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This 16 page Class Notes was uploaded by Jennifer Fry on Wednesday October 7, 2015. The Class Notes belongs to PHYS 215 at Ball State University taught by Zamlauski-Tucker in Summer 2015. Since its upload, it has received 27 views. For similar materials see Human Physiology in Science at Ball State University.
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Date Created: 10/07/15
Week 7 notes Physiology Class 215 Jennifer Fry 10515 Cardiac Physiology 0 The circulatory system has 3 main components 0 O O O O O The heart establishes a pressure gradient to pump the blood The blood vessels are passageways for the distribution of pumped blood throughout the body The blood is a transport medium serving the needs of body cells The pulmonary circulation is a loop of blood vessels between the heart and the lungs The systemic circulation is the circuit of blood vessels between the heart and other body systems The human heart is about the size of a st It is located in the chest cavity posterior to the breastbone in between the lungs and superior to the diaphragm It is the organ responsible for supplying blood and oxygen to the body 0 The heart wall consists of 3 layers 0000 The endocardium is the inner layer of epithelium The myocardium is the middle layer of cardiac muscle tissue The epicardium is the external membrane Cardiac muscle bers are interconnected by intercalated discs They form a functional syncytia How it goes 0 O O O O 0 While the heart is relaxed venous blood ows from the right atrium into the RV through the open tricuspid valve The RA then contracts and more blood ows into the right ventricle The RV then contracts the tricuspid valve closes and the pulmonary valve opens When the muscular wall of the RV contracts the blood inside the heart chamber is put under pressure and the tricuspid valve closes Blood exists through the pulmonary semilunar valve into the pulmonary trunk which divides to form the right and left pulmonary arteries Blood returns from the lungs through the pulmonary veins After contraction of the left ventricle the aortic valve closes and the mitral valve opens Blood ows from the left atrium into the left ventricle The left atrium contracts more blood ows into the left ventricle The left ventricle contracts again the mitral valve closes and the aortic valve opens Blood ows into the aorta The action of heart valves ensure that blood ows in the proper direction 0 AV valves Tricuspid on the right and bicuspid on left Allow blood to ow from the atria into the ventricles Occurs when atria pressure is greater than ventricular pressure during ventricular lling During ventricular emptying c When ventricular pressure exceeds atrial pressure the pulmonary arteries and aorta o 2sounds o LubDub o The AV valves close 0 Prevents the blood from owing backwords o Semilunar valves Close when the pressure in the ventricles falls below the pressure in the pulmonary on the right and aortic on the left Open when the ventricular pressures exceed the pressures in 0 When the valves between the atria and ventricles close a quotlubquot sound is heard 0 When the valves in the pulmonary and aortic arteries leaving the heart close a quotdubquot sound is heard followed by a longer pause LubDub if 23 Br kslcm Thomson Cardiac Physiology 2 0 Cardiac Muscle 0 Remember A TABLE 92 Timing and Type of Murmur in Various Heart Valve Disorders PATTERN HEARD TYPE Gil TllM lNG DEF W lTllll STETH DS39COPE VALUE DEFECT MURMU R VALUE DISORDER COMMENT lUIbJNhlSIIED Hlp Stenotic Systolic Stenotic semilunar A whistling systolic murmur signi es that a valve that value should be open during systole la semilunar value does not open completely truthDupmhistle Stenotic Diastolic Stenotic PM value A whistling diastolic murmur signi es that a valve that should be open during diastole an AV valve does not open completely curliJESwishelDup Insuf cient Systolic insuf cient ll A swishy systolic murmur signi es that a valve that value should be closed during systole lain AU value does not close completely LulleDupaSwish Insuf cient Diastolic insuf cient A swishy diastolic murmur signi es that a valve that semillunar valve should be closedl during diastole la semilunar value does not close completely Primary involuntary Only in the heart Mononucleated Has own inherent rhythm and can contract without an external stimulus Has faint striations and are branched Gap junctions are common Plasma Innamum rhea otf aclkia mart 35m 35ng Hilde insole bers 3 ammunm II39IH IEi39 39IIEEAWEIiI39Ii Action Gap Ely notion potential lntemalaterd slim I Pacemaker Potential and Cardiac Channels 0 Potassium channel K permeability decreases between action potentials 0 Sodium channel Not voltage gated Slow inward leak between action potentials o Ttype calcium channel Transient opens before membrane threshold is reached Opens in the second half of the pacemaker potential 0 Ltype calcium channel Opens