Cardiovascular System Functions and Anatomy
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Questions and Answers

What is the primary role of the cardiovascular system in delivering substances to tissues?

  • To transport nutrients and hormones to inactive tissues
  • To return oxygenated blood to the heart
  • To deliver oxygen and nutrients to active tissues (correct)
  • To remove waste products from inactive tissues

    • Which statement about systemic circulation is correct?

  • It operates at lower pressure compared to pulmonary circulation.
  • It circulates blood directly to the lungs.
  • It carries oxygenated blood away from the heart to the body. (correct)
  • It only transports deoxygenated blood.

    • During isovolumetric contraction, what occurs in the heart?

  • All heart valves open and blood is ejected.
  • Ventricular pressure rises without a change in volume. (correct)
  • The heart is in a state of complete relaxation.
  • Blood flows from the ventricles to the atria.

    • What is the function of one-way valves in veins?

    <p>To prevent backflow and promote blood movement toward the heart.</p> Signup and view all the answers

    What can happen if mean arterial pressure (MAP) falls below 60 mmHg for an extended time?

    <p>The organs may experience insufficient blood flow and become ischemic.</p> Signup and view all the answers

    Which of the following factors does NOT influence arterial blood pressure?

    <p>Skeletal muscle activity</p> Signup and view all the answers

    How does decreasing blood vessel diameter affect total peripheral resistance (TPR)?

    <p>It increases total peripheral resistance.</p> Signup and view all the answers

    What distinguishes cardiac muscle fibers from skeletal muscle fibers?

    <p>Cardiac muscle fibers are involuntary and branched.</p> Signup and view all the answers

    What is the primary mechanism for increasing blood flow to active tissues during exercise despite the overall sympathetic vasoconstriction?

    <p>Chemical signaling that reduces vascular responsiveness</p> Signup and view all the answers

    How do baroreceptors respond when blood pressure becomes too high?

    <p>They inhibit the cardioacceleratory center and stimulate the cardioinhibitory system.</p> Signup and view all the answers

    What is the effect of local metabolites on blood flow during exercise?

    <p>They enhance the dilation of arterioles in active muscle beds.</p> Signup and view all the answers

    According to Poiseuille’s Law, which factor among the following has the greatest influence on blood flow resistance?

    <p>Radius of the blood vessel</p> Signup and view all the answers

    What happens to blood flow to the kidneys during exercise as compared to a resting state?

    <p>It decreases substantially to prioritize blood flow to active muscles.</p> Signup and view all the answers

    What must occur to maintain Mean Arterial Pressure if cardiac output decreases?

    <p>Total Peripheral Resistance must increase.</p> Signup and view all the answers

    How does the body primarily adjust to maintain a constant Mean Arterial Pressure?

    <p>By regulating the resistance of the end of blood vessels.</p> Signup and view all the answers

    Which factor primarily contributes to the regulation of blood pressure via vessel diameter?

    <p>Total Peripheral Resistance.</p> Signup and view all the answers

    What is the main equation for calculating Cardiac Output?

    <p>CO = HR x SV.</p> Signup and view all the answers

    What happens to blood flow when arterioles are relaxed?

    <p>Blood flows freely.</p> Signup and view all the answers

    Which of the following would NOT contribute to an increase in Cardiac Output?

    <p>Decrease in Stroke Volume.</p> Signup and view all the answers

    What physiological mechanism is involved in vasoconstriction?

    <p>Nerve signals causing contraction of muscle fibers.</p> Signup and view all the answers

    How does an increase in heart rate affect stroke volume and blood pressure?

    <p>It decreases stroke volume and increases blood pressure.</p> Signup and view all the answers

    If blood pressure needs to be maintained under stress, what can the body do?

    <p>Increase heart rate and/or stroke volume.</p> Signup and view all the answers

    What is the normal Cardiac Output at rest?

    <p>5 L/min.</p> Signup and view all the answers

    What condition results from a restriction in blood supply to tissues, often leading to chest pain?

    <p>Angina pectoris</p> Signup and view all the answers

    Which part of the heart initiates the electrical impulse that begins the heartbeat?

    <p>Sinoatrial node</p> Signup and view all the answers

    Which of the following correctly describes the effect of sympathetic stimulation on heart rate?

    <p>Increases heart rate and contractility</p> Signup and view all the answers

    During vigorous exercise, how much can coronary blood flow increase compared to resting levels?

    <p>4-6 times</p> Signup and view all the answers

    In terms of myocardial oxygen utilization at rest, how much oxygen does the myocardium extract from coronary blood compared to other tissues?

    <p>70-80%</p> Signup and view all the answers

    What does the Rate Pressure Product (RPP) indicate about the heart?

    <p>It estimates myocardial workload</p> Signup and view all the answers

    How does the electrical signal travel through the heart after it starts at the sinoatrial node?

    <p>SA node → AV node → Bundle of His → Purkinje fibers</p> Signup and view all the answers

    What primarily causes myocardial infarction during impaired coronary blood supply?

    <p>A blood clot within coronary vessels</p> Signup and view all the answers

    Which of the following areas has the lowest intrinsic heart rate?

    <p>Ventricular tissue</p> Signup and view all the answers

    What is the purpose of a stress test in cardiovascular assessment?

    <p>To evaluate myocardial blood flow</p> Signup and view all the answers

    What happens to total peripheral resistance (TPR) during steady-rate exercise?

    <p>TPR decreases as a response to vasodilation in active muscles.</p> Signup and view all the answers

    How does cardiac output (CO) change during graded exercise?

    <p>CO gradually increases in response to rising exercise intensity.</p> Signup and view all the answers

    What effect does upper body exercise have compared to leg exercise at submaximal power outputs?

    <p>Upper body exercise requires greater oxygen consumption.</p> Signup and view all the answers

    In the context of blood pressure response, which statement is true about maximal exercise?

