Abstracts and Test 2 Earning up to 5 points for Test # 2 based on topics of Frog Heart Lab: –Regulation of pacemaker cells by temperature, hormones, neurotransmitters, antagonists –Heart block: 1 st, 2 nd, and 3 rd degree –The conducting system –Strategies for prolonging survival of in vitro organs Cardiac Cycle Animation

1QQ #24 for 10:30 Write each letter and circle the letter of correct statements. a)Heart murmurs are caused by the closure of heart valves. b)The first heart sound is produced by the closure of the atrioventricular valves. c)Blood is about 65% plasma. d)Pacemaker cells produce action potentials that last about milliseconds. e)Chordae tendonae and papillary muscles prevent eversion of the semilunar valves.

1QQ #24 for 11:30 Write each letter and circle the letter of correct statements. a)The buffy coat is thicker in a person with an infection. b)The first heart sound is produced by the closure of the atrioventricular valves. c)Blood is about 45% plasma. d)Pacemaker cells produce action potentials that last about milliseconds. e)The tricuspid valve is situated between the right ventricle and the pulmonary artery.

F=Q=ΔP/R Flow = Pressure gradient/Resistance from Ohm’s Law (V=IR) R = 8Lη/πr 4 Q= ΔP πr 4 8Lη Poiseulle’s equation S 8 Double radius … 16x flow Half radius….1/16 th flow R = 8Lη/πr 4

Cardiac Output = Heart Rate X Stroke Volume What regulates heart rate? CO = HR x SV 5L/min = 72 beat/min x 70 ml/beat The Cardiac Cycle animation S 1 What regulates Stroke Volume?

Figure SA node cells do not have stable resting membrane potential, spontaneously produce AP, are Pacemaker cells S 5 S 4

Figure Intrinsic Rate = 100 beat/min S 15 2 effects of Parasymp: hyperpolarization & slower depolarization

Effect of “Beta blockers” NEEPIACh mAChR Effect of atropine Beta-adrenergic receptors S 6 Recall: CO = HR x SV

Fibrous connective tissue between atria and ventricles prevents the conduction of action potential. Only route is via AV node, bundle of His, bundle branches, Purkinje fibers, and to ventriclular myofibers. What prevents the AP from being conducted from ventricles to atria? S 7

1 st Heart Sound = Closure of Atrioventricular (AV) valves at beginning of Ventricular Systole 2nd Heart Sound = Closure of Semilunar valves at beginning of Ventricular Diastole S 8 “Sis-toe-lee” “die-ass-toe-lee”

Figure Systolic Diastolic Ejection Fraction = SV/EDV Atrial Fibrillation Ventricular Fibrillation & Defibrillation Stroke Volume Animation S 9

Events are same for Cardiac Cycle for Right Side of Heart; only difference is lower systolic pressures in right atrium and right ventricle. S 10

CO = HR x SV 5L/min = 72 beat/min x 70 ml/beat 35 L/min = ? beat/min x ? ml/beat S 1 So far, we’ve dealt with the factors that control Cardiac Output by changing heart rate. + sympathetic - parasympathetic The Cardiac Cycle animation

Figure Stroke Volume Animation S 2

Frank-Starling Law of the Heart FS LoH = SV is proportional to EDV Ventricular Function Curve Does not depend on hormones or nerves Assures that the heart adjusts its output based on VENOUS RETURN Ways to enhance Venous Return: 1) muscle contractions 2) “respiratory pump” 3) venoconstriction S 3 ↑VR→ ↑EDV → ↑SV

Respiratory pump Muscle pump Mechanical pump for bedridden patients

Fig Low EDV High EDV Length-tension “curve” for Cardiac muscle Overinflation of ventricles leads to less effective pumping S 4

Overinflation of ventricles results in reduction in stroke volume S 5 Treatments? …..diuretics

Contractility NE from Symp postganglionics & EPI from Adrenal medulla Note: cardiac myofibers NOT innervated by parasympathetic division Increase Ejection Fraction S 6

3 Effects of Sympathetic Stimulation 1: Increase rate of contraction 2: Increase peak tension 3: Decrease twitch duration S 7 Why should the contraction be shorter?

Summary: Control of Stroke Volume End diastolic volume (preload) Contractility (strength of ventricular contraction due to adrenergic stimulation) Pressure in arteries that must be overcome = Afterload FS LoH S 8

Afterload is analogous to trying to pump more air into a tire that is already fully inflated (heart contracting to overcome diastolic pressure.) High blood pressure increases the workload of the heart….. Cardiac hypertrophy….increase chance of irregular conduction of AP through heart S 9 Hypertrophic cardiomyopathy

CO = HR x SV 5L/min = 72 beat/min x 70 ml/beat 35 L/min = ? beat/min x ? ml/beat S 11 Factors that control Cardiac Output by changing heart rate and stroke volume. + sympathetic - parasympathetic VR and EDV (FSLoH) Contractility (catecholamines) Afterload (MAP)