when threshold is reached Responsible for the rising phase LEI Wh uiwv Thomam Learning 31 5 7 Eallntlunadl 9quot1El FE action promritual 39 10 EL 21 E 3i Q E 4i 5U v I Jami quot v Slew W l P39Ev Fwy unchanged 7 7 11333quot pammilalj melmsen o Authorhythmic Cells Nodes Bundles and Fibers 0 SA node Right atrial wall near the superior vena cava 7080 bpm 0 AV node Base of the right atrium near the septum 4060 bpm 0 Bundle of His Tract of cells running from the AV node to the interventricular septum and dividing into right and left branches 2040 bpm o Purkinje bers Run from the bundle of His and spread through the ventricular myocardium 2040 bpm ecuum n u I I u u nunLuau lnmaratriall new mricwentrieullar Sinuat ial Aw 391ng 3m node 39 Left atnlu m lntemedal Lair pathway branch of bundle of His Right 39 r Lari branch vEntnielle all bundle on1 His Eight I gt r ventniclla FMMHEE inners Fig 91 pt 24 Phases of the Cardiac Action Potential 0 Phase 0 Rapid depolarization Opening of voltage gated sodium channels Potassium channels close 0 Phase 1 initial repolarization O O O Opening of transient potassium channels Sodium channels start to close Phase 2 Plateau phase Calcium enters through Ltype calcium channels Opening of delayed and ir potassium chane Phase 3 repolarization Kir potassium conductance increases Phase 4 resting membrane potential 0 Cardiac Waves 0 O O Rest Diastole P wave Not ring of SA node Atrial depolarization PR segment Current ows though the AV node QRS complex Depolarization of the ventricles Atrial repolarization ST segment Ventricles contract and empty T wave Ventricular repolarization TP interval Ventricles relaxing and lling Arrhythmia O O O O 0 Variation from normal rhythm and sequence of excitation Tachycardia Bradycardia Extrastoles premature beats Common deviation Atrial utter Rapid regular atria depolarization 200380 bpm Atrial Fibrillation Rapid irregular atrial depolarization No P waves Irregular ventricular rhythm Puse de cit Ventricular brillation Serious rhythmic abnormality 4 minutes before brain damage or death Hearth block Normal atrial Lower than normal ventricular rate erinullar brillatian 1 Wu GENEH Imml r lm Tamra ruin I imamam Tumu mum 7 m3 ans DRE ans H mm mm Flu mm mm Myanmth lnl39am nn bean attach F Ernamm Liil39i39l39l39l Fa k I W r r r r gilt 15 Immlqi Haart rain Sympame a a vltgr and epinephrine Pammmpame e mm D LIIum E Hi h lt Thurman Learning Extrinsic can all ll Stroke Il39 llu me r I Etriri th of i1 Hillno contraBrion lll39l uniism untill1 Dquot I Sympathetic I andsplniphrlni volume 10715 The Blood Vessels and Blood Pressure llntriznsiri control I I End39pdllasmile J I lifenous return E agrdialt output Hm rt rah Stroke volume 1 7i Emanuel3 council II1 II IlrI5l39E t rlllrt39ill Pa aa il39mpathe o 39 ELIE ssion ae v lquot 39 a W Epinephrine l 39 U ln li l n mu ii f ll L Venous return EWUEE39E li Thum1m L mln i Organs that receive excessive blood ow digestive organs kidneys and skin Blood is maintained at a relatively constant composition Accomplished by the digestive organs kidneys and skin They can withstand temporary reduction in blood ow The blood ow distributed to other organs is less Supplying their metabolic needs And adjusted to their level of activity They do not tolerate signi cant reductions in blood 0 Flow rate of blood ow through a vessel 0 O O O O O O O F delta PR Delta P The pressure difference between the beginning and end of a vessel F blood ow ls from an area of higher pressure to an area of lower pressure pressure gradient R resistance Opposition to blood ow through a vessel Depends on 3 factors 0 Blood viscosity Vessel length Vessel radius major determinant o A slight change in radius produces a signi cant 0 The vascular tree Consists of arteries arterioles capillaries venules and veins The systemic and pulmonary circulations each consist of a closed 0 O 0 system of vessels change in blood ow Arteries carry blood away from the heart to the tissues Arteries branch into arterioles near an organ 0 Regulation of the diameter of arterioles supplying an organ adjusts the volume of blood sent to that organ 0 Arterioles branch into capillaries the smallest vessels 0 They are the microscopic exchange vessels with all cells offering blood that supplies the metabolic needs of the cells 0 Capillaries merge into venules that send blood into small veins 0 Venules and veins return blood to the heart Arteries 0 Large radius 0 Little resistance to blood ow 0 Elastic recoil in the walls Drives the ow of blood during cardiac relaxation ventricular diastole Due to a thick middle layer of smooth muscle with elastic bers 0 Expand from a large volume of blood sent into them when the heart pumps blood ventricular systole 0 When heart relaxes the stretched arteries passively recoil o Pushes the excess blood toward the tissues 0 Ensures a continuous ow of blood to the tissues Arterial blood pressure 0 O Arteries are compliant distensible During ventricular