    <p>Maximal SBP may exceed 200 mmHg with reduced TPR.</p> Signup and view all the answers

    What is the primary factor contributing to hypotensive recovery after light to moderate exercise?

    <p>Blood pooling in skeletal muscle vascular beds during recovery.</p> Signup and view all the answers

    What is one major difference between concentric and eccentric contractions during resistance exercise?

    <p>Eccentric contractions are associated with muscle lengthening and greater resistance.</p> Signup and view all the answers

    Which equation correctly represents mean arterial pressure (MAP)?

    <p>MAP = DBP + [1/3 (SBP - DBP)]</p> Signup and view all the answers

    What is the relationship between systolic blood pressure (SBP) and cardiac output (CO) during steady rate exercise?

    <p>SBP initially rises then stabilizes as CO increases.</p> Signup and view all the answers

    How does the blood pressure response differ between upper body and lower body exercise during maximal effort?

    <p>Lower body exercise typically achieves higher SBP compared to upper body exercise.</p> Signup and view all the answers

    What primary factor influences blood flow resistance according to Poiseuille's Law?

    <p>Radius of the blood vessel</p> Signup and view all the answers

    Which receptors are primarily responsible for detecting high blood pressure and regulating cardiovascular responses?

    <p>Baroreceptors</p> Signup and view all the answers

    How do local metabolites influence blood flow during exercise?

    <p>By reducing alpha adrenergic receptor responsiveness</p> Signup and view all the answers

    What happens to blood flow distribution to the kidneys during vigorous exercise compared to resting conditions?

    <p>Decreases markedly</p> Signup and view all the answers

    Which physiological response occurs when blood pressure drops upon standing due to gravity?

    <p>Activation of the sympathetic nervous system</p> Signup and view all the answers

    What distinguishes systemic circulation from pulmonary circulation?

    <p>Systemic circulation delivers oxygenated blood throughout the body.</p> Signup and view all the answers

    Which statement accurately describes the function of isovolumetric contractions in the heart?

    <p>They involve a rise in ventricular pressure with unchanged volume.</p> Signup and view all the answers

    What impact does an increase in total peripheral resistance (TPR) have on blood pressure?

    <p>It increases blood pressure by reducing vessel diameter.</p> Signup and view all the answers

    Which parameter is NOT a direct contributor to cardiac output (CO)?

    <p>Cardiac Volume (CV)</p> Signup and view all the answers

    What is a consequence of venous pooling in the circulatory system?

    <p>It may induce fainting due to decreased cerebral blood flow.</p> Signup and view all the answers

    How does an increase in stroke volume affect mean arterial pressure (MAP)?

    <p>It increases MAP, assuming total peripheral resistance remains stable.</p> Signup and view all the answers

    What primarily influences the blood pressure gradient in the circulatory system?

    <p>The pressure drop across systemic vascular resistance.</p> Signup and view all the answers

    Which characteristic of cardiac muscle fiber structure is accurately described?

    <p>Cardiac muscle fibers are striated and branched.</p> Signup and view all the answers

    What happens to systolic blood pressure (SBP) during the early stages of steady-rate exercise?

    <p>SBP rapidly increases.</p> Signup and view all the answers

    How does total peripheral resistance (TPR) change during steady-rate exercise?

    <p>TPR decreases as arterioles in active muscles dilate.</p> Signup and view all the answers

    Which physiological change occurs with maximal exercise regarding systolic blood pressure (SBP)?

    <p>SBP may exceed 200 mmHg despite reduced TPR.</p> Signup and view all the answers

    What is the relationship between cardiac output (CO) and total peripheral resistance (TPR) during maximal exercise?

    <p>CO increases while TPR decreases.</p> Signup and view all the answers

    In patients undergoing hypotensive recovery post-exercise, what causes the blood pressure to drop below pre-exercise levels?

    <p>Blood pooling in muscles during recovery.</p> Signup and view all the answers

    What differentiates upper body exercise (UBE) from lower body exercise (LBE) in terms of physiological strain at submaximal power output?

    <p>UBE is associated with higher heart rate, ventilation, and blood pressure than LBE.</p> Signup and view all the answers

    What is the impact of concentric contractions on peripheral vasculature during resistance exercise?

    <p>They compress peripheral vasculature, increasing resistance.</p> Signup and view all the answers

    Which condition is associated with the highest oxygen consumption (VO2) during submaximal exercise?

    <p>Upper body exercise.</p> Signup and view all the answers

    What primarily contributes to the exaggerated blood pressure response observed during exercise?

    <p>Increased cardiac output paired with peripheral resistance changes.</p> Signup and view all the answers

    Which parameter is necessary to calculate total peripheral resistance (TPR)?

    <p>Mean arterial pressure (MAP)</p> Signup and view all the answers

    What electrical event does the QRS complex in an ECG primarily represent?

    <p>Ventricular depolarization and atrial repolarization</p> Signup and view all the answers

    Which term describes the condition where tissue death occurs due to a local lack of oxygen?

    <p>Infarction</p> Signup and view all the answers

    Which mechanism is responsible for vasodilation during exercise in active muscle tissue?

    <p>Decreased sympathetic activity</p> Signup and view all the answers

    What is the correct relationship between the Rate Pressure Product (RPP) and exercise intensity?

    <p>RPP has a linear relationship with exercise intensity</p> Signup and view all the answers

    Which statement about intrinsic heart rate is true?

    <p>It can increase with neuronal input from the sympathetic nervous system</p> Signup and view all the answers

    What is the primary role of the coronary circulation in the heart?

    <p>To supply oxygen and nutrients to the myocardium</p> Signup and view all the answers

    Which area of the heart has the lowest intrinsic rate of pacemaking?

