Introduction to Cardiovascular Physiology Lecture Sep 16

Question 1

What is the primary role of the cardiovascular system?

Answer 1

it provides a mass transit system to move materials around the body and an exchange surface for movement of materials into and out of the vascular space.

Question 2

Explain the relative percentages of water in the intracelular, extra-cellular, interstitial, and plasma spaces

Answer 2

intracellular water is about 66%

Extra cellular water is about 33%

The extracellular water can be divided into interstitial water and plasma water. THe total blood volume is about 5 liters

Question 3

How are the pulmonary and systemic circulations arranged? How is the circulation to systemic organs arranged? WHy is this significant for overal circulation?

Answer 3

The pulmonary circulation and the systemic circulation are arranged in series.

Systemic organs represent individual circulations arranged in parallel.

This allows
blood flow to individual systemic organs to be independently controlled.

Question 4

What two variables determine the flow through the CV system?

Answer 4

Flow through a tube is directly proportional to the pressure difference across the tube and inversely proportional to the resistance offered by frictional forces at the surface.

Question 5

What equation describes flow through the CV system?

Answer 5

FLOW = ∆P/R

Question 6

What is flow through the circulation equal to?

Answer 6

cardiac output from the heart pump (right and left heart output are equal here)

Question 7

What is resistance in the circulation a result of?

What is the term for this?

Answer 7

it’s the result of frictional forces as blood passes through the consecutive segments (artery, arteriole, capillary, veings)

This is called total peripheral resistance (TPR)

Question 8

What is the controllable variable in the CV system?

Answer 8

the mean arterial pressure (MAP)

Question 9

How is the basic flow equation rearranged to determine Mean arterial pressure?

Answer 9

MAP = CO x TPR

with CO being cardiac output and TPR being total peripheral resistance

Question 10

Describe the path of blood through the CV system starting at the vena cava.

Answer 10

1. Deoxygenated blood from the extremities and lower organs enter through the inferior vena cava, while blood from above the heart enters through the super vena cava
2. Blood from the vena cavas are dumped into the right atrium.
3. It is then pumped form the right atrium into the right ventricle through the tricuspid valve
4. Blood from the right ventricle is pushed up through the pumononic valve into the pulmonary artery which will bring it to the lungs for oxygenation.
5. Blood that has been oxygenated will be pumped back into the heart through the pulmonary veings into the left atrium
6. The blood will then be pumped through the mitral valve to the left ventricle
7. the left ventricle will pump the blood up through the aortic valve into the aorta, which will carry the blood into circulation: aorta > arteries > arterioles > capillaries > venuoles > veine > vena cava…repeat

Question 11

What two variables determine cardiac output?

What is the CO equation?

Answer 11

stroke volume (SV) – volume per beat

heart rate (HR) - beats per minutes

CO = HR x SV

Question 12

What happens in ventricular systole?

WHat happens in ventricular diastole?

Answer 12

During ventricular diastole, the pressur in the left atrium is higher than the pressure in the left ventricle. THis pushes the inlet valve open, allowing blood form the atrium into the ventricle.

When pressure in the ventricle reaches a certain point, the mitral valve will close

(diastole is the filling of the ventricle)

During ventricular systole, the pressure is now higher in the left ventricle than it is in the aorta, so the aortic valve opens and blood is pumped up and out into the aorta.

when pressure decreases in the ventricle, the aortic valve closes and the cycle repeats

Question 13

What will you hear in a heart whose valves have stenosis?

Answer 13

a systolic murmur

Question 14

Describe the excitable properties of the heart

Answer 14

Heart rate is established by pacemaker cells in the sinoatrial node in the right ventricular wall.

These spontaneously depolarize and reach a threshold and fire off an action potential. (normal rate is 60 bpm–10 bp originally, but vagus nerve keeps it down to 60)

The action potentials are then conducted throguh electrical connections from cell to cell, which makes a wave of excitation that spreads through the atrium, the septum, and out into the ventricular muscles.

This can be monitored by EKG

Question 15

What determines arterial pressure?

Answer 15

how much blood enters (CO) and how easily it can flow through the system (TPR)

Question 16

What are the primary roles for the following:

arteries

aterioles

capillaries

veins

Answer 16

Arteries – conduit vessels
Arterioles – resistance vessels
Capillaries – exchange vessels
Veins - capacitance vessels

Question 17

Capillaries have the smallest diameter, so why don’t they have the highest resistance?

What does have the highest resistance in the CV system?

Answer 17

Capillaries have such a vast cross sectional area that net resistance is actually quite low.

The arterioles have the highest resistance in the system

Question 18

When at rest, where is most of the blood in our bodies? why?

Answer 18

Most of it is in veins because veings ar emore compliant and will hold more.

Question 19

WHat is the average mean arterial pressure?

Answer 19

100 mmHg

Question 20

What does short term control of MAP depend on?

What does long term control of MAP depend on?

Answer 20

Short-term (acute) control of arterial pressure depends primarily upon the operation of the arterial baroreceptor reflex.

Long-term (chronic) control of arterial pressure depends primarily on control of blood volume which depends upon the operation of the kidneys.

Question 21

Describe the aterial baroreceptor reflex.

Answer 21

1. There are baroreceptors in the aortic arch and in the carotid sinuses.
2. WHen blood pressure goes up, the vessels will stretch, causing the baroreceptors to fire action potentials. When blood pressure decreases, the baroreceptors will not fire as rapidly.
3. THe APs are conducted to the medulla, which will be able to tell if the action potentials are not coming fast enough.
4. If that is the case, the medulla will turn on sympathetic nerves that will increase the stroke volume and heart rate in order to increase cardiac output and MAP.

Question 22

Where is the set point for mean arterial pressure established?

Answer 22

It’s established in the medullary cardiovascular center.

Question 23

Which branch of the autonomic nerbous system will work to increase blood pressure?

Which will branch will work to decrease blood pressure?

Answer 23

The sympathetic will try to increase blood pressure

the parasympathetic will try to decrease blood pressure

Question 24

What happens to heart rate when you stand up from a sitting position?

Why? (Mechanistically)

Answer 24

Heart rate increases.

1. WHen you stand up, blood shifts from the central venous pool to the feet due to gravity
2. This causes an increase in the venous pressure in the lower extremities and decreases central venous pressure (which is where the sensors are)
3. The decrease in central pressure will decrease the cardiac output and arterial pressure will fall as well.
4. THe firing of the baroreceptors will decrease, which the medulla will sense
5. In response, the medulla will increase sympathetic activity and decrease parasympathetic activity
6. Sympathetic nervous system will:
   - increase heart rate
   - increase contractility
   - increase venous construction
   - increase arteriolar constriction
   - increase fluid retention from the kidney (this one is more long term)

Question 25

Why do people who are bed ridden becomes very dizzy when sitting up?

Answer 25

Being bed ridden promptes fluid loss and dehydration. When you’re dehydrated you don’t have enough blood volume to compensate for the decrease in central venous pressure when you stand up.