Cardiovascular Responses to Acute Exercise PDF

The Cardiovascular System and Its Control Dianne Salvaleon Why is the heart important in physical activity? "Just because someone is “in shape” doesn’t mean their heart is.” -VCU Health https://www.vcuhealth.org/news/how-exercise-strengthens-and-changes-an-athletes-heart In 2012, Olympic gold medali...

The Cardiovascular System and Its Control Dianne Salvaleon Why is the heart important in physical activity? "Just because someone is “in shape” doesn’t mean their heart is.” -VCU Health https://www.vcuhealth.org/news/how-exercise-strengthens-and-changes-an-athletes-heart In 2012, Olympic gold medalist swimmer Dana Vollmer set a world record even as a genetic condition threatened to stop her heart at any moment. She has long-QT syndrome, one of several inherited heart diseases that can send patients into cardiac arrest. Pistol Pete- Maravich was a renowned basketball player, averaging 38 shots and 44 points per game at Louisiana State University; averaged 24 points per game over 10 years as a professional, won 1 scoring title, and was inducted into the Basketball of Fame a year before his death. He died suddenly while playing a game of pick-up basketball at 40 years of age, evidently without prior symptoms, and his single RCA anomaly was implicated as the cause of death (4). His autopsy showed an 8-mm RCA, and a 2-mm LAD with normal distribution; died from subsequent myocardial disease, perhaps from myocarditis, and not from congenital coronary artery disease as previously assumed. In this chapter we’ll look at: Heart Blood Flow Myocardium Extrinsic Control of Heart Activity Explain how blood ows through the heart. Describe the myocardium Distinguish the systems that control heart activity List and describe the characteristics of the three types of blood vessels De ne pulse and blood pressure fl fi Describe blood volume, rbc, blood viscosity And relate them to exercise and physical activity Vascular System Blood Pressure Distribution of Blood Blood Blood Volume and Composition Red Blood Cells Blood Viscosity Functions: Delivery of oxygen and other nutrients Removal of carbon dioxide and other metabolic waste products Transport of hormones and other molecules Support ]thermoregulation and control of body uid balance Maintenance of acid-base balance Regulation of immune function The cardiovascular system serves a number of important functions in the body and supports every other physiological system. The major cardiovascular functions can be grouped into six categories: The cardiovascular system delivers oxygen and nutrients to, and removes carbon dioxide and metabolic waste products from, every cell in the body. It transports hormones (chapter 4) from endocrine glands to their target receptors. The cardiovascular system supports body temperature regulation (chapter 12), and the blood’s bu ering capabilities help control the body’s pH. The cardiovascular system maintains appropriate uid balance across the uid compartments of the body and helps prevent infection from invading organisms. Although this is just an abbreviated list of roles, the cardiovascular functions listed here are important for understanding the physiological basis of exercise and sport. Obviously these roles change and become even more critical with the challenges imposed by exercise. fl fl All physiological functions and virtually every cell in the body depend in some way on the cardiovascular system. Any system of circulation requires three components: ff fl Cardiovascular System System of Circulation 3 components A Pump A system of channels or tubes A uid medium All physiological functions and virtually every cell in the body depend in some way on the cardiovascular system. Any system of circulation requires three components Pump : heart Channels and tubes: veins, arteries Fluid medium: blood fl ffi fi fl * in order to keep blood circulating, the heart must generate su cient pressure to drive blood through the continuous network of blood vessels in a closed-loop system. Thus the primary goal of the cardiovascular system is to ensure that there is adequate blood ow throughout the circulation to meet the metabolic demands of the tissues. Let’s rst look at the heart. Video link: (scan the qr code) Heart Muscular pump composed of cardiac muscle bers Located in the mediastinum in the center of the thoracic cavity (more on the left side) Primary pump that circulates blood through the entire cardiovascular system 2 atria (receiving chambers) 2 ventricles (discharging chambers) The heart, a muscular pump made up of cardiac muscle bers, could be considered a muscle rather than an organ. It has four chambers, or cavities, and beats an average of 60–100 beats per minute (bpm) or about 100,000 times in one day. Each time the cardiac muscle contracts, blood is ejected from the heart and pushed throughout the body within the blood vessels. fi fi The heart is located in the mediastinum in the center of the