CH. 20 - THE HEART
I. ANATOMY
A. DOUBLE - BARRELED PUMP (Fig. 20.1, p. 675)
1. PULMONARYè LUNGS
2. SYSTEMICè BODY
B. SHAPE & LOCATION (Fig. 20.2, p. 677)
1. FIST-SIZED
2. MEDIASTINUM
3. BLUNT CONE
a. APEX - lower, left
b. BASE - upper, center
C. PERICARDIAL SAC = PERICARDIUM, fluid-filled sac (Fig. 20.3, p. 678)
1. PARIETAL PERICARDIUM
a. Outer Fibrous - C.T., anchors heart in mediastinum
b. Inner SEROUS membrane, continuous with. . .
2. VISCERAL PERICARDIUM = EPICARDIUM, on heart
3. PERICARDIAL FLUID - in cavity, between membranes
D. 4 CHAMBERS (Fig. 20.7, p. 682)
1. ATRIUM (2)
a. superior, thin-walled, receives blood, L & R
b. MUSCULI PECTINATI = PECTINATE MUSCLES
2. VENTRICLE (2)
a. inferior, thick-walled, pumps blood, L & R
b. TRABECULAE CARNEAE
E. 4 SEPTA - walls
1. INTERATRIAL - FOSSA OVALIS, FORAMEN OVALE
2. INTERVENTRICULAR
3. ATRIOVENTRICULAR - L & R
F. 4 VALVES 1. TRICUSPID - Right A.V. * CHORDAE TENDINEAE
(Fig. 20.9, 2. PULMONARY SEMILUNAR &
p. 684) 3. BICUSPID/MITRAL - Left A.V. * PAPILLARY MUSC.
4. AORTIC SEMILUNAR
G. BLOOD PATHWAY (Fig. 20.10, p. 685) KNOW steps 1-15
II. HISTOLOGY
A. HEART SKELETON - fibrous C.T. (Fig. 20.11, p. 687)
B. HEART WALL - 3 layers (Fig. 20.4, p. 679)
1. EPICARDIUM = VISCERAL PERICARDIUM + fat, outer
a. protection from friction
2. MYOCARDIUM - cardiac muscle, striated, middle, thickest
a. INTERCALATED DISKS - é strength/elasticity/elec. (p. 687)
b. DIADS - T-tubule + 1 sarcoplasmic reticulum
3. ENDOCARDIUM = ENDOTHELIUM + C.T., innermost
a. ê friction of blood through heart
b. Valves - double-layer endocardium
C. CONDUCTING SYSTEM (Fig. 20.13, p. 688)
1. SINOATRIAL NODE (S.A.)
a. Pacemaker - A.P. approx 70X/min - fastest
b. Upper R. atrium
c. Atria contract 1st from top è down
2. ATRIOVENTRICULAR NODE (A.V.)
a. A.P. from S.A.èA.V. Node which SLOWS/DELAYS A.P. by
.15 secèA.V. BUNDLEè L & R BUNDLE BRANCHESè
PURKINJE FIBERS (apex) è branch up to ventricle wall
b. Ventricles contract 2nd from bottom è top
c. “Wring-out” blood up into pulmonary artery & aorta
III. ELECTRICAL PROPERTIES
A. A.P. - due to RMP in cardiac muscle (Fig. 20.14, p. 690)
1. Cardiac contraction is slower & prolonged - PLATEAU phase
2. Channels
A.P. èNa+ FAST open è depolar. è Ca2+ SLOW open
èprolonged plateau, slows repolarization è K+ opensè repol.
B. AUTORHYTHMIC - sets own pace, no ext. stim., stim. 1è stim. all
1. S.A. node sets the pace
2. ECTOPIC - other parts initiate beat - problems
C. EKG or ECG - ELECTRICAL not mechanical activity (Fig. 20.16, p. 692)
1. P-Wave = Atrial depolarization (contraction)
2. QRS complex = Ventricular depolar (contraction) + Atrial
repolarization (relax-hidden)
3. T-Wave = Ventricular repolarization (relax)
4. ARRHYTHMIAS - abnormal ECG (Tab. 20.1, p. 693)
a. Height, length, duration of Intervals
b. Measure time between events (PQ, PR, QT, etc.)
IV. CARDIAC CYCLE (Fig. 20.18 & 20.19, p. 695 & 698 & Tab. 20.2, p. 696-697)
A. SYSTOLE = contract/pump
B. DIASTOLE = dilate(relax)/fill
C. ATRIAL SYSTOLE = 1st heart sound “lub” = closing of A.V. valves @ end
D. VENTRICULAR SYSTOLE = 2nd sound “dup” = closing of semilunars @ end
E. ATRIAL & VENTRICULAR DIASTOLE = 3rd sound, blood filling vent.
F. CARDIAC OUTPUT = RATE/BEAT X STROKE VOLUME
1. Rest C.O. = 72/min X 70 ml. = 5 liters/minute
2. Exercise C.O. = 190/min X 115 ml. = 22 liters/minute
3. B.P. = ventricular systole/diastole = 120/80
V. REGULATION
A. INTRINSIC - in heart
1. STARLING’S LAW states that: C.O. = VENOUS RETURN (V.R.)
é in V.R.èStretches cardiac muscle (PRELOAD) & S.A. nodeè
é C.O.
B. EXTRINSIC - due to N.S. or hormones (Fig. 20.22, p. 703)
1. PARASYMPATHETIC - Vagus N., inhibitory
a. Acetylcholineè75 beats/minè50 beats/min
HYPERPOLARIZATION - away from 0, é RMP, more neg
2. SYMPATHETIC - Cardiac N., excitatory
a. N.E. è75 beats/minè200 beats/min
HYPOPOLARIZATION - towards 0, ê RMP, less neg.
3. HORMONAL - Epinephrine, like N.E., but slower, prolonged
VI. HOMEOSTASIS -
A. BLOOD PRESSURE (B.P.) ( Fig. 20.23, p. 705)
1. BARORECEPTORS in Carotid/Aorta sense D B.Pè to 2. . . .
2. CARDIOREGULATORY CENTER in Medullaè
a. IF B.P. is éè Parasympatheticèslows heartè ê B.P.
b. IF B.P. is êè Sympatheticèstimulates heartèé B.P.
B. pH & CO2 (Fig. 20.24, p. 706)
1. CHEMORECEPTORS in Cardioregulatory center in Medulla
2. é CO2, ê pH, è SYMP è Stimulates Heart, é B.P.
3. ê CO2, é pH, è PARA è Slows Heart, ê B.P.
C. O2
1. CHEMORECEPTORS in Carotid & Aorta
2. Large ê O2 è é SYMP è é heart rate
3. é O2 to normal è ê SYMP è ê heart rate back to normal
D. EXTRACELLULAR IONS
1. é OR ê [K+] è ê heart rate
a. Double [K+] è death, i.e. by injection
2. é [Ca2+]è é contraction, ê heart rate & vice versa
E. TEMPERATURE
1. é Temperature è é Heart rate & vice versa