Energy and Energy Loss

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What is pressure energy?

Stored (potential) energy that is not moving yet.

What creates pressure energy?

The heart contracting (squeezing).

What is the main form of energy carried by circulating blood?

Pressure energy.

What does pressure energy do?

It has the ability to do work and gets blood moving.

What is kinetic energy?

Energy an object has because it is moving.

What two things does kinetic energy depend on?

Mass and velocity.

How does mass affect kinetic energy?

More mass = more kinetic energy at the same speed.

How does velocity affect kinetic energy?

Faster velocity = more kinetic energy.

Why does a golf ball have more kinetic energy than a ping-pong ball moving at the same speed?

The golf ball has more mass.

What type of energy does blood have once it is flowing?

Kinetic energy.

What is gravitational energy?

Stored (potential) energy based on height or position.

How does height affect gravitational energy?

An object higher up has more gravitational energy relative to a lower position.

How does gravitational energy apply to blood?

Blood higher in the body

What are the three forms of energy in blood?

Pressure energy

What is the formula for total energy?

Total energy = pressure + kinetic + gravitational.

Why does blood flow?

Because total energy at one location is different from total energy at another location.

What is a pressure gradient?

A difference in energy/pressure between two locations that causes blood to move.

Does blood keep 100% of its energy as it travels through the body?

No

What are the three types of energy loss?

Viscous

What is viscosity?

How thick a fluid is.

How does thicker blood affect energy loss?

Thicker blood causes more viscous energy loss and more resistance to flow.

What is hematocrit?

The percentage of red blood cells in the blood.

What is the normal hematocrit approximately?

45%.

What happens when hematocrit increases?

Blood becomes thicker

What happens when hematocrit decreases?

Blood becomes thinner

What is anemia?

A condition involving a low hematocrit/red blood cell level.

Why does blood move more easily with anemia?

The blood is thinner

Why is the reduced viscous loss in anemia not necessarily a good thing?

It is caused by having too few red blood cells.

What is frictional loss?

Energy lost when blood energy is converted into heat because of friction.

What causes frictional loss?

Blood rubbing against vessel walls or against adjacent layers of blood.

How does friction occur during laminar flow?

Adjacent layers of blood slide past each other

What is inertial loss?

Energy lost when blood changes its velocity.

What is inertia?

A fluid's natural tendency to resist a change in its velocity.

When does inertial energy loss occur?

When blood speeds up or slows down.

What is pulsatile flow?

Blood flow that constantly speeds up and slows down in arteries with each heartbeat.

Why does pulsatile flow cause inertial loss?

Blood repeatedly changes velocity.

What is phasic flow?

Variable-speed blood flow in veins.

Why does phasic flow cause inertial loss?

The blood's velocity changes.

What happens to blood velocity at a stenosis?

It increases dramatically at the narrowest point.

Where is velocity highest in a stenosis?

At the narrowest part of the vessel.

What happens to blood velocity after a stenosis?

It decreases as the vessel widens again.

Why does stenosis cause inertial energy loss?

Blood speeds up at the narrowing and then slows down after it.