Chapter 20 Cardiovascular System: The

AP2 Chap. 20: Cardio Syst-Heart 1 Cardiovascular System: The Heart

I. Fxns of the heart II. Size, Shape, & Location of the heart III. of the heart IV. Route of flow thru the heart V. Histology VI. Electrical Properties VII. Cardiac Cycle VIII. Mean Arterial BP IX. Regulation of the heart X. Heart & Homeostasis XI. FX of aging on the heart

AP2 Chap. 20: Cardio Syst-Heart 2 Cardiovascular System • Heart is actually 2 pumps:  1st pump receives O2 poor blood from the body and pumps it to the lungs –  2nd pump receives O2 rich blood from the lungs and pumps it to the body – Systemic Circulation Fig. 20.1 pg 679

AP2 Chap. 20: Cardio Syst-Heart 3 I. Functions of the Heart

AP2 Chap. 20: Cardio Syst-Heart 4 I. Fxns of the heart 1. Generating BP (blood pressure) Pg 680 Figure 20.2a – Contractions of the ♥ generate the BP, wh/ is responsible for blood mvment thru vessels 2. Routing Blood – ♥ is the interchange between pulmonary & systemic circulation, thus insuring better oxygenation of bld going to tissues 3. Insuring One-Way blood flow – Valves of the heart are 1-way thus insuring no backflow 4. Regulating Blood Supply – As metabolic needs of the tissues Δ the heart can Δ rate & force of contraction to aid the tissues AP2 Chap. 20: Cardio Syst-Heart 5 II. Size, shape, & location of the ♥

AP2 Chap. 20: Cardio Syst-Heart 6 II. Size, shape, & location of the ♥ • •

superior &apex back and its basedirected mediastinum with within the blunt cone shaped likea closed fist, left. inferiorly tothe coming forward Lies obliquely ~ sizeofa AP2 Chap. 20: CardioSyst-Heart Pg 685 Figure 20.5c Posterior View Pg 684Figure20.5a Front View 7 III. Anatomy of the ♥ A. B. Heart Wall C. External Anatomy & Coronary Circulation D. Heart Chambers & Valves

AP2 Chap. 20: Cardio Syst-Heart 8 III. Anatomy of the heart: Pericardium • A sac surrounding the heart made of 2 layers that can also be called the pericardial sac. • It can Δ in size to accommodate more fluid or Δ in heart size

1. Fibrous Pericardium Pg 681 Figure 20.3 – Aids in holding the heart in place 2. Serous Pericardium – Reduces friction as the heart beats and is made up of 3 regions: a) Parietal Pericardium • Lies just under & Lines #1 b) Pericardial Cavity • Lies between a) & c) filled with • Helps reduce friction as heart moves in the pericardial sac c) Visceral Pericardium • Lines the exterior surface of the heart 9 III. Anatomy of the Heart: Heart Wall • Has 3 main layers: 1. Epicardium • Outermost layer that protects from Pg 682 Figure 20.4 friction 2. Myocardium • Middle layer responsible for contraction 3. • Innermost layer & protects from friction created by flowing blood • Simple squamous epi over CT • Heart valves are modified Endocardium • Atria (top chambers) – Mainly smooth w/some raised areas called that are separated by smooth parts by a ridge called cristae terminalis • Ventricles (bottom chambers) – Have large ridges called 10 III. Anatomy of the Heart: External Anatomy & Coronary Circulation

Right Auricle Left Auricle

There is also a posterior Interventricular Sulcus

AP2 Chap. 20: Cardio Syst-Heart 11 III. Anatomy of the Heart: External Anatomy & Coronary Circulation

These come from the These veins come from the body with O poor blood and 2 lungs with O Rich blood and empty into the right 2 empty into the left atrium. + Coronary Sinus 12 III. Anatomy of the Heart: External Anatomy & Coronary Circulation

These exit the heart This major exits the heart carrying O2 poor blood to the carrying O2 rich blood to the lungs body.