chest cavity; however, it is not exactly centered; more of the heart is on the left side of themediastinum than the right (see Figure 5-2 ). At about the size of a st and shaped like an upside-down pear, the heart lies directly behind the sternum. The tip of the heart at the lower edge is called the apex. Heart Muscular pump composed of cardiac muscle bers About the size of a st Shaped like an upside down pear 60-100 beats per minute (average) 100,000 times in one day The heart, a muscular pump made up of cardiac muscle bers, could be considered a muscle rather than an organ. It has four chambers, or cavities, and beats an average of 60–100 beats per minute (bpm) or about 100,000 times in one day. Each time the cardiac muscle contracts, blood is ejected from the heart and pushed throughout the body within the blood vessels. The heart is located in the mediastinum in the center of the chest cavity; however, it is not exactly centered; more of the heart is on the left side of themediastinum than the right (see Figure 5-2 ). fi fi fi At about the size of a st and shaped like an upside-down pear, the heart lies directly behind the sternum. The tip of the heart at the lower edge is called the apex. Heart Layers Heart Layers endocardium: inner layer of the heart lining the heart chambers; a very smooth, thin layer that serves to reduce friction as the blood passes through the heart chambers myocardium: thick, muscular middle layer of the heart; contraction of this muscle layer develops the pressure required to pump blood through the blood vessels pericardium: a double-layered pleural sac enclosing the heart epicardium: outer layer of the heart; visceral pericardium (inner layer of the sac) Parietal pericardium: outer layer of the sac Fluid between the two layers of the same reduces friction as the heart beats The wall of the heart is quite thick and is composed of three layers (see Figure 5-3 ): 1. The endocardium is the inner layer of the heart lining the heart chambers. It is a very smooth, thin layer that serves to reduce friction as the blood passes through the heart chambers. 2. The myocardium is the thick, muscular middle layer of the heart. Contraction of this muscle layer develops the pressure required to pump blood through the blood vessels. 3. The epicardium is the outer layer of the heart. The heart is enclosed within a double-layered pleural sac, called the pericardium. The epicardium is the visceral pericardium, or inner layer of the sac. The outer layer of the sac is the parietal pericardium. Fluid between the two layers of the sac reduces friction as the heart beats. Heart Chambers divided into four chambers two atria, or upper chambers (receiving chamber); blood returning to the heart collects here two ventricles, or lower chambers (discharging chamber); have thicker myocardium Interatrial septum and interventricular septum divide chambers intro right and left side Intertrial septum: a thin wall of tissue; in adults, functions so that there is no blood shunting between right and left atrium Inter ventricular septum: wall of cardiac muscle; allows for proper ow of blood supply ; serve as conduit for electrical conduction; communication between the atrium and ventricles The heart is divided into four chambers or cavities (see again Figure 5-3). There are two atria, or upper chambers, and two ventricles, or lower chambers. These chambers are divided into right and left sides by walls called the interatrial septum and the interventricular septum. thin wall of tissue that separates the right and left atria of the heart. In adult life, its main function is to separate the two atrial chambers so that there is no shunting of blood between them The atria are the receiving chambers of the heart. Blood returning to the heart via veins rst collects in the atria. The ventricles are the pumping chambers. They have a much thicker myocardium and their contraction ejects blood out of the heart and into the great arteries. fl fl fi The interventricular septum is the wall of cardiac muscle and membranous tissue that separates the left and right ventricles. Its purpose is to allow for the proper ow of blood supply through the circulatory system and to serve as a conduit for electrical conduction and communication between the atrium and ventricles Heart Valves Function: restraining gates to control the direction of blood ow allow blood to ow only in a forward direction Tricuspid valve: controls the opening between the right atrium and the right ventricle Pulmonary valve: prevents blood that has been ejected into the pulmonary artery from returning to the right ventricle as it relaxes Mitral Valve: Blood ows through to the left ventricle and cannot go back up into the left atrium Aortic valve: located between the left ventricle and the aorta. Four valves act as restraining gates to control the direction of blood ow. They are situated at the entrances and exits to the ventricles (see Figure 5-4 ). Properly functioning valves allow blood to ow only in a forward direction by blocking it from returning to the previous chamber. fl fl fl fl fi fl fl fi Tricuspid valve: an atrioventricular valve (AV), meaning that it controls the opening between the right atrium and the right ventricle. Once the blood enters the right ventricle, it cannot go back up into the atrium again. The pre x tri-, meaning three, indicates that this valve has three lea ets or cusps. 