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Questions and Answers
What is the primary action of angiotensin II as it relates to blood vessels?
What is the primary action of angiotensin II as it relates to blood vessels?
How does angiotensin II directly affect the kidneys?
How does angiotensin II directly affect the kidneys?
What role does Atrial Natriuretic Peptide (ANP) play in blood pressure regulation?
What role does Atrial Natriuretic Peptide (ANP) play in blood pressure regulation?
Which mechanism does angiotensin II utilize to increase blood pressure over a longer duration?
Which mechanism does angiotensin II utilize to increase blood pressure over a longer duration?
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What is the consequence of angiotensin II's effect on renal arterioles?
What is the consequence of angiotensin II's effect on renal arterioles?
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What is the primary function of the heart valves?
What is the primary function of the heart valves?
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Which chamber of the heart receives deoxygenated blood?
Which chamber of the heart receives deoxygenated blood?
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What role do HCN channels play in cardiac physiology?
What role do HCN channels play in cardiac physiology?
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Which of the following is characteristic of the QRS complex on an ECG?
Which of the following is characteristic of the QRS complex on an ECG?
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What distinguishes the left atrioventricular (AV) valve from the right AV valve?
What distinguishes the left atrioventricular (AV) valve from the right AV valve?
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Which statement about pulmonary circulation is correct?
Which statement about pulmonary circulation is correct?
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What is the primary role of cyclic AMP (cAMP) regarding heart rate?
What is the primary role of cyclic AMP (cAMP) regarding heart rate?
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Which ECG wave is essential for preparing the heart for the next cycle?
Which ECG wave is essential for preparing the heart for the next cycle?
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Which of the following correctly describes the function of the P wave?
Which of the following correctly describes the function of the P wave?
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How is stroke volume defined?
How is stroke volume defined?
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Which factor is NOT a determinant of stroke volume?
Which factor is NOT a determinant of stroke volume?
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What is the relationship described by the Frank-Starling Law?
What is the relationship described by the Frank-Starling Law?
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What effect does noradrenaline have on the heart?
What effect does noradrenaline have on the heart?
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Which heart sound is associated with the closure of the AV valves?
Which heart sound is associated with the closure of the AV valves?
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What is true about the cardiac output of a resting heart?
What is true about the cardiac output of a resting heart?
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Which hormone is primarily associated with lowering heart rate?
Which hormone is primarily associated with lowering heart rate?
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Which of the following statements about afterload is accurate?
Which of the following statements about afterload is accurate?
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Which physiological factor primarily influences contractility?
Which physiological factor primarily influences contractility?
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During intense exercise, which of the following changes occur in response to sympathetic stimulation?
During intense exercise, which of the following changes occur in response to sympathetic stimulation?
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Which of the following impacts heart rate the least?
Which of the following impacts heart rate the least?
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In athletes, what happens to the stroke volume during rest compared to non-athletes?
In athletes, what happens to the stroke volume during rest compared to non-athletes?
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Which factor is primarily responsible for blood flow rate in vessels?
Which factor is primarily responsible for blood flow rate in vessels?
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What is the correct formula to calculate Mean Arterial Pressure (MAP)?
What is the correct formula to calculate Mean Arterial Pressure (MAP)?
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Which mechanism helps counteract a decrease in blood pressure during hemorrhage?
Which mechanism helps counteract a decrease in blood pressure during hemorrhage?
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During increased muscular activity, what happens to blood flow in the cardiovascular system?
During increased muscular activity, what happens to blood flow in the cardiovascular system?
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Which condition leads to increased vascular resistance?
Which condition leads to increased vascular resistance?
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What role do baroreceptors play in blood pressure regulation?
What role do baroreceptors play in blood pressure regulation?
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What happens to pulse pressure when there is an increase in stroke volume?
What happens to pulse pressure when there is an increase in stroke volume?
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How does vascular compliance differ between arteries and veins?
How does vascular compliance differ between arteries and veins?
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Which of the following is NOT a factor influencing vascular resistance?
Which of the following is NOT a factor influencing vascular resistance?
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What is the consequence of increased vascular compliance in veins?
What is the consequence of increased vascular compliance in veins?
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What sensory receptors are involved in detecting blood gasses?
What sensory receptors are involved in detecting blood gasses?
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Which of the following has the greatest total cross-sectional area in the circulatory system?
Which of the following has the greatest total cross-sectional area in the circulatory system?
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What initiates the Renin-Angiotensin system?
What initiates the Renin-Angiotensin system?
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What effect does a decreased vascular diameter have on blood flow?
What effect does a decreased vascular diameter have on blood flow?
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What is the primary purpose of capillary networks in the body?
What is the primary purpose of capillary networks in the body?
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Study Notes
Cardiovascular Physiology
-
Heart Structure:
- Blood enters the right atrium via the superior vena cava, inferior vena cava, and coronary sinus; blood enters the left atrium via four pulmonary veins.
- Valves: Ensure one-way blood flow by preventing backflow.
- Chambers: Four chambers (right atrium, right ventricle, left atrium, left ventricle) with specific roles in the cardiac cycle.
- Systemic Circulation: Left side of the heart pumps oxygenated blood to body tissues (except lungs).
- Pulmonary Circulation: Right side of the heart pumps deoxygenated blood to lungs for oxygenation.
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Heart Valves:
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Atrioventricular Valves: Located between atria and ventricles;
- Left AV valve - bicuspid
- Right AV valve - tricuspid
- Semilunar Valves: Aortic and pulmonary valves, critical for blood ejection from the heart.
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Atrioventricular Valves: Located between atria and ventricles;
Cardiac Electrophysiology
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Pacemaker Potential: Governed by HCN (hyperpolarization-activated cyclic nucleotide-gated) ion channels; initiates spontaneous action potentials in pacemaker cells.