13 III. Anatomy of the Heart: External Anatomy & Coronary Circulation

Blood flow to the coronary blood vessels isn’t continuous. • contracts blood vessels get compressed & blood doesn’t readily flow • Cardiac Muscle relaxes  Blood vessels aren’t compressed & blood flow thru the coronary blood vessels resumes

AP2 Chap. 20: Cardio Syst-Heart 14 III. Anatomy of the Heart: External Anatomy & Coronary Circulation Major Arteries (A) supplying heart tissue • Lie within the & interventricular sulci. • Rt. & Lt. (CA) – Major A’s supplying blood to heart – Exit the just as it leaves the heart and lie w/in the coronary sulcus – Right is smaller in diameter than left Branches of the Rt.CA Branches of the Lt.CA Pg 685 Figure 20.6a • Rt. Marginal A • Ant. Interventricular A • Supply bld to lat’l – Supplies most of wall of the rt the ant. heart • Left Marginal A • Post’r Interventricular – Supplies bld to the A. lat. lt. ventricle • Supplies bld to • Circumflex A the posterior & – supplies most of inferior region of the posterior the heart heart.

15 III. Anatomy of the Heart: External Anatomy & Coronary Circulation Major veins (V) draining the heart tissue

• Great Cardiac V Pg 685 Figure 20.6a – Major draining the tissue on the left side of the heart • – Drains the right margin of the heart • Both empty into the Coronary Sinus – Empties into the right atrium

AP2 Chap. 20: Cardio Syst-Heart 16 III. Anatomy of the heart: Chambers & Valves – –

3 openings: Upper Rchamber 3. 2. 1. Right Atrium

Coronary Sinus Inferior Vena Cava – – –

Drains the Heart Drians Drains upperbody Pg 686Figure20.7 LowerBody • • Interatrial

– – Foremen Ovale/Fossa piece oftissuethat Ovalis separates L fromRatrium

• 4 uniformopenings: Upper L chamber

 Ovale, anopening and formsthe circulation thatseals bypass pulmonary embryo &fetusto between theatriaina Left Atrium

Pulmonary Veins 2. 1. Septum

getting O Drains lungsafter 2 fromeachlung  2

Ovalis

17 III. Anatomy of the heart: Chambers & Valves – –

Opens tothe Lower Rchamber Right Ventricle pulmonary trunk Pg 686Figure20.7 • •

– – Thick muscularpieceof Each ventriclehas1 from Rventricle tissue thatseparatesL midline outflow routenear large, superiorlyplaced

Opens totheaorta Lower L chamber Left Ventricle 

18 Semilunar Valves • Composed of 3 pocket like Between the R Between L ventricle semilunar cusps/flaps the ventricle and the and the Aorta free inner borders meet in Pulmonary Trunk the center of the arteries to block blood flow.

III. Anatomy of the heart: Chambers & Valves 19 Atrioventricular Valves Bicuspid Valve – Composed of cusps/ Between the R Between the flaps allow blood to atrium and R L atrium and flow from atrium to the ventricle L ventricle ventricles but because 3 cusps/flaps 2 cusps/flaps of design help to prevent back flow

III. Anatomy of the heart: Chambers & Valves 20 Pg 687 Figure 20.9 • Blood pushing out of the ventricle causes enough pressure to push the semilunar valves open while at the same time causing the atrioventricular valves to seal with the help of the and the . As the ventricle relaxes the semilunar valves get sucked back effectively sealing them while the atrioventricular valves open • Chordae Tendineae • Strong CT strings that connect to the cusps of AV-valves • Papillary Muscle • Cone-shaped muscular pillars, that contract when V contract & prevent

flaps from protracting 21 IV. Route of blood flow thru the heart

AP2 Chap. 20: Cardio Syst-Heart 22 Pg 688 Figure 20.10

AP2 Chap. 20: Cardio Syst-Heart 23 Cardiac Cycle

• Arteries: • BLUE: – Carries blood away – Deoxygenated blood from the heart • RED • Veins: – Oxygenated blood – Carries blood toward the heart

