biophysics

what is the name of the biophysical variable that determines blood flow?

pressure gradient

capacitance

the ability of the veins to receive blood drained from the body

compliance is involved in what side of circulation?

venous side of circulation

what is the formula for cardiac output?

stroke volume x heart rate

what would the hemodynamic consequences of a more rigid aorta be during systole?

increase resistance, heart must work harder = increased afterload of heart

what component of the Ohm Law could explain the higher blood pressure in chronic kidney disease?

vascular resistance

why is the higher pulmonary blood pressure during exercise remain close to the resting values?

the lung vascular bed distends

what determines the higher afterload in severe cases of heartworm disease in dogs?

higher vascular resistance

what determines blood flow?

Ohm's law

Ohm's law

pressure gradient / resistance

why does systemic circulation require higher pressure?

the heart needs to pump blood to the entire body = far distance, needs pressure to be able to propel the blood

In systemic circulation there will be ______ pressure and ______ blood flow

1. higher

2. same

during systemic circulation what do the small arterioles and arteries provide to the body?

Small arterioles and arteries offer about half the vascular resistance (47%) in the body

In systemic circulation, veins carry ___, arteries carry ___

• deoxygenated blood from the body to the heart

• oxygenated blood from the heart to the body

what occurs in systole during systemic circulation?

During ventricular contraction, the pressure in the left ventricle becomes higher than the aorta → blood flow to entire body

what does the windkessel phenomenon explain?

explains steady blood flow from the arteries to the rest of the body despite there being two phases of the cardiac cycle

veins reserve

volume

arteries reserve

energy and pressure

explain the function of arterioles in systemic circulation

Arterioles are high-resistance vessels that regulate the distribution of blood flow to various capillary beds in. the body

what happens during systole in terms of the windkessel phenomenon?

During systole, the blood volumes stretches the aorta like a rubberband to eject the blood through the capillaries of the circulatory system

what happens during diastole in terms of the windkessel phenomenon?

the elastic fibers coil and energy conserved from diastole is placed back into the system to further help propel the blood along the capillaries

what structures and their features allow for compliance in terms of the windkessel phenomenon?

Aorta, pulmonary artery, and their branches have a large amount of elastin in their walls that make them very compliant

pulmonary circulation has ___ pressure, __ blood flow

1. lower

2. same

what supplies most of the volume in the body and by how much?

64% of volume in the body is supplied by veins

describe the pressure gradient and volume distribution of veins regarding pulmonary circulation

Pressure gradient around veins is low but the volume distribution is high

why is pressure low for pulmonary circulation?

In pulmonary circulation, the lungs are near the heart, it will not require much pressure for the blood to get to either structure

explain the mean blood pressure of pulmonary circulation

Mean blood pressure is lower than systemic circulation to avoid a higher hydraulic pressure in the lung capillary

why do we want to avoid high pressure in pulmonary circulation

High pressure will result in filtration (hydraulic pressure > oncotic pressure) → fluid will leak into the interstitial space → liquid will enter the alveoli of the lung → interstitial lung edema

explain systole in terms of pulmonary circulation

During ventricular contraction, the pressure in the right ventricle becomes higher that the pulmonary artery, and blood flows to the lungs

In pulmonary circulation, veins carry _______ ; arteries carry _____

1. oxygenated blood to the heart

2. deoxygenated blood to the lungs

resistance =

1/(radius^4)

what will happen to resistance if you increase the radius of the blood vessel?

decreased resistance

what will happen to resistance if you decrease the radius of the blood vessel?

increased resistance

what are the commonly effected geographical areas for brisket disease?

