chap. 19– the heart (cardiology)
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Chap. 19– The Heart (Cardiology). Chap. 19 (Heart) Study Guide. Critically read Chapter 19 pp. 719-739 before 19.5 “ Blood Flow” s ection Comprehend Terminology (those in bold) Study-- Figure questions, Think About It questions, and Before You Go On (section-ending) questions - PowerPoint PPT PresentationTRANSCRIPT
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Chap. 19– The Heart (Cardiology)
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Chap. 19 (Heart) Study Guide 1. Critically read Chapter 19 pp. 719-739 before
19.5 “Blood Flow” section2. Comprehend Terminology (those in bold)3. Study-- Figure questions, Think About It
questions, and Before You Go On (section-ending) questions
4. Do Testing Your Recall— 1, 2, 4-8, 11-195. Do True or False– 1-4, 7, 9-106. Do Testing Your Comprehension-- #1
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What are you going to do with your heart?
♥ “The best and most beautiful things in the world cannot be seen or even touched—they must be felt with the heart.” --Hellen Keller
♥ “Happiness comes only when we push our brains and hearts to the farthest reaches of which we are capable.”--Leo C. Rosten
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I. Overview of cardiovascular system
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§ Introduction
• The circulatory system—
– Three component: the pump, the passageway, and the transport medium
– What are they respectively?
• The pump--
• The passageway--
• The transport medium--
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§ Two circuits in the cardiovascular system (1)
1. Pulmonary circulation—
– Function?
– The route?
• R. ventricle Pulmonary arteries Lungs Pulmonary veins L. atrium
Figure 19.119-6
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LungsPulmonarycapillaries
Pulmonarycirculation
Right side ofheart
= O2-rich blood= O2-poor blood
Pulmonaryveins
Pulmonaryarteries
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2. Systemic circulation—
– Functions?
– The route? (Students work on it.)
• Starts which chamber of the heart? Major vessels? Destinations? Two major veins? Ends at which chamber of the heart?
Fig. 19.119-8
§ Two circuits in the cardiovascular system (2)
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Left sideof heart
Systemiccirculation
Organsystems
= O2-rich blood= O2-poor blood
Systemicarteries
Systemiccapillaries
Systemicveins
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II. Gross anatomy of the heart
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§ Shape and size of the heart
• Base – broad superior portion
• Apex - inferior end (a blunt point)
• 3.5 in. wide at base, 5 in. from base to apex, and 2.5 in. anterior to posterior
• weighs 10 oz (300 gram; size of your fist)
Fig. 19.2
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Base of heart
Apex of heart
AortaSuperior
vena cava
Diaphragm19-12
Next Topic
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§ Heart Position (1)
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§ Heart Position (2)
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§ Heart Position (3)
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§ Pericardial sac (pericardium) -1• Def. the double-walled, membranous
covering that encloses the heart
• Function– Friction free
• Peircardial fluid— Figure x
Cardiac Disorders here (Table 19.3):
• Pericarditis– inflammation here
• Pericardial effusion– fluid in pericardial cavity
• Cardiac tamponade– accumulation of fluid here
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Figure x
Pericardial cavity
Heart
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§ Pericardial sac (pericardium) - 2
1. Parietal pericardium– 2 SUBLAYERS– A-outer, tough/fibrous layer (CT) + B-deep thin
serous layer– turns inward . . . forms #2 below
2. Visceral pericardium (a.k.a. epicardium of heart wall)– INNER, thin, smooth, moist serous layer – covers heart surface
3. Pericardial cavity: between 1 + 2 above– filled with ____________________
Fig. 19.3
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2
3
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Functions?
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§ Heart Wall (from outermost layer)1. Epicardium (a.k.a. visceral pericardium)
– serous membrane covers heart
2. Myocardium– thick muscular layer– fibrous skeleton - network of collagenous and
elastic fibers (special section for this one)
3. Endocardium - smooth inner lining– What type of epi.? Simple _________ epi.– Continuous with endothelium cells . . .
Fig. 19.3
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1
3
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§ Fibrous skeleton of the heart (1) – What is it? Four CT rings fuse with . . .
– Structure details– Four fibrous rings, surrounds the 4 valves; in sheets of tissue that interconnect these rings
– Location? In the walls between …
Figure 19.819-22
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(Rear)Fibrous skeleton including fibrous rings
Left AV valve
Right AV valve
Aortic valve
Ventricularmyocardium
Pulmonary semilunarvalve
(Front) 19-23
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§ Fibrous skeleton of the heart (2)
Functions–
– 1. Structure support-- firm base of the heart valves and openings of great vessels
– 2. It anchors the cardiac muscle
– 3. An electrical insulator:• Separate the atria from the ventricles
and direct A.P. to specific pathways
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Checkpoint Questions
1. Does most of the heart lie to the right or left of the median plane?
2. Name, in order, the three layers of the heart wall beginning with the outermost layer.
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§ Heart Chambers• 4 chambers—
– A. right and left ATRIA– auricles? Ear-like structures . . .