AP2 Chap. 20: Cardio Syst-Heart 24 Lung Tissue

Body Tissue Right Left Atrium Atrium

Right Left Ventricle Ventricle

AP2 Chap. 20: Cardio Syst-Heart 25 Tricuspid Bicuspid Valve Valve

Pulmonary Aortic Semilunar Semilunar Valve Valve

AP2 Chap. 20: Cardio Syst-Heart 26 Aorta Pulmonary Arteries Coronary Arteries

Aorta

Inferior Vena Pulmonary Cava Veins

Superior Vena Cava Pulmonary Trunk

Coronary Sinus

AP2 Chap. 20: Cardio Syst-Heart 27 Body Tissue

Inferior Vena Cava

Superior Vena Cava

Coronary Sinus

• Deoxygenated blood drains into the Right atrium via the: – The inferior vena cava drains the lower body tissue – The superior vena cava drains the upper body tissue 28 – The coronary sinus drains the heart tissue Right Atrium

• The right atrium fills with deoxygenated blood

AP2 Chap. 20: Cardio Syst-Heart 29 Right Atrium

Tricuspid Valve

• Deoxygenated blood goes from the right atrium

thru the tricuspid valve into the right ventricle. 30 Right Ventricle

• The right ventricle fills with deoxygenated blood

31 Pulmonary Semilunar Valve

Pulmonary Trunk

Right Ventricle

• Deoxygenated blood is squeezed from the right ventricle thru the pulmonary semilunar valve into the pulmonary trunk. 32 Pulmonary Arteries

Lung Tissue

Pulmonary Trunk

• The pulmonary trunk splits into the right and left pulmonary arteries carrying deoxygenated blood in to the right and left lungs respectively to pick up oxygen and drop off carbon dioxide. 33 Lung Tissue

• In the lungs CO2 is exchanged for O2

AP2 Chap. 20: Cardio Syst-Heart 34 Lung Tissue

Left Atrium Pulmonary Veins

• The right and left pulmonary veins carry the newly oxygenated blood back to the left atrium from the right and left lungs respectively. 35 Left Atrium

• The left atrium fills with freshly oxygenated blood.

36 Left Atrium

Bicuspid Valve

Left Ventricle

• The oxygenated blood is pumped from the left atrium thru the bicuspid valve into the left ventricle. 37 Left Ventricle

• The left ventricle fills with freshly oxygenated

blood. 38 Aorta

Aortic Semilunar Valve

Left Ventricle

• Oxygenated blood is squeezed from the left ventricle thru the aortic semilunar valve into the aorta. 39 Aorta Coronary Arteries Body Aorta Tissue Aortic Semilunar Valve

• The aorta splits into the right and left coronary arteries carrying oxygenated blood to the heart tissue. 40 Aorta Coronary Arteries Body Aorta Tissue

• Then the aorta continues to carry the oxygenated

blood to the body tissues. 41 V. Histology A. Heart Skeleton B. Cardiac Muscle C. Conducting System

AP2 Chap. 20: Cardio Syst-Heart 42 V. Histology: Heart Skeleton

• Consists of a plate of fibrous CT that serves 3 purposes: 1. Supports both the semilunar & atrioventricular valves to insure they don’t collapse 2. Acts as electrical insulation between the atria & ventricles 3. Acts as a point of Figure 20.11 attachment for cardiac Pg 690 muscle AP2 Chap. 20: Cardio Syst-Heart 43 V. Histology: Cardiac Muscle (CM) Figure 20.11 • CM cells joined by intercalated Pg 690 disks that allow action potentials to move directly from 1 cell to the next, thus cardiac muscle cells fxn as a unit – Intercalated disks are a combo of desmosomes (wh/hold cells together) & gap junctions (wh/ allow for cell to cell communication) • Elongated, branching • CM cells have a slow onset as cells w/ 1 or 2 centrally well as period of contraction located nuclei. due to Ca2+ mvmt along • Like skeletal muscle actin myofibrils. & myosin are organized • Has a good blood supply to to form sarcomeres. support aerobic respiration Arrangement of both the – ATP prod’d with: Smooth ER & transverse • Glucose, Fatty Acids, Lactic Acid tubules varies but fxns • CM doesn’t develop O -debt essentially the same. 2 44 V. Histology: Conducting System (CS) • Consists of modified CM-cells that form 2 nodes & a conducting bundle. (both of which are made up of small diameter cells to slow action potential) 1. SA-Node 2. AV-Node • SA-node initiates action potentials that spread across the atria & cause them to contract SA-node • At the AV-node action potential  slows allowing atria to complete AV-node contraction & ventricles to fill  • Next it follows along the AV AV bundle bundle, Rt & Lt  & . Rt & Lt Bundle braches – This causes the contraction of the  ventricles from the apex of the Purkinje fibers heart toward the base 45 V. Histology: Conducting System (CS) • The CS of the heart consists of modified CM-cells that form 2 nodes & a conducting bundle. 1. SA-Node medial to the opening of the superior vena cava • A.k.a. Pacemaker (generates spontaneous action potentials) 2. AV-Node- medial to the tricuspid valve SA-node AV-node AV bundle Rt & Lt Bundle braches Purkinje fibers

