Week 5 - The Cardiovascular System

Question 1

What system does the CV system work closely with?

Answer 1

Pulmonary system/respiratory system known as cardiopulmonary or cardiorespiratory system.

Question 2

What are the 3 main functions of the Cardiorespiratory system?

Answer 2

• Transport of O2 and nutrients to tissues
• Removal of metabolic wastes from tissues (CO2).
• Regulation of body temperature.

Question 3

What are the two major adjustments of blood flow during exercise?

Answer 3

• Increase cardiac output
• Redistribution of blood flow from inactive organs to active muscle

Question 4

Capillaries

Answer 4

exchange O2, CO2, and nutrients with tissues

Question 5

Pulmonary circuit of the circulatory system
- Side of the heart?
- What type of blood does it pump and where?
- What blood returns and where?

Answer 5

• Right side of the heart
• Pumps deoxygenated blood from right ventricles to the lungs via pulmonary arteries.
• Returns oxygenated blood to the left atrium of the heart via pulmonary veins.

Question 6

Systemic circuit of the circulatory system
- Side of the heart?
- What type of blood does it pump and where?
- What blood returns and where?

Answer 6

• Left side of the heart
• Pumps oxygenated blood from the left ventricle to the whole body via the aorta (largest artery in body).
• Returns deoxygenated blood to the right atrium of the heart via the vena cavae - superior vena cava returns blood from head, neck and arms + inferior vena cava returns blood from lags and lower torso (largest vein)

Question 7

Match each description to a blood vessel:
a) resistance vessels
b) exchange vessels
c) capacitance vessels

Answer 7

a) Arteries
b) Capillaries
c) Veins

Question 8

How does reducing vessel diameter by half affect blood flow?

Answer 8

If we half vessel diameter and thus vasoconstrict blood vessels, this decreases blood flow by around 16 times.

Question 9

Outline structural components of an artery and their importance.

Answer 9

1) Surrounded by collagen and elastin: important role in helping the arteries to deal with high pressure of blood entering from the left ventricle.

2) Endothelium layer which is the tissue in direct contact with the blood: its important as blood flow over the endothelium triggers a cascade of physiological responses which mean the blood vessels are able to vasodilate and get blood flow to working muscles.

3) Smooth muscle: its important in the arteries ability to change resistance and therefore be able to redistribute blood flow from inactive organs to the working muscles.

Question 10

What two structural components of capillaries help the exchange of nutrients and gases in the capillaries?

Answer 10

1) Thin endothelial layer and small diameter: only big enough for 1RBC therefore rbc close to border of the capillary and surrounding tissue which aids gaseous exchange.

2) Slow speed of travel: gaseous exchange to surrounding tissues.

Question 11

Describe the 4 components of blood?

Answer 11

1) Plasma: liquid proportion of blood (55%), contains ions, proteins and hormones.

2) RBC/erythrocytes: contain hemoglobin to carry oxygen

3) WBC: important in preventing infection

4) Platelets: important in blood clotting.

The two principal components: plasma and cells

Question 12

Hematocrit

Answer 12

% of blood composed of erythrocytes (42%)

Question 13

What is the mean arterial pressure of the systemic circuit?

Answer 13

100 mm Hg

Question 14

How does pressure change across the systemic circulation?

Answer 14

Mean arterial pressure decreases

• Pressure is high as the blood leaves the left ventricle of the heart (100 mm Hg)
• The main resistance to flow is by arteries and arterioles (resistance vessels).
• Pressure decreases across capillaries, venules and large veins and pressure returning to the heart (vena cava) is 0 mm Hg.

Question 15

Resistance to flow

Answer 15

measure of hindrance or opposition to blood flow through a vessel, caused by friction between the blood in the vessel wall.

Question 16

Total peripheral resistance

Answer 16

sum of resistances to flow in all individual organs

Question 17

Dary’s law

Answer 17

Blood flow = Pressure/Resistance

Question 18

Relationship between blood flow, pressure and resistance.

Answer 18

Blood flow is:
- directly proportional to the pressure difference between the two ends of the system (P1-P2, the pressure gradient) (e.g. left ventricle and right atrium).
- Inversely proportional to resistance.

Pressure is proportional to the difference between MAP (100mmHg) and right atrial pressure (0mmHg)

Question 19

What 3 factors does resistance depend on? - which one is the most important factor?

