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Questions and Answers
What is the primary function of the right side of the heart?
Which component of blood constitutes the majority of total blood volume?
What role does the SA node play in the heart?
Which blood vessels primarily store blood in the circulatory system?
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What is a unique feature of the pulmonary artery?
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How does increased plasma volume affect blood dynamics?
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What is the function of the valves in the heart?
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What primarily determines the composition of the total blood volume in an individual?
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What is the primary reason the aorta is thicker than other blood vessels?
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Which function do arterioles perform during exercise?
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When does vasodilation typically occur in arterioles?
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How does exercise affect the amount of blood flow to the muscles?
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What role do valves in the venous system play?
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What is the equation that defines cardiac output?
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What mechanism helps prevent venous pooling when standing upright?
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What do we call the vessels that can control resistance to blood flow?
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Study Notes
Blood Vessels
- The aorta is the largest vessel in the body, with a diameter of 2.5cm. It has a thicker muscle wall than other vessels because it is under more pressure.
- Vessel diameter and thickness decrease as they branch away from the aorta. Capillaries are very small and thin, increasing surface area for diffusion.
- Arterioles control blood flow to individual organs, redistributing blood flow during exercise.
- Arterioles can be controlled extrinsically by the brain or intrinsically by the vessel itself.
- At rest, arterioles are vasoconstricted but vasodilate when more blood flow is needed to an organ.
- Vasodilation occurs when there are high levels of carbon dioxide (CO2) and low levels of oxygen (O2).
- Arterioles are known as resistance vessels because they can control the resistance to blood flow.
Blood Flow Redistribution During Exercise
- Exercise increases blood flow dramatically.
- Blood flow is redistributed from organs like the intestines to working muscles.
- The percentage of blood going to the brain stays the same, even though the overall blood volume increases.
- This redistribution ensures that working muscles receive adequate oxygen and nutrients, and waste products like CO2 are removed.
Venous System
- Venous system has low pressure, compared to the arterial system, making it easy to distend (stretch) and hold blood.
- Venous pooling occurs when blood accumulates in the lower limbs due to gravity, which is dangerous as it can lead to fainting due to reduced blood flow to the brain.
Muscle Pump
- The muscle pump helps prevent venous pooling by moving blood against gravity.
- Muscles squeeze the veins, forcing blood upwards.
- Valves in the veins prevent blood from flowing back down.
Cardiac Output (Q)
- Cardiac output (Q) is the total volume of blood pumped by each ventricle per minute.
- Q = heart rate x stroke volume (SV).
- Stroke volume (SV) is the volume of blood ejected by each ventricle with each beat.
- SV = end diastolic volume (heart relaxed) - end systolic volume (heart contracted).
Functions of Cardiovascular System
- Delivery: Oxygen and nutrients to muscles.
- Removal: CO2 from tissues to lungs and other waste products.
- Transport: Hormones.
- Maintenance: Homeostasis and pH balance.
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Protection:
- Hydration (blood plasma is mainly water)
- Fighting infection (white blood cells)
Components of the Cardiovascular System
- Closed Loop System: All parts of the system are connected.
- Fluid Medium: Blood.
- Channels: Blood vessels.
- Pump: Heart.
Structure of the Heart
- Two Sections (Two Pumps): Right side (deoxygenated blood) and left side (oxygenated blood).
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Right Side (Pulmonary):
- Receives deoxygenated blood from the body via the vena cava.
- Blood travels through the AV valve to the right ventricle.
- Blood is pumped to the lungs via the pulmonary artery (only artery carrying deoxygenated blood) for oxygenation.
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Left Side (Systemic):
- Receives oxygenated blood from the lungs via the pulmonary vein (only vein carrying oxygenated blood).
- Blood travels through the AV valve to the left ventricle.
- Blood is pumped to the body via the aorta.
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Other Features:
- Four valves prevent backflow of blood.
- A septum divides the heart into two sections. The left ventricle is thicker (more muscle) because it needs more force to pump blood throughout the body.
Electrical Activity of the Heart
- SA Node: The pacemaker of the heart, generating electrical signals that control heart rate.
- The electrical signal travels from the SA node to the AV node, then through the septum and out to the branches of the heart.
Composition of Total Blood Volume
- Plasma: Mostly water (55%), with the proportion varying depending on individual hydration.
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Formed Elements:
- Mostly red blood cells (over 99% of formed elements).
- White blood cells and platelets.
- Plasma volume increases more than red blood cell volume during hydration, leading to a decrease in the red blood cell percentage in the blood.
- This is beneficial because it increases blood volume overall, making it easier for blood to flow throughout the body.
Vascular System
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Blood Storage:
- Venous system: 64% of blood volume.
- Arterial system: 10% of blood volume.
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Description
This quiz covers important concepts related to blood vessels, including the structure and function of the aorta, arterioles, and capillaries. It also explores how blood flow is redistributed during exercise, focusing on the mechanisms of vasodilation and vasoconstriction. Test your knowledge on these critical aspects of human physiology!
