Lecture 18 - Cardiovascular System II

How many types of blood vessels are there at the basic level?

3

The same ______ layers are found in arteries and veins

Tissue

A?

Tunica interna (intima)

B?

Tunica media

C?

Tunica externa (adventitia)

Tissue layers of arteries differ based on their distance from the…

Left ventricle

Which is closer to the heart, elastic or muscular arteries?

Elastic

What does the elasticity or muscularity of a vessel contribute to

Blood pressure

The study of blood flow and the physical forces governing the cardiovascular system

Hemodynamics

Flow rate equation:

F= P/R

In the flow rate equation, what is F?

Flow rate

In the flow rate equation, what is P?

Pressure

In the flow rate equation, what is R?

Resistance

Volume of blood that passes per unit time

Flow rate

The force blood exerts against chamber/vessel walls

Pressure

Opposition or friction encountered by blood as it moves through the vessels

Resistance

Difference in pressure between the beginning and end of a blood vessel

Pressure gradient

What is the pressure here?

40 mmHg

What is the pressure here?

80 mmHg

Contraction of heart provides _____

Pressure

Pressure decreases as blood flows through vessels due to ______

Resistance

Measure of hindrance to blood flow caused by friction between the moving fluid and the stationary walls

Resistance

Higher resistance means_____ blood flow can pass through at a given pressure

Less

Friction between molecules

Viscosity

Is viscosity constant in blood?

Yes

Friction between blood and vessel

Vessel length & radius

What does resistance depend on?

Viscosity, vessel length, and radius

If a vessel's radius is halved (via vasoconstriction), the resistance to flow increases by __ times

16

Because of the Pressure, Resistance and total area of the tubes, the speed of blood flow varies in different parts of the _______ _______

Circulatory system

A?

Aorta

B?

Arteries

C?

Arterioles

D?

Capillaries

E?

Venules

F?

Veins

G?

Vena cava

A?

Left ventricle

B?

Large arteries

C?

Arterioles

D?

Capillaries

E?

Veins and venues

Volume of blood pumped per minute by each ventricle

Cardiac output

Cardiac rate x stroke volume

Cardiac output

Average resting cardiac rate

70 beats/min

Average stroke volume

78-80 ml per beat

Cardiac output in a resting adult

4-6 L/min

Cardiac output is equivalent to…

Blood volume in the body

To regulate the Cardiac Output you must regulate what additional factors?

Rate and/or the volume

Cardiac rate is regulated by…

Nerves and hormones

Stroke volume is regulated by…

Blood volume and vascular resistance

What regulates stroke volume in the short term?

Vascular resistance

What regulates stroke volume in the long term?

Blood volume

In absence of neural stimulation, heart will beat according to what?

SA node

If SA node was in complete control, would would happen to the heart rate

The heart rate would always be the same

Which two systems modify the heart rate?

Autonomic nervous system and endocrine system

What does the sympathetic nervous system release to increase heart rate?

Norepinephrine

What do the adrenal glands release to increase heart rate?

Epinephrine

What does the parasympathetic nervous system release to lower heart rate?

Acetylcholine

Does norepinephrine increase or decrease heart rate?

Increase

Does epinephrine increase or decrease heart rate?

Increase

Does acetylcholine increase or decrease heart rate?

Decrease

How is the cardiac rate regulated

ANS and hormones

What does nerve does the brain use to increase heart rate?

Sympathetic nerve

Does the sympathetic nerve increase or decrease heart rate?

Increase

What nerve does the brain use to decrease heart rate

Vagus nerve

Does the vagus nerve increase or decrease heart rate?

Decrease

What do the adrenal glands use to increase heart rate?

Adrenaline/epinephrine

A?

Parasympathetic nerve

B?

Sympathetic nerve

What will nerve “A” cause the heart rate to do?

Slow (parasympathetic)

What will nerve “B” cause the heart rate to do?

Increase (sympathetic)

What 3 factors regulate stroke volume?

Contractility, End Diastolic Volume (EDV), Total Peripheral Resistance (TPR)

The strength of ventricular contraction

Contractility

The amount of blood in the ventricles just before they contract (end of diastole)

End Diastolic Volume (EDV)

The pressure the ventricles have to work against (afterload)

Total Peripheral Resistance (TPR)

Any force that causes the ventricles to contract with more force will increase ______ _______

Stroke volume

Any force that causes the ventricles to contract with more force will increase stroke volume; this in turn increases ______ ______

Cardiac output

ANS control of stroke volume regulated almost entirely by which nervous system

Sympathetic

Does epinephrine increase or decrease contraction strength

Increase

A number of hormones increase ventricular contractility, list 3

Insulin, glucagon, thyroid hormone

Force of ventricular contraction varies in response to stretching of what?

Ventricular wall

“When the rate at which blood flows into the heart from the veins (venous return) changes, stretching of the ventricular wall changes, causing the ventricle to contract with greater or lesser strength so that the stroke volume (output) matches the venous return (input).” What law is this?

Starling’s law

According to Starling’s law, if the amount of blood that returns increases, cardiac muscle will

contract ______ to compensate

More

Increased blood volume =

Increased myocardial stretch

Increased myocardial stretch =

Increased force to pump blood out

Starling’s law, in simple terms

The more a heart fills, the stronger the force of contraction

Stroke volume also depends on amount of ____ opposing contraction

Force

Increased arterial pressure causes stroke volume to ______

Decrease

Where is TPR (afterload) determined after contraction starts?

Aorta

Increased resistance=

Increased pressure

Increased pressure=

Increased afterload

Increased afterload =

Decreased stroke volume

What 3 factors regulate blood pressure?

Blood volume, peripheral resistance, cardiac rate

An increase in blood volume, peripheral resistance, cardiac rate, would increase what?

Blood pressure

Blood volume can be regulated by what organ(s)?

Kidneys

What increases total peripheral resistance? (TPR)

Vasoconstriction

Which nervous system increases cardiac output and raises blood pressure?

Sympathetic system

How are changes in blood pressure detected?

Baroreceptors

Stretch receptors located in the aortic arch and the carotid sinuses

Baroreceptors

Where are baroreceptors located?

Aortic arch and carotid sinuses