Seeley/Anatomy and Physiology

Lecture Outline

CHAPTER OVERVIEW: This chapter discusses the heart in detail. The location, structure, histology, cellular properties, and mechanism of contraction of the heart and cardiac muscle are discussed. The functions of the heart in relation to the entire cardiovascular system are considered. The events of the cardiac cycle, normal and abnormal heart sounds, and the regulation of the heart are described in detail. The role of the heart in homeostasis is discussed.

OUTLINE (four or five fifty-minute lectures):

Chapt. Object.	Topic Outline, Chapter 20	Figures & Tables	Trnspcy. Acetates	Trnspcy. Masters
1	I. Size, Form and Location of the Heart	Fig. 20.2, pp.604-605	TA-245-TA-247
	A. In the Thoracic Cavity
	1. Size of a Closed Fist
	2. Region of Mediastinum
	B. Orientation
	1. Apex Inferior
	2. Base Superior

	II. Anatomy of the Heart
	A. Four Chambers	Fig. 20.3, p.606	TA-248
2	A. Pericardium	Fig. 20.4, p.606	TA-249
	1. Fibrous Pericardium
	a. Holds Heart in Place
	b. Continuous with CT of Great Vessels & Diaphragm
	c. Outer Layer
	2. Serous Pericardium
	a. Reduces Friction
	b. Components
	1). Parietal Pericardium Lining Fibrous Pericardium
	2). Visceral Pericardium Covering Heart Itself
	3). Pericardial Cavity with Pericardial Fluid	Clinical Note, p.602
	B. Heart Wall
3	1. Layers	Fig. 20.5, p.607	TA-250
	a. Epicardium
	b. Myocardium
	c. Endocardium
	2. Special Structures
	a. Musculi Pectinati
	b. Crista Terminalis
	c. Trabeculae Carneae
4	C. External Anatomy	Fig. 20.6a-c, pp. 607-608	TA-251 TA-252
	1. Atrial Auricles
	2. Great Veins
	a. Superior and Inferior Venae Cavae - R. Atrium
	b. Four Pulmonary Veins - L. Atrium
	3. Great Arteries
	a. Pulmonary Trunk - L. Atrium
	b. Aorta - L. Ventricle
	4. Coronary Blood Supply	Fig. 20.7, p.609; Clinical Focus, p.610	TA-253
	a. Landmarks
	1). Coronary Sulcus - Separates Atria from Ventricles
	2). Ant. & Post. Interventricular Grooves - Separate Ventricles
	b. Coronary Arteries	Predict Quest. 1
	1). Off Aorta to Supply Heart
	2). Left Coronary Artery
	a). Anterior Interventricular Artery
	b). Marginal Branch
	c). Circumflex Branch
	3). Right Coronary Artery & Posterior Interven-tricular Artery
4	D. Heart Chambers and Valves
	1. Right and Left Atria	Fig. 20.8, p.611	TA-254
	a. Interatrial Septum
	b. Fossa Ovalis
	2. Right ant Left Ventricles
	a. Interventricular Septum
	b. Interventricular Grooves = Surface Landmark
	3. Atrioventricular Valves
	a. Tricuspid Valve - Separates R. Atrium from R. Ventricle
	b. Bicuspid (or Mitral) Valve - Separates L. Atrium from L. Ventricle
	c. Structure of Atrioventricular Valves	Fig. 20.9a, p.611
	1). Valve Flaps (2 or 3)
	2). Chordae Tendineae
	3). Papillary Muscles
	4. Semilunar Valves	Fig. 20.9b, p.611
	a. Aortic Semilunar Valve
	b. Pulmonary Semilunar Valve
	c. Three Valve Flaps

	III. Route of Blood Flow Through the Heart	Fig. 20.3, p.606	TA-248
	A. Double Pump
	B. Right Heart
	1. Heart to Lungs
	2. Through Pulmonary Trunk and Pulmonary Arteries
	3. Returned to Left Heart
	C. Left Heart
	1. Heart to Body
	2. Through Aorta
	3. Returned to Right Heart