systole Stroke volume enters the arteries About 13 as much blood leaves the arteries at this time No blood enters the arteries during diastole The blood continues to leave the arteries by elastic recoil Systolic pressure The maximum pressure in arteries when blood is ejected into them during ventricular systole Diastolic pressure The minimum pressure in arteries when the blood is draining off into the remainder of the vessels during ventricular diastole Blood pressure 0 0 It is measured by a sphygmomanometer The cuff they wrap around your arm When the pressure in the cuff is greater than the brachial artery Blood ow is blocked through the vessel No sound is heard through a stethoscope placed over the brachial artery at the inside of the elbow When the pressure in the cuff is slowly released Vibrations and sound occur when it falls just below systolic pressure The rst heart sound indicates systolic pressure 120 mm Hg When the falling cuff pressure drops below diastolic pressure Vibrations and sound disappears This indicated diastolic pressure 80 mm Hg The pulse pressure is the difference the systolic and diastolic pressures 12080 O O O E D Pressure mm lllg r Emksl ole x Thomsoni Learning 12E 1 DD 80 The equation is Mean arterial pressure diastole pressure 13 the pulse pressure As one example from the previous data 80 13 40 93 This average is weighted as about 23 of the cardiac cycle is spent in diastole Cuff pressure Blood pressure Time Arterioles O O 0 Offer high resistance to blood ow Mean arterial blood pressure is systemic arterioles drops signi cantly This pressure drop drives the ow of blood Their pressure is not pulsatile Arteriolar radii can be changed to alter the distribution of blood ow to organs and to regulate arterial blood pressure Vasoconstriction narrowing and vasodilation enlargement Middle layer of smooth muscle is subject to neural hormonal and local chemical control The vascular tone of this smooth muscle establishes a baseline of vascular resistance This ongoing tone makes changes in radius size possible Local control of arteriolar resistance 0 Determines the distribution of the cardiac output 0 The driving force for blood ow is identical to all organs 0 Differences in arteriolar resistance varies between organs Determines the distribution of blood they receive 0 During exercise More blood ow is shifted to the skeletal muscles Less ows to the digestive tract Arterioles to the skeletal muscle dilate offering less resistance Arterioles serving the digestive tract constrict 0 Local chemical in uences on the resistance of arterioles Local metabolic changes Histamine release 0 Local physical in uences Heat dilate and clod constrict Myogenic responses to stretch Local chemical changes 0 Increased metabolic activity Ex Exercise 0 Local concentration of 02 decreases o This and other local chemical changes relax the smooth muscles wall in arterioles 0 They dilate by this response called active hyperemia 0 Less metabolic activity causes the opposite condition and response of the arterioles o Histamine release Synthesized and stored in special connective tissue cells Promotes vasodilation Other local chemical changes 0 Other local chemical changes that relax the smooth muscle in arterioles causing vasodilation are Increased C02 Increased acidity Increased K ion concentration Increased osmolarity salt Adenosine release Prostaglandin release 0 Local vasoactive mediators also have an effect 0 Local physical changes that in uence arteriolar radius 0 Heat produces vasodilation 0 Cold produces vasoconstriction o Arteriolar smooth muscle that is passively stretched increases its tone 0 By reactive hyperemia arterioles in a region dilate when other local blood vessels are blocked o By pressure autoregulation local mechanisms in the arterioles keep blood ow constant when there are wide variations in the mean arterial blood pressure driving the blood Extrinsic sympathetic signaling 0 Controls arteriolar radii This regulates blood pressure Sympathetic neurons supply the smooth muscle in the walls of most arterioles 0 Increased sympathetic signaling produces generalized arteriolar vasoconstriction Increases the total peripheral resistant TPR Many arterioles constrict to produce this effect Organs supplied by these constricting vessels receive less blood ow 0 However some arterioles serving organs dilate during this increase in TPR MAP II 0 Mean arterial pressure MAP epuals Cardiac output x TPR As the TPR increases 0 The mean arterial pressure increases by direct proportion Arterioles serving organs skeletal muscles during exercise that dilate during TPR increases receive more blood as the MAP increases Alpha1 receptors 0 O O O 0 Binding produces vasoconstriction Cerebral vessels lack these kind of receptors Subject to local controls Skeletal and cardiac muscle tissue have local control mechanisms that override generalized sympathetic control mechanisms Parasympathetic innervation is absent