Lesson 94 CR

What is a pressure gradient

pressure will go from higher pressure to lower pressure

What is flow

volume of fluid (blood/air) passing through vessel per unit time (L/min)

What is flow’s importance to the body

-ensures oxygen, nutrients, removal of waste

What is Ohm Law

Q=P/R

Q (flow)

P (pressure mmHg)

R (resistance)

What determines blood flow

pressure gradient

What does poiseuille’s law express

the largest impact on resistance is vessel radius

What is capacity or compliance (definition)

ability of hollow organ to stretch & expand in response to pressure

Compliance equation

C= ∆P/∆V

C (compliance)

∆P (change in pressure)

∆V (change in volume)

Pulmonary and systemic circulation have the same ________ but different _______

flow; pressures

Does pulmonary or systemic circulation have a higher mean BP

higher mean BP= systemic

lower mean BP= pulmonary

Why is pressure less in pulmonary

to avoid high hydraulic pressure in lung capillaries (that can lead to lung edema)

In systole of pulmonary circuit which ventricle has increased pressure compared to pulmonary artery

higher pressure in R ventricle compared to pulmonary artery (causes blood flow to lung)

The circulatory system is never empty but what can change?

changes in flow (volume/time)

What is responsible for maintaining a low pressure system in the pulmonary circuit

Lower pulmonary vascular resistance

In systole of systemic circulation pressure in which ventricle is greater than aorta pressure. What does this cause

pressure in L ventricle ↑ than aorta → blood flow to body

What does the windkessel pnenomenon describe. How is this important in arterial circulation?

larger arteries (aorta, pulmonary artery, main branches) have lot of elastin → stretchy (high compliance) → during systole they stretch → during diastole they snap like a rubber band → recoil allows steady blood flow during diastole

What effect does elastic nature of larger arteries have on the heart

decreased work of the heart

What is the effect of rigid arteries

↑ systolic BP

↓ pulsatility

↓ diastolic BP (↓ coronary perfusion to heart & ↑ L ventricular workload)

↑ afterload on heart (its not ejecting all of the blood that it is supposed to)

What causes hypoxia-induced pulmonary hypertension in cattle (Brisket disease) & ascites in broilers

edema caused by high capillary hydrostatic pressure

How does an increase in sympathetic tone lead to and increase in blood pressure

vasoconstriction & hypertension (afterload increased)

How does chronic kidney disease in dogs and cats cause increased blood pressure

increased preload (because retained water and salt)

increased cardiac output

How does renin-angiotensin-aldosterone system (RAAS) cause increase blood pressure

increased vascular resistance

increase preload (retained water + salt) → ↑ blood flow

How does exercise impact oxygen consumption

increased O2 consumption (need more O2 for ATP production)

CO (cardiac output) equation

CO= stroke volume x heart rate

CO (volume/time)

What 3 mechanisms keep stroke volume when there is a decrease in ventricle filling at increased heart rates

1) increased force of contraction → increase stoke volume

2) vasoconstriction

3) More blood heart receives → the more it ejects (Frank-starting mechanism)

How do you increase the force of contraction

increase of sympathetic stimulation

catecholamines act on beta1-adrenoceptors

What does mobilization of splanchnic blood volume (movement of blood from splanchnic compartment to circulation) do

causes vasoconstriction (through sympathetic stimulation)

Local vasodilation in ________ occurs during exercise

skeletal muscle (by CO2)

BP=

CO x total peripheral resistance (TPR)

What is the blood pressure at submaximal exercise and why

systemic BP constant (because of baroreceptor reflex regulation)

What is the blood pressure at maximal exercise

increase in BP

During exercise a paradoxical relationship is seen where pulmonary arterial pressure ___ and pulmonary vascular resistance __

During exercise a paradoxical relationship is seen where pulmonary arterial pressure __increased_ and pulmonary vascular resistance _decreased_

What does recruitment and distention of pulmonary vessels cause in exercise

↓ pulmonary vascular resistance (↑ radius)

↑ pulmonary vascular conductance

↑ pulmonary capillary volume

Where is primary damage from dirofilaria immitis infection seen

heart, pulmonary artery, lungs

How does heartworm cause R side heart failure

increase vascular resistance and in afterload to right side of the heart

What does eosinophilia from heartworm infection cause

vascular damage & lung disease

Does heartworm cause pulmonary hyper or hypotension

pulmonary hypertension

What is preload

amount of blood in the ventricles before contraction

What is afterload

resistance the heart faces when ejecting blood