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What is the primary role of baroreceptors in the cardiovascular system?
What is the primary role of baroreceptors in the cardiovascular system?
When arterial blood pressure decreases, what happens to the firing rate of baroreceptors?
When arterial blood pressure decreases, what happens to the firing rate of baroreceptors?
Which of the following hormones is primarily responsible for increasing heart rate and blood pressure in response to environmental stress?
Which of the following hormones is primarily responsible for increasing heart rate and blood pressure in response to environmental stress?
What effect does the baroreceptor reflex have when blood pressure is elevated?
What effect does the baroreceptor reflex have when blood pressure is elevated?
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What is the function of Antidiuretic Hormone (ADH) when blood pressure is low?
What is the function of Antidiuretic Hormone (ADH) when blood pressure is low?
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What mechanism do kidneys use to control long-term blood pressure?
What mechanism do kidneys use to control long-term blood pressure?
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Which hormone is a potent vasoconstrictor and helps reduce urine output in response to low blood pressure?
Which hormone is a potent vasoconstrictor and helps reduce urine output in response to low blood pressure?
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What occurs in the body when baroreceptors detect an increase in arterial blood pressure?
What occurs in the body when baroreceptors detect an increase in arterial blood pressure?
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What occurs during isovolumetric contraction?
What occurs during isovolumetric contraction?
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What is the definition of stroke volume (SV)?
What is the definition of stroke volume (SV)?
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What results in the first heart sound (S1)?
What results in the first heart sound (S1)?
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What triggers the opening of the AV valves?
What triggers the opening of the AV valves?
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What is end systolic volume (ESV)?
What is end systolic volume (ESV)?
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Which of the following describes cardiac output (CO)?
Which of the following describes cardiac output (CO)?
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What does the second heart sound (S2) indicate?
What does the second heart sound (S2) indicate?
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What characterizes abnormal heart sounds, or murmurs?
What characterizes abnormal heart sounds, or murmurs?
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What initiates the depolarization of myocardial cells?
What initiates the depolarization of myocardial cells?
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Which ion is primarily responsible for the plateau phase of the myocardial action potential?
Which ion is primarily responsible for the plateau phase of the myocardial action potential?
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How is Ca2+ primarily removed from cardiac muscle cells during relaxation?
How is Ca2+ primarily removed from cardiac muscle cells during relaxation?
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What effect does digitalis have on cardiac muscle contractions?
What effect does digitalis have on cardiac muscle contractions?
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Which of the following agents would positively influence ventricular contractility?
Which of the following agents would positively influence ventricular contractility?
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What is the main difference in Ca2+ sources between cardiac and skeletal muscle?
What is the main difference in Ca2+ sources between cardiac and skeletal muscle?
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What happens during the initial repolarization phase of the myocardial action potential?
What happens during the initial repolarization phase of the myocardial action potential?
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What effect do catecholamines have on ventricular contractility?
What effect do catecholamines have on ventricular contractility?
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What role does the plateau phase play in cardiac muscle contractions?
What role does the plateau phase play in cardiac muscle contractions?
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An increase in sympathetic activity primarily affects which aspect of ventricular function?
An increase in sympathetic activity primarily affects which aspect of ventricular function?
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Which condition is likely to result in decreased ventricular contractility?
Which condition is likely to result in decreased ventricular contractility?
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What initiates the electrical communication in the heart?
What initiates the electrical communication in the heart?
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What is the term used to describe how hard the heart must work to eject blood?
What is the term used to describe how hard the heart must work to eject blood?
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Which of the following correctly describes the role of calcium in ventricular contractility?
Which of the following correctly describes the role of calcium in ventricular contractility?
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Which statement about parasympathetic influence on ventricular contractility is true?
Which statement about parasympathetic influence on ventricular contractility is true?
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What effect do hyperkalemia and acidosis have on ventricular contractility?
What effect do hyperkalemia and acidosis have on ventricular contractility?
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What is the function of angiotensin II in the body?
What is the function of angiotensin II in the body?
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Which type of hypertension accounts for the majority of cases?
Which type of hypertension accounts for the majority of cases?
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Which of the following is NOT a contributing factor for primary hypertension?
Which of the following is NOT a contributing factor for primary hypertension?
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What is a characteristic feature of cardiovascular hypertension?
What is a characteristic feature of cardiovascular hypertension?
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Which condition can lead to secondary hypertension due to hormone secretion?
Which condition can lead to secondary hypertension due to hormone secretion?
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What is the primary mechanism by which aldosterone helps regulate blood pressure?
What is the primary mechanism by which aldosterone helps regulate blood pressure?
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Which type of hypertension is associated with identifiable causes like renal artery occlusion?
Which type of hypertension is associated with identifiable causes like renal artery occlusion?
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What physiological change occurs in renal hypertension?
What physiological change occurs in renal hypertension?