    <p>Ventricular tissue</p> Signup and view all the answers

    What role does the AV node play in the conduction system of the heart?

    <p>It delays the electrical signal to allow for proper filling of the ventricles</p> Signup and view all the answers

    What physiological change occurs in the myocardium during vigorous exercise?

    <p>Coronary blood flow increases significantly</p> Signup and view all the answers

    Which neurotransmitter is associated with sympathetic stimulation of the heart?

    <p>Norepinephrine</p> Signup and view all the answers

    What mechanism is primarily employed to maintain mean arterial pressure (MAP) when cardiac output decreases?

    <p>Increasing total peripheral resistance</p> Signup and view all the answers

    Which statement best describes the relationship between stroke volume (SV) and heart rate (HR) in affecting cardiac output (CO)?

    <p>Increasing HR or SV will lead to an increase in CO.</p> Signup and view all the answers

    How does adjusting blood vessel diameter help regulate blood pressure?

    <p>By altering peripheral resistance to impact blood flow and pressure.</p> Signup and view all the answers

    What happens to blood flow when arterioles undergo vasoconstriction?

    <p>Blood flow decreases due to increased resistance.</p> Signup and view all the answers

    What is the impact of increased total peripheral resistance (TPR) on blood pressure if cardiac output remains steady?

    <p>BP increases with an increase in TPR.</p> Signup and view all the answers

    During exercise, which physiological change is likely to occur to ensure an adequate supply of blood to the muscles?

    <p>Increased stroke volume while simultaneously decreasing vascular resistance.</p> Signup and view all the answers

    What occurs to the mean arterial pressure (MAP) if both cardiac output and total peripheral resistance (TPR) decrease simultaneously?

    <p>MAP decreases due to decreased blood flow.</p> Signup and view all the answers

    In the scenario of arterioles being relaxed, what is the expected change in blood flow?

    <p>Blood flow increases similarly to how water flows when a hose nozzle is removed.</p> Signup and view all the answers

    When attempting to raise cardiac output during physical activity, which factors can be manipulated?

    <p>HR, SV or both can be increased to elevate cardiac output.</p> Signup and view all the answers

    What is the primary effect of increasing heart rate during exercise on mean arterial pressure (MAP)?

    <p>MAP will increase due to enhanced cardiac output.</p> Signup and view all the answers

    Study Notes

    Key Functions of the Cardiovascular System

    • Delivers oxygen and nutrients to active tissues.
    • Returns deoxygenated blood to the lungs.
    • Transports heat (byproduct of cellular metabolism) and hormones.

    Circulatory System

    • Consists of the heart and blood vessels.
    • The heart is a dual pump.
    • Two blood flow circuits:
      • Systemic circulation: Carries oxygenated blood from the heart to the body and returns deoxygenated blood back to the heart.
      • Pulmonary circulation: Circulation between the heart and lungs.
    • Arteries carry blood away from the heart, but they may not always be oxygenated.

    Heart Structure and Function

    • The heart has two types of cells:
      • Electrical: Responsible for the heart's electrical pathway.
      • Contractile: Responsible for the heart's mechanical function.
    • The heart is a muscular organ responsible for pumping blood throughout the body.

    ### Heart Anatomy

    • Four chambers:
      • Right atrium
      • Right ventricle
      • Left atrium
      • Left ventricle
    • Four valves:
      • Atrioventricular valves:
        • Tricuspid (right)
        • Bicuspid/mitral (left)
      • Semilunar valves:
        • Pulmonary
        • Aortic

    Heart Contraction Terms

    • Diastole: Resting phase of the heart.
      • End Diastolic Volume (EDV): Volume of blood in the heart during diastole.
    • Systole: Contraction phase of the heart.
      • End Systolic Volume (ESV): Volume of blood in the heart during systole.
    • Stroke Volume (SV): Amount of blood ejected by the heart with each beat (EDV-ESV).
    • Isovolumetric: Constant volume.
      • Isovolumetric contraction: Brief period when all heart valves are closed, ventricular pressure rises, but volume remains unchanged.
      • Isovolumetric relaxation: Brief period when all heart valves are closed, ventricular pressure drops, but volume remains unchanged.

    Venous Return

    • One-way valves prevent backflow and keep blood moving toward the heart.
    • Smooth muscle layer helps regulate blood flow in veins.
    • Skeletal muscle pump: Alternate compression and relaxation of skeletal muscles help return blood to the heart.

    Distribution of Blood at Rest

    • Venous pooling: Excess blood pooling in the lower extremities can cause fainting due to insufficient cerebral blood flow.

    Varicose Veins

    • Veins fail to maintain one-way blood flow.
    • Blood accumulates, leading to distended and painful veins.
    • Phlebitis: Inflammation and deterioration of the venous wall.
    • Exercise cannot prevent varicose veins, but it can minimize complications.

    Blood Pressure Gradient

    • Mean blood pressure decreases from the aorta to the venae cavae as blood travels away from the heart.
    • The greatest decrease in blood pressure occurs in the small arteries and arterioles.
    • Blood pressure continues to decrease through the capillaries and veins as blood returns to the heart.

    Blood Pressure

    • Systolic blood pressure (SBP): The pressure exerted during ventricular contraction.
    • Diastolic blood pressure (DBP): The pressure exerted during ventricular relaxation.

    Mean Arterial Pressure (MAP)

    • MAP represents the perfusion pressure of organs.
    • MAP below 60 mmHg for a significant period can cause organ ischemia.
    • MAP = DBP + [⅓(SBP-DBP)]

    Hypertension

    • High blood pressure.
    • Hardened arteries and neural hyperactivity increase resistance.
    • 95% of cases are idiopathic (cause unknown).

