional to 1/cross-sectional area
V is proportional to 1/radius squared
What is the affect of CO2 on the cerebral vasculature?
CO2 plays a key role in the control of cerebral vascular flow. In increase in arterial Pco2 will cause dilation of blood vessels in the brain, while a decrease in arterial Pco2 will lead to vasoconstriction.
When someone hyperventilates, they "blow off" carbon dioxide, leading to a decrease in arterial Pco2, cerebral vasoconstriction, and therefore to an increase in cerebral vascular resistance. This leads to decreased blood flow to the brain, which can result in cerebral hypoxia. This can cause a person to feel faint and have blurred vision
What two factors influence pulse pressure?
stroke volume and arterial compliance
How might arteriosclerosis affect a person's pulse pressure?
Arteriosclerosis is a hardening of the arteries, which would lead to a decrease in arterial compliance. This would cause an increase in systolic pressure, a decrease in diastolic pressure, and therefore a widening of the pulse pressure, which is the difference between the two.
What is VEGF?
vascular endothelial growth factor.
(1) important for growth and survival of endothelial cells under normal physiological conditions
(2)while endothelial cells don't secrete VEGF, other cells types do during hypoxic conditions
(3)The hypoxic conditions that occur in muscles during exercise are a potent stimulus for VEGF production in muscle cells
(4) regular exercise can lead to significant endothelial proliferation and growth of new capillaries in muscle.
What is malignant hypertension?
This is not a specific type of hypertension, but instead describes hypertension with evidence of end-organ damage, such as acute renal failure or mental status changes.