– B. right and left VENTRICLES
• 3 sulci (grooves)— on the surface• Largely fat and coronary blood vessels– A. Atrioventricular (coronary) sulcus-
– B+C. Anterior and posterior interventricular sulci
Figure 19.5 a+b
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19-27Anterior viewCoronary sulcus?
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19-28Posterior view
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§ Heart Chambers – Internal (Fig. 19.7)
1. Interatrial septum– wall that separates atria
2. Pectinate muscles– internal ridges of myocardium
in right atrium and both auricles; (@ absorber)
3. Interventricular septum– wall that separates ventricles
4. Trabeculae carneae– internal ridges in both
ventricles (@ absorber)
Wave/sound absorber
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Checkpoint Questions
1. Which heart chamber has the thickest walls? What is the significance of this structural difference?
2. Do the atrial pectinate muscles more nearly resemble the ventricular papillary muscles or the trabeculae carneae?
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§ Heart valves (1)1. Two atrioventricular (AV) valves—
– A. Right AV valve– also called the tricuspid valve
– B. Left AV valve– also called . . .
• Function--blood from the atria to ventricles . . .Figure 19.8 (a,b)
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Aorta
Superior vena cava
Pulmonary valve
Pulmonary veins
Right atrium
Right AV valve
Right ventricle
Inferior vena cava
Pulmonary artery
Pulmonary veins
Left atrium
Left AV valveAortic valve
Chordae tendineae
Papillary muscle
Left ventricle
Interventricular septum
19-33Superior views of these valves – next slide
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Right AV valve
Left AV valveAortic/pulmonary valve
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Heart valves (2)
2. Chordae tendineae—
– Structure–
• Fibrous cords anchor the cusps to the ventricle walls via papillary muscles
– Function–
• Prevent valves from being _________
Figure 19.7, 19.819-35
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Right atrium
Right AV valve
Direction ofbackflow ofblood
Right ventricle
Papillary muscle
Chordae tendineae
Septum
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Right AV valve seen from within the right ventricle
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§ Heart valves (3)
3.Semilunar valves include: One ______ valve and one __________ valveA. Where are they located respectively? • Major arteries leave the ventricles
B. How to prevent them from everting?• Anatomical structure— leakproof “seam”
C. Function– (of all valves)• Ensure unidirectional flow of blood
Figure 19.7 and Fig. Z
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Aorta
Superior vena cava
Pulmonary valve
Pulmonary veins
Right atrium
Right AV valve
Right ventricle
Inferior vena cava
Pulmonary artery
Pulmonary veins
Left atrium
Left AV valve
Aortic valveChordae tendineae
Papillary muscle
Left ventricle
Interventricular septum
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Next slide
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Direction of backflow of blood
Leakproof“seam”
Aortic valve
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(Right or Left Ventricle)
(Pulmonary trunk or Aorta)
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§ Valve Mechanics (Fig. 19.9, 19.19)
Ventricles filling & isovolumetric contraction– AV valves open (semilunar valves close);
blood flows from atria to ventricles (v. fillings)
– AV valves open/closed (circle one)—S1– ventricle pressure continues to rise– Momentarily before ventricle ejection
Ventricles ejection & isovolumetric relaxation
– semilunar valves open (AV valves close); – ventricle ejection; ventricle pressure drops– semilunar valves open/closed (circle one)—S2– Isovolumetric relaxation
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Operation of Atrioventricular Valves
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S1
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Operation of Semilunar Valves
S2
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Before You Go On (p. 730)
• Reminder: Remember to go over each question of Before You Go On in the text.
• P. 730– Trace the flow of blood through the heart, naming each chamber, valve, and the great vessels in order (from the superior vena cava to the aorta). Do it yourself. Fig. 19.9 is a great figure to help you with this.