2. Pulmonary valve: a semilunar valve, with the pre x semi- meaning half and the term lunar meaning moon, indicate that this valve looks like a half moon. Located between the right ventricle and the pulmonary artery, this valve prevents blood that has been ejected into the pulmonary artery from returning to the right ventricle as it relaxes. 3. Mitral valve: also called the bicuspid valve, indicating that it has two cusps. Blood ows through this atrioventricular valve to the left ventricle and cannot go back up into the left atrium. 4. Aortic valve: a semilunar valve located between the left ventricle and the aorta. Blood leaves the left ventricle through this valve and cannot return to the left ventricle. Blood Flow through the heart Video link: (scan the qr code) Pair up! Answer the activity Blood Flow through the heart BLOOD FLOW THROUGH THE HEART The ow of blood through the heart is very orderly (see Figure 5-5 ). It progresses through the heart to the lungs, where it receives oxygen; then goes back to the heart; and then out to the body tissues and parts. The normal process of blood ow is: fl fl fl fl 1. Deoxygenated blood from all the tissues in the body enters a relaxed right atrium via two large veins called the superior vena cava and inferior vena cava. 2. The right atrium contracts and blood ows through the tricuspid valve into the relaxed right ventricle. 3. The right ventricle then contracts and blood is pumped through the pulmonary valve into the pulmonary artery, which carries it to the lungs for oxygenation. 4. The left atrium receives blood returning to the heart after being oxygenated by the lungs. This blood enters the relaxed left atrium from the four pulmonary veins. 5. The left atrium contracts and blood ows through the mitral valve into the relaxed left ventricle. 6. When the left ventricle contracts, the blood is pumped through the aortic valve and into the aorta, the largest artery in the body. The aorta carries blood to all parts of the body. BLOOD FLOW THROUGH THE HEART 1. Deoxygenated blood from all the tissues in the body enters a relaxed right atrium via two large veins called the superior vena cava and inferior vena cava. 2. The right atrium contracts and blood ows through the tricuspid valve (right AV Valve) into the relaxed right ventricle. 3. The right ventricle then contracts and blood is pumped through the pulmonary valve into the pulmonary artery, which carries it to the lungs for oxygenation. 4. The left atrium receives blood returning to the heart after being oxygenated by the lungs. This blood enters the relaxed left atrium from the four pulmonary veins. 5. The left atrium contracts and blood ows through the mitral valve (left AV valve) into the relaxed left ventricle. 6. When the left ventricle contracts, the blood is pumped through the aortic valve and into the aorta, the largest artery in the body. The aorta carries blood to all parts of the body. The ow of blood through the heart is very orderly (see Figure 5-5 ). It progresses through the heart to the lungs, where it receives oxygen; then goes back to the heart; and then out to the body tissues and parts. The normal process of blood ow is: fl fl fl fl fl fl 1. Deoxygenated blood from all the tissues in the body enters a relaxed right atrium via two large veins called the superior vena cava and inferior vena cava. 2. The right atrium contracts and blood ows through the tricuspid valve into the relaxed right ventricle. 3. The right ventricle then contracts and blood is pumped through the pulmonary valve into the pulmonary artery, which carries it to the lungs for oxygenation. 4. The left atrium receives blood returning to the heart after being oxygenated by the lungs. This blood enters the relaxed left atrium from the four pulmonary veins. 5. The left atrium contracts and blood ows through the mitral valve into the relaxed left ventricle. 