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What is the primary function of the sino-atrial (SA) node?
What is the primary function of the sino-atrial (SA) node?
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What is the significance of the delay at the Atrioventricular (AV) node?
What is the significance of the delay at the Atrioventricular (AV) node?
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How does the conduction velocity change as the impulse transitions from the atria to the ventricles?
How does the conduction velocity change as the impulse transitions from the atria to the ventricles?
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What does the conduction of action potentials from the SA node primarily affect?
What does the conduction of action potentials from the SA node primarily affect?
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What is the heart rate typically generated by the SA node?
What is the heart rate typically generated by the SA node?
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Which structure conducts impulses from the atria to the ventricles?
Which structure conducts impulses from the atria to the ventricles?
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The conduction velocity through the AV node is approximately:
The conduction velocity through the AV node is approximately:
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What happens to the discharge rate when impulses pass through the bundle branches and Purkinje fibers?
What happens to the discharge rate when impulses pass through the bundle branches and Purkinje fibers?
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Study Notes
Unit 6: Physiology of the Cardiovascular System-CVS
- The cardiovascular system (CVS) is composed of the heart, blood vessels, and blood.
- The CVS is responsible for transporting materials to and from all parts of the body.
- Substances transported include nutrients, water, gases, oxygen, nutrients from gastrointestinal tract, wastes, immune cells, antibodies, clotting proteins, hormones, metabolic wastes, heat, and carbon dioxide.
- The heart acts as the pumping center.
- Atria receive blood returning from blood vessels.
- Ventricles pump blood into blood vessels.
- Blood vessels are categorized as arteries, capillaries, and veins.
- Arteries distribute blood to various organs.
- Capillaries are the major sites of nutrient, metabolic end product, and fluid exchange between blood and tissues.
- Veins collect blood and return it to the heart.
- Blood is a fluid transporting materials to and from cells.
- The CVS involves two circulations: pulmonary and systemic.
- Pulmonary circulation circulates blood from the right ventricle to the lungs and back to the left atrium.
- Systemic circulation circulates blood from the left ventricle to the tissues and back to the right atrium.
- The blood flow pathway through the heart and lungs involves vena cavae, pulmonary arteries, left atrium, left ventricle, right atrium, right ventricle, pulmonary veins, aorta, and branches.
- Pulmonary circulation has low resistance and low pressure.
- Systemic circulation has high resistance and high pressure (120/80 mmHg).
- Blood flows through multiple subcircuits in different organs.
- Blood flow is unidirectional.
Functions of the CVS
- The main function of the CVS is to transport materials throughout the body.
- This includes delivering oxygen, nutrients, and other essential substances to cells and removing waste products.
- The CVS also plays roles in regulating blood pressure and temperature, and in transporting hormones and immune cells.
Components of the CVS
- The heart acts as the pumping center.
- Blood vessels (arteries, capillaries, and veins) conduct blood to various organs, exchange materials between blood and tissues, and return blood to the heart, respectively.
- Blood itself is a fluid circulating around the body, carrying materials to and from cells.
Heart
- The heart is a hollow muscular organ that plays a central role in pumping.
- Located in the thoracic cavity.
- It's enclosed by a membranous sac called the pericardium, which contains pericardial fluid that lubricates the heart.
- The heart wall consists of three layers: epicardium (outer), myocardium (middle), and endocardium (inner).
- The heart is vertically divided into left and right sides by a septum.
- The heart has four chambers: two atria and two ventricles.
- Atrioventricular (AV) valves (tricuspid and mitral) prevent backflow of blood between atria and ventricles.
- Semilunar valves (pulmonary and aortic) prevent backflow of blood between ventricles and arteries.
- The heart receives arterial blood from coronary arteries.
- Resting coronary blood flow = 250 ml/min, 5% CO.
Cardiac Muscle (Myocardium)
- Two types of cardiac muscle: contractile and autorhythmic.
- Contractile muscles make up 99% of the heart and responsible for pumping.
- Autorhythmic muscles (1%) make pacemakers and conduct signals.
- Pacemakers include the SA node (sinoatrial node).
- The SA node is the primary pacemaker of the heart.
- Conduction fibers transmit action potentials through the heart.
- Cardiac muscle cells are smaller than skeletal muscles, striated, mono-nucleated, and connected through intercalated disks with desmosomes and gap junctions.
Excitation-Contraction Coupling in Cardiac Muscle
- Action potentials originate spontaneously in pacemaker cells and spread to contractile cells via gap junctions.
- Myocardial cell excitation results in Na+ influx, depolarization of sarcolemma and T-tubules, Ca2+ influx, Ca2+ release, Ca2+ binding to troponin C, and myocardial contraction.
- Relaxation occurs when Ca2+ unbinds from and is pumped back into the sarcoplasmic reticulum.
