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What causes a heart murmur during blood flow?
What causes a heart murmur during blood flow?
Blood flow is always from regions of lower pressure to regions of higher pressure.
Blood flow is always from regions of lower pressure to regions of higher pressure.
False
What is the formula to calculate cardiac output?
What is the formula to calculate cardiac output?
CO = HR × SV
Resistance is directly proportional to both fluid viscosity and the __________ of the vessel.
Resistance is directly proportional to both fluid viscosity and the __________ of the vessel.
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Match the following factors affecting resistance with their effects:
Match the following factors affecting resistance with their effects:
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Which of the following statements about cardiac output is true?
Which of the following statements about cardiac output is true?
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Sympathetic nerve fibers release acetylcholine in the heart.
Sympathetic nerve fibers release acetylcholine in the heart.
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What happens to stroke volume after significant blood loss?
What happens to stroke volume after significant blood loss?
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What is the primary function of systemic circulation?
What is the primary function of systemic circulation?
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In pulmonary circulation, the pulmonary arteries carry oxygenated blood.
In pulmonary circulation, the pulmonary arteries carry oxygenated blood.
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What ions are primarily restored to their original locations during repolarization of cardiomyocytes?
What ions are primarily restored to their original locations during repolarization of cardiomyocytes?
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The TMP is maintained at a plateau just below ___ mV throughout phase 2.
The TMP is maintained at a plateau just below ___ mV throughout phase 2.
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Which blood vessels connect veins and arteries?
Which blood vessels connect veins and arteries?
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Match the following types of blood vessels with their functions:
Match the following types of blood vessels with their functions:
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What is the main role of the thick, elastic structure of arteries?
What is the main role of the thick, elastic structure of arteries?
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The ___ period in the cardiac cycle allows the heart cells to reset before the next depolarization.
The ___ period in the cardiac cycle allows the heart cells to reset before the next depolarization.
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What occurs during the Absolute Refractory Period of the heart?
What occurs during the Absolute Refractory Period of the heart?
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Phase 4 of the action potential in cardiomyocytes has a membrane potential of 0 mV.
Phase 4 of the action potential in cardiomyocytes has a membrane potential of 0 mV.
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What is the primary characteristic of ion channels in terms of selectivity?
What is the primary characteristic of ion channels in terms of selectivity?
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In Phase 2 of the action potential, there is a small constant inward current of __________.
In Phase 2 of the action potential, there is a small constant inward current of __________.
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Match the phases of action potential with their primary characteristics:
Match the phases of action potential with their primary characteristics:
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Which channels are responsible for the depolarization of the membrane potential in Phase 0?
Which channels are responsible for the depolarization of the membrane potential in Phase 0?
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The inward rectifier channels allow K+ to flow out of the cell during the resting phase.
The inward rectifier channels allow K+ to flow out of the cell during the resting phase.
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What characterizes the voltage-sensitive gating of cardiac ion channels?
What characterizes the voltage-sensitive gating of cardiac ion channels?
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What neurotransmitter does the parasympathetic nervous system release to decrease heart rate?
What neurotransmitter does the parasympathetic nervous system release to decrease heart rate?
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The sinoatrial (SA) node is responsible for generating impulses approximately 75 times per minute.
The sinoatrial (SA) node is responsible for generating impulses approximately 75 times per minute.
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What is the normal range of stroke volume (SV) in milliliters?
What is the normal range of stroke volume (SV) in milliliters?
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The electrocardiogram detects the heart’s _____ and electrical activity.
The electrocardiogram detects the heart’s _____ and electrical activity.
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Match the heart structures with their functions:
Match the heart structures with their functions:
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Which of the following factors can affect stroke volume?
Which of the following factors can affect stroke volume?
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Atrial fibrillation can be detected through an abnormal electrocardiogram (ECG).
Atrial fibrillation can be detected through an abnormal electrocardiogram (ECG).
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What is the role of the right leg electrode in electrocardiography?
What is the role of the right leg electrode in electrocardiography?
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The ____ wave indicates ventricular repolarization.
The ____ wave indicates ventricular repolarization.
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What is the first electrical signal wave seen on an ECG during atrial depolarization?
What is the first electrical signal wave seen on an ECG during atrial depolarization?
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Which vessel is the largest in the circulatory system?
Which vessel is the largest in the circulatory system?
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Arterioles have larger diameters than arteries.
Arterioles have larger diameters than arteries.
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What is the primary function of capillaries?
What is the primary function of capillaries?
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Blood pressure rises during __________ contraction and falls when the ventricles relax.
Blood pressure rises during __________ contraction and falls when the ventricles relax.
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What is found in veins that helps prevent the backflow of blood?
