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THE HEART
H E AT H E R L D R A K EN E W Y O R K C H I R O P R A C T I C C O L L E G E , 2 0 1 3
S A L A D I N, “ U N I T Y O F F O R M A N D F U N C T I O N ”
The Circulatory System
OVERVIEW
Objectives
Define and distinguish between the pulmonary and systemic circuits
Describe the general location, size, and shape of the heart
Describe the pericardial sac that encloses the heart
PULMONARY and SYSTEMIC CIRCUITS
Cardiovascular System Consists of the heart and the blood vessels that carry
the blood to and from the body’s organs
2 major divisions Pulmonary circuit Systemic circuit
2 DIVISIONS
Pulmonary Circuit Carries blood to the lungs for gas exchange and returns it to the heart
The right side of the heart serves the pulmonary circuit Receives blood that has circulated throughout the body, unloaded its oxygen
and nutrients, and picked up a load of carbon dioxide/other wastes.
Pumps into the pulmonary trunk, which divides into right and left pulmonary arteries, transporting into alveoli, carbon dioxide unloaded/oxygen loaded.
Oxygen-rich blood then flows via pulmonary veins to the left side of the heart
Systemic Circuit Supplies blood every organ of the body, including other parts of the
lungs and wall of the heart itself
Pulmonary Circuit
Right side of the heart serves the pulmonary circuit
Superior/inferior vena cava
Right atrium Tricuspid valve Right ventricle Pulmonic semilunar
valves Pulmonary artery Lungs for gas
exchange Pulmonary vein Aortic semilunar
valves Left atrium Mitral valve Left ventricle Ascending aorta Aortic arch Body
2 DIVISIONS
Pulmonary Circuit Carries blood to the lungs for gas exchange and returns
it to the heartSystemic Circuit
Supplies blood every organ, including wall of the heart itself
Blood leaves the left side of the heart via the aorta, taking an inverted U-turn, the aortic arch, and passes downward, dorsal to the heart
Systemic Circuit
Systemic Circuit
Supplies blood every organ of the body, including other parts of the lungs and wall of the heart itself
Blood leaves the left side of the heart via the aorta, taking an inverted U-turn, the aortic arch, and passes downward, dorsal to the heart
Fig. 19.1b
Aortic arch gives off arteries that supply the head, neck, and upper limbs.
The aorta then travels through the thoracic & abdominal cavities and gives off arteries to the organs
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
O2-poor,CO2-richblood
O2-rich,CO2-poorblood
Systemic circuit
O2CO2
Systemic Circuit
Supplies:
- Every organ
- Heart muscle
- Parts of the lungs
Systemic Circuit
After circulating through the body, the now-deoxygenated systemic blood returns to the right side of the heart mainly via:
Superior vena cava (draining the head, neck, upper limbs and thoracic organs)
Inferior vena cava (drains organs below the diaphragm)
Fig. 19.1
Putting it all together
Pulmonary AND Systemic Circuits
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O2
O2CO2
Pulmonary circuit
O2-poor,CO2-richblood
O2-rich,CO2-poorblood
Systemic circuit
CO2
POSITION of the HEART
Base – broad superior portion
of heart – point of attachment
for the great vessels
Apex – the inferior end tapers
to a blunt point
Fig. 19.2cCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Superiorvena cava
Right lung
Parietalpleura (cut)
Pericardialsac (cut)
Aorta
Pulmonarytrunk
Baseofheart
Apexof heart
Diaphragm(c)
Fig. 19.2b
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Posterior
Lungs
Pericardialcavity
Leftventricle
Interventricularseptum
Anterior
Sternum
Rightventricle
Thoracicvertebra
(b)
Position of Heart
Fig. 19.2a
Thoracic cavity in the mediastinum and deep to the sternum
Tilted towards the left – 2/3 of heart is in left of median
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(a)
Sternum
3rd rib
Diaphragm
THE PERICARDIUM
Pericardium - heart is enclosed in a double-walled sac
Parietal pericardium – the outer wall has a tough, superficial fibrous layer
Serous layer – turns inward at the base of the heart and forms the visceral pericardium (epicardium) covering the heart surface
Fig. 19.3a
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pericardialcavity
Myocardium
Endocardium
Epicardium
Pericardial sac
Fig. 19.3bCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pericardialcavity
Pericardialsac:
Fibrouslayer
Serouslayer
Epicardium
PERICARDITIS
inflammation of the pericardium –
membrane becomes dry and produces a painful friction rub
Pericardial cavity – space between the parietal and visceral membranes, contains pericardial fluid – Allows the heart to beat
without friction
QUIZ
1. Distinguish between the pulmonary and systemic circuits and state which part of the heart serves each one
2. Make a two color sketch of the pericardium;
1. Use one color for the fibrous pericardium and another for the serous pericardium and another for the serous pericardium and show their relationship to the heart wall and pericardial activity