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Figure 19.10Fig. 19.9 Pathway of blood flow through the heart
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III. The Coronary Circulation
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§ Coronary arteries
Left C.A.Right C.A.19-47
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§ Coronary Arterial Supply• 1. Left coronary artery (LCA)– 2 branches
– 1A--anterior interventricular branch• supplies blood to interventricular septum and
anterior walls of both ventricles
– 1B--circumflex branch (Fig. 19.10 a+b)• passes around left side of heart in coronary sulcus,
supplies left atrium and posterior wall of left ventricle; it gives off a left marginal branch (1C)
• 2. Right coronary artery (RCA)– 2 branches– 2A--right marginal branch
• supplies lateral side of R atrium and ventricle
– 2B--posterior interventricular branch• supplies posterior walls of ventricles
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1A
1B
2A
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1C 2A
2B
1B
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§ Anastomoses of coronary arteries1. Definition (Anastomosis) – a point where
two blood vessels join/merge; this is arterial anastomoses
2. Where? Anterior interventricular branch of LCA joins the posterior interventricular branch of RCA
3. Function– provide collateral (alternative) routes of blood supply to a tissue (the heart)
Fig. x
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Chest pain and Heart Attack
• Angina pectoris--– partial obstruction of coronary blood flow can
cause chest pain – pain caused by ischemia, often activity
dependent
• Myocardial infarction (heart attack)-- – complete obstruction causes death of cardiac
cells in affected area– pain or pressure in chest that often radiates
down left arm
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§ Venous Drainage of Heart• 10% drains directly into right atrium and
ventricle via multiple thebesian veins
• 90% returns to right atrium via: (Fig. 19.10)– A. great cardiac vein
• blood from anterior interventricular sulcus
– B. middle cardiac vein (post. interventricular v.) • from posterior sulcus
– C. left marginal vein
The above three (A, B, C) empty into the coronary sinus before emptying into the ____________ (which chamber of the heart?)
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A
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B
C
A
or posterior interventricular v.
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IV. Cardiac conduction system
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§ 19.3 Cardiac muscle & conduction system
Heart has its own pacemaker, nerves MODIFY the heart rate & contraction strength.
• Beat rhythmically, _________beats per min.– Pacemaker? Where? (next slide)– Myogenic and autorhythmic
– Regulation by autonomic nerve system
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§ Cardiac Conduction System (1)
I. Properties– myogenic - heartbeat originates from within
____________________– Originated from what cells (1% of heart cells)?
cardiac muscles become specialized into autorhythmic cells (cardiac conduction system)
– What do autorhythmic cells do?–regular, spontaneous depolarization
II. Components– next slide
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Cardiac Conduction System (2)– Autorhythmic cells
1. SA (sinoatrial) node: pacemaker, initiates heartbeat, sets heart rate; where?
2. AV node: electrical gateway to ventricles; where?
• fibrous skeleton– insulates atria from ventricle
3. AV bundle: pathway for signals from AV node
4. Right and left bundle branches: divisions of AV bundle that enter interventricular septum
5. Purkinje fibers: upward from apex spread throughout ventricular myocardium
Fig. 19.12 + X
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Cardiac Conduction System
1
2
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1. Sinoatrial(SA) node
Rightatrium
2. Internodalpathway
5a. Rightbranchof bundleof His Right
ventricle
6. Purkinjefibers
Leftventricle
5b. Left branchof bundle of His
4. Bundle of His or AV bundle
3. Atrioventricular(AV) node
Interatrialpathway
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Students-- work on this one at home
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Checkpoint Question
Which chamber of the heart is first to receive the electrical signal that induces the heart to contract?
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V. Cardiac muscle
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§ Cardiac vs. skeletal m.(1)Skeletal M. Cardiac M.
(cardiocyte)Fibers & their control
•Fibers independent•Voluntary
•Interlocking cells; (next)•Involuntary
Nervous control by
•Somatic motor neurons
• Autonomic nervous sys.
Initiation of contraction
•Requires input from motor neurons
• by autorhythmic cells in heart
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§ Cardiac vs. skeletal m.(2)
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1. Cardiac myocytes—size, thickness etc.
2. T (transverse) tubules– smaller
3. Presence of intercalated discs– (see next slide)
4. Mitochondria—5. Myoglobin and glycogen--
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§ Intercalated discs (of cardiac muscle cells)
• Def. specialized zigzag structures joining cardiac muscle cells end to end
• Containing three distinctive features not found in skeletal muscle; what are they?
Figure 19.11 a-c
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Figure 19.11a light micrograph
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Next slide
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One myocyte is shown (colored).
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1-- interdigitating folds
2—mechanical junctions– two types; fascia adherens and desmosomes
3—electrical (gap) junctions--19-70
Structure of an
intercalated disc
13
2
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Plasma membranes of adjacentcardiac muscle fibers
Desmosome
Gap junction
Intercalated disc
Actionpotential 19-71
Fascia adherens
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§ Intercalated discs
1. Function of interdigitating folds--
2. Functions of fascia adherens and desmosome –
• Types of adhering junction
• Mechanically, hold cells together
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§ Intercalated discs
3. Functions of gap junction (connexons):
• Allows action potentials to spread . . .
• Therefore, cardiac cells form functional syncytia— cardiac cells excited and contract as a single unit
Q--Does the atria and the ventricle each form a separate unit?