6. When the left ventricle contracts, the blood is pumped through the aortic valve and into the aorta, the largest artery in the body. The aorta carries blood to all parts of the body. Myocardium Cardiac muscle Thickness varies at various location accdg to amt. of stress placed on it Left ventricle Thickest muscular wall caused by role in pumping blood to systemic circulation at rest, during normal and vigorous physical exertion The cardiac muscle is collectively called the myocardium or myocardial muscles. * the left ventricle is the most powerful pump of the four heart chambers because it myst generate su cient pressure to pump blood through the entire body. * When a person is sitting or standing , the left ventricle must contact with enough force to overcome the e ect of gravity, which tends to pool blood in the lower ff ffi extremities. Myocardium Left Ventricle NOTE: Adaptations in response to exercise training (aerobic and resistance) or diseases (high blood pressure, valvular heart disease) Hypertrophy Pumping capacity In response to either training or disease, over time the left ventricle adapts by increasing its size (hypertrophy) and pumping capacity, Myocardium Coronary arteries Supplies blood to the heart Blood ow increases to the (CA) when the heart is in between contractions Susceptible to atherosclerosis fl fl atherosclerosis or narrowing by the accumulation of plaque and in ammation Myocardium Contract as a single unit Striated in appearance Intercalated discs hold individual muscle bers so that they don’t pull apart during contractions Gap junctions allow rapid transmission of action potential Myocardial bers are homogenous Involuntary contractions are strong, quick and continuous Strength of contraction are modi ed fi fi fi by autonomic nervous system Cardiac Conduction System Special tissue within the heart is responsible for conducting an electrical impulse stimulating the di erent chambers to contract in the correct order. The path that the impulses travel is as follows: 1. The sinoatrial (SA) node, or pacemaker, is where the electrical impulses begin. From the sinoatrial node, a wave of electricity travels through the atria, causing them to contract, or go into systole. 2. The atrioventricular node is stimulated. 3. This node transfers the stimulation wave to the atrioventricular bundle (formerly called bundle of His). 4. The electrical signal next travels down the bundle branches within the interventricular septum. ff fi 5. The Purkinje bers out in the ventricular myocardium are stimulated, resulting in ventricular systole. Cardiac Conduction System SA generates impulse Impulse travels to atria and then AV node. AV node connects electrical impulse from atria to ventricle. Impulse is delayed for 0.13s as it passes through AV node to AV bundle From bundle of His divides into right and left pathways stimulating the right and left ventricles towards the apex of the heart. An electrocardiogram (EKG or ECG) provides a graphic wave record of the electrical signal as it moves through the conduction system of the heart. It can be used to aid clinical diagnoses, for example in someone who has had a myocardial infarction in the past or is at risk for one in the future. ECG provides no information about the pumping capacity of the heart, only its electrical activity. The P wave represents atrial depolarization and occurs when the electrical impulse travels from the SA node through the atria to the AV node. The QRS complex represents ventricular depolarization and occurs as the impulse spreads from the AV bundle to the Purkinje bers and through the ventricles. fi The T wave represents ventricular repolarization. Atrial repolarization cannot be seen, because it occurs during ventricular depolarization (QRS complex). Cardiac Cycle Video link: (scan the qr code) The P wave represents atrial depolarization and occurs when the electrical impulse travels from the SA node through the atria to the AV node. The QRS complex represents ventricular depolarization and occurs as the impulse spreads from the AV bundle to the Purkinje bers and through the ventricles. fi The T wave represents ventricular repolarization. Atrial repolarization cannot be seen, because it occurs during ventricular depolarization (QRS complex). Extrinsic Control of the Heart RATE and FORCE of contraction can be altered Parasymphatetic nervous system Decrease in HR, force of contraction of the Ventricles Sympathetic nervous system Increase in HR, force of contraction of the Ventricles Endocrine system (Hormones) Norepinephrine and epinephrine: stimulate heart, increasing it’s rate and contractility Although the heart initiates its own electrical emulates, both RATE and FORCE of contraction can be altered. Norepinephrine and epinephrine (rel. by adrenal medulla Norepinephrine and epinephrine stimulate heart increasing it’s rate and contractility. Normal RHR varies from 60-100 bo With endurance training RHR can decrease to 35 bpm VA S C U L A R S Y S T E M Composed of blood vessels or pipes that circulate blood throughout the body. Arteries: large, thick-walled vessels that carry the blood away from the heart; walls contain a large layer of smooth muscle; contact/relax to change size of lumen *lumen: channel where blood ows (e.g. pulmonary artery, aorta, coronary arteries, arterioles)Capillaries Capillaries: thin-walled network of tiny blood vessels referred to as a capillary bed; site of oxygen and nutrient di usion from blood to body tissue; CO2 and waste products di use from body tissues into the bloodstream. diameter is small = takes time for di usion As blood exits a