Biology 2313 Week 6 Notes
Biology 2313 Week 6 Notes Biology 2313
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This 4 page Class Notes was uploaded by Ednjon Parilla on Saturday October 1, 2016. The Class Notes belongs to Biology 2313 at University of Texas at El Paso taught by Dr. Zaineb Al-Dahwi in Fall 2016. Since its upload, it has received 7 views. For similar materials see Human Anatomy & Physiology II in Science at University of Texas at El Paso.
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Date Created: 10/01/16
Chapter 18: The Heart – Cardiac Output (Continued) Aspects of EKG Key P – Q Interval: beginning of Atria Overall Segments Depolarization to the beginning Sub-segments Ventricular Depolarization Types of Waves Q – T Interval: beginning of In-between Wave Ventricular Depolarization to the Intervals end of Ventricular Repolarization o S – T Segment: Prolonged depolarization = Plateau Phase Within the Q – T interval Sequence of EKG P Wave o Atria depolarization o Initiated by SA Node (sinoatrial node) Between P Wave + QRS Complex o Atria depolarization is complete o Impulse is delayed at the AV Node (atrioventricular node) QRS Complex o Ventricular depolarization begins at the apex Moves from the apex + upward Blood is therefore pumped out + up into arteries o Atria repolarization occurs at the same time Between QRS Complex + T Wave o Ventricular depolarization is complete T Wave Summary of Events During the Cardiac Cycle Cardiac Cycle: ALL mechanical events associated with blood flow through the heart during ONE COMPLETE HEARTBEAT Mechanical events take place after electrical events (shown in EKG) Cardiac cycle consists of: Pressure of blood EKG Events of the heart Different vocab for the heart: Contraction = Systole Relaxation = Diastole 1) Ventricular Filling Mid-to-late diastole Both atria + ventricle are relaxed Blood moves into the ventricle with passive mechanisms Atria starts to contract 2) Ventricular Systole Atria in diastole Pressure: increases; closes the Atrioventricular Valve Causes papillary muscles to contract pulls chordae tendineae ensures closure of the valve Done receiving blood! Both valves are closed (by ballooning in the cusps) Isovolumetric Contraction Phase Ventricle contracts Increases the blood pressure in the ventricle to the point where it exceeds the blood pressure in the aorta o Once this point is reached; the blood pressure causes the opening of the valve between the ventricle and aorta Ventricular Ejection Phase Blood leaves the ventricle and enters the aorta Not all of the blood is ejected! 3) Isovolumetric Relaxation Early diastole Occurs after the T Wave Ventricles relax Pressure: goes down in ventricle; blood backflows into aorta Closes the valve at the base of aorta (semilunar valve) o Dicrotic Notch: closure of the aortic or pulmonic valve at the onset of ventricular diastole (shown on the pressure graph as a low dip) Short amount of time o Pressure is less than the pressure in the atrium st Starts the cycle again into Ventricular Filling (1 Step) ↳ Take home messages: a. Blood flow is depended on the difference in blood pressure between the chambers b. Blood flows down a pressure gradient through any available opening c. Contraction occurs AFTER depolarization d. Relaxation occurs AFTER repolarization Mechanical Event occurs AFTER electrical event Cardiac Output New Terms End-diastolic Volume (EDV): the volume of blood at the end of ventricular relaxation End-systolic Volume (ESV): the volume/amount of blood remaining in the heart after ventricular contraction Stroke Volume (SV): blood ejected from ventricle during ONE COMPLETE HEARTBEAT Found in the Cardiac Cycle Equations Cardiac Output = Heart Rate × Stroke Volume CO = HR × SV Heart Rate is the # of heartbeats within a given time period Stroke Volume = End-diastolic Volume – End-systolic Volume SV = EDV – ESV o EDV= SV More blood volume outside; more ejected o EDV = SV Less blood volume; less ejected o ESV = SV More blood left in the heart; less ejected o ESV = SV Less blood left in the heart; more ejected Factors Affecting EDV EDV is the most important intrinsic factor! Also known as “Preload” o Degree to which cardiac muscle cells will be stretched just before contraction Controls SV Frank Starling of the Heart = Preload; SV Venous Return: the rate of blood flow back to the heart Limits Cardiac Output Factors the Increase EDV Speed of Venus Return Volume of blood in different chambers o Slow Heart Rate: Allows more time to fill the ventricle Collects higher amount of blood Increases EDV; increases Cardiac Output o Exercise: Stretches skeletal muscles Muscles need more oxygen in order to do work More blood, increases EDV therefore increases Cardiac Output o Fast Heart Rate: Not enough time to fill ventricles Collects lower amount of blood Decreases EDV; decreases SV; decreases Cardiac Output Factors Influencing ESV Related to Sympathetic Nervous System Modifies the activity of the heart o Increases contractility of the heart (contractile cardiac muscles) Goal is to decrease ESV to increase the SV ESV = SV Influenced by Extrinsic Factor (sympathetic NS activation) Sympathetic Nervous system controls the SA Node + AV Node Increases contractility in contractile cardiac muscles o Increases calcium entering contractile cardiac muscle cells Positive Factors Norepinephrine binds to the Beta Adrenergic Receptor o Promotes the activation of the Sympathetic Nervous System Allows more calcium channels to open Epinephrine o Released by Adrenal Glands o Increases contractibility Decreases ESV, increases SV, increases Cardiac Output Negative Factors Calcium Channel Blockers: agents blocking calcium channels Afterload: process that takes place in people with hypertension o This factor is not present in healthy people! o Hypertension = disease in which pressure in the aorta is always higher than pressure in the ventricle
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