GROSS ANATOMY OF THE HEART
OBJECTIVES Describe the 3 layers of the heart wall
Identify the four chambers of the heart
Identify the surface features of the heart and correlate them with its internal four-chambered anatomy
Identify the four valves of the heart
Trace the flow of blood through the four chambers of the heart and adjacent blood vessels
Describe the arteries that nourish the myocardium & veins that drain it
HEART WALL
3 layers: Epicardium
Myocardium
Endocardium
HEART WALL
Epicardium Thin, serous layer that
covers external surface
Consists mainly of a simple squamous epithelium overlaying thin aereolar tissue
Some locations also include thick layer of adipose tissue
Some locations thin and transluscent to show myocardium
Myocardium of the Heart
Myocardium
Thick, muscular middle layer – composed of cardiac muscle
Thickest layer – performs the work of the
heart
Thickness is proportional to the workload on the individual chambers
Muscle spirals around the heart, so when the ventricles contract, they exhibit a twisting/wringing motion
Endocardium of the Heart
Endocardium
Thin layer lining the inside of the chambers
Simple squamous endothelium overlaying thin aereolar tissue
Has no adipose tissue
Covers the valve surfaces and is continuous with the endothelium of the bl vessels
ANIMATION OF BLOOD FLOW THROUGH HEART
http://www.wellesley.edu/Biology/Courses/111/AdultHeart.gif
Fig. 19.9-1Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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1Blood enters right atrium from superiorand inferior venae cavae.
Aorta
Superiorvena cava
Rightpulmonaryveins
Rightatrium
Right AV(tricuspid) valve
Rightventricle
Inferiorvena cava
Left pulmonaryartery
Pulmonary trunk
Left pulmonaryveins
Left ventricle
Left AV(bicuspid) valve
Aortic valve
Left atrium
Fig. 19.9-2Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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1
2
1Blood enters right atrium from superiorand inferior venae cavae.
Blood in right atrium flows through rightAV valve into right ventricle.
Aorta
Superiorvena cava
Rightpulmonaryveins
Rightatrium
Right AV(tricuspid) valve
Rightventricle
Inferiorvena cava
Left pulmonaryartery
Pulmonary trunk
Left pulmonaryveins
Left ventricle
Left AV(bicuspid) valve
Aortic valve
Left atrium
Fig. 19.9-3Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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2
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2
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1Blood enters right atrium from superiorand inferior venae cavae.
Blood in right atrium flows through rightAV valve into right ventricle.
Contraction of right ventricle forcespulmonary valve open.
Aorta
Superiorvena cava
Rightatrium
Right AV(tricuspid) valve
Rightventricle
Inferiorvena cava
Left pulmonaryartery
Pulmonary trunk
Left pulmonaryveins
Left ventricle
Left AV(bicuspid) valve
Aortic valve
Left atrium
Rightpulmonaryveins
Fig. 19.9-4Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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1Blood enters right atrium from superiorand inferior venae cavae.
Blood in right atrium flows through rightAV valve into right ventricle.
Contraction of right ventricle forcespulmonary valve open.
Blood flows through pulmonary valveinto pulmonary trunk.
Aorta
Superiorvena cava
Rightatrium
Right AV(tricuspid) valve
Rightventricle
Inferiorvena cava
Left pulmonaryartery
Pulmonary trunk
Left pulmonaryveins
Left ventricle
Left AV(bicuspid) valve
Aortic valve
Left atrium
Rightpulmonaryveins
Fig. 19.9-5Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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1Blood enters right atrium from superiorand inferior venae cavae.
Blood in right atrium flows through rightAV valve into right ventricle.
Contraction of right ventricle forcespulmonary valve open.
Blood flows through pulmonary valveinto pulmonary trunk.
Blood is distributed by right and leftpulmonary arteries to the lungs, where itunloads CO2 and loads O2.
Aorta
Superiorvena cava
Rightatrium
Right AV(tricuspid) valve
Rightventricle
Inferiorvena cava
Left pulmonaryartery
Pulmonary trunk
Left pulmonaryveins
Aortic valve
Left atrium
Rightpulmonaryveins
Left ventricle
Left AV(bicuspid) valve
Fig. 19.9-6Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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1Blood enters right atrium from superiorand inferior venae cavae.
Blood in right atrium flows through rightAV valve into right ventricle.
Contraction of right ventricle forcespulmonary valve open.
Blood flows through pulmonary valveinto pulmonary trunk.
Blood is distributed by right and leftpulmonary arteries to the lungs, where itunloads CO2 and loads O2.
Blood returns from lungs via pulmonaryveins to left atrium.
