Cardio

Question 1

What is the equation for the net filtration

Answer 1

Net filtration pressure = (Pc - Pi) - (Pi c - Pi i)

Question 2

What is one equation for CO?

Answer 2

CO = HR * SV

Question 3

What is the relationship between tube (vessel) cross sectional area and fluid velocity through that tube(vessel)?

Answer 3

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.

Question 4

What nerves are involved in the baroreceptor reflex?

Answer 4

The glossopharyngeal nerve (IX)

The vagus nerve (X)

Question 5

What would be the result of stimulating the afferent portions of the glossopharyngeal and vagus nerves?

Answer 5

This would lead to bradycardia and hypotension via the baroreceptor reflex.

Question 6

What message would be sent (to the brain) if the glossopharyngeal and vagus nerves were severed?

Answer 6

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.

Question 7

What is the vagus nerve’s role in determining basal heart rate?

Answer 7

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.

Question 8

What does the pulmonary capillary wedge pressure measure?

Answer 8

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.

Question 9

When a balloon-tipped catheter is placed in the pulmonary artery and is deflated, what pressure is being measured?

Answer 9

The pulmonary artery pressure. In this case, the pressure measured should give both a systolic and diastolic reading (e.g., 25/8 mmHg)

Question 10

Can a catheter placed in the pulmonary artery be used to measure left ventricular peak systolic pressure?

Answer 10

No.

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.

Question 11

Can the right atrial pressure be measured or approximated by a catheter placed in the pulmonary artery?

Answer 11

No.

Question 12

What happens to total peripheral resistance when an organ is removed?

Answer 12

It increases.

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.

Question 13

Describe the Fick equation for calculation of CO in words

Answer 13

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.

Question 14

Which segment of the systemic resistance has the greatest resistance? What is the correlation to blood pressure?

Answer 14

The arterioles. This “greatest” resistance is reflected in the fact that the greatest drop in blood pressure is also observed across the arterioles.

Question 15

When is the sarcomere length of the left ventricular muscle fibers the greatest?

Answer 15

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.

Question 16

When is the sarcomere length of the left ventricular muscle fibers the shortest?

Answer 16

At the end of systole, when the left ventricular volume is the lowest.

Question 17

Which vascular compartment contains the greatest proportion of the total blood volume? Roughly what proportion does it contain? Is the proportion altered by posture?

Answer 17

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

Question 18

Rank the velocity of blood flow from highest to lowest by vessel type.

Answer 18

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

Question 19

What is the affect of CO2 on the cerebral vasculature?

Answer 19

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

Question 20

What two factors influence pulse pressure?

Answer 20

stroke volume and arterial compliance

Question 21

How might arteriosclerosis affect a person’s pulse pressure?

Answer 21

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.

Question 22

What is VEGF?

Answer 22

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.

Question 23

What is malignant hypertension?

Answer 23

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.

Question 24

How might brain stem injury affect heart rate?

Answer 24

The vagal nuclei are located in the brain stem, and vagal tone provides the dominant control of basal heart rate, slowing the intrinsic firing of the heart. Damage to the brain stem would therefore likely cause the heart rate to increase.