46 VI. Electrical Properties A. Action potentials B. Autorhythmicity of cardiac muscle C. Refractory periods of cardiac muscle D. Electrocardiogram

AP2 Chap. 20: Cardio Syst-Heart 47 VI. Electrical Properties

• CM have a resting membrane potential (RMP) • Depends on the permeability of the PM – Low permeability to Na+ and Ca2+ – Higher permeability to K+ • Once their threshold is reached….an Action Potential results

AP2 Chap. 20: Cardio Syst-Heart 48 VI. Electrical Properties: Action Potentials Permeability Δ’s during and action potential in CM 1. Depolarization Phase – Voltage-Gated (VG) Na+ channels open (Na+ rushes in) – VG K+ channels close (K can’t get out) – VG Ca2+ channels begin to open (Ca2+ goes in) 2. Early Repolarization & Plateau Phase – VG Na+ channels close (Na+ can’t get in) – Some VG K+ channels open causing “early” repolarization • K+ goes out in a rush – VG Ca2+ channels are open, prod’ing the plateau by further slowing repolarization (Ca2+ coming in) 3. Final Repolarization Phase – VG Ca2+ channels close Action potentials in CM last longer – Many VG K+ channels open than in SM SM 2 ms CM 200-500ms 49 VI. Electrical Properties: Action Potentials

• Gap junctions w/in • Calcium-induced calcium intercalated disks do release (CICR) allow action potentials – Movement of the Ca2+ into to transfer between the cell stimulates the CM-cells, but they do release of Ca2+ from the slow the rate of the sarcoplasmic reticulum action potential • Ca2+ binding facilitates the between them. interaction between actin & myosin to produce the contraction of CM.

AP2 Chap. 20: Cardio Syst-Heart 50 VI. Electrical Properties: Autorhythmicity of the heart • Autorhythmicity means at regular intervals it is self- • Even with the SA-node stimulating setting the rhythm of the heart there are some • SA-node’s pacemaker other CM-cells that can cells generate action generate spontaneous potentials spontaneously & AP’s, the SA node is just @ regular intervals. quicker than the others – This is the initial step toward full heart contraction. thus setting the pace. These other regions are – Prepotential is the beginning of the spontaneously called Ectopic Focuses. developing local potential in – Ex/ AV-bundle the pacemaker cells – Artificial EF’s can be • Unlike other CM-cells, created by changing the 2+ CM-cell membrane’s Ca is primarily permeability responsible for the depolarization phase in pacemaker cells. 51 VI. Electrical Properties Refractory periods of CM • Time it takes to begin another AP. – Absolute – Relative • CM has a prolonged depolarization & thus a prolonged RP. This allows time for cardiac muscle to relax b4 the next action potential causes a contraction. Electrocardiogram • Records the electrical activities of the heart. • Can be used as a diagnostic tool. • P-wave Depolarization of atria • QRS-wave Depolarization ventricles (AV-node R&L bindle branches, & Purkinje fibers) • T-wave repolarization of ventricles

52 VII. Cardiac Cycle • Repetitive pumping process that begins w/the onset of CM contraction and ends with the A. Events occurring during ventricular B. Events occurring during ventricular C. Heart Sounds D. Aortic Pressure Curve

AP2 Chap. 20: Cardio Syst-Heart 53 VII. Cardiac Cycle Heart: 2separatecircuitsinthesameorgan O 2 Lungs forO poorbloodfrombody Pulmonary Valve Each Ventricle can beconsidereda Tricuspid Valve RIGHT SIDE Produce major forcecausingbloodtoflow thru Each atriacanbeconsidered a R Ventricle R Atrium pulmonary & systemic arteries(respectively)     