Aorta
Superiorvena cava
Rightpulmonaryveins
Rightatrium
Right AV(tricuspid) valve
Rightventricle
Inferiorvena cava
Left pulmonaryartery
Pulmonary trunk
Left pulmonaryveins
Left ventricle
Left AV(bicuspid) valve
Aortic valve
Left atrium
Fig. 19.9-7Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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1Blood enters right atrium from superiorand inferior venae cavae.
Blood in right atrium flows through rightAV valve into right ventricle.
Contraction of right ventricle forcespulmonary valve open.
Blood flows through pulmonary valveinto pulmonary trunk.
Blood is distributed by right and leftpulmonary arteries to the lungs, where itunloads CO2 and loads O2.
Blood returns from lungs via pulmonaryveins to left atrium.
Blood in left atrium flows through left AVvalve into left ventricle.
Aorta
Superiorvena cava
Rightpulmonaryveins
Rightatrium
Right AV(tricuspid) valve
Rightventricle
Inferiorvena cava
Left pulmonaryartery
Pulmonary trunk
Left pulmonaryveins
Left ventricle
Left AV(bicuspid) valve
Aortic valve
Left atrium
Fig. 19.9-8Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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1Blood enters right atrium from superiorand inferior venae cavae.
Blood in right atrium flows through rightAV valve into right ventricle.
Contraction of right ventricle forcespulmonary valve open.
Blood flows through pulmonary valveinto pulmonary trunk.
Blood is distributed by right and leftpulmonary arteries to the lungs, where itunloads CO2 and loads O2.
Blood returns from lungs via pulmonaryveins to left atrium.
Blood in left atrium flows through left AVvalve into left ventricle.
Aorta
Superiorvena cava
Rightpulmonaryveins
Rightatrium
Right AV(tricuspid) valve
Rightventricle
Left pulmonaryartery
Pulmonary trunk
Left pulmonaryveins
Left ventricle
Left AV(bicuspid) valve
Aortic valve
Left atrium
Contraction of left ventricle (simultaneous withstep 3 ) forces aortic valve open.
Fig. 19.9-9Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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1Blood enters right atrium from superiorand inferior venae cavae.
Blood in right atrium flows through rightAV valve into right ventricle.
Contraction of right ventricle forcespulmonary valve open.
Blood flows through pulmonary valveinto pulmonary trunk.
Blood is distributed by right and leftpulmonary arteries to the lungs, where itunloads CO2 and loads O2.
Blood returns from lungs via pulmonaryveins to left atrium.
Blood in left atrium flows through left AVvalve into left ventricle.
Blood flows through aortic valve intoascending aorta.
Aorta
Superiorvena cava
Rightpulmonaryveins
Rightatrium
Right AV(tricuspid) valve
Rightventricle
Left pulmonaryartery
Pulmonary trunk
Left pulmonaryveins
Left ventricle
Left AV(bicuspid) valve
Aortic valve
Left atrium
Contraction of left ventricle (simultaneous withstep 3 ) forces aortic valve open.
Fig. 19.9-10Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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1Blood enters right atrium from superiorand inferior venae cavae.
Blood in right atrium flows through rightAV valve into right ventricle.
Contraction of right ventricle forcespulmonary valve open.
Blood flows through pulmonary valveinto pulmonary trunk.
Blood is distributed by right and leftpulmonary arteries to the lungs, where itunloads CO2 and loads O2.
Blood returns from lungs via pulmonaryveins to left atrium.
Blood in left atrium flows through left AVvalve into left ventricle.
Blood flows through aortic valve intoascending aorta.
Blood in aorta is distributed to every organ inthe body, where it unloads O2 and loads CO2.
Aorta
Superiorvena cava
Rightpulmonaryveins
Rightatrium
Right AV(tricuspid) valve
Rightventricle
10
Left pulmonaryartery
Pulmonary trunk
Left pulmonaryveins
Left ventricle
Left AV(bicuspid) valve
Aortic valve
Left atrium
Contraction of left ventricle (simultaneous withstep 3 ) forces aortic valve open.
Fig. 19.9Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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1Blood enters right atrium from superiorand inferior venae cavae.
Blood in right atrium flows through rightAV valve into right ventricle.
Contraction of right ventricle forcespulmonary valve open.
Blood flows through pulmonary valveinto pulmonary trunk.
Blood is distributed by right and leftpulmonary arteries to the lungs, where itunloads CO2 and loads O2.
Blood returns from lungs via pulmonaryveins to left atrium.
Blood in left atrium flows through left AVvalve into left ventricle.
Blood flows through aortic valve intoascending aorta.
Blood in aorta is distributed to every organ inthe body, where it unloads O2 and loads CO2.
Blood returns to heart via venae cavae.