What is found in veins that helps prevent the backflow of blood?
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Match the following terms with their definitions:
Match the following terms with their definitions:
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The velocity of blood flow through capillaries is high to ensure rapid nutrient delivery.
The velocity of blood flow through capillaries is high to ensure rapid nutrient delivery.
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What term describes the total cross-sectional area effect on blood flow velocity?
What term describes the total cross-sectional area effect on blood flow velocity?
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Study Notes
Heart Sounds
- Laminar flow occurs when blood flows smoothly through valves and vessels in concentric layers.
- Turbulent flow, which results in a murmur, can occur due to:
- Blood flowing rapidly through a narrowed valve (stenosis).
- Blood flowing backwards through a damaged, leaky valve (insufficiency).
- Blood flowing between atria or ventricles through a hole in the wall separating them (septal defect).
Blood Circulation
- Blood flow always moves from an area of higher pressure to an area of lower pressure.
- Hydrostatic pressure is the pressure exerted by any fluid.
- Resistance is the friction that impedes flow between two points.
- Flow rate is directly proportional to the pressure difference and inversely proportional to the resistance.
Flow Rate
- Flow Rate = Pressure Difference / Resistance
- Flow rate is directly proportional to the pressure difference and inversely proportional to the resistance.
Resistance
- Resistance is determined by:
- Viscosity (influenced by dehydration and anemia).
- Length of the vessel (remains constant).
- Radius of the vessel (can vary).
- Resistance is directly proportional to viscosity and length, and inversely proportional to the fourth power of the vessel's radius.
Cardiac Output
- Cardiac output is the volume of blood each ventricle pumps per unit time, typically measured in liters per minute.
- Cardiac output is calculated by multiplying heart rate (HR) by stroke volume (SV): CO = HR × SV.
- Heart rate and stroke volume don't always change in the same direction.
- Changes in heart rate and stroke volume can have opposing effects on cardiac output.
Heart
- The heart receives a rich supply of sympathetic and parasympathetic nerve fibers.
- Sympathetic postganglionic fibers innervate the entire heart and release norepinephrine.
- Parasympathetic fibers terminate primarily on specialized cells in the atria and release acetylcholine.
Control of Heart Rate
- Heart rate is regulated by the autonomic nervous system (involuntary).
- Sympathetic nervous system releases catecholamines (epinephrine and norepinephrine), increasing heart rate.
- Parasympathetic nervous system releases acetylcholine, decreasing heart rate.
Stroke Volume
- Stroke volume is the volume of blood pumped out of the left ventricle during each systolic contraction.
- Normal stroke volume is the difference between end-diastolic volume (volume before contraction) and end-systolic volume (volume after contraction).
- The normal range for stroke volume is about 50-100 ml.
Control of Stroke Volume
- Changes in stroke volume can be influenced by:
- Preload (end-diastolic volume).
- Sympathetic nervous system input to the ventricles.
- Afterload (arterial pressure against which the ventricles pump).
Cardiac Conducting System
- The cardiac conducting system facilitates the coordinated contraction of the heart.
- The sequence of impulse generation and conduction is as follows:
- Sinoatrial node (SA node) generates the impulse (approximately 75 times per minute).
- Atrioventricular node (AV node) delays the impulse, allowing the atria to complete pumping.
- Atrioventricular bundle (Bundle of His) conducts the impulse from atria to ventricles.
- Right and left bundle branches conduct the impulse through the interventricular septum.
- Subendocardial conducting network (Purkinje fibers) depolarize the contractile cells of both ventricles, initiating ventricular contraction.
Heart
- An electrocardiogram (ECG) is a tool for assessing the heart's rhythm and electrical activity.
- Sensors attached to the skin detect electrical signals produced by the heart with each beat.
- Abnormal ECG readings can reveal conditions such as atrial fibrillation, cardiovascular disease, heart valve disease, thickened hear walls and pericardial effusion.
- ECG has limited diagnostic value as it cannot detect mechanical issues with the heart.
Placement of Electrodes in Electrocardiography
- 12 leads are used, each with a different combination of reference (negative pole) and recording (positive pole) electrodes, providing different angles for viewing the electrical activity of the heart.
- The 12 leads are composed of:
- 6 precordial electrodes (V1-V6).
- 6 different pairings from 3 limb electrodes (left arm, right arm, and left leg).
- Right leg electrode serves as reference.
- Ambulatory ECG monitoring and Exercise ECG are additional methods.
Normal ECG
- P wave represents atrial depolarization.
- PR interval reflects the short physiological delay at the AV node.
- QRS complex represents ventricular depolarization:
- Q wave: initial downward deflection.
