Week 8: Haemodynamics and Blood Pressure Regulation Flashcards
What is the unit for blood pressure?
mmHg (the force per unit area of blood pushing against the vessels walls that contain it.)
What are the 3 main things that blood pressure is determined by?
- Blood volume 2. Cardiac output (heart rate x stroke volume) 3. Total peripheral vascular resistance (PVR)
What is the formula for blood pressure?
BP=CO*PVR
If you lose 10% of your blood volume, will you have a decrease in blood pressure?
No, you can lose about 10-20% of your blood without any changes to BP due to the compensatory mechanisms that monitor it
What are the 3 things that the level of peripheral vascular resistance depends on?
- Blood viscosity 2. Vessel length - the longer the vessel the greater the friction. 3. Vessel diameter (the bigger the better)
What is the equation for blood flow?
Blood flow (Q’ or F)=∆P/R
What is the formula for mean arterial pressure?
Mean arterial pressure=Diastolic Pressure+((systolic - diastolic pressure)/3)
Define systolic pressure
the peak arterial pressure following a left ventricle ejection
What are the 3 broad main mechanisms that regulate blood flow?
Autoregulation, neural mechanisms (baroreceptor and chemoreceptor reflexes) and endocrine mechanisms (can be local or whole body).
What are the 2 types of autoregulation of blood flow and explain them.
- 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.
What is the equation for friction?
Where F = Flow, deltaP = pressure gradient, r = radius, eta = viscosity, l = length
What is the difference between blood flow and blood velocity?
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)
Describe the relationship between blood flow and blood velocity with vasodilation.
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)
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.
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.
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Why do you simultaneoulsy take a radial and femoral pulse? What might a difference between these 2 indicate?
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.
What causes the first and second sound of the heart beat and when can this be heard on an ECG?
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
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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)
Would decrease all of them as it is inhibiting the SA node which is the pacemaker cell - therefore, decreased cardiac output
Phenylephrine is an alpha1-adrenergic receptor agonist, if this was administered to a patient, what effect would if have on mean arterial blood pressure?
would increase due to the vasoconstriction of the peripheral vessels.
What effect would epinephrine administration to a patient have on systolic, diastolic pressure?
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.
What is the formula for Blood pressure, Cardiac output and stroke volume (they have different formulas lol)
BP = Cardiac output x peripheral vascular resistance
Cardiac output = stroke volume x heart rate
Stroke volume = end diastolic volume - end systolic volume