1. Colorado

2. Wyoming

3. New Mexico

4. Utah

what species are affected by brisket disease?

cattle

how does the cow react when it has less available oxygen supply (brisket disease)?

pulmonary vasoconstriction increases to divert blood to better-oxygenated regions of the lung to try and improve perfusion

what affect will vasoconstriction have on the cow (brisket disease)?

vasoconstriction will significantly increase resistance to blood flow in pulmonary circulation, making it harder for the heart to pump blood through the lungs (increased afterload)

what will increased afterload lead to in the cow (brisket disease)?

will lead to edema since blood does not properly eject from right ventricle toward pulmonary artery and causes backflow into right ventricle

ascites syndrome

pulmonary hypertension in broilers seen in as an edema in their abdomen due to hypoxia

hypertension in cats effects

• tricks the cat’s kidneys into thinking blood pressure is too low

• The RAAS system is activated → retains salt and water

• More fluid = more blood volume → increases cardiac output

what increases in hypertension in cats?

increase in pre-load

During moderate exercise, the body will have decreased ventricular filling and high heart rate. What factors allow stroke volume to be maintained despite these conditions?

1. Increase stroke volume by enhancing contractibility

2. Venous return

3. Frank-starling mechanism

what mechanism of action is taking place to increase contractility during exercise (to maintain stroke volume)?

catecholamines act on beta-1-adrenoreceptors to increase sympathetic activity

explain how venous return helps maintain stroke volume during moderate exercise

• Vasoconstriction promotes mobilization of splanchnic blood volume

• The skeletal muscle activity and the thorax (respiration rate) will also promote mobilization of venous return (blood from viscera sent back to heart)

explain how the frank-sterling mechanism helps maintain stroke volume during moderate exercise

The more blood the heart receives, the more blood it will eject

During rest, how much oxygenated blood from the heart will the skeletal muscles receive?

about 15%

during exercise how much oxygenated blood from the heart will skeletal muscles receive?

about 80%

what is the effect of carbon dioxide in exercise?

potent vasodilator that increases the radius of the arterioles to help with metabolic demand of skeletal muscles

how much oxygenated blood will the coronary ALWAYS receive whether at rest or in exercise?

about 5%

what is the blood pressure in submaximal exercise?

Systemic blood pressure is relatively constant due to the baroreceptor reflex

what is the blood pressure in maximal exercise? (explain process)

1. Increasing the intensity of the exercise

2. leads to an increase resistance of blood vessels,

3. increase heart rate

4. increase cardiac output

5. increase blood pressure

what areas are included in the primary damage to the animal from heartworm?

heart, pulmonary arteries, and lungs through adult worms living in the pulmonary arteries

heartworm is a _________ disease

vector-borne

what causes heartworm disease?

nematode Dirofilaria immitis

heartworm disease is mainly characterized by

adult worms in the pulmonary arteries

what is the process of pulmonary hypertension caused by heartworm disease?

1. Immature adult worms initiate endothelial damage and vascular inflammation by causing eosinophilia

2. Activation of leukocytes and platelets to try and help with endothelial damage; proliferative factors released

3. Proliferative endarteritis

explain proliferative endarteritis in regards to pulmonary hypertension in canine heartworm

narrowing of vessels leads to increased vascular resistance and increased afterload

in regards to heartworm disease, what does higher vascular resistance often correlate with?

more severe heartworm case

what is the infective stage of the heartworm?

L3 stage transmited to new host when the vector mosquito feeds

how long after infection will the immature adult enter the vascular system of the host in regards to heartworm?

70-100 days

how long does it take for heartworms to mature in the host?

2-3 months

what determines the effect of primary damage in canine heartworm?

1. number of worms

2. duration of infection

3. reaction of host

flow (Q)

the volume of fluid (blood or air) passing through a vessel or airway per unit of time

what is the clinical significance of flow?

blood flow ensures oxygen and nutrients are delivered to tissues and waste products are removed

resistance (R)

the opposition to flow through a vessels or airway, often influenced by the diameter of the vessel or airway and the viscosity of the fluid

laminar flow

a smooth, orderly flow pattern in which fluid moves in parallel layers with minimal mixing

what characterizes laminar flow?

reynolds number less than 2000

what is the clinical significance of laminar flow?

predominant in small airways and blood vessels; disruptions can indicate pathology

compliance

the ability of a hollow organ to stretch and expand in response to pressure

compliance formula

change in pressure / change in volume