    Factors Influencing Arterial Blood Pressure

    • MAP = CO x TPR, where CO = HR x SV
    • Increased blood pressure with increased:
      • Blood volume
      • Heart rate
      • Stroke volume
      • Blood viscosity
      • Total peripheral resistance (TPR)
    • TPR is influenced by vessel diameter, length, and viscosity.

    Altering Cardiac Output (CO) to Change Mean Arterial Pressure

    • Maintaining constant flow in and out of a vessel maintains a constant MAP.
    • Increased CO (e.g., during exercise) increases MAP because of increased flow and resistance.
    • The body adjusts vascular resistance to maintain MAP within a healthy range.

    Total Peripheral Resistance (TPR)

    • The body uses vessel diameter to regulate blood pressure.
    • Vasoconstriction (narrowing) or vasodilation (widening) of blood vessels changes TPR.

    Cardiac Output (CO)

    • CO is the amount of blood ejected by one ventricle in one minute.
    • Resting CO is approximately 5 L/min.
    • To increase CO, increase heart rate (HR), stroke volume (SV), or both.

    CO and TPR Relationship

    • MAP = CO x TPR
    • TPR = MAP/CO
    • At rest, typical values are:
      • SBP = 126 mmHg
      • DBP = 80 mmHg
      • CO = 5 L/min
      • TPR = 19 mmHg/L

    Steady Rate Exercise

    • During the initial minutes of steady rate exercise, rapid increases in CO lead to a rapid increase in SBP.
    • Vasodilation in active muscles lowers TPR, allowing for increased blood flow to the peripheral vasculature.
    • As exercise continues, SBP gradually decreases as arterioles in active muscles continue to dilate, further decreasing TPR.
    • Muscle contraction and relaxation "milk" blood back to the heart (venous return).

    Graded Exercise

    • SBP increases rapidly at the start of exercise and increases linearly with exercise intensity.
    • DBP remains unchanged or decreases slightly.
    • Maximal SBP can reach 200 mmHg or higher, even with reduced TPR, reflecting high CO during intense exercise.

    Blood Pressure Response to Exercise

    • Resistance exercise:
      • Concentric (shortening) contractions compress peripheral vasculature, increasing resistance.
      • The magnitude of the increase depends on the intensity of effort and the amount of muscle mass used.

    Submaximal Upper Body Exercise (UBE)

    • UBE requires greater oxygen consumption than lower body exercise at any submaximal power output.
    • This is due to:
      • Lower mechanical efficiency
      • Recruitment of stabilizing muscles
      • Greater physiological strain
    • Leads to higher heart rate, ventilation, blood pressure, and perceived exertion (RPE).

    Maximal Upper Body Exercise

    • VO2 values are typically 20-30% lower than during lower body exercise.
    • Lower maximal heart rate and pulmonary ventilation.
    • Smaller muscle mass activated.

    CO and TPR Example

    • SBP = 210 mmHg
      • DBP = 90 mmHg
      • CO = 20 L/min
      • TPR = 6.5

    Hypotensive Recovery Response

    • After sustained light to moderate exercise, SBP temporarily falls below pre-exercise levels for up to 12 hours.
    • This is due to blood pooling in skeletal muscle vascular beds during recovery.

    Clinical Significance of Exaggerated Blood Pressure Response

    • Increased risk of developing hypertension.
    • Increased risk of cardiovascular mortality and events.
    • Evidence of cardiac hypertrophy (increased heart muscle).

    Heart's Blood Supply

    • The heart chambers do not receive nutrients from the blood they contain.
    • Coronary circulation supplies the heart muscle with approximately 5% (250 mL) of total cardiac output.
    • The right and left coronary arteries branch from the aorta behind the aortic valve.
    • Arteries divide into a dense capillary network to nourish the myocardium.
    • The coronary sinus and anterior cardiac veins collect blood and deliver it directly to the right atrium.

    Myocardial Oxygen Utilization

    • At rest, the myocardium extracts 70-80% of oxygen from coronary blood flow.
    • Other tissues typically use only 25% of oxygen from blood flow.
    • During vigorous exercise, coronary blood flow increases 4-6 times above resting levels.

    Impaired Coronary Blood Supply

    • Myocardial muscle is purely aerobic.
    • Interrupted blood flow leads to chest pain (angina pectoris).
    • Exercise increases energy demands, making it a diagnostic tool for myocardial blood flow (ischemia).
    • A blood clot in a coronary vessel results in myocardial infarction (heart attack).
      • Damage can range from mild to severe.
    • Ischemia: Restricted blood supply to tissues.
    • Hypoxia: Deprivation of oxygen supply to a region of the body.
    • Infarction: Tissue death due to oxygen deprivation.

    Rate Pressure Product (RPP)

    • Provides an estimate of myocardial workload (oxygen uptake).
    • RPP = SBP x HR.
    • RPP has a linear relationship with exercise intensity.
    • Chronic exposure to high myocardial workload can lead to cardiac hypertrophy.

    Cardiovascular Regulation and Integration

    • Cardiac muscle can maintain its own rhythm (heart rate).
    • Without extrinsic stimuli, the intrinsic heart rate is approximately 100 BPM.
    • Extrinsic control (neural and hormonal factors) can adjust heart rate from 40 BPM at rest to 220 BPM during intense exercise.

    ### Autorhythmic/Automaticity

    • The heart can beat on its own without external commands.
    • It does not rely on a nerve to initiate contraction.

    Intrinsic Regulation of Heart Rate

    • The sinoatrial (SA) node initiates the heart's electrical signal.
    • The signal propagates through the atrioventricular (AV) node, bundle of His, and Purkinje fibers.
    • The AV node delays the signal for 0.10 seconds, allowing the atria to contract before ventricular filling.
    • Ventricles contract approximately 0.06 seconds after stimulation.