capillary bed, it returns to the heart through a vein Veins: carry blood back to the heart; has thinner walls than arteries; have valves that allow the blood to move only toward the heart; preventing back ow (e.g. superior vena cava; inferior vena cava,) Note: Muscular action against the veins and skeletal muscle contractions help in the movement of blood The arteries are the large, thick-walled vessels that carry the blood away from the heart. The walls of arteries contain a thick layer of smooth muscle that can contract or relax to change the size of the arterial lumen. The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs. The largest artery, the aorta, begins from the left ventricle of the heart and carries oxygenated blood to all the body systems. The coronary arteries then branch from the aorta and provide blood to the myocardium. As they travel through the body, the arteries branch into progressively smaller-sized arteries. The smallest of the arteries, called arterioles, deliver blood to the capillaries. Capillaries: Capillaries are a network of tiny blood vessels referred to as a capillary bed. Arterial blood ows into a capillary bed, and venous blood ows back out. Capillaries are very thin walled, allowing for the di usion of the oxygen and nutrients from the blood into the body tissues (see Figure 5-8). Likewise, carbon dioxide and waste products are able to di use out of the body tissues and into the bloodstream to be carried away. fl ff ff fl ff fl fl ff Since the capillaries are so small in diameter, the blood will not ow as quickly through them as it does through the arteries and veins. ff fl Vascular System This means that the blood has time for an exchange of nutrients, oxygen, and waste material to take place. As blood exits a capillary bed, it returns to the heart through a vein Veins The veins carry blood back to the heart (see Figure 5-8). Blood leaving capillaries rst enters small venules, which then merge into larger veins. Veins have much thinner walls than arteries, causing them to collapse easily. The veins also have valves that allow the blood to move only toward the heart. These valves prevent blood from back owing, ensuring that blood always ows toward the heart. The two large veins that enter the heart are the superior vena cava, which carries blood from the upper body, and the inferior vena cava, which carries blood from the lower body. fl fi fl Blood pressure in the veins is much lower than in the arteries. Muscular action against the veins and skeletal muscle contractions help in the movement of blood. Pulse and Blood Pressure Blood pressure (BP) : measurement of force exerted by the blood against the wall of a blood vessel. Systolic blood pressure: represents highest pressure in the artery that occurs during ventricular systole. (When the ventricle forces blood throug the artery) Diastolic blood pressure: represents the lowest pressure in the artery that occurs during ventricular diastole (when the ventricle is lling) Pulse (P): the surge of blood caused by the heart contraction; equated to heart rate What are the sites for pulse? Blood pressure (BP) is a measurement of the force exerted by blood against the wall of a blood vessel. During ventricular systole, blood is under a lot of pressure from the ventricular contraction, giving the highest blood pressure reading—the systolic pressure. The pulse(P) felt at the wrist or throat is the surge of blood caused by the heart contraction. This is why pulse rate is normally equal to heart rate. During ventricular diastole, blood is not being pushed by the heart at all and the blood pressure reading drops to its lowest point—the diastolic pressure. Therefore, to see the full range of what is occurring with blood pressure, both numbers are required. fl fi fl ff Blood pressure is also a ected by several other characteristics of the blood and the blood vessels. These include the elasticity of the arteries, the diameter of the blood vessels, the viscosity of the blood, the volume of blood owing through the vessels, and the amount of resistance to blood ow. Feel your pulse at these sites: Blood pressure (BP) is a measurement of the force exerted by blood against the wall of a blood vessel. During ventricular systole, blood is under a lot of pressure from the ventricular contraction, giving the highest blood pressure reading—the systolic pressure. The pulse(P) felt at the wrist or throat is the surge of blood caused by the heart contraction. This is why pulse rate is normally equal to heart rate. During ventricular diastole, blood is not being pushed by the heart at all and the blood pressure reading drops to its lowest point—the diastolic pressure. Therefore, to see the full range of what is occurring with blood pressure, both numbers are required. fl fl ff Blood pressure is also a ected by several other characteristics of the blood and the blood vessels. These include the elasticity of the arteries, the diameter of the blood vessels, the