Week 9 Flashcards
1
Q
What are the two main functions of the heart in circulation?
Back:
A
- The right side pumps deoxygenated blood to the lungs (pulmonary circulation).
- The left side pumps oxygenated blood to the body (systemic circulation).
2
Q
Name the four chambers of the heart and their roles.
A
- Right atrium: Receives deoxygenated blood from the body
- Right ventricle: Pumps blood to the lungs
- Left atrium: Receives oxygenated blood from lungs
- Left ventricle: Pumps blood to the body
3
Q
What are the four heart valves and their functions?
A
- Tricuspid valve: Right atrium → right ventricle
- Pulmonary valve: Right ventricle → pulmonary artery
- Mitral valve: Left atrium → left ventricle
- Aortic valve: Left ventricle → aorta
(All prevent backflow of blood)
4
Q
What is the role of the superior and inferior vena cava?
A
They deliver deoxygenated blood from the body to the right atrium.
5
Q
Describe the journey of blood through the right side of the heart.
A
Blood enters right atrium → tricuspid valve → right ventricle
Right ventricle contracts → pulmonary valve opens
Blood is sent to lungs via pulmonary arteries
6
Q
Describe the journey of blood through the left side of the heart.
A
Oxygenated blood enters left atrium via pulmonary veins
Mitral valve opens → blood enters left ventricle
Left ventricle contracts → aortic valve opens → blood goes to body via aorta
7
Q
What occurs during atrial systole?
A
The atria contract, pushing blood into the ventricles through the tricuspid and mitral valves.
8
Q
What occurs during ventricular systole?
A
The ventricles contract, closing AV valves and opening pulmonary and aortic valves to eject blood.
9
Q
What is the role of the pulmonary veins?
A
They carry oxygen-rich blood from the lungs to the left atrium
10
Q
What is the function of the septum in the heart?
A
It separates the right and left sides of the heart, preventing mixing of oxygenated and deoxygenated blood.
11
Q
What is the main function of the heart valves?
A
To ensure unidirectional blood flow through the heart by opening to allow blood through and closing to prevent backflow.
12
Q
What controls heart valve movement?
A
Valve action is passively controlled by pressure changes in the heart chambers.
13
Q
What are the four heart valves and their locations?
A
- Tricuspid valve: Right atrium → right ventricle
- Pulmonary valve: Right ventricle → pulmonary artery
- Mitral (bicuspid) valve: Left atrium → left ventricle
- Aortic valve: Left ventricle → aorta
14
Q
How many leaflets (cusps) does each valve have?
A
Tricuspid: 3 cusps
Pulmonary: 3 cusps
Mitral: 2 cusps
Aortic: 3 cusps
15
Q
What causes the first heart sound (LUB)?
A
Closure of atrioventricular (AV) valves:
Tricuspid and Mitral valves
Occurs at the start of ventricular systole.
16
Q
What causes the second heart sound (DUB)?
A
Closure of semilunar valves:
Pulmonary and Aortic valves
Occurs at the start of ventricular diastole.
17
Q
What determines if a valve opens or closes?
A
Opens: When pressure behind the valve is greater than in front
Closes: When pressure in front exceeds that behind
18
Q
What is the intrinsic conduction system of the heart?
A
A network of specialized cardiac muscle cells that initiates and coordinates the heartbeat, enabling the heart to contract rhythmically without external stimulation.
19
Q
What is the function of the SA node?
A
The SA node (sinoatrial node) is the natural pacemaker of the heart. It generates electrical impulses that cause the atria to contract.
20
Q
What is the role of the AV node?
A
The AV node delays the electrical impulse, allowing the atria to fully contract and push blood into the ventricles before they contract.
21
Q
List the conduction pathway of the heart in order.
A
SA node →
Atria →
AV node →
Bundle of His →
Left & Right bundle branches →
Purkinje fibres →
Ventricular contraction
22
Q
What do the waves of an ECG represent?
A
P wave: Atrial depolarization
P-Q segment: Signal delay at AV node
QRS complex: Ventricular depolarization & atrial repolarization
T wave: Ventricular repolarization
23
Q
What is preload (EDV) in the heart?
A
Preload is the end-diastolic volume—the amount of blood in the ventricles before they contract. It affects stroke volume via the Frank-Starling law.