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VI. Electrical activity of heart (autorhythmic cells)
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§ 19.4 Heart Autorhythmic Cells1. Two types of cardiac muscle cells:A. 1% are autorhythmic cells (our focus
on this section)– – Function?
• AP— Yes• Contraction– No
B. 99% --contractile cells– Function?
• AP— No initiation of own Action Potential
• Contraction– Yes 19-75
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§ Heart autorhythmic cells2.Autorhythmic cells act as pacemaker:
• How? Their m. potential slowly depolarizes (drifts) between AP, until . . . …
Figure 19.13
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Pacemaker potentials & action potentials of the
SA node
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A
BC
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§ Heart autorhythmic cells3. Details of pacemaker activity: (vs.
AP in nerve and skeletal m.):
A. Slow depolarization:i. K+ voltage-gated channels slowly closeii. (No voltage-gated Na+ channels),
instead sodium leak channels are used; So, sodium ions move in/out
iii. Transient Ca+2 channels open—Calcium ions move inward
All these make the inside becomes depolarized Thus, pacemaker p. toward threshold 19-78
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§ Heart autorhythmic cellsB. Rising phase of the action potential:
• Once, reach threshold p., long-lasting Ca+2 channels open; . . .
• Influx of calcium ions
C. The falling phase:
• as usual, potassium ions efflux
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§ Heart autorhythmic cells4.Autorhythmic cells are self excitable:
– Without nervous stimulation– They initiate AP cyclically, which
trigger rhythmic beating– Each depolarization of SA node sets
off one heartbeat (every 0.8 sec.)
– They form the conduction system of the heart (see Figure 19.12)
– It excites the other components in the system
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§ Heart autorhythmic cells5. The spread of cardiac excitation:
In a coordinated sequence:A-First, atrial excitation– From SA node to
atria; How? through gap junctions; via internodal and interatrial pathways as well; Result– a single smooth contraction of the pair of atria (Fig. Y)
B-Second, from the atria to the ventricles—AV node is the only point of electrical contact
from the atria to the ventriclesC-Finally, ventricular excitation--
from AV node to the bundle of His, . . .Result– a single smooth contraction in ventricles 19-81
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Interatrial pathwayRight atrium Left atrium
SA node
Internodalpathway
AV node
Purkinjefibers
Right ventricle Left ventricle
Bundleof His
1st
beat
2nd beat
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VII. contractile activity of heart
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Our focus
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§ Cardiac contractile cells
1. Action potential is initiated by: the pacemaker cells
3 phases: – Rising– Plateau– …
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§ Cardiac contractile cells2.The detail of action potential: A.Rising phase • Massive sodium ions influx causes
depolarization and AP
B.Plateau phase• Primarily caused by opening of calcium
channels• Also caused by temp. reduction in outflow of
_____________ ions
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§ Cardiac contractile cellsC.Falling phase
• Primarily caused by ____________ outflow• Closing of calcium channels contribute to
this as well
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Review slide— ID A, B, C, D, E below
B
D
C
E
A
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§ Cardiac contractile cells
3.Contractile response
Compare to skeletal muscle:
• Longer period of cardiac contraction
• Longer refractory period
How? Why? (next)
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Action potential
Refractory period
Contractile response
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§ Cardiac contractile cellsA.Longer period of cardiac contraction
– 3x longer compared to skeletal m.– Caused by entry of calcium ions which
induce more calcium ions release from the sarcoplasmic reticulum
– Purpose– this increased contractile time ensures emptying blood into ventricles and arteries
Fig. 11.13 (skeletal muscle)
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Latentperiod
Contractiontime
Relaxationtime
Muscletwitch
Contractileresponse
Actionpotential
Stimulation
In skeletal muscle
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§ Cardiac contractile cellsB.Longer refractory period
• Caused chiefly by inactivation of the sodium ion channels
• Consequences/Purpose– Cardiac muscle cannot be re-stimulated until contraction is almost over, therefore summation and tetanus of cardiac m. is impossible
• This ensures . . .
Compared to Fig. 11.13 (Shown previously; in skeletal m.)
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§ ECG (Electrocardiogram)1. Def. A record of the overall electrical activity
in all the cardiac muscle cells from the body surface
– NOT a recording of a single action potential in a single cell
– ECG recording represents . . .electrical activity detected by electrodes at 2 different points
Figure 19.15 (ECG) 93
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§ ECG (Electrocardiogram)
2.Components of the ECG correlate to cardiac events (Fig. 19.16 in the next slide)
• P wave— atrial depolarization when the electrical impulse spreads across the atria
• QRS complex— • T wave— ventricular repolarization
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P
Q
R
S
TP
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P
QRS
T