Week 5 - The Cardiovascular System Flashcards by Aaron Reber

What system does the CV system work closely with?

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

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What are the 3 main functions of the Cardiorespiratory system?

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

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

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

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Capillaries

exchange O2, CO2, and nutrients with tissues

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

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.

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

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)

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

a) Arteries
b) Capillaries
c) Veins

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How does reducing vessel diameter by half affect blood flow?

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

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Outline structural components of an artery and their importance.

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.

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

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.

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Describe the 4 components of blood?

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

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Hematocrit

% of blood composed of erythrocytes (42%)

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What is the mean arterial pressure of the systemic circuit?

100 mm Hg

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How does pressure change across the systemic circulation?

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.

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Resistance to flow

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

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Total peripheral resistance

sum of resistances to flow in all individual organs

Dary’s law

Blood flow = Pressure/Resistance

Relationship between blood flow, pressure and resistance.

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)

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

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

Local vascular resistance

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

Equation for resistance.

length x viscosity/ radius4

Sources of vascular resistance

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

Oxygen consumption equation

cardiac output x A-V oxygen difference

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

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.

Fick equation

relationship between cardiac output, a-VO2 difference, and V02 V02 = Q x a-v O2 difference

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?

- 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.

Baroreceptors

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

Muscle mechanoreceptors

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

Muscle chemoreceptors (muscle metaboreceptors)

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

Exercise pressor reflex

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

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

Baroreflex is reset during exercise

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

Central command and exercise pressor reflex

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

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.

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

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

Neural response of arterial baroreceptors to hypotensive stimulus.

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.

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

Mitral - left atrium to left ventricle Tricuspid - right atrium to right atrium Prevent backflow of blood from the ventricles into the atria.

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

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

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

In series

How are electrical impulses conducted between heart muscle cells?

by intercalated discs