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Cyclic AMP (cAMP): Modulates HCN channel currents, impacting automaticity and heart rate.
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Electrocardiogram (ECG):
- Measures heart's electrical activity via electrodes on limbs and chest.
- Produces 12 tracings from various lead combinations.
- Used to detect abnormalities in conducting pathway, heart enlargement, heart damage, and cause of chest pain.
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ECG Waves and Cardiac Events:
- P Wave: Atrial depolarization (contraction).
- QRS Complex: Ventricular depolarization (contraction).
- T Wave: Ventricular repolarization (relaxation).
The Cardiac Cycle
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Phases of the Cycle:
- Atrial depolarization (P wave), atrial systole.
- Ventricular depolarization (QRS complex), ventricular systole.
- Ventricular repolarization (T wave), ventricular diastole.
- Cycle repeats.
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Cardiac Output (CO):
- Volume of blood ejected per ventricle in a minute.
- CO = Heart Rate (HR) x Stroke Volume (SV).
- At rest, CO is typically ~5 L/min at HR 70 bpm and SV 70 mL.
Heart Sounds
- Auscultation: Listening to heart sounds.
-
Heart Sounds: Caused by blood turbulence and closing heart valves.
- S1 ("lubb"): AV valve closure.
- S2 ("dupp"): Semilunar valve closure.
- S3 and S4: Less audible sounds from blood turbulence in filling phases.
Athletic Heart Adaptations
- Hypertrophy: Increased cardiac chamber volume and SV, up to 200 mL/beat.
- Lower Resting Heart Rate: Enhanced cardiovascular health, often below 70 bpm in trained athletes.
Factors Affecting Stroke Volume (SV)
- Preload: Ventricular stretch before contraction; influenced by venous return.
- Contractility: Heart muscle's inherent ability to contract; influenced by physiological / pharmacological factors.
- Afterload: Pressure the ventricles must overcome to eject blood; inversely related to SV.
Preload
- Frank-Starling Law: Increased preload leads to stronger heart contractions, thus enhancing SV. Preload also depends on duration of diastole and venous return.
Contractility
- Factors influencing contractility:
- Positive inotropic agents: Increase contractility (noradrenaline).
- Negative inotropic agents: Decrease contractility (acidosis).
Afterload
- Resistance ventricles must overcome to eject blood; influenced by systemic vascular resistance and blood pressure.
- Higher afterload leads to lower stroke volume.
Regulation of Heart Rate
- Mechanoreflexes: Receptors relaying information about body position to the cardiovascular centre; ↑ heart rate with exercise.
- Chemoreceptors: Monitor blood chemistry (O2, CO2, pH); affect heart rate and respiration in response to changes in blood chemistry.
- Baroreceptors: Monitor blood pressure; crucial for maintaining blood pressure homeostasis.
- Sympathetic Regulation: Noradrenaline released from sympathetic nerves, increasing heart rate and contractility.
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Hormonal Influence:
- Acetylcholine slows heart rate.
- Adrenaline and noradrenaline significantly increase heart rate and myocardial contractility during stress.
- Thyroid hormones enhance cardiac contractility, increasing heart rate.
- Ion Concentrations: Changes in Na+, K+, and Ca2+ levels affect heart rate and contractility
Haemodynamics and Blood Flow Dynamics
- Blood Flow: Driven by pressure differences between heart and blood vessels. Blood flows through narrow arterioles, capillaries, and venules, encountering resistance.
- Capillary Networks: Extensive network of small vessels that connects to body cells, facilitating exchange of oxygen, nutrients, and waste products.
- Blood Distribution During Activity: Venoconstriction reduces blood volume in reservoirs, assisting in maintaining blood pressure during increased muscular activity.
- Vascular Compliance: Tendency of vessels to expand in response to pressure increases; venous system has high compliance, acting as a blood reservoir.
Blood Pressure
- SBP: Systolic Blood Pressure - peak pressure.
- DBP: Diastolic Blood Pressure - lowest pressure.
-
MAP: Mean Arterial Pressure - average pressure.
- MAP = DBP + 1/3 (SBP - DBP)
- Pulse Pressure: Difference between systolic and diastolic pressure; reflects stroke volume and vascular compliance.
Blood Flow Rate
- Vessel Diameter: Critical for flow rates; wider vessels lead to slower flow for optimal exchange. Smaller vessels have increased cross-sectional area, leading to decreased velocity.
Pressure, Flow, and Resistance
- Blood flow calculated using Darcy's Law: Q = ΔP/R. factors determining blood flow are pressure difference and resistance.
Vascular Resistance
- Vessel Lumen Size: Narrower lumen increases resistance.
- Blood Viscosity: Higher viscosity (e.g., dehydration) increases resistance.
- Vessel Length: Longer vessels increase resistance.
Summary of Blood Pressure Regulation
- Systems such as Baroreceptors, Chemoreceptors, Renin-Angiotensin System, and Atrial Natriuretic Peptide (ANP) regulate blood pressure through diverse mechanisms.
Renin-Angiotensin System
- Renin initiates a cascade, producing angiotensin II, a potent vasoconstrictor, increasing systemic blood pressure; also affects kidney salt and water retention.
Atrial Natriuretic Peptide (ANP)
- Reduces blood volume by promoting sodium and water excretion and vasodilation.
Capillary Blood Distribution During Activity
- Venoconstriction is responsible in reducing blood volume stored in blood reservoirs during intense muscle activity.
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Description
Test your knowledge on the structure and function of the heart in this cardiovascular physiology quiz. Explore topics such as heart chambers, circulation types, and the role of heart valves. Perfect for students and enthusiasts alike!