Myocardial Action Potentials
- Myocardial action potentials differ from skeletal muscle action potentials primarily due to the plateau phase.
- The plateau phase occurs during depolarization.
- It prevents tetanic contraction and allows ventricular filling, which is crucial for efficient cardiac function.
Electrical Excitation of the Heart
- Electrical communication in the heart begins with action potential generation in the autorhythmic cells.
- SA node discharges impulses, causing the wave of depolarization to spread through the atria and to the ventricles.
- The AV node delays the impulse before the action potential enters the ventricles, ensuring that atrial contraction completes before ventricular contraction.
Sequence of Excitation
- Sinoatrial (SA) node (pacemaker) in the right atrium initiates the electrical impulse for the heartbeat.
- Internodal pathways conduct the impulse from the SA node to the AV node.
- Atrioventricular (AV) node in the base of the right atrium delays the impulse to allow for complete atrial contraction.
- AV bundle (bundle of His) transmits the impulse to the ventricles.
- Bundle branches conduct impulses to the left and right ventricles.
- Purkinje fibers rapidly spread the impulse throughout the ventricles, initiating ventricular contraction.
Control of Heart Rate
- Heart rate is regulated by the autonomic nervous system (sympathetic and parasympathetic divisions) and hormones.
- Sympathetic stimulation speeds up the heart rate by increasing the slope of the pacemaker potential and increasing the permeability to Na+ and Ca2+ ions.
- Parasympathetic stimulation slows down the heart rate by increasing K+ permeability, hyperpolarizing the cell, and decreasing Ca2+ permeability.
- Hormones such as epinephrine and thyroid hormones can increase heart rate, and insulin and glucagon can have less of an immediate response.
Control of Stroke Volume
- Stroke volume is affected by factors such as preload, contractility, and afterload.
- Preload, or end-diastolic volume (EDV), is the volume of blood in the ventricles before contraction. Increased EDV stretches the ventricular walls, increasing the force of contraction (Frank-Starling mechanism).
- Contractility is the force of contraction of the ventricular myocardium, which is also regulated by nervous and hormonal systems.
- Afterload refers to the resistance the ventricles must overcome to eject blood into the aorta.
Heart Sounds
- Heart sounds are generated by the vibrations created by the closure of heart valves.
- First heart sound (S1) is caused by the closure of the atrioventricular valves.
- Second heart sound (S2) is caused by the closure of the semilunar valves.
Abnormal heart sounds (Murmurs)
- Abnormal heart sounds (murmurs) often indicate valvular diseases such as stenosis (stiff/narrowed valves) or insufficiency (leaky valves).
Cardiovascular Shock
- Circulatory shock is a life-threatening condition where the body's organs and tissues lack adequate blood flow.
- Shock can be classified into different types, such as hypovolemic, cardiogenic, neurogenic, anaphylactic, and septic shock.
Control of Blood Pressure
- Blood pressure is regulated by multiple mechanisms, including local, neural, and hormonal factors.
- Local control: tissues regulate their own blood flow based on metabolic demand.
- Neural control: the central nervous system, particularly the medulla oblongata, coordinates reflex mechanisms to control blood pressure, including the baroreceptor reflex.
- Hormonal control: Various hormones like epinephrine, ADH, and angiotensin II can alter blood pressure. Kidneys play a crucial role in long-term blood pressure control by regulating blood volume through the renin-angiotensin-aldosterone system.
Hypertension
- Hypertension is characterized by persistently elevated blood pressure.
- Categorized as primary (essential) or secondary hypertension, based on an underlying cause (or the lack of one, for essential).
- Common causes of secondary hypertension include renal disorders, endocrine issues, and some vascular or nervous system problems.
- Hypertension causes significant damage to blood vessels over time, increasing the risk of many serious health consequences.
Hypotension
- Hypotension is characterized by significantly low blood pressure.
- It can lead to insufficient blood flow and can be life threatening.
Electrocardiography (ECG)
- An ECG is a tool for evaluating the electrical events of the heart.
- It's a recording of the electrical activity generated by the heart, spread by body fluids (like blood or interstitial fluid), and recorded on the surface of the skin.
- An ECG records the sum of multiple action potentials from many heart muscle cells.
- Different waves and components on ECG correspond to specific phases of cardiac excitation and contraction.
- The ECG displays P-wave (atrial depolarization), QRS complex (ventricular depolarization), and T wave (ventricular repolarization).
- Different intervals and segments on ECG measure specific events of heart activity, such as P-R intervals (delay through AV node) or Q-T Intervals (ventricular depolarization and repolarization).
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Description
Explore the intricate details of the cardiovascular system, including its components, functions, and the critical roles played by the heart, blood vessels, and blood. This quiz will help reinforce your understanding of how nutrients and gases are transported throughout the body and the distinctions between pulmonary and systemic circulation.