    ### Electrocardiogram (ECG/EKG)

    • Records the electrical activity of the heart.
    • P wave: Atrial depolarization.
    • QRS complex: Ventricular depolarization and atrial repolarization.
    • T wave: Ventricular repolarization.
    • ECG abnormalities can indicate coronary heart disease.
      • ST segment depression may indicate a myocardial infarction.

    ### Relationship Between Pressure Changes and ECG

    • Atrial depolarization signals atrial contraction, leading to a slight increase in blood volume and ventricular pressure.
    • Ventricular depolarization triggers contraction and the generation of maximal pressure, followed by ventricular repolarization.

    Areas of the Heart Capable of Initiating a Rhythm

    • The lower a heart region's intrinsic heart rate, the slower it beats.
    • Sinoatrial node: 60-100 BPM.
    • Atrial tissue: 60-100 BPM.
    • AV node: 40-60 BPM.
    • Ventricular tissue: 20-40 BPM.

    Extrinsic Heart Rate Regulation

    • Neural influences modify the inherent rhythm of the myocardium to adjust heart rate based on exercise demands.
    • Heart rate range can be between 20-200 BPM depending on fitness level.

    ### Sympathetic and Parasympathetic Control

    • Sympathetic stimulation:
      • Release of catecholamines (norepinephrine and epinephrine).
      • Tachycardia: Increased heart rate.
        • Increased SA node depolarization, faster HR.
        • Increased contractility.
    • Parasympathetic influence:
      • Release of acetylcholine (vagal influence).
      • Bradycardia: Decreased heart rate.
        • Slower SA node depolarization, slower HR.

    ### Exercise and Blood Flow

    • Parasympathetic neural control:
      • Excitation of the iris, gallbladder, and coronary arteries.
      • Inhibition of gut sphincters, intestines, and skin vasculature.
      • During exercise onset, HR increases due to parasympathetic inhibition.

    ### Sympathetic Control on Blood Flow

    • Norepinephrine (NE) through adrenergic fibers in the smooth muscle of small arteries, arterioles, and precapillary sphincters regulates blood flow.
    • Inactive tissue (vasoconstriction):
      • Renal, splanchnic, and inactive skeletal muscle.
      • Leads to systemic vasoconstriction in inactive muscle.
    • Active tissue (vasodilation):
      • Active skeletal muscle:
        • Decreases sympathetic nervous system (SNS) activity.
        • Vasodilation occurs in working muscles to deliver more blood.

    ### Neural Response During Exercise

    • Anticipatory response:
      • Decreased parasympathetic activity.
      • Increased sympathetic activity.
    • Exercise:
      • Early parasympathetic inhibition.
      • More intense sympathetic stimulation.
    • These changes lead to:
      • Increased heart rate and contractility.
      • Increased arterial blood pressure.
      • Vasodilation of active skeletal muscles.
      • Vasoconstriction of skin, gut, and spleen.
      • Vasoconstriction increases venous return.

    ### Functional Sympatholysis

    • Sympathetic neural activity on blood vessels typically causes vasoconstriction.
    • The body utilizes local changes in muscle metabolites and other substances to reduce vascular responsiveness to sympathetic stimulation, resulting in vasodilation in active muscles.

    ### Peripheral Input Control of Cardiovascular Response

    • The initial signal to drive the cardiovascular system comes from higher brain centers.
    • Feedback from peripheral receptors fine-tunes the response:
      • Chemoreceptors: Sensitive to blood oxygen, carbon dioxide, and pH levels.
      • Baroreceptors: Sensitive to changes in arterial blood pressure.
      • Muscle mechanoreceptors: Sensitive to force and speed of muscular movement.
        • Located in the heart, skin, and joints.
      • Metaboreflex muscle chemoreceptors:
      • Sensitive to muscle metabolites such as potassium and lactic acid.
      • Contribute to the exercise pressor reflex.

    Blood Pressure Response to Standing

    • When standing, gravity pulls blood down, leading to a decrease in blood pressure.
    • Baroreceptors in the carotid arteries and aorta detect this change.
    • Baroreceptors stimulate the sympathetic nervous system, increasing heart rate, contractility, and vasoconstriction to increase blood pressure and maintain adequate blood flow to the brain.

    ### Baroreceptors

    • Located in the aortic arch and common carotid arteries.
    • Detect changes in blood pressure.
    • If blood pressure is too high:
      • Baroreceptors stimulate the cardioinhibitory center of the brain to lower blood pressure.
      • They inhibit the cardioacceleratory center.
      • To lower blood pressure:
        • Heart rate is reduced.
        • Cardiac output (CO) is decreased.
        • The vasomotor center is inhibited.
        • Arterial vasodilation occurs.
      • Homeostasis is restored.

    ### Chemoreceptors

    • Sensitive to oxygen, carbon dioxide, and pH levels in the blood.
    • Detect changes in these levels.
    • If oxygen levels decrease and pH decreases (more acidic) with an increase in carbon dioxide:
      • Chemoreceptors stimulate the cardioacceleratory center of the brain.
      • The cardioinhibitory center is inhibited.
      • Increased CO.
      • The respiratory center is stimulated, increasing breathing rate.
      • Increased oxygen and pH.
      • Carbon dioxide levels decrease.
      • Homeostasis is restored.

    Blood Flow Regulation

    • Flow = Pressure x Resistance.
    • Total peripheral resistance (TPR) is important for regulating blood flow.
    • Factors influencing TPR:
      • Physical characteristics of blood (viscosity).
      • Size of individual vessels (length and diameter).

    ### Poiseuille's Law

    • Quantifies blood flow resistance.
    • Flow = (pressure gradient x vessel radius^4)/(vessel length x viscosity)
    • Vessel diameter is the most influential factor.
    • Vessel length and blood viscosity have less of an impact because they are generally constant.
    • Even small changes in vessel diameter can significantly alter blood flow.

