cardaic output (group 1 ).docx

OUTLINE - INTRODUCTION - EXPRESION OF cardiac output - Distribution of cardiac output - Regulation of cardiac output - Clinical correlate Introduction Cardiac output is the amount of blood pumped by each ventricle of the heart in a minute. It is usually talked about when talking abo...

OUTLINE - INTRODUCTION - EXPRESION OF cardiac output - Distribution of cardiac output - Regulation of cardiac output - Clinical correlate Introduction Cardiac output is the amount of blood pumped by each ventricle of the heart in a minute. It is usually talked about when talking about the blood pumped from the left ventricle. It is vital for maintaining proper blood circulation throughout the body. Without it, tissues wouldn\'t get enough oxygen and nutrients, leading to various health issues. Cardiac output is also important in maintaining blood pressure, assessment of cardiac function and so much more. The average resting cardiac output is about 5 L/min, although it varies depending on age, sex, body build, diurnal variations, emotional conditions, exercise, posture and sleep. Expression of cardiac output - **Heart Rate (HR):** This represents how fast the heart is beating, it is the number of times the heart beats per minute, measured in beats per minute (bpm). Heart rate can vary based on factors such as physical activity, stress, and hormonal influences. **Normal heart rate :** about 72bpm - **Stroke Volume (SV):** is the amount of blood pumped out by the heart with each beat, typically measured in millilitres (mL) per beat. **Normal stroke volume :** 70ml per beat - **Minutes volume**: this is the amount of blood pumped out by each ventricle per 1 minute. It is calculated by the product of stoke volume and heart rate. It is measured in liters per minute Mathematically : Minutes volume : stroke volume [×]{.math.inline} heart rate \ [70 × 10^ − 3^L  × 72 = 5.04 *L*/*min*]{.math.display}\ Normal minute volume : 5L/min The calculation of cardiac output provides valuable information about the heart\'s efficiency in pumping blood throughout the body. Changes in heart rate or stroke volume can significantly impact cardiac output. For example, an increase in heart rate during exercise or stress can raise cardiac output to meet increased metabolic demands, while factors affecting stroke volume, such as alterations in preload or contractility, can also influence cardiac output. **Distribution of cardiac output** The whole volume pumped out of the right ventricle is surely going to the lungs to become oxygenated but that of the left ventricle is pumped into different part or regions of the body based on the metabolic activity in that area or region. The heart itself receives the least amount of blood while the liver receives the most blood supply Regulation of cardiac output - Nervous regulation - Frank starling mechanism - Hormonal regulation - Baroreceptor Reflex - Chemical Factors: Nervous regulation - **Sympathetic Nervous System (SNS) stimulation**: When the body needs to increase cardiac output, such as during exercise or in response to stress, the SNS is activated. This leads to the release of neurotransmitters like adrenaline, which increase heart rate (positive chronotropic effect) and enhance myocardial contractility (positive inotropic effect). As a result, the heart pumps blood more vigorously, increasing cardiac output. - Parasympathetic Nervous System (PNS) stimulation: Conversely, during periods of rest or relaxation, the PNS becomes more active. PNS stimulation decreases heart rate (negative chronotropic effect), slowing down the heart\'s pumping action and reducing cardiac output. Hormonal Regulation: - Epinephrine(adrenaline)and norepinephrine release from the adrenal medulla under stress or exercise bind to the receptors in the heart and blood vessels which increased heart rate and contractility. Directly increasing the cardiac output. - Thyroid hormones (THs) are synthesized in the thyroid gland, and they circulate in the blood to regulate cells, tissues, and organs in the body. In particular, they exert several effects on the cardiovascular system.  Baroreceptor Reflex: Baroreceptors are specialized sensors located in the walls of blood vessels, particularly in the carotid sinus and aortic arch. They detect changes in blood pressure. These receptors play a crucial role in regulating blood pressure by sensing changes in vessel wall stretch caused by alterations in blood pressure. When blood pressure increases, baroreceptors detect the stretch in the arterial walls and send signals to the cardiovascular control center in the medulla oblongata of the brain.  In response to this input, the control center orchestrates a series of reflex adjustments to bring the blood pressure back to within the normal range. Conversely, if blood pressure drops, baroreceptors trigger an increase in sympathetic activity and a decrease in parasympathetic activity, resulting in an increase in heart rate and stroke volume to raise cardiac output and restore blood pressure to normal levels. Chemical Factors: Various chemical factors, including changes in blood pH, oxygen levels, and carbon dioxide levels, can influence cardiac output. For example, during exercise, muscle cells produce more carbon dioxide and release more acidic metabolites. Chemoreceptors in the body sense these changes and signal the cardiovascular control centres to increase sympathetic activity and decrease parasympathetic activity, leading to an increase in heart rate and stroke volume to meet the increased oxygen demand of the muscles. Clinicals correlate 1. Heart failure 2. Arrhythmias 3. Shock 4. Tachycardia 1\. Heart Failure: - Heart failure occurs when the heart cannot pump enough blood to meet the body\'s needs. - Caused by conditions like coronary artery disease, hypertension, or heart attacks. - Symptoms include fatigue, shortness of breath, and fluid retention due to reduced cardiac output. 2\. Arrhythmias : - Arrhythmias are abnormal heart rhythms that disrupt the heart\'s pumping ability. - Conditions like atrial fibrillation or ventricular tachycardia can lead to irregular heartbeats. - This disruption can decrease cardiac output and may cause complications like stroke or heart failure. 3\. Shock: - Shock is a condition characterized by inadequate blood flow and reduced tissue oxygenation. - Causes include cardiogenic shock (related to heart dysfunction), mechanical/obstructive shock, hypovolemic shock (due to low blood volume), and distributive shock. - In all types, decreased cardiac output contributes to insufficient tissue perfusion, potentially leading to organ damage or failure. 4\. Tachycardia: - Tachycardia refers to a heart rate exceeding the normal resting rate (over 100 bpm). - Causes can include anxiety, infection, hypoglycemia, hypovolemia, or hyperthyroidism. - Tachycardia at rest may indicate underlying issues affecting cardiac output. In summary, the clinical relevance of cardiac output lies in its role as a key determinant of cardiovascular function and hemodynamic stability. By monitoring cardiac output, healthcare professionals can diagnose, manage, and optimize treatment for various cardiovascular diseases, ultimately improving patient outcomes and quality of life.