24
Q
What is afterload in the heart?
A
Afterload is the resistance the ventricles must overcome to eject blood, primarily determined by arterial pressure (e.g., in the aorta or pulmonary artery).
25
What is contractility?
Contractility refers to the force of heart muscle contraction, independent of preload and afterload, and is influenced by calcium availability and sympathetic stimulation.
26
What does the QRS complex represent on an ECG?
Ventricular depolarization (contraction) and simultaneous atrial repolarization (relaxation).
27
What ensures coordinated contractions of the atria and ventricles?
The intrinsic conduction system ensures the atria contract first, followed by the ventricles, allowing efficient blood flow through the heart.
28
What is the cardiac cycle?
The cardiac cycle includes all events in one complete heartbeat, involving atrial and ventricular systole (contraction) and diastole (relaxation).
29
What happens during atrial diastole?
Atria are relaxed and passively fill with blood from the body (right atrium) and lungs (left atrium). AV valves are closed initially.
30
What triggers atrial systole, and what occurs during it?
Triggered by SA node depolarization; atria contract, pushing blood into ventricles as AV valves open.
31
What is ventricular diastole, and what is EDV?
Ventricles relax and fill with blood; AV valves open once ventricular pressure drops. End-Diastolic Volume (EDV) is the blood volume in the ventricles at the end of diastole (preload).
32
What is isovolumetric contraction in ventricular systole?
Ventricles begin to contract; AV valves close, semilunar valves remain closed, volume stays the same while pressure builds.
33
What happens during the ejection phase of ventricular systole?
Ventricular pressure exceeds arterial pressure; semilunar valves open and blood is ejected. Remaining blood is the end-systolic volume (ESV).
34
What does the Wiggers Diagram illustrate?
It shows the relationship between ECG signals, heart sounds, pressure changes, and ventricular volume during the cardiac cycle—primarily using the left side of the heart.
35
What is the formula for calculating cardiac output (CO)?
Cardiac Output (CO) = Heart Rate (beats/min) × Stroke Volume (L/beat)
36
What is heart rate and what regulates it?
Heart rate is the number of heartbeats per minute. It is regulated by the sinoatrial (SA) node and modulated by the autonomic nervous system and hormones (e.g., adrenaline).
37
What is stroke volume (SV)?
Stroke volume is the volume of blood ejected from one ventricle with each heartbeat.
38
Name the three main factors that influence stroke volume.
Contractility
End-diastolic volume (Preload)
Afterload
39
How does contractility affect stroke volume?
Increased contractility results in a stronger contraction, increasing stroke volume.
40
What is preload and how does it affect stroke volume?
Preload is the volume of blood in the ventricles at the end of diastole. The higher the preload (end-diastolic volume), the stronger the contraction, increasing stroke volume (Frank-Starling mechanism).
41
What is afterload and how does it affect stroke volume?
Afterload is the pressure the ventricles must overcome to eject blood. Increased afterload makes it harder to eject blood, potentially reducing stroke volume.
42
What is venous return and why is it important?
Venous return is the flow of blood back to the heart through the veins. It is crucial for maintaining stroke volume, blood pressure, and overall cardiac output.
43
How does venous return relate to stroke volume?
An increase in venous return leads to an increase in stroke volume, as more blood filling the heart during diastole stretches cardiac muscle fibers, resulting in a stronger contraction (Frank-Starling mechanism).
44
What is the function of vein valves in venous return?
Vein valves prevent backflow of blood, ensuring unidirectional flow towards the heart, and help overcome the effects of gravity, especially in the lower body.
45
How does the skeletal muscle pump aid venous return?
Contractions of skeletal muscles compress nearby veins, pushing blood toward the heart. One-way valves prevent backward flow, especially during physical activity.
46
How does the respiratory pump help in venous return?
During inhalation, the diaphragm moves downward, increasing abdominal pressure and decreasing thoracic pressure, creating a pressure gradient that moves blood from abdominal veins to the heart.
47
What are the physiological benefits of venous return?
Venous return supports effective circulation, ensures adequate preload (ventricular filling), contributes to optimal cardiac output, and helps maintain stable blood pressure during both rest and activity.
48
What is the main function of blood vessels?
Blood vessels form a closed circulatory system that transports blood throughout the body, delivering oxygen, nutrients, and hormones while removing waste products.