    Exercise and Blood Flow

    • Nerves and local metabolites dilate arterioles in active muscle beds, increasing blood flow.
    • Visceral vasoconstriction and the muscle pump help direct blood to the central circulation.
    • Example:
      • Kidneys:
        • Rest: 1100 mL per minute (20% of CO).
        • Exercise: 250 mL per minute (1% of CO).

    Active Muscle

    • At rest, only 1 out of 40 capillaries in muscle are open.
    • Opening dormant capillaries during exercise has three key functions:
      • Increases muscle blood flow.
      • Allows for a large blood volume with minimal increases in blood flow velocity.
      • Increases the effective surface area for gas exchange between blood and muscle fibers.
      • Local factors (autoregulatory mechanisms) involved:
        • Decreased pH.
        • Increased PCO2 (carbon dioxide).
        • Increased ADP.
        • Increased intracellular calcium (Ca++).
        • Increased temperature.

    Key Functions of the Cardiovascular System

    • Delivers oxygen and nutrients to active tissues.
    • Returns deoxygenated blood to the lungs.
    • Transports heat and hormones.

    Circulatory/Cardiovascular System

    • The heart is a dual pump.
    • Two blood flow circuits:
      • Systemic circulation: Heart and system, travels everywhere in the body besides the lungs.
      • Pulmonary circulation: Heart and lungs, travels only to the lungs for gas exchange.
    • Differences between the circuits:
      • Pulmonary circuit has shorter blood flow distance.
      • Systemic circulation has higher pressure.
    • Arteries carry blood away from the heart, but it may not always be oxygenated.
    • Systemic circulation carries oxygenated blood away from the heart and returns deoxygenated blood back to the heart.

    Heart Cell Types

    • Electrical cells create the electrical pathway for heart contractions.
    • Contractile cells are responsible for the mechanical force of heart contraction.

    Heart Structure and Function

    • Skeletal muscle characteristics: striated tubular fibers, multi-nucleated, voluntary, attached to the skeleton.
    • Cardiac muscle characteristics: striated branched fibers, uninucleated, involuntary, only found in the heart walls.

    Anatomy of the Heart

    • Four chambers:
      • Right atrium
      • Right ventricle
      • Left atrium
      • Left ventricle
    • Four valves:
      • Atrioventricular valves:
        • Tricuspid (right)
        • Bicuspid/mitral (left)
      • Semilunar valves:
        • Pulmonary
        • Aortic

    Terms and Definitions for Heart Contraction

    • Diastole: Rest phase of the heart.
      • End Diastolic Volume (EDV): The volume of blood in the heart during diastole.
    • Systole: Contraction phase of the heart.
      • End Systolic Volume (ESV): The volume of blood in the heart during systole.
    • EDV - ESV = Stroke Volume (SV): The amount of blood ejected with each heartbeat.
    • Isovolumetric: Same volume.
      • Isovolumetric contraction: Brief period when all heart valves are closed, ventricular pressure increases, but volume stays the same.
      • Isovolumetric relaxation: Brief period when all heart valves are closed, ventricular pressure decreases, but volume stays the same.

    Venous Return

    • One-way valves: Prevent backflow and move blood towards the heart.
    • Smooth muscle layer: Helps regulate blood flow.
    • Skeletal muscle pump: Alternate contraction and relaxation of skeletal muscles to move blood back to the heart.

    Distribution of Blood at Rest

    • Venous pooling: Can cause fainting due to insufficient blood flow to the brain.
    • A significant amount of blood is stored in the lower body, making it harder for the brain to receive blood quickly.

    Varicose Veins

    • Veins lose their one-way blood flow property.
    • Blood pools causing vein distention and pain.
    • Phlebitis: Venous wall inflammation that progresses to deterioration, requiring vessel removal.
    • Exercise does not prevent varicose veins but minimizes complications.

    Blood Pressure Gradient

    • Mean arterial pressure (MAP) decreases from aorta to venae cavae.
    • Decreases as blood moves further from the heart through arteries.
    • Greatest decrease in small arteries and arterioles.
    • Continues to decrease through capillaries and veins back to the heart.

    Blood Pressure

    • Systolic blood pressure (SBP): Pressure during ventricular contraction.
    • Diastolic blood pressure (DBP): Pressure during ventricular relaxation.

    Mean Arterial Pressure (MAP)

    • Represents the perfusion pressure of organs.
    • MAP below 60 mmHg for a considerable amount of time can result in insufficient blood flow and organ ischemia.
    • MAP = DBP + [⅓(SBP-DBP)]

    Hypertension

    • Hardened arteries and neural hyperactivity increase resistance.
    • 95% are idiopathic (cause unknown).

    Factors Influencing Arterial Blood Pressure

    • MAP = CO x TPR, where CO = HR x SV
    • Increased BP with increased:
      • Blood volume
      • Heart rate
      • Stroke Volume
      • Blood viscosity
      • Total Peripheral Resistance (TPR)
    • TPR = diameter, length, viscosity
      • Vessel length remains constant after adulthood.
      • TPR is mainly regulated by vessel diameter (vasoconstriction).

    MAP and Cardiac Output Changes

    • A constant MAP is maintained with constant flow in and out of the vessel.
    • An increase in HR, SV, and overall flow during exercise increases pressure, as the vessel cannot accommodate the increased flow.
    • Constant MAP is maintained by adjusting resistance at the ends of vessels.
    • If CO decreases, TPR must increase to maintain MAP.

    Total Peripheral Resistance (TPR)

    • Regulates blood pressure by adjusting vessel diameter.
    • Nerves control muscle fibers causing vasoconstriction or vasodilation.

    Cardiac Output (CO)

    • Amount of blood ejected by one ventricle per minute.
    • At rest, CO = 5 L/min.
    • Increases by increasing HR, SV, or both.