2 pick-up Movement fromHightoLow pressure The Ventricles The Atria 

Body todropoff O O primer 2 richbloodfromlungs power Bicuspid Valve Aortic Valve LEFT SIDE L Ventricle pumps L Atrium pumps     

2 &pick-upCO 54 2 VII. Cardiac Cycle

• Time frame between cycles can vary widely from 0.25s in newborns to 1s or more in well trained Systole V. athletes • Systole: to contract – Ventricular systole – Atrial systole • Diastole: to dilate – Ventricular diastole – Atrial diastole

• Without “reference” to V or A. Systole A. It is referring to V only Diastole V.

AP2 Chap. 20: Cardio Syst-Heart 55 VII. Cardiac Cycle 56 relaxation contraction contraction isovolumic isovolumic /causes the semilunar valves /causes the semilunar wh flows into relaxing V’s flows into relaxing V’s decreases below that in the decreases below that aorta causing pulmonary trunk & toward the the blood to flow back V’s to close. When the valves close all valves are closed and no blood pressure to cause the semilunar to cause the semilunar pressure and pulmonary valves of the aorta the blood arteries to open pushing is greater in V’s through (Pressure trunk or than in the Pulmonary aorta) with blood) begin to contract but no but to contract blood) begin with because of blood occurs movement enough isn’t yet great the pressure valves to open the As V’s relax pressure w/in relax As V’s Once the V’s have enough have V’s Once the Brief interval in which the V’s (filled (filled V’s which the interval in Brief

– – – Period of Period of ejection Period of Period of Period

• • • VII. Cardiac Cycle: 5 periods

1. Period of Isovolumic Contraction: heart is contracting but vol isn’t Δing b/c valves are not open 2. Period of Ejection: semilunar valves open & blood is ejected 3. Period of Isovolumic Relaxation: heart muscle is relaxing but vol doesn’t Δ b/c no valves are open 4. Passive Ventricular Filling when blood flows from higher pressure in veins & atria into the lower pressured relaxed ventricles 5. Active Ventricular Filling results when atria contract & pump blood into the ventricles

AP2 Chap. 20: Cardio Syst-Heart 57 Figure 20.18 pg 698 58 VII. Cardiac Cycle: Events of:

Ventricular Systole Ventricular Diastole • Contraction of V closes AV • Relaxation of the V results in closing of the semilunar valves, valves, opens semilunar opens the AV valves, & valves, & ejects blood from movement of bld into V the heart • Most bld mvmt occurs when bld moves from higher pressure in • End diastolic volume: vol of veins & atria to the lower bld just b4 it contracts pressure (sucking) relaxing V’s • End Systolic Volume: vol of • Contraction of the Atria bld after contraction completes filling

Heart Sounds • 1st Sound: “Lubb”  Closure of the AV Valves • 2nd Sound  “Dupp” Close of the Semilunar Valves • Possible 3rd sound  Turbulent blood flow

59 VIII. Mean Arterial Blood Pressure

AP2 Chap. 20: Cardio Syst-Heart 60 VIII. Mean Arterial Blood Pressure (MAP) • Ave. bld pressure in the aorta MAP= CO X PR • Cardiac Output (CO)  amount of bld pumped thru the heart per minute – CO= heart rate X stroke volume – Stroke Volume is the amount of bld pumped thru the heart per beat • Equal to ( end-diastolic volume – end-systolic volume) • This can Δ based on 2 things – Venus return (amount of bld coming into heart) increases SV – Increased ventricular contraction can increase SV • Peripheral Resistance (PR)  total resistance to bld flow thru bld vessels • Cardiac reserve  difference btwn resting & exercising CO 61 Figure 20.21 Factors affecting MAP pg 704

AP2 Chap. 20: Cardio Syst-Heart 62 IX. Regulation of the Heart A. Intrinsic Regulation B. Extrinsic Regulation

AP2 Chap. 20: Cardio Syst-Heart 63 IX. Regulation of the heart

To maintain homeostasis, the amount of blood pumped by the heart must vary dramatically