at arterioles Cardiovascular control center 0 O O The medulla The integrating center for sending signals through sympathetic motor pathways to the arterioles Medulla regulates blood pressure along with several hormones Epinephrine and norepinephrine Reinforce sympathetic activity Secreted by the adrenal medulla Vasopressin and angiotensin Vasoconstrictors Vasopressin controls water balance Angiotensin controls salt balance Capillaries O O O O 0 Exchange accomplished mainly by diffusion Enhanced by thin walls and narrow openings of capillaries plus their branching Capillary walls Single at layer of epithelial cells Called the endothelium Capillaries are very abundant Large surface area to serve cells The blood through capillaries is slow Due to the tremendous crosssectional area of all capillaries in the area Enhances the opportunity for diffusion Compared to arterioles Resistance offered by capillaries is low due to the large cross sectional areas of these microscopic vessels Capillary pores O O 0 Allow the passage of small watersoluble substances lons and glucose Lipidsoluble substances dissolve through the lipid bilayer Tight junctions connect the walls of capillary cells in the brain and from the bloodbrain barrier Histamine increases capillary permeability e Brooksl Cnle Thomson Mammy capillary Waltertilled pore 7 Plasma llnterstltial llulcl E rlclolhelial cell Plums proteins generally camel cross Impulan wall Prlg39gihas I p quot I j l C Plasma Lllpldiaaoluhll 39 membrane nu hmnm 39 mdmhalllal cellar H that K Moose 39 i amlno as de 39 Emhongeable 7 I lquot 39 proteins are v quot moved some WEF 39 I I soluble trampad wholemeal pass through pores Transport across capillary well Celllary bleed flew eentrel i Preeeeillery eehinetere eurreuntl eeeilleriee A eehineter ie e ring et emeeth mueeie ereuntl the entrance te e eeeillery eentreetien ef theee eehineter39e re ueee the bleed fleeing inte the eapllleriee in en ergen The l39EIEit liiEIl39i ef theee eehinetere leg en eeereieing el celetel mueele hee the eeeeite eti eet lit meterterlele ie e thereughfere ehennel frem en er39leriele tee eeeiller y Eeme eaeillanee are EEW EEI by them Blood Pressure is regulated 0 Mean arterial pressure cardiac output X total peripheral resistance 0 Cardiac output Heart rate X stroke volume Heart rate depends on autonomic control plus some hormone signaling Stroke volume depends on sympathetic stimulation 0 Stroke volume also increases by venous return Venous return depends Total peripheral resistance Several factors 0 Such as venous vasoconstriction and the skeletal muscle pump 0 Depends on the radius of arterioles plus blood viscosity 0 Radius size depends on Sympathetic stimulation to the arterioles Local metabolicchemical Hormonal controls 0 Effective circulating blood volume in uences the blood volume returning to the heart This blood volume depends on capillary exchange which in the long term means controlling salt and water balance 0 Mean arterial pressure is controlled by longterm and shortterm measures 0 The baroreceptor re ex o Is a shortterm mechanism for regulating blood pressure 0 Baroreceptors are found in the carotid sinus and aortic arch Sensitive to uctuations in pulse pressure 0 Baroreceptors generate action potentials through afferent pathways to a cardiovascular integrating center in the medulla Autonomic nervous system Center in the medulla alters the ratio of sympathetic and parasympathetic activity to the heart and blood vessels 0 The baroreceptor re ex o Arterial blood pressure becomes elevated opposite for drop 0 Baroreceptors detect this change Increase the rate of action potentials ring along afferent pathways from the receptors to the medulla o The cardiovascular center interprets this input Sympathetic output decreases Parasympathetic output increases 0 Decrease in Heart rate Stroke volume Arteriolar resistance Venous resistance veins dilate 0 Cardiac output and total peripheral resistance decrease o The elevated blood pressure returns to normal 0 Other re exes and responses in uence blood pressure 0 Left atrial receptors and hypothalamic osmoreceptors regulate salt and water balance Control plasma volume for longterm blood pressure regulation 0 Chemoreceptors in the carotid and aortic arteries Sensitive to low 02 and high acid levels in the blood Increase respiratory activity to reverse these trends 0 Behaviors and emotions from the cerebral cortexhypothalamus in uence cardiovascular responses 0 Exercise modi es cardiovascular responses 0 The hypothalamus controls skin arterioles for temperature regulation 0 Vasoactive substances have an effect 0 Hypertension 0 Cause largely unknown 0 Secondary hypertension Secondary to other primary problems Categories are 0 Renal from the reninangiotensin mechanism 0 Cardiovascular Endocnne Neurogenic o 90 of hypertension cases are primary Potential causes include Defects in salt management by the kidneys Excessive salt intake Diets low in