Vascular Physics (Exam 1) Anatomy Class

What system does circulation flow in? What does it have?

A closed system pathway

Has an energy gradient

Cardiovascular circulation is influenced by

Cardiac function

Elasticity of walls (compliance)

Smooth muscle tone

Vessel dimensions

Blood moves from ___ pressure to ___ pressure

High to low pressure

Name the vessels from highest to lowest pressure

Aorta (heart)

Arteries

Arterioles

Capillaries

Venules

Veins

Vena cava

What is energy?

Capability of doing work

How does energy dissipate?

Dissipates in form of heat

Energy is lost via friction

What is power?

How fast work is performed

Unit of power

Watts = Joules / Seconds

What is work?

Total energy transferred from one form to another over time

Unit for work

Joules

What is velocity?

Speed that blood is moving

Unit for velocity

Cm / second

What is potential energy?

Stored energy

Unit for potential energy

mm/Hg AKA millimeters of mercury

What does mm/Hg represent?

Force exerted on vessel walls

What is kinetic energy?

Energy due to its motion

Movement & velocity of blood

What is total energy?

Potential energy + Kinetic energy = Total energy

What is total energy always equal to?

100

If potential energy decreases, then kinetic energy _____?

Increases

What relationship does potential & kinetic energy have?

Inverse relationship

If one increases, the other decreases

Total will always come out to 100

What is pressure?

Amount of force on a vessel

Unit for pressure

mm/Hg

What gradient is needed for blood flow?

Pressure gradient

More pressure gradient causes _____ blood flow

More blood flow

More resistance causes ____ pressure gradient

More

What does Q, P, and R stand for in equations?

Q = flow

P = pressure

R = resistance

What is hydrostatic pressure?

Plays a role in blood flow

Pressure from fluid at rest due to force of gravity

Ex: standing all day causes swollen legs due to hydrostatic pressure

Factors of hydrostatic pressure

Height of vessel (h)

Density of blood (p)

Gravity (g)

What is volumetric flow (Q)?

Flow rate

Units for volumetric flow (Q)

mL/sec

What is viscosity? What does it cause?

Blood thickness

Causes flow resistance

What’s a product of viscosity?

Heat

Unit for viscosity

Poise

Higher viscosity = ____ velocity

Higher viscosity = LESS velocity

Lower viscosity = _____ velocity

Lower viscosity = higher velocity

Relationship between viscosity & velocity

Inverse relationship

What is friction?

Resistance of movement between cell layers or vessel walls

What affects friction & resistance?

Diameter

Thinner diameter means ___ flow & ___ resistance

Less flow & more resistance

Larger diameter means ___ flow & ___ resistance

More flow & less resistance

What is laminar flow?

Results from friction

Blood flow closest to the vessel wall has less blood flow, and more friction & resistance (from rubbing against vessel wall)

Where is the most blood flow?

Center of the vessel

What area has the most accurate blood velocity?

Center of the vessel

What is inertia?

Resistance of blood flow to directional change or speed

What begins initial inertia?

Aorta

Can energy be created or destroyed?

No, it just takes on different forms (potential energy to kinetic)

Net energy never changes (always at 100%)

What is Bernoulli’s Principle? What relationship does it have?

Pressure/velocity relationships

Inversely related

Maintains same energy throughout

What energy is velocity considered as?

Kinetic energy

What energy is pressure considered as?

Potential energy

If velocity increases, pressure must ____ to preserve net energy

Decrease

(Based on Bernoulli’s principle)

What relationship does pressure & velocity have?

Inverse

High pressure means ___ velocity

Low pressure means ____ velocity

High pressure = low velocity

Low pressure = high velocity

At site of blockage or stenosis, how is the pressure and speed?

Lower pressure & Higher speed

Right BEFORE & AFTER, the site of stenosis, how is the pressure and speed?

Higher pressure & Lower speed

At what site is potential energy the lowest?

At the site of stenosis (where kinetic energy is highest)

What is Poiseuille’s Law?

Relationships between pressure, flow volume, & resistance

What is vessel radius?

r^4

(radius to the fourth power)

Causes a pressure gradient

Is vessel radius directly or indirectly proportional to flow velocity?

Indirectly proportional to flow velocity

Other conditions that affect flow

Viscosity & length of vessel

Anything that increases friction will cause flow to ____

Decrease

What is resistance?

Force opposing blood flow (impedance)

What influences resistance?

Arterioles (60%)

Highest resistance vessels due to their radius & walls

Is flow directly or inversely proportional to resistance?

Inversely proportional

More resistant = less flow

Less resistant = more flow

What factors increase resistance?

Smaller radius

Longer vessel

Thicker fluid

What determines amount of blood leaving the heart?

Arterial pressure & peripheral resistance

What is peripheral resistance?

Pushback at the end

Does resistance increase or decrease as we go further from the heart?

Increase since vessels continue to split and narrow

What Doppler flow does peripheral resistance affect?

Diastolic

Peripheral resistance flow reversal at rest vs. after exercise?

At rest, LE has reversal component

After exercise, little to no flow reversal

How does higher resistance affect flow, velocity, and pressure?

Higher resistance = higher velocity, but less flow & pressure

What happens in fight or flight response?

Hypothalamus activates adrenal gland & produces epinephrine

Stimulates sympathetic nervous system

Vasodilation or constriction of vessels

What happens during sympathetic nervous system?

Increased blood flow to muscles & brain

Increased heart rate

Dilated pupils & respiratory passage

Sweat glands stimulated

Vasoconstriction of blood vessels

What happens in parasympathetic system?

Opposite of sympathetic

How to control BP?

Change blood vessel diameter & blood distribution

Sympathetic & parasympathetic activity affects ____, ____, and ____ to control HR & force of contraction?

Veins, arteries, and heart

What is compliance? How much more can veins stretch than arterial?

Ability to stretch

Venous = 20x larger than arterial

What is capacitance?

Change in fluid volume over time

“Capacity”

Venous system has ____% of blood volume

70%

Holds onto blood until needed

In curved vessels, how is the velocity on the outer edges?

Higher velocity at outer edge of vessel

Explain direction of blood flow & pressure distribution in Laminar Flow

Blood moves in uniform direction

Pressure equally distributed throughout & exerts force in all directions