    Cardiac Output and TPR Relationships

    • MAP = CO x TPR or TPR = MAP/CO
    • MAP = DBP + [⅓ (SBP-DBP)]
    • TPR = DBP + [⅓ (SBP-DBP)]/ CO
    • At rest:
      • SBP = 126, DBP = 80, CO = 5 L/min, TPR = 19mmHg/L.

    Steady-Rate Exercise

    • Increased blood flow (CO) in the first minutes of exercise rapidly increases SBP.
    • Vasodilation in active muscles decreases TPR to increase peripheral blood flow.
    • As exercise continues, SBP gradually decreases as arterioles dilate further, lowering TPR.
    • Muscle contraction and relaxation pump blood back to the heart (venous return).

    Graded Exercise

    • SBP increases rapidly at the start and increases linearly with exercise intensity.
    • DBP remains unchanged or decreases slightly.
    • Maximal SBP can reach 200+mmHg despite reduced TPR, likely due to increased CO during maximal exercise in those with high aerobic capacity.

    Blood Pressure Response to Exercise

    • Resistance Exercise:
      • Concentric contractions compress peripheral vasculature increasing resistance.
      • Magnitude of increase depends on effort intensity and muscle mass used.

    Submaximal Upper Body Exercise (UBE)

    • Requires greater oxygen consumption than lower body exercise at the same power output.
    • Lower mechanical efficiency leads to higher physiological strain.
    • Greater recruitment of stabilizing muscles.
    • Higher HR, ventilation, BP, and perceived exertion.

    Maximal Upper Body Exercise

    • VO2 values are typically 20-30% lower than lower body exercises.
    • Lower maximum HR and pulmonary ventilation due to smaller muscle mass activated.

    Cardiac Output and TPR Example with Exercise

    • Assume:
      • SBP = 210, DBP = 90, CO = 20 L/min
    • TPR = DBP + [⅓ (SBP-DBP)]/ CO
    • TPR = 6.5

    Hypotensive Recovery Response

    • After sustained moderate exercise, SBP temporarily decreases below pre-exercise levels for up to 12 hours in both healthy and hypertensive individuals.
    • Mechanism: Blood pools in skeletal muscle vascular beds during recovery.

    Clinical Significance of Exaggerated Blood Pressure Response

    • May increase risk for future hypertension development.
    • Increased risk for cardiovascular mortality and events.
    • Indicates cardiac hypertrophy (enlarged heart).

    Heart's Blood Supply

    • Coronary circulation supplies heart muscle with approximately 5% (250 ml) of total cardiac output.
    • Right and left coronary arteries originate from the aorta behind the aortic valve.
    • Arteries branch into capillary networks that supply the myocardium (heart muscle).
    • Coronary sinus and anterior cardiac veins collect blood and empty into the right atrium.

    Myocardial Oxygen Utilization

    • Myocardium extracts 70-80% of oxygen from coronary blood flow at rest, higher than other tissues (25%).
    • During vigorous exercise, coronary blood flow increases 4-6 times above resting levels.

    Impaired Coronary Blood Supply

    • Heart muscle is purely aerobic, relying on oxygen.
    • Disrupted blood flow results in chest pain (angina pectoris).
    • Exercise increases energy demand, making stress tests a diagnostic tool for myocardial blood flow (ischemia) and detecting limitations.
    • Blood clots in coronary vessels lead to myocardial infarction (heart attack), causing varying levels of damage.
    • Ischemia: Restriction in blood supply to tissues.
    • Hypoxia: Lack of adequate oxygen supply to a region of the body.
    • Infarction: Tissue death due to lack of oxygen.

    Rate Pressure Product (RPP)

    • Non-invasive estimation of myocardial workload (oxygen uptake).
    • RPP = SBP x HR
    • Linear relationship with exercise intensity.
    • Chronic exposure to higher RPP can cause cardiac hypertrophy.

    Cardiovascular Regulation and Integration

    • Cardiac muscle has an intrinsic rhythm (heart rate).
    • Without outside stimuli, the intrinsic heart rate is 100 BPM.
    • Extrinsic control (neurohumoral factors) adjusts heart rate from 40 BPM at rest to 220 BPM at peak exercise.

    Autorhythmicity/Automaticity

    • The heart can beat independently without external stimulus.
    • Doesn't rely on a nerve to initiate contraction.

    Intrinsic Regulation of Heart Rate

    • Membrane potential changes lead to depolarization, initiating the contraction signal.
    • Starts at the sinoatrial (SA) node, then propagates outwards.
    • Sequence: SA node to atrioventricular (AV) node, to Purkinje fibers, to the bundle of His.
    • The signal travels upwards along the ventricular walls.
    • AV node delays the electrical signal for 0.10 seconds to allow atrial contraction before ventricular filling.
    • Ventricles receive the signal and contract after 0.06 seconds.

    Electrocardiogram (ECG/EKG)

    • Records electrical activity of the heart:
      • P wave: Atrial depolarization.
      • QRS complex: Ventricular depolarization and atrial repolarization simultaneously.
      • T wave: Ventricular repolarization.
    • ECG abnormalities can indicate coronary heart disease.
      • ST segment depression can be a sign of myocardial infarction (heart attack).

    Relationship between Pressure Changes and EKG

    • Atrial depolarization leads to atrial contraction, increasing ventricular pressure slightly.
    • Ventricular depolarization through the AV node causes ventricular contraction and the generation of maximal pressure.
    • Eventually, ventricular repolarization occurs, followed by relaxation and a decrease in pressure.

    Areas of the Heart and Intrinsic Rhythm Rate

    • The lower the area in the heart, the lower the intrinsic rate:
      • Sinoatrial node (SA node): 60-100 BPM.
      • Atrial tissue: 60-100 BPM.
      • AV node: 40-60 BPM.
      • Ventricular tissue: 20-40 BPM.

