Week 8: Haemodynamics and Blood Pressure Regulation

Question 1

What is the unit for blood pressure?

Answer 1

mmHg (the force per unit area of blood pushing against the vessels walls that contain it.)

Question 2

What are the 3 main things that blood pressure is determined by?

Answer 2

1. Blood volume 2. Cardiac output (heart rate x stroke volume) 3. Total peripheral vascular resistance (PVR)

Question 3

What is the formula for blood pressure?

Answer 3

BP=CO*PVR

Question 4

If you lose 10% of your blood volume, will you have a decrease in blood pressure?

Answer 4

No, you can lose about 10-20% of your blood without any changes to BP due to the compensatory mechanisms that monitor it

Question 5

What are the 3 things that the level of peripheral vascular resistance depends on?

Answer 5

1. Blood viscosity 2. Vessel length - the longer the vessel the greater the friction. 3. Vessel diameter (the bigger the better)

Question 6

What is the equation for blood flow?

Answer 6

Blood flow (Q’ or F)=∆P/R

Question 7

What is the formula for mean arterial pressure?

Answer 7

Mean arterial pressure=Diastolic Pressure+((systolic - diastolic pressure)/3)

Question 8

Define systolic pressure

Answer 8

the peak arterial pressure following a left ventricle ejection

Question 9

What are the 3 broad main mechanisms that regulate blood flow?

Answer 9

Autoregulation, neural mechanisms (baroreceptor and chemoreceptor reflexes) and endocrine mechanisms (can be local or whole body).

Question 10

What are the 2 types of autoregulation of blood flow and explain them.

Answer 10

1. Intrinsic mechanisms - achieved through metabolic controls like CO2 and potassium and local paracrine and autocrine factors There are also some local hormones (NOTE: NOT SYSTEMIC) that cause vasoconstriction. 2. Extrinsic mechanisms - broken into neuronal and systemic hormonal Looks to change mean arterial pressure to make sure the brain gets enough blood.

Question 11

What is the equation for friction?

Answer 11

Where F = Flow, deltaP = pressure gradient, r = radius, eta = viscosity, l = length

Question 12

What is the difference between blood flow and blood velocity?

Answer 12

The blood flow is the amount of blood flowing per unit time (ml/min) The blood velocity is the distance travelled per unit timer (mm/min)

Question 13

Describe the relationship between blood flow and blood velocity with vasodilation.

Answer 13

with vasodilation comes an increase in flow (due to increased radius), but a decrease in velocity (due to the increased surface area) velocity=flow/(cross sectional area)

Question 14

The 3 mechanisms that regulate blood flow are autoregulation, neural mechanisms and endocrine mechanisms. THe neural mechanims are baroceptor and chemoreceptor flexes. Explain the baroceptor mechanism if the mean arterial blood pressure decreases upon standing.

Answer 14

Question 15

The 3 mechanisms that regulate blood flow are autoregulation, neural mechanisms and endocrine mechanisms. THe neural mechanims are baroceptor and chemoreceptor flexes. Explain the chemorecptor mechanism if homeostasis is disturbed.

Answer 15

Question 16

Fill the blanks

Answer 16

Question 17

Why do you simultaneoulsy take a radial and femoral pulse? What might a difference between these 2 indicate?

Answer 17

To see if there is a delay between the 2. A delay could indicate narrowing of the aorta or obstruction below the left sub-clavian artery.

Question 18

What causes the first and second sound of the heart beat and when can this be heard on an ECG?

Answer 18

First sound: the bicuspid (mitral) and tricuspid valve closing (atrio-ventricular valves). –> heard in middle of the QRS complex.

Second sound: the semi-lunar valves closing –> heard just after the T wave

Question 19

Fill the blanks

Answer 19

Question 20

If a right vagal stimulation was administered to the patient (inhibits the SA node). What effect would this have on cardiac output (heart rate, and stroke volume - diastolic and systolic pressure)

Answer 20

Would decrease all of them as it is inhibiting the SA node which is the pacemaker cell - therefore, decreased cardiac output

Question 21

Phenylephrine is an alpha1-adrenergic receptor agonist, if this was administered to a patient, what effect would if have on mean arterial blood pressure?

Answer 21

would increase due to the vasoconstriction of the peripheral vessels.

Question 22

What effect would epinephrine administration to a patient have on systolic, diastolic pressure?

Answer 22

Epinephrine increases sympathetic activity which therefore will increase systole but decrease diastolic pressure.

Systolic pressure is when your heart muscles are contracting and is the force that the blood pushes on your artieries.

Diastolic pressure is when your heart is relaxing inbetween beats (this is when it is passively filling)

Remember that epinephrine causes vasodilation in the heart, but vasoconstriction in your peripherals. So it can increase cardiac output and deliver blood to important tissue faster.

Question 23

What is the formula for Blood pressure, Cardiac output and stroke volume (they have different formulas lol)

Answer 23

BP = Cardiac output x peripheral vascular resistance

Cardiac output = stroke volume x heart rate

Stroke volume = end diastolic volume - end systolic volume