• Intrinsic Regulation: • Extrinsic Regulation: – Results from normal fxnal – Involves neural & hormonal characteristics of the heart control – Doesn’t depend on – Neural: sympathetic & neuronal or hormonal parasympathetic reflexes regulation – Hormonal: epi & norepi from the adrenal medulla

AP2 Chap. 20: Cardio Syst-Heart 64 IX. Regulation of the heart

Intrinsic Regulation • As venous return increases, end-diastolic volume increases. The greater the end-diastolic volume, the greater the stretch on the ventricular walls. • Preload extent to wh/ventricular walls are stretched • Cardiac muscle exhibits a length vs. tension relationship. Meaning the longer it gets the more power it contracts with. • Venous Return: – amount of bld returning to heart @ each cardiac cycle • Starlings law of the heart – Increased Preload causes the CM-fibers to contract w/greater force & prod a greater stroke volume – Afterload- pressure the contracting ventricles must overcome to move bld.

65 IX. Regulation of the heart Extrinsic Regulation Nervous System Control • Cardioregulatory center of the medulla oblongata regulates the parasympathetic & sympathetic nervous control of the heart – PNS • Supplied by the vegus nerve • Postganglionic neurons secrete Ach  increases membrane permeability to K+  hyperpolarizes the membrane  slows down action potentials  decreases heart rate – SNS • Supplied by cardiac nerves • Postganglionic neurons secrete norepi  increases membrane permeability to Na & Ca  depolarization of the membrane  speeds up action potentials increases heart rate & force of contraction Hormonal Control • Epi & Norepi get released from the adrenal medulla into bld as a result of SNS stimulation – Long lasting FX compared to NS stimulation 66 – Increases the rate & force of CM contraction. X. Heart & Homeostasis A. Effect of BP

B. Effect of pH, CO2, & O2 C. Effect of Extracellular Ion [ ] D. Effect of Body Temperature

AP2 Chap. 20: Cardio Syst-Heart 67 X. Heart & Homeostasis Pumping efficiency of the heart plays an important role in the maintenance of homeostasis. BP in systemic circulation must be maintained at a level high enough to achieve any XΔ that must occur. And conditions of metabolic activity may Δ thanks to exercise & rest

FX of BP FX of Extracellular ion [ ] • Baroreceptors are those that • Increase or decrease in monitor BP (Stretch receptors) extracellular K  decrease • Decrease in BP in heart rate baroreceptor reflexes increase • Increase in extracellular Ca SNS stimulation & decrease  increased force of PNS stimulation of heart.  contraction & decrease increase in heart rate & force heart rate of contraction – Decreased Ca opposite FX

FX of Body Temperature • Increase in body temp  increase in heart rate • Decrease in body temp  decrease in heart rate 68 Fig 20.23 Pg 708

AP2 Chap. 20: Cardio Syst-Heart 69 X. Heart & Homeostasis

FX of pH, CO2, & O2

Chemoreceptors (CR) monitor blood pH, CO2, and O2 Response: • All regulatory • Medullary CR reflexes mechanisms fxning –  CO2 &  pH together respond to: •  SNS &  PNS –  blood pH stimulation of the heart –  blood CO2 levels • CR reflex –  blood O2 levels – Stimulated by  O2 levels • Produce an increase in • Decreased heart rate & heart rate & vasoconstriction vasoconstriction • Lowered O2 increases respiratory rate wh/ activates the SNS stimulation of the heart

AP2 Chap. 20: Cardio Syst-Heart 70 Pg 709 Fig 20.24

AP2 Chap. 20: Cardio Syst-Heart 71 XI. FX of Aging of the heart

AP2 Chap. 20: Cardio Syst-Heart 72 XI. FX of Aging of the heart

• Aging results in gradual changes to the heart that are mostly seen when exercising • Abnormal enlargement (Hypertrophy) of the L. ventricle is common • Max Heart rate may decrease • Increase in abnormal valve fxn & arrhythmia • Increased O2 consumption, req’d to pump same amount of bld, make age-related more severe • Exercise improves fxnal capacity of heart at all ages

AP2 Chap. 20: Cardio Syst-Heart 73