viscosity of the blood, the volume of blood owing through the vessels, and the amount of resistance to blood ow. DISTRIBUTION OF BLOOD Varies considerably depending on the immediate needs of a speci c tissue compared to other areas of the body. General rule: most metabolically active tissue will receive greatest blood supply. fi Changes in the distribution of cardiac output are controlled by the sympathetic nervous system, primarily by increasing or decreasing arteriolar diameter (lumen). Return of Blood to the Heart Cardiovascular system requires mechanical assistance to overcome the force of gravity and assist the return of venous blood from the lower part of the body to the heart. Three basic mechanisms Valves in the veins Return of Blood to the Heart Three basic mechanisms Valves in the veins Muscle pump Respiratory pump: changes in pressure of abdominal and thoracic cavities during breathing One directional ow Preventing back ow and pooling of blood in the lower body fl fl Respiratory pump: Changes in pressure in the abdominal and thoracic cavities during breathing assist blood return to the heart by creating a pressure gradient between the veins and the chest cavity. BLOOD Blood Function Transportation: delivering o2 and fuel substrates and carrying away metabolic by-products Temperature regulation: picks up heat from the exercising muscle and delivers it to body organs where it can be dissipated to the environment Acid-base (pH) balance: Bu ers acids produced by anaerobic metabolism and maintains proper pH for metabolic processes Three functions primary to exercise and sport Transportation: delivering o2 and fuel substrates and carrying away metabolic by-products Temperature regulation: picks up heat from the exercising muscle and delivers it to the send where it can be dissipated to the environment (more about this on another chapter) Bu ers acids produced by anaerobic metabolism and maintains proper pH for metabolic processes. ff ff Total blood volume varies. It would depend on indv’s size, body composition and state of training. Larger blood volume are associated with greater lean body mass and higher levels of endurance On average, (normal body size, normal PA) total blood volume ranges from 5-6 L in men and 4-5 L in women Blood Volume Total Blood Volume: Depend on indv’s size, body composition and state of training Ave: 5-6 L in men; 4-5 L in women Greater lean muscle mass ang higher levels of endurance training: Larger BV Blood Composition 55% plasma of TBV 10% decrease during intense exercise in heat 10% increase or more with endurance training of acclimation to heat 45% formed elements RBC WBC: protect body from infection by directly destroying through phagocytosis or forming antibodies Platelets: cell fragments that are required for blood coagulation Blood in composed of plasma and formed elements Plasma 50-60 % of TBV but can decrease to 10 % of it’s normal amt with intense exercise in heat OR increase by 10% or more with endurance training or acclimation to heat. Plasma: 90% water, 7, plasma proteins, 3% nutrients, electrolytes, wastes, enzymes, gases etc Formed elements 40-45% ofTBV, consist of RBC (99%), WBC + platelets (thrombocytes) ( 1%) Blood coagulation is needed to prevent excessive blood loss. Red Blood Cells Erythrocytes Mature RBC No nucleus/ cannot reproduce 4 months : normal lifespan Impt to maintain balance of destruction and production RBC transport Oxygen Attached to hemoglobin On average: 15g of hemoglobin / 100 ml of TBV; 20ml of oxygen can be bound to 100ml of blood RBCs are placed with new cells on a reoccurring basis Decreases in their number or function can hinder oxygen deliver - a ecting exercise performance ff Global: protein, heme: iron (where o2 attaches) Blood Viscosity Refers to thickness of the blood Typically blood viscosity is twice than that of water; increases as hematocrit increases Hematocrit: the percentage by volume of red cells in your blood Number of RBC increase is good for maximal oxygen transport Accompanied by increase of plasma volume For optimal physical perforce, a low-normal hematocrit with normal to slightly elevated RBC is desirable Remember: if the uid is viscous, the more resistant it is to ow. Hematocrit: percentage of TBV composed of formed elements (formed elements/tbv) average: 41-50% in male adults; 36-44% in female adults No increase of plasma volume would result to viscous blood; reduced blood ow increase vascular resistance fl fl fl *this combination facilitates oxygen transport and is a result of Cardiovascular adaptation to training (to be discussed later) In closing We looked at the the cardiovascular system and reviewed the structure and function of the cardiovascular system. We learned how blood ow are regulated to meet the body’s needs and fl explored the role of cardiovascular system in transporting and delivering oxygen and nutrients to the body’s cells while cleaning away metabolic wastes including carbon dioxide.