	IV. Histology
	A. Heart Skeleton	Fig. 20.10, p.612	TA-255
	1. Fibrous CT Rings Support Heart Valves
	2. Electrically Isolates Atria from Ventricles
	3. Point of Attachment of Cardiac Muscle
5	B. Cardiac Muscle	Fig. 20.11, p.613	TA-256
	1. Striated, Branched, Uninucleate Cells
	2. Smooth Sarcoplasmic Reticulum
	a. Less Organized than in Skeletal Muscle
	b. T-tubule system Important
	3. Slow Onset of contraction - Related to Ca²⁺ Diffusion
	4. Primarily Aerobic Respiration - No O₂ Debt Possible	Predict Quest. 2
	5. Functional Syncytium of Bundles or Sheets of Cells
	a. Desmosomes
	b. Gap Junctions
6	C. Conducting System	Fig. 20.12, p.614	TA-257
	1. Structures
	a. Sinoatrial Node (SA Node) - R. Atrium
	b. Atrioventricular Node (AV Node) - R. Atrium
	c. Atrioventricular Bundle
	d. R & L Bundle Branches - Interventricular Septum
7	e. Purkinje Fibers - Large Diameter Cardiac Muscle Fibers
	2. Functions
	a. SA Node with Spontaneous Action Potentials = Pacemaker
	b. Depolarization Spreads from Node to Other Cardiac Cells
	c. Atria Contract before Ventricles Depolarized
	1). Preferred Depolariza-tion Path to AV Node (0.04 sec.)
	2). 0.11 sec. Delay at AV Node
	d. Action Potentials along Bundles to Purkinje Fibers and Ventricular Fibers
	e. Ventricular Contractions
	1). Apex to Base	Predict Quest. 3
	2). Wringing Action

	V. Electrical Properties 1. Resting Membrane Potentials (details Chapter 9)
8	A. Action Potentials	Fig. 20.13, p.615; Clinical Note, p.617		TM-63
	1. Rapid Depolarization - Na⁺ Fast Channels Open
	2. Rapid Partial Repolarization
	3. Prolonged Slow Repolarization (Plateau Phase) - Slow Ca²⁺ Channels
	4. Final Rapid Depolarization - K⁺ Channels Open and Ca²⁺ Channels Close
9	B. Autorhythmicity of Cardiac Muscle	Fig. 20.14, p.616		TM-64
	1. Spontaneous Depolarizations
	a. Fastest in SA Node 70-80 Beats per min.
	b. Slow Channels
	2. Ectopic Foci	Predict Quest. 4
10	C. Refractory Period of Cardiac Muscle
	1. Extended Due to Plateau Phase
	2. Absolute Refractory Period Ensures Relaxation Nearly Complete Before Next Contraction
	3. Summation and Tetany Impossible	Predict Quest. 5
11	D. Electrocardiogram	Table 20.1, p. 618; Fig. 20.15, p.619; Clinical Note, p.619	TA-258	TM-65
	1. P Wave - Atrial Depolarization
	2. QRS Complex - Ventricular Depolarization
	3. T Wave - Ventricular Repolarization
	4. PQ Interval (PR Interval)
	a. Time Between Beginning of P Wave and Beginning of QRS Complex
	b. 0.16 sec.
	c. Time of Atrial Contraction
	5. QT Interval
	a. Time Between Beginning of QRS Complex and End of T Wave
	b. 0.3 sec.
	c. Time of Ventricular Contraction

12	VI. Cardiac Cycle 1. Repetitive Pattern of Pumping Action	Fig. 20.16, p.620; Fig. 20.17, p.622; Table 20.2, pp.623-624; Clinical Note, p.621 (See Fig. 20.18, p.625; Predict Quest. 6		TM-66
	A. Systole and Diastole
	1. Atrial Systole and Diastole	Fig. 20.17, p.622		TM-66
	2. Ventricular Systole and Diastole	Fig. 20.17, p.622		TM-66
	a. Period of Isometric Contraction
	1). After AV Valves Have Closed
	2). Before Semilunar Valves Have Opened
	b. Ejection Phase
	1). AV Valves Remain Closed
	2). Semilunar Valves Forced Open
	c. Early Diastole and Isometric Relaxation
	1). After Semilunar Valves have Closed
	2). Before Semilunar Valves have Opened
	3. Cardiac Output or Minute Volume	Predict Quest. 7
	a. End Diastolic Volume - End Systolic Volume = Stroke Volume
	b. Stroke Volume X Heart Rate = Cardiac Output or Minute volume
	c. Cardiac Reserve = Ability to Increase Cardiac Output
	d. Major Determinant of Arterial Blood Pressure (MABP = CO X PR, where PR Stands for Peripheral Resistance to Blood Flow)
13	B. Aortic Pressure Curve
	1. Peak Pressure During Ventricular Contraction
	2. Incisura or Dicrotic Notch
	a. Follows Closure of Aortic Semilunar Valve
	b. Pressure Increase Caused by Elastic Recoil of Aorta
14	C. Heart Sounds	Clinical Focus, p.626
	1. First Heart Sound (Lubb)
	a. Vibrations Due to Closure of AV Valves
	b. Beginning of Ventricular Systole
	2. Second Heart Sound (Dupp)
	a. Vibrations Due to Closure of Semilunar Valves
	b. Near End of Ventricular Systole
	3. Third Heart Sound
	a. Normal, but Usually too Faint to be Heard
	b. Turbulent Flow of Blood from Atria to Ventricles
	c. Marks end of First Third of Ventricular Diastole