- R wave: upward deflection.
- S wave: subsequent downward deflection crossing the isoelectric line.
- T wave represents ventricular repolarization.
Sequence of Cardiac Excitation
- Areas of depolarization are marked by a yellow color in the depiction.
- The electrocardiogram monitors the spread of these signals.
Absolute Refractory Period of Heart
- Occurs during and after an action potential, preventing re-excitation of the excitable membrane.
- It is impossible for contractions to summate.
- Functionally, it allows the ventricles to fill while they are relaxed.
Properties of Cardiac Ion Channels
- Selectivity: permeable to a single ion type.
- Voltage-sensitive gating: specific TMP range required for opening.
- Time-dependence: some channels (fast Na+ channels) close after opening, requiring a return to resting TMP before reopening.
Action Potential in Cardiomyocytes (0-4 Phases)
- Phase 4: Resting phase (-90 mV) maintained by outward K+ leak through inward rectifier channels.
- Phase 0: Depolarization:
- Na+ influx raises TMP above -90 mV.
- Na+ channels open at -70 mV, rapidly depolarizing the cell.
- Ca2+ channels open at -40 mV, causing a steady Ca2+ influx.
- Phase 1: Early repolarization:
- TMP becomes slightly positive.
- K+ channels open, returning TMP to 0 mV.
- Phase 2: Plateau phase:
- Ca2+ channels remain open, with a small, constant inward current.
- K+ leaks out through delayed rectifier channels.
- Countercurrents balance, maintaining TMP at a plateau.
- Phase 3: Repolarization:
- Ca2+ channels inactivate.
- Persistent K+ outflow brings TMP back to -90 mV.
- Normal ionic gradients are restored by pumps.
Blood Circulation
- Two closed blood circulation circuits:
- Systemic circulation: delivers oxygen-rich blood and nutrients to all body cells, removing waste.
- Pulmonary circulation: sends oxygen-poor blood to the lungs for oxygenation and carbon dioxide removal.
- Blood in the pulmonary veins is oxygenated, unlike the oxygen-poor blood in pulmonary arteries.
Blood Circulation
- Systemic and Pulmonary Circuits:
- Pulmonary: Deoxygenated blood from the body enters the right atrium, then the right ventricle through the tricuspid valve, and travels to the lungs for oxygenation.
- Systemic: Oxygenated blood from the lungs enters the left atrium, then the left ventricle through the bicuspid (mitral) valve, and is distributed to the body.
Blood Circulation
- Three main types of blood vessels:
- Arteries: carry oxygenated blood away from the heart.
- Veins: carry deoxygenated blood from tissues back to the heart.
- Capillaries: tiny vessels connecting arteries and veins, facilitating substance exchange.
Arteries
- Thick, elastic walls to withstand high pressure and control vessel diameter.
- Vary in size, with the largest being the aorta, branching into smaller arteries, ultimately ending in arterioles.
- Arterioles connect to capillaries.
Venules and Veins
- Microscopic vessels originating from capillaries, merging to form veins, carrying blood to the heart through large veins like the vena cava.
- Parallel to the network of arteries and arterioles.
- Have thinner walls, less smooth muscle and elastic tissue, but larger lumens compared to arteries and arterioles, reducing resistance and increasing blood flow.
- Contain flap-like valves, acting as blood reservoirs.
Capillaries
- Smallest diameter blood vessels.
- Connect smallest arterioles and venules.
- Form a semipermeable layer enabling exchange of substances between blood and tissue fluid surrounding cells.
- Highly dense in metabolically active tissues with high oxygen and nutrient demands.
Effect of Blood Pressure, Cross-Sectional Area and Flow Velocity on Blood Vessels
- Relationship between total cross-sectional area and flow velocity is inversely proportional.
- The slow blood movement through capillaries maximizes time for substance exchange.
Blood Pressure
- The force exerted by blood against vessel walls, usually referring to arterial pressure.
- Fluctuates with the cardiac cycle.
- Maximum pressure during ventricular contraction is systolic pressure.
- Lowest pressure during ventricular relaxation is diastolic pressure.
Blood Pressure
- Ventricular contraction ejects blood into arteries during systole, increasing arterial pressure.
- Only about one-third of stroke volume leaves arteries during systole; the rest remains, increasing arterial pressure.
- Arterial walls recoil passively during diastole, driving blood into arterioles.
- As blood leaves arteries, arterial volume and pressure decrease.
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Description
This quiz covers key concepts related to heart sounds, blood circulation, and flow dynamics. It explores laminar and turbulent flow, the effects of various heart conditions on blood movement, and the principles governing flow rate and resistance. Test your understanding of these crucial physiological topics!