    Extrinsic Heart Rate Regulation

    • Neural influences overlay the heart's natural rhythm.
    • Adjust heart rate for exercise anticipation and intensity changes.
    • Range: 20 - 200 BPM depending on fitness levels.

    Sympathetic and Parasympathetic Control

    • Sympathetic stimulation:
      • Catecholamines (NE/Epinephrine): Increase heart rate (tachycardia).
      • Effects: Increased SA node depolarization, increased HR, increased contractility.
    • Parasympathetic influence:
      • Acetylcholine/vagal influence: Decreases heart rate (bradycardia).
      • Effects: Decreased SA node depolarization, reduced HR.

    Exercise and Blood Flow

    Parasympathetic Neural Control

    • Periphery:
      • Excitation of iris, gallbladder, coronary arteries.
      • Inhibition of gut sphincters, intestines, and skin vasculature.
      • During exercise onset, HR increases by inhibiting the PNS.

    Sympathetic Control on Blood Flow

    • Mechanism: Norepinephrine through adrenergic fibers located in smooth muscle of small arteries, arterioles, and precapillary sphincters.
    • Inactive Tissues: (Vasoconstriction)
      • Renal, splanchnic, and inactive skeletal muscle.
      • Produces systemic vasoconstriction.
    • Active Tissues: (Vasodilation)
      • Active muscle
      • Decreases SNS activity.

    Neural Response During Exercise

    • Anticipatory Response:
      • Decreased parasympathetic activity.
      • Increased sympathetic activity.
    • Exercise:
      • Initial parasympathetic inhibition, then sympathetic stimulation as exercise intensity increases.
    • Effects:
      • Increased HR and contractility.
      • Increased arterial blood pressure.
      • Vasodilation in active skeletal muscles.
      • Vasoconstriction in skin, gut, spleen, etc., enhancing venous return.

    Functional Sympatholysis

    • Sympathetic neural activity on blood vessels usually causes vasoconstriction.
    • Local changes in muscle metabolites during exercise reduce vascular responsiveness to alpha adrenergic receptor activation, resulting in vasodilation despite sympathetic activation.

    Peripheral Input Control of CV Response

    • Initial signal for cardiovascular responses comes from higher brain centers.
    • Fine-tuned by feedback from:
      • Chemoreceptors: Sensitive to blood O2, CO2, and pH levels.
      • Baroreceptors: Sensitive to changes in arterial blood pressure.
      • Muscle mechanoreceptors (heart, skin, joints): Sensitive to force and speed of muscular movement.
      • Metaboreflex muscle chemoreceptors: Sensitive to muscle metabolites like K+ and lactic acid, responsible for the exercise pressor reflex.
    • All of these detect changes in chemistry or pressure.

    BP Response to Standing

    • Gravity-induced drop in BP occurs when standing up due to blood pooling in the lower extremities.
    • Baroreceptors in the carotid and aorta detect this drop.
    • The brain responds by activating the sympathetic nervous system, increasing HR, contractility, CO, and blood volume.
    • Alpha 1 receptors cause blood vessel constriction to counteract the pressure drop.

    Baroreceptors

    • Located in the aortic arch and common carotid artery.
    • High BP stimulates baroreceptors, sending signals to the brain.
    • Brain response:
      • Inhibits cardioacceleratory center, stimulating cardioinhibitory center.
      • Goal: Reduce BP by lowering CO.
      • Mechanism:
        • Reduced HR, leading to decreased CO.
        • Inhibition of vasomotor center: Vessel constriction is prevented.
        • Arterial vasodilation occurs, reducing BP.
      • Homeostasis is restored.

    Chemoreceptors

    • Sensitive to oxygen and carbon dioxide levels.
    • In disturbed homeostasis (decreased O2 and pH, increased CO2):
      • Chemoreceptors are stimulated.
      • Reflex response:
        • Cardioinhibitory center is inhibited.
        • Cardioacceleratory center is stimulated, increasing CO.
        • Respiratory center is stimulated, increasing breathing rate.
      • Increased O2, pH, and decreased CO2 levels restore homeostasis.

    Blood Flow Regulation

    • Flow = Pressure x Resistance
    • Factors determining TPR (resistance to blood flow):
      • Physical characteristics of the blood (viscosity).
      • Size of individual vessels:
        • Length of conducting tube.
        • Diameter of blood vessel.

    Poiseuille's Law

    • Quantifies blood flow resistance.
    • Flow = Pressure gradient x vessel radius^4/ vessel length x viscosity
    • Vessel diameter has the most significant impact.
    • Vessel length and blood viscosity have less impact as they are relatively constant.
    • Small changes in vessel diameter create large changes in blood flow.

    Exercise and Blood Flow

    • Nerves and local metabolites dilate arterioles in active muscle beds.
    • Visceral vasoconstriction and muscle pump deliver blood to the central circulation.
    • Example:
      • Kidneys: Rest = 1100 ml/minute (20% of CO), Exercise = 250 ml/minute (1% of CO).

    Active Muscle

    • Dormant capillaries (1 out of 40 open) at rest.
    • Opening dormant capillaries during exercise increases blood flow to muscle and provides a large blood volume with a minimal increase in blood flow velocity.
    • Increased surface area for gas and nutrient exchange.
    • Local factors (autoregulatory mechanisms):
      • Decreased pH
      • Increased PCO2
      • Increased ADP
      • Increased calcium
      • Increased temperature

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    Description

    Explore the key functions and structures of the cardiovascular system in this informative quiz. Understand the roles of the heart, blood vessels, and the pathways of systemic and pulmonary circulation. Test your knowledge of heart anatomy and physiology as you dive into this essential topic.

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