Answer 19

1) Length of the vessel
2) Viscosity of the blood
3) Radius of the vessel (greatest influence)

Question 20

Local vascular resistance

Answer 20

the resistance to blood flow in an organ or tissue calculated from pressure and local organ/tissue flow.

Question 21

Equation for resistance.

Answer 21

length x viscosity/ radius4

Question 22

Sources of vascular resistance

Answer 22

• MAP decreases throughout the systemic circulation.
• Largest BP drop and vascular resistance to blood flow occurs across the arterioles (resistance vessels).

Question 23

Oxygen consumption equation

Answer 23

cardiac output x A-V oxygen difference

Question 24

Arteriovenous difference (a-vO2) - Define it and explain the influence of exercise.

Answer 24

Amount of oxygen that is taken up from 100ml of blood (difference between oxygen content of blood between arterial blood and venous blood).
Increases during exercise due to increased oxygen uptake in tissues which is used for oxidative ATP production.

Question 25

Fick equation

Answer 25

relationship between cardiac output, a-VO2 difference, and V02

V02 = Q x a-v O2 difference

Question 26

Central command theory of CV control - Where does the initial signal to “drive” CV system at the beginning of exercise come from? CV response/control is then fine-tuned by what afferent feedback systems?

Answer 26

• Higher brain centers due to centrally generated motor signals at the onset of exercise
• Heart mechanoreceptors, muscle chemoreceptors, and baroreceptors feedback to the CV control center.

Question 27

Baroreceptors

Answer 27

sensitive to changes in arterial blood pressure and try to maintain BP homeostasis

Question 28

Muscle mechanoreceptors

Answer 28

consist of muscle spindles and golgi tendon organs
they are sensitive to force and speed of muscular movement

Question 29

Muscle chemoreceptors (muscle metaboreceptors)

Answer 29

sensitive to changes in chemical environment (H+ ions, C02, changes in pH)

Question 30

Exercise pressor reflex

Answer 30

peripheral feedback to the medulla oblongata to amend the CV response to exercise

Question 31

If baroreceptors work rapidly to maintain BP homeostasis, why do we see a continued increase in systolic BP with exercise?

Answer 31

Baroreflex is reset during exercise

Question 32

What two factors play an active role in resetting the arterial baroreflex during exercise?

Answer 32

Central command and exercise pressor reflex

Question 33

Describe the concept of the cardiovascular system using the water tower analogy.

Answer 33

Heart (pump) pumps out blood from left ventricle to the aorta (water tower) at high pressures. The aorta then sends the blood through the arterioles (faucets) which is responsible for controlling blood flow to the correct tissues. The blood is used in capillary beds (sinks) where its taken up by surrounding tissues/organs (houses). Remaining blood flows out into the venules controlled by skeletal muscle pump (accessory pump) which returns blood into large veins to return to the heart.

Baroreceptors (sensor) detect the pressure in the aorta and feedback to the medulla oblongata (controller) which can either increase HR/contractility of the heart or activate the sympathetic NS to vasoconstrict arterioles to change flow to different vascular beds of the human body.

Question 34

Are tissues/organs arranged in parallel or in series? What does this mean?

Answer 34

In parallel - this means that each tissue/organ receives its own supply of oxygenated blood from the heart.

Question 35

Neural response of arterial baroreceptors to hypotensive stimulus.

Answer 35

Aortic arch and carotid sinus baroreceptors detect hypotensive stimulus (low bp) they increase sympathetic cardiac nerve activity which increases total pressure resistance, by vasoconstricting blood vessels, and increase cardiac output. This results in an increase in BP back to normal.

Question 36

What are the two atrioventricular valves? What are their roles?

Answer 36

Mitral - left atrium to left ventricle
Tricuspid - right atrium to right atrium

Prevent backflow of blood from the ventricles into the atria.

Question 37

What are the two semilunar valves? What are their roles?

Answer 37

Aortic semilunar vale located between the aorta and the left ventricle of the heart
Pulmonary semilunar valve is located between the pulmonary artery and right ventricle of the heart

prevent backflow of blood from the heart’s major arteries into the ventricles

Question 38

The heart pumps blood into two different circulations: pulmonary and systemic. Are the two pumps arranged in series or in parallel?

Answer 38

In series

Question 39

How are electrical impulses conducted between heart muscle cells?

Answer 39

by intercalated discs