4 Two Types of Cardiac Muscle Cells Ordinary: make up 95%- 99% of all heart muscle cells.Also called worker cells or contractile cellsBiochemically similar to red skeletal muscleSlow to fatigueSpecialized: make up remaining 1%-5%Also called autorhythmic or automatic cellsResponsible for initiation and/or transportation of electrical impulses through the heartpacemaker potentialDenny Agustiningsih
10 The HR can be increased about 3 times in exercise Resting heart rate is about beats/min (lower in athletes because they have large stroke volumes)The HR can be increased about 3 times in exerciseAbove about 200 beats/min the heart would not have time to fill properly therefore nature limits the rateRate is controlled by the autonomic nervous systemDenny Agustiningsih
12 Control of Heart by ANS Sympathetic innervation- + heart rate+ strength of contraction+ conduction velocityParasympathetic innervation- heart rate- strength of contraction- conduction velocityDenny Agustiningsih
13 Autonomic nervous system modulates the frequency of depolarization of pacemaker Sympathetic stimulation (neurotransmitter = NE ); binds to b1 receptors on the SA nodal membranesParasympathetic stimulation (neurotransmitter = ACh ); binds to muscarinic receptors on nodal membranes; increases conductivity of K+ and decreases conductivity of Ca2+How do these neurotransmitters get these results?
15 Major Hormonal Influences NE/EThyroid hormones+ inotropic+ chronotropicalso causes an increase in CO by BMREstrogen/ TestosteronDenny Agustiningsih
16 Ionic influences Effect of elevated [K+]ECF dilation and flaccidity of cardiac muscle at concentrations 2-3 X normal (8-12 meq/l)Effect of elevated [Ca++] ECFspastic contractionDenny Agustiningsih
17 Effect of body temperature Elevated body temperatureHR increases about 10 beats for every degree F elevation in body temperatureContractile strength will increase temporarily but prolonged fever can decrease contractile strength due to exhaustion of metabolic systemsDecreased body temperaturedecreased HR and strengthDenny Agustiningsih
18 Direct Stretch on SA node Stretch on the SA node will increase Ca++ and/or Na+ permeability which will increase heart rateDenny Agustiningsih
19 Terminology Chronotropic (+ increases) (- decreases) Dromotropic Anything that affects heart rateDromotropicAnything that affects conduction velocityInotropicAnything that affects strength of contractioneg. Caffeine would be a + chronotropic agent (increases heart rate)Denny Agustiningsih
20 Ca, K mV +20 -90 K out K out ∞ Ca in (L-Type) plateau Na in K out ∞ Ca in (L-Type)plateauCa, KNa inDenny Agustiningsih
21 AP of Contractile Cardiac cells Action potentials of cardiac contractile cells exhibit prolonged positive phase (plateau) accompanied by prolonged period of contractionEnsures adequate ejection timePlateau primarily due to activation of slow L-type Ca2+ channels
29 The Body as a ConductorThis is a graphical representation of the geometry and electrical current flow in a model of the human thorax. The model was created from MRI images taken of an actual patient. Shown are segments of the body surface, the heart, and lungs. The colored loops represent the flow of electric current through the thorax for a single instant of time, computed from voltages recorded from the surface of the heart during open chest surgery.
31 ECG examines how depolarization events occur in the heart If a wavefront of depolarization travels towards the electrode attached to the + input terminal of the ECG amplifier and away from the electrode attached to the - terminal, a positive deflection will result. If the waveform travels away from the + terminal lead towards the - terminal, a negative going deflection will be seen. If the waveform is travelling in a direction perpendicular to the line joining the sites where the two leads are placed, no deflection or a biphasic deflection will be produced.
32 R T P Q S Serabut purkinje – ventrikel Nodus SA – atrium Atrium (ototnya lebih sedikit)Klw siklusnya atrium - atrial cyteSirkulasi-peredaran darahSiklus-kontraksi dan relaksasiPQRSTDenny Agustiningsih
37 ECG Complexes Kontraksi – sistol Ventrike kaknan-memoma darah ke paru Ventrikel kiri-memompa darah keseluruh jantungPintu masuk – katub yang menghubgungkan dengan atrium (valam atrioventricualr)Pintu keluar kiri - aortaPintu keluar kanan – katub pulmu\onalTujuan awal kontraksi untuk membuka pintu keluar (aorta)
38 ECG Description ECG description amplitude (voltage) width (duration) recorded in mmpositive or negative or biphasicwidth (duration)
39 ECG in PerspectiveECG recording of electrical activity not the mechanical functionECG does not depict abnormalitiesECG does not record all the heart’s electrical activity
41 Excitation-Contraction Coupling in Cardiac Contractile Cells Ca2+ entry through L-type channels in T tubules triggers larger release of Ca2+ from sarcoplasmic reticulumCa2+ induced Ca2+ release leads to cross-bridge cycling and contraction
42 Frank-Starling LawPreload, or degree of stretch, of cardiac muscle cells before they contract is the critical factor controlling stroke volume
43 Extrinsic Factors Influencing SV Contractility is the increase in contractile strength, independent of stretch and EDVIncrease in contractility comes fromIncreased sympathetic stimuliHormones - epinephrine and thyroxineCa2+ and some drugsIntra- and extracellular ion concentrations must be maintained for normal heart function
44 Modulation of Cardiac Contractions Figure 14-30
47 Depolarisasi mendahului kontraksi Repolarisasi mendahului relaksasi Kontraksi jantung tidak melalui otakListrik-otot atrium-kontraksi--ketika sampai di ventrikel-ventrike berkontraksiGap junctionKontraksi otot jantung-otot pekerjaOtot pekerja memiliki aktin & myosinMendapat rangsang sehingga ionRepolarisasi = fase istrahatKontraksi & relaksasi-aktin & myosinSebagian kalsium pergi ke aktin & myosin untuk berikatan dengan troponin C, sebagian ke retikulum sarkoplasmaRetikulum sarkoplasma-tempat penyimpanan ion calsium (ada pintu yang disebut , hanya terbuka untuk kalsium)-masuk ke sitosolDenny Agustiningsih
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