Aorta
Superiorvena cava
Rightpulmonaryveins
Rightatrium
Right AV(tricuspid) valve
Rightventricle
Inferiorvena cava 11
10
11
Left pulmonaryartery
Pulmonary trunk
Left pulmonaryveins
Left ventricle
Left AV(bicuspid) valve
Aortic valve
Left atrium
11
Contraction of left ventricle (simultaneous withstep 3 ) forces aortic valve open.
HEART – FIBROUS SKELETON
Has a meshwork of collagenous and elastic fibers that make up a fibrous skeleton
Fibrous rings have multiple functions: Structural support for heart, esp around valves and
openings of great vessels
Anchors the myocytes and gives them something to pull against
Serves as electrical insulation b/w atria and ventricles, so the atria cannot stimulate the ventricles directly
Elastic recoil aids in refilling the heart
THE 4 CHAMBERS
Superior Chambers Right atria Left atria
Receiving chambersfor blood returningto the heart
Inferior chambers: Right ventricle Left ventricle
The pumps that ejectblood into the arterieskeep it flowingaround body
VALVES – Atrioventricular Valves
A). Atrioventricular (AV) Valves Located between the
atria and the ventricles Flaps consist of
connective tissue & endocardium.
They are attached to collagen cords called chordae tendinae. 1). Tricuspid 2). Bicuspid or Mitral
Valve
VALVES – Semilunar Valves
B). Semilunar (SL) Valves Lead into the large
arteries
Formed from 3 moon-shaped cusps
1). Aortic Semilunar Valve
2). Pulmonary Semilunar Valve
BLOOD FLOW – AV Valves - STEP 1
When the heart is relaxed, the AV flaps hang open
BLOOD FLOW – AV Valves – STEP 2
When the ventricles contract the AV valves are pressed closed from the ventricular side.
Blood is pushed against the AV valve which closes and it pushes against the SL valve which opens
BLOOD FLOW – Semilunar Valves - STEP 1
When the ventricle relaxes blood pressure is higher in the vessels, which closes the SL valve
BLOOD FLOW – Semilunar Valves – STEP 2
BLOOD FLOW THROUGH THE HEART
1. Blood enters right atrium from superior and inferior venae cavae
2. Blood in the right atrium flows through right AV valve into the right ventricle
3. Contraction of right ventricular forces pulmonary valve open
4. Blood flows through pulmonary valve into pulmonary trunk
5. Blood is distributed by right and left pulmonary arteries to the lungs, where it unloads CO2 and loads O2
6. Blood return from lungs via pulmonary arteries to left atrium
7. Blood in left atrium flows through left AV valve into left ventricle
8. Contraction of left ventricle (simultaneous with step 3) forces aortic valve open
BLOOD FLOW THROUGH THE HEART
9. Blood flows through the aortic valve into ascending aorta
10. Blood in aorta is distributed into every organ in the body, where it unloads O2 and loads CO2
11. Blood returns to heart via venae cavae
BLOOD FLOW THROUGH THE HEART
QUIZ TIME
Trace the pathway of a single erythrocyte from the inferior vena cava to the aortic arch, naming each vessel and structure it passes through, and noting when it is oxygenated, and when it is deoxygenated.
CORONARY ARTERY BLOOD FLOW
QUIZ QUESTION
Trace the path of a single erythrocyte from the aorta to the posterior apex of the heart, if the right coronary artery is blocked at just after its attachment to the aorta?
How would the left anterior portion of the heart receive blood supply with the same blockage?
This theory is called COLLATERAL CIRCULATION The flow of blood to an area via an alternative route via vessel
anastomoses
CLINICAL CORRELATION
What if multiple coronary arteries were clogged? So much that there was not enough blood to fuel the heart?
Angina pectoris chest pain/pressure due to temporary ischemia
deficiency of blood to cardiac muscle
O2 deprived myocardium shits to anaerobic fermentation, producing lactic acid, which stimulates pain receptors in the heart.
MYOCARDIAL INFARCTION (MI) – heart attack
VENOUS DRAINAGE
Refers to the route by which blood leaves an organ.
20% of coronary blood empties directly into multiple small thebesian veins into the right atrium/ventricle
VENOUS DRAINAGE
80% returns to the right atrium via this route:
Great cardiac vein – Collects blood from anterior heart,
travels w.anterior interventric artery
Carries blood from apex to coronary sulcus, arcs left, empties into coronary sinus
Posterior interventricular (middle cardiac) vein Collects bl from posterior aspect of
heart
Left marginal vein Travels from apex up left margin,
empties into coronary sinus
Coronary sinus Large transverse vein in coronary
sulcus, empties blood into right atrium
QUIZ
3. Name the three layers of the heart and describe their structural differences
4. What are the functions of the fibrous skeleton?
5. Trace the flow of blood through the heart, naming each chamber and valve in order
6. What are the three principle branches of the left coronary artery? Where are they located on the heart surface? What are the branches of the right coronary artery, and where are they