49
What are the three main types of blood vessels?
Arteries - Carry blood away from the heart
Capillaries - Microscopic vessels for gas and nutrient exchange
Veins - Carry blood toward the heart
50
What type of blood do arteries typically carry?
Arteries usually carry oxygen-rich blood, except for the pulmonary arteries, which carry oxygen-poor blood.
51
What is the primary function of capillaries?
Capillaries are the site of gas exchange and nutrient/waste transfer between the blood and tissues. Their walls are one cell thick to allow efficient diffusion.
52
How do veins differ from arteries in structure?
Veins have thinner walls and less elastic tissue compared to arteries. They also contain valves to prevent the backward flow of blood, particularly in the limbs.
53
What are the three layers in the walls of arteries and veins?
Tunica Intima - Endothelium lining
Tunica Media - Smooth muscle and elastic fibers
Tunica Externa - Connective tissue for support
54
What is the role of valves in veins?
Valves prevent the backward flow of blood, ensuring unidirectional flow, especially in veins of the limbs.
55
How do capillaries facilitate gas and nutrient exchange?
Capillaries have a single layer of endothelial cells, which allows rapid diffusion of oxygen, nutrients, carbon dioxide, and waste products between the blood and tissues.
56
How are arteries structured to withstand high pressure?
Arteries have thick, elastic walls composed of smooth muscle and elastic fibers that allow them to withstand and maintain the high pressure generated by the heart's pumping action.
57
What role do arteries play in blood flow regulation?
Arteries are responsible for carrying oxygenated blood to various parts of the body and regulating blood flow through smooth muscle contraction and relaxation to maintain pressure.
58
What is Mean Arterial Pressure (MAP)?
MAP represents the average arterial pressure throughout one cardiac cycle. It provides a better estimate of tissue perfusion than systolic or diastolic pressure alone.
59
Why is MAP important for tissue perfusion?
A MAP of at least 60 mmHg is required to maintain adequate organ perfusion and supply blood to vital organs.
60
How is MAP calculated?
MAP ≈ Diastolic Pressure + 1/3 (Systolic – Diastolic). It reflects the fact that the heart spends more time in diastole than systole.
61
What is the normal range for MAP?
The normal MAP is approximately 70–100 mmHg.
62
How do systolic and diastolic pressures differ in blood pressure?
Systolic Pressure: Peak pressure during heart contraction (100–140 mmHg)
Diastolic Pressure: Minimum pressure during heart relaxation (60–90 mmHg)
63
What creates and maintains the pressure gradient in the circulatory system?
The pressure gradient is created by:
The pumping action of the heart
The resistance offered by blood vessels, especially arterioles.
64
Why are arteries referred to as pressure reservoirs?
Arteries have thick, elastic, and muscular walls that expand to absorb pressure during systole and recoil during diastole, helping to maintain continuous blood flow.
65
What happens to pressure as blood flows through the arterial pathway?
Pressure gradually decreases from arteries to arterioles to capillaries due to friction between blood and vessel walls and increasing resistance in smaller vessels.
66
Why are veins referred to as volume reservoirs?
Veins have thin, stretchable walls that allow them to store a large volume of blood without significantly increasing pressure. About 60–70% of blood volume resides in veins at rest.
67
How does the pressure compare between the arterial system and the venous system?
Arterial system: High pressure
Venous system: Low pressure
68
How do the wall structures of arteries and veins differ?
Arteries: Thick, muscular, and elastic
Veins: Thin and compliant
69
What is blood volume in relation to MAP?
The amount of blood pumped per minute by each ventricle. The cardiovascular system is a closed system - the more fluid in the closed system, the greater the pressure
70
What is total peripheral resistance in relation to MAP?
The resistance to blood flow in the systemic circulation. If resistance increases with vasoconstriction (i.e. the diameter of the blood vessels decreases), MAP increases
71
What is cardiac output in relation to MAP?
The amount of blood pumped per minute by each ventricle. The higher the cardiac output, the higher the MAP, as there is more blood being pumped through the vessels
72
What is the baroreceptor reflex?
A rapid negative feedback mechanism that helps maintain stable blood pressure by adjusting heart rate, stroke volume, and vascular resistance.
73
Where are baroreceptors located?
Baroreceptors are stretch receptors located in the aortic arch and carotid bodies.
