BIO 141 Lecture 7 notes
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This 5 page Class Notes was uploaded by Camryn McCabe on Friday February 19, 2016. The Class Notes belongs to Biol 141 at a university taught by Janelle Malcos in Spring 2016. Since its upload, it has received 30 views.
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Date Created: 02/19/16
Cardiovascular System Lecture 7 notes Consists of: o Heart Consists of 2 types of cardiac cell (muscle and conductive) and fibrous cells o Associated blood vessels Consist mainly of smooth muscle Functions: o Transport of gases, nutrients, waste o Regulation of blood pressure Heart: muscle cells bound to a fibrous tissue o Skeleton of heart: valves and associated structures Fibrous (form of connective tissue; helps make things stretchy/elastic) skeleton Functions: Structural support for the heart Provides something for muscle cells to pull against Electrical insulation that helps regulate heart beat o Organized structure Starts as a tube (during embryonic development) Muscle of the heart can be “unwound” from its mature form Complex organization allows for contraction of chambers to move blood o 2 types of cardiac cells 1- cardiomyocytes (muscle cells) Striated, branched, can be excited and can excite each other, can contract 2- conductive cells Initiate and communicate action potentials for heart beat These 2 work together to cause heart contraction based on action potentials o Intercalated discs- collection of proteins that connect cardiac cells at branch points 1. Desmosomes Provide a physical connection between neighboring cells Allows muscle cells to pull on each other without damaging membrane (w/o pulling them apart) Cardiovascular System Lecture 7 notes 2. Gap junctions Provide cytoplasmic connection Made of proteins that are non-specific leak- channels Allow sodium to diffuse between cells during depolarization o Results in excitation of neighboring cells and propagation of action potentials o Chambers of the heart 4 chambers exist that collect and pump blood to either the heart or lungs 2 atria (right and left) o Thin-walled muscle o Pumps blood to ventricles 2 ventricles (right and left) o Thick-walled muscle o Pumps blood to lungs (right) and body (left) o Great vessels Bring blood to atria OR take blood away from ventricles Right side: Superior and inferior vena cava (to atrium) o Veins; merge and dump blood together in atria) Pulmonary trunk (from ventricle) o Artery; branches into 2 branches: right and left pulmonary artery Left side: Pulmonary veins (to atrium) Aorta (from ventricle) o Main artery taking blood away from heart to rest of body Arteries: take blood AWAY from heart Veins: bring blood BACK to heart Pulmonary = lungs AV= atrioventricular (separate atria from ventricles) Right AV and Left AV Allow for flow of blood from atria to ventricle o NOT ventricle to atria (in a healthy person) Semilunar valves- separate ventricles from great vessels Aortic valve- separates left ventricle form aorta Cardiovascular System Lecture 7 notes Pulmonary valve- separates right ventricle from pulmonary trunk They prevent blood from leaking back into ventricles o Blood flow through heart Atria Flows from superior and inferior vena cava (from body) TO right atrium Flows from pulmonary veins (from lungs) TO left atrium Valves Right atrium pumps blood through right AV valve TO ventricle Left atrium pumps blood through left AV valve TO ventricle Ventricles Flows from right ventricle TO pulmonary trunk (to lungs) Flows from left ventricle TO Aorta (to body) Right structures = oxygen poor Left structures = oxygen rich The two sides of the heart work simultaneously Conduction system of the heart o Cells that initiate and regulate a heart beat o Causes an action potential to initiate in atria, DOWN to the ventricle’s base, then UP the ventricle sides o Includes: sinoatrial node, atrioventricular node, atrioventricular bundle and Purkinje fibers o SA node cells – considered the pacemaker and are located in the right atria SA node- grouping of conductive cells Excitation of SA node cells results in excitation (and contraction) of surrounding muscle cells in ATRIA ONLY Excited 60-100 times per minute (fastest of conductive cells) Electrical signal can pass to neighboring cells of atria Electrical signal cannot pass into ventricles because of fibrous skeleton SA node cells do not have a stable RMP This is because of cation leak channels Cardiovascular System Lecture 7 notes o Allow sodium to diffuse into cell o More leak channels than pumps contributes to the fact that there’s not a stable RMP No stimulus required, because of leak channels This results in depolarization to threshold W/O neuronal excitation = auto-rhythmic = can contract on its own o AV node = “electrical gateway” into ventricles AV node cells conduct action potential to additional conductive cells of the ventricles Fibrous skeleton does not allow signal to travel outside the right atrium, so it goes through AV node Electrical signal causes contraction Without SA node action potential, AV node cells are excited 60-80 times per minute (slower than SA node cells) o AV bundle cells conduct action potential to the base of the ventricles Without SA node or AV node action potential, bundle cells are excited 40-60 times per minute o Purkinje fiber cells conduct action potential to muscle cells of ventricle walls Without SA node, AV node, or bundle action potential, Purkinje cells are excited 20-40 times per minute Mechanism of a heartbeat - contraction (summarized) o Cells of the SA node triggers an action potential (do this bc of pacemaker potential; bc they’re leaky, allows cations to leak in) o Action potential moves through the two atria causing contraction This is also called atria systole (=contraction) (diastole is relaxed) o The action potential depolarizes the cells of the AV node This is also called ventricular systole (diastole is relaxed) o Action potential propagated down the AV bundle cells o Action potential propagated throughout the ventricles, causing contraction from the bottom up (toward the major vessels, (Great vessels)) o Process starts of again, and again… Cardiovascular System Lecture 7 notes
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