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Lecture

electrophysiology

3 Pages
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Department
Biology
Course Code
BIL 118
Professor
O' Sullivan

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Description
Electrophysiology  Sinus node is located at the top right atrium o Also known as the "natural pacemaker" controlling heart rate o Increases with physical activity and decreases when relaxing o Electrical signal rapidly spreads from the Sinus node across the right atrium and left atrium  Only one area where atria and ventricles are electrically connected o Atrioventricular node or AV node deep in center of heart o All electrical signals from atrium must pass through AV node in order to get to ventricles o AV node is connected to the Bundle of His o Branches into a right bundle (to right ventricle) and left bundle (to left ventricle)  Fibers that branch out to distant ventricular tissues are called Purkinje Fibers Blood pressure  Baroreceptors near aorta and carotid arteries monitor blood pressure  Abnormal blood pressure → signal send to medulla  Cardiac center changes heart rate → cardiac output  Vasomotor center changes diameter of blood vessels  Shock: blood pressure too low o Insufficient nutrients for cells with a high metabolism (heart, brain) o Caused by excessive bleeding or extensive vasodilation o Treated with vasoconstrictors such as epinephrine (adrenaline), atropine o [NOTE] International name for adrenaline is now epinephrine Regulation of the Cardiac Cycle  Heart has unique ability to beat (contract) on its own  Assisted by nerves and hormones in blood but functions without them  Impulse leaves SA node and passes through both atria → causing them to contract  From AV node impulse passes down to the Bundle of His  Bundle of His branches and spreads through both ventricles via Purkinje fibers → ventricles contact Cardiac output as a function of stroke volume and heart rate  The volume of blood pumped by one ventricle during one beat is called the stroke volume  Cardiac Output = Stroke Volume x Heart Rate (number of ventricular contractions/min)  ↑Force of contraction → ↑Stroke volume → ↑Cardiac output Regulation of heart rate → Cardiac output is influenced by several factors Autonomic Nervous System  Heart is innervated by the autonomic nervous system (ANS) o The autonomic nervous system has 2 divisions o These division are called parasympathetic and sympathetic o Parasympathetic fibres decrease heart rate via the vagus nerve o Sympathetic fibres increase heart rate  Cardiac Inhibitory Centre o Found in the medulla oblongata of the brain stem
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