	VII Regulation of the Heart	Clinical Focus, pp.633-634
15	A. Intrinsic Regulation
	1. Venous Return Determines End Diastolic Volume and Preload
	2. Starling's Law of the Heart	Fig. 20.19, p.627		TM-67
	a. Stretch of Cardiac Muscle Produces Stronger Contractions
	b. Increased Venous Return Leads to Greater Cardiac Output
	3. Afterload = Pressure Needed to Move Blood into the Aorta
16, 17	B. Extrinsic Regulation	Fig. 20.20, p.628	TA-259
	1. Cardioregulatory Center and Chemoreceptors in Medulla Oblongata
	2. Parasympathetic Control
	a. Vagus Nerve
	b. Decreases Heart Rate and (Small) Decrease in Force; up to 20% Decrease in Cardiac Output
	c. Acetylcholine
	1). Hyperpolarization
	2). Opens Ligand Gated K⁺ Channels
	3. Sympathetic Control	Predict Quest. 8
	a. Cardiac Nerves
	b. Increases Heart Rate and Contractility; up to 100% Increase in Cardiac Output
	c. Norepinephrine
	1). Hypopolarization
	2). b -Adrenergic Activation of cAMP Second Messenger System
	4. Hormonal Control
	a. Epinephrine and Norepinephrine in Blood from Adrenal Medulla
	b. Longer Lasting than Neural Stimulation
	c. Increases Heart Rate and Force of Contraction

18	VIII. Heart and Homeostasis	System Interactions, p. 636
	A. Effect of Blood Pressure	Fig. 20.20, p.628	TA-259
	1. Baroreceptor Reflex
	a. Stretch Receptors in Internal Carotid Artery and Aorta
	b. Sympathetic Fibers from Cardioacceleratory Center
	c. Parasympathetic Fibers from Cardioinhibitory Center
	d. Increased BP Increases Parasympathetic Activity and Decreases Sympathetic Activity
	e. Decreased BP Increases Sympathetic Activity and Decreases Parasympathetic Activity	Fig. 20.21, p.630		TM-68
	B. Effect of pH, Carbon Dioxide, and Oxygen	Fig. 20.22, p.631		TM-69
	1. Central Chemoreceptors Sensitive to Decreased pH and Increased CO₂ in Medulla Oblongata
	2. Peripheral Chemoreceptors Sensitive to Decreased O₂ in Aorta and Carotid Bodies; More Important in Regulation of Respiration and Blood Vessel Constriction
	C. Effect of Extracellular Ion Concentrations
	1. K⁺, Ca²⁺, and Na⁺ and Effects on Membrane Potentials
	2. K⁺ Heart Block
	D. Effect of Body Temperature
	IX. Systems Pathology	Systems Interactions, p. 636; Predict Quest. 9

IMPORTANT CONSIDERATIONS: Four major topic areas covered above are: basic anatomy of the heart, histology and electrical properties of cardiac muscle, the cardiac cycle, and the regulation of the heart and its relation to homeostasis. Being familiar with the pattern of circulation of blood through the heart and the cardiovascular system is of special importance to those students planning on careers in the health related professions. There are pharmacological implications for clinical practice in knowing where the blood goes after leaving the site of administration of therapeutic agents.

Autorhythmicity and the plateau of the action potential give trouble to students who did not get a solid grasp of the ideas associated with membrane potentials when they were presented in Chapter 9. Some backtracking may be necessary to ensure that students do get these concepts, since they are fundamental to understanding the control mechanisms regulating cardiac function.

The pressure relationships which are so important to a clear understanding of the cardiac cycle are not necessarily familiar to the student. Students may need to be helped to see that it is the pressure difference and not the cardiac muscle itself that maintains the flow of blood through the cardiovascular system. Another common misconception that students may have is that the heart contracts and immediately ejects blood. Be sure that they understand that initially both the atrioventricular valves and the semilunar valves are closed, until the pressure on the blood is sufficient to force the semilunar valves open and eject the blood.

Understanding of the extrinsic regulatory mechanisms require remembering the discussions on the parasympathetic and sympathetic divisions of the autonomic nervous system covered in Chapter 16. Students should be encouraged to review this material if they cannot remember it.

Students should be able to predict (and explain) changes in heart rate and/or force of contraction that follow changes in any of the following: blood pressure, pH, oxygen content of the blood, carbon dioxide content of the blood, body temperature, and/or extracellular concentrations of important ions (sodium, potassium, calcium, chloride).

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