74
What happens when blood pressure increases in the baroreceptor reflex?
Baroreceptors detect stretch and signal the brain.
Parasympathetic stimulation: Decreases heart rate.
Sympathetic inhibition: Decreases heart rate, stroke volume, and causes vasodilation, reducing blood pressure.
75
What happens when blood pressure decreases in the baroreceptor reflex?
Baroreceptors signal the brain.
Parasympathetic inhibition: Increases heart rate.
Sympathetic stimulation: Increases heart rate, stroke volume, and causes vasoconstriction, increasing blood pressure.
76
What is the role of the renin-angiotensin-aldosterone system (RAAS) in blood pressure regulation?
RAAS helps restore blood pressure homeostasis by regulating blood volume and vascular resistance, increasing blood pressure when it is low.
77
What triggers the RAAS?
A decrease in blood pressure, which reduces stretch in the aortic wall and carotid bodies, stimulates baroreceptors to activate RAAS.
78
What is the first step in the RAAS cascade?
The juxtaglomerular cells in the kidneys release renin in response to low blood pressure.
79
How does renin affect blood pressure regulation?
Renin converts angiotensinogen (from the liver) into angiotensin I, which is then converted into angiotensin II in the lungs.
80
What is the role of angiotensin II in blood pressure regulation?
- Vasoconstriction: Narrows blood vessels, increasing peripheral resistance.
- Stimulates the release of ADH (antidiuretic hormone) and stimulates thirst, increasing blood volume.
- Stimulates aldosterone secretion, increasing sodium and water reabsorption, raising blood volume and pressure.
81
What does aldosterone do in blood pressure regulation?
Aldosterone increases sodium reabsorption in the kidneys, which leads to increased water retention, raising blood volume and blood pressure.
82
What is autoregulation of blood flow?
Autoregulation is the local ability of tissues to adjust blood flow to meet metabolic demands, despite fluctuations in systemic blood pressure.
83
What are the two main mechanisms of autoregulation?
- Myogenic Mechanism: Smooth muscle responds to changes in vessel stretch.
- Metabolic Mechanism: Blood flow adjusts based on local metabolic activity (e.g., oxygen and carbon dioxide levels).
84
How does the myogenic mechanism of autoregulation work?
- Increased pressure: Causes vessel constriction (vasoconstriction).
- Decreased pressure: Causes vessel relaxation (vasodilation).
This maintains stable blood flow despite pressure changes.
85
What metabolic factors trigger vasodilation in autoregulation?
- Decreased oxygen (O₂)
Increased carbon dioxide (CO₂)
- Increased hydrogen ions (H⁺)
These signals promote vasodilation to increase blood flow.
86
Why is autoregulation important in organs like the heart, brain, and skeletal muscles?
These organs have high metabolic demands, and autoregulation ensures optimal oxygen and nutrient delivery during both activity and rest.
87
What is capillary exchange and why is it important?
Capillary exchange is the movement of gases, nutrients, and waste between blood and tissues through capillary walls. It enables delivery of oxygen/nutrients and removal of CO₂/waste, maintaining tissue health and homeostasis.
88
What are the main structural features of capillaries that allow exchange?
Walls one cell thick (endothelium)
Tiny pores allow passage of water and small solutes
Large molecules like proteins cannot pass through
89
What are the two main forces governing capillary exchange?
Hydrostatic Pressure – pushes fluid out of capillaries
Oncotic Pressure – pulls fluid into capillaries due to plasma proteins
90
What is Net Filtration Pressure (NFP) and what does it determine?
NFP = Hydrostatic Pressure – Oncotic Pressure
Positive NFP: fluid exits capillary (filtration)
Negative NFP: fluid enters capillary (reabsorption)
91
What happens at the arterial end of a capillary during exchange?
High hydrostatic pressure
Lower oncotic pressure
Positive NFP → fluid exits capillary (delivers oxygen/nutrients to tissue)
92
What happens at the venous end of a capillary during exchange?
Lower hydrostatic pressure
Oncotic pressure remains high
Negative NFP → fluid re-enters capillary (removes waste and CO₂)
93
What happens to the fluid that is not reabsorbed by capillaries?
~90% of filtered fluid is reabsorbed at venous end
~10% enters the lymphatic system, which returns it to circulation and prevents edema