fruits vegetables and dairy products 0 Plasma protein abnormalities 0 Variation in the gene that encodes for angiotensinogen Endogenous digitalislike substance 0 Baroreceptors adapt to hypertension Regulate blood pressure maintain it at higher level 0 Excessive vasopressin Complications of hypertensions O Congestive heart failure Stroke Heart attack Without complications hypertension is without symptoms It can be treated with therapy 0 Orthostatic hypotension results from transient inadequate sympathetic activity This is a fall in blood pressure Circulatory shock 0 When blood pressure drops to a point where blood ow becomes inadequate 0 There are 4 main types Hypovolemic caused by a fall in blood volume Cardiogenic due to a weakened heart Vasogenic from widespread vasodilation due to a release of vasodilator substances Neurogenic from widespread vasodilation but not from the release of vasodilator substances 0 Compensatory measure for circulatory shock include Baroreceptor re ex with increased sympathetic activity and decreased parasympathetic activity to the heart increased heart rate Fluid shifts in the capillaries and interstitial uid autotransfusion Responses by the liver urinary system and thirst sensation Veins return blood to the heart 0 Large radii Low resistance Velocity of blood ow increase in the veins 0 0 Pulmonary vessels 9 1 392 Smaller total crosssectional area 793 Veins are thinnerwalled and less elastic Systemic arteries O Hold 60 of the blood volume of the body at rest Extrinsic factors can drive this blood to the heart for pumping Venous return 0 O O The volume of blood entering each atrium per minute Venous return is enhanced by Increased sympathetic stimulation of the veins Vasoconstriction Increased skeletal muscle activity Compresses veins and increases venous pressure Various mechanisms counteract the effect of gravity on venous return The closure of valves inside veins ensures that blood does not ow backward The respiratory pump creates a pressure gradient in the chest cavity drawing uid toward the heart 0 Figure 1030 and 31 in book Interstitial uid 0 O O O 20 of the ECF is blood plasma 80 of the ECF is interstitial uid Exchange between the interstitial uid and plasma membranes of tissue cells can be active Ex Active carriermeditated transport or diffusion Ex Diffusion Exchange across the capillary wall between the plasma and interstitial uid is largely passive Diffusion across the capillary walls is important in solute exchange Ex Gases Only the passage of plasma proteins is limited Some substances cross the capillary wall by bulk ow from higher uid pressure to lower uid pressure Starling s Hypothesis 0 Implies that Through a semipermeable capillary wall Hydrostatic pressure shifts uids outwards While the oncotic pressure of the plasma albumin protein holds uid within the capillary starling Forces The capillary wall acts as a sieve 0 Plasma proteins remain in the capillary wall Unable to pass through the pores in the capillary wall 0 Reabsorption Net inward movement of uid from the interstitial uid into the capillary Occurs when inwarddriving pressure exceeds an outward opposing pressure Bulk Flow 0 Capillary blood pressure o The hydrostatic pressure exerted on the inside of capillary walls by the blood This forces uid out of the capillaries the outward pressure 0 The plasmacolloid pressure 0 Encourages uid movement into the capillaries the inward pressure The plasma has a higher protein concentration compared to the interstitial uid Produces a water concentration difference 0 Water enters the plasma from the interstitial uid by osmosis o The interstitial uid hydrostatic pressure Pressure exerted on the outside of the capillary wall by the interstitial uid It has a small value 0 The interstitial uidcolloid osmotic pressure is also insigni cant in most cases as plasma proteins normally remain in the blood plasma 0 Arteriolar end of the capillary Outward pressure is greater than the inward pressure Fluid leaves the capillary by this difference Ultra ltration occurs 0 Venule end of the capillary Inward pressure is greater than the outward pressure Outward pressure has dropped due to a drop of blood pressure at this end compared to the arteriolar end Reabsorption occurs 0 Bulk ow regulates the distribution of uid between the blood plasma and interstitial uid Edema 0 An accumulation of uid in the interstitial uid 0 Can be caused by A reduced concentration of plasma proteins allows a drop in the main inward pressure More uid enters the interstitial uid An increased permeability of the capillary wall allows more plasma proteins to pass from the blood uid into the interstitial uid An increased venous blood pressure increases the capillary blood pressure This elevates the outward pressure along the capillary wall Blockage of lymph vessels retains uid in the interstitial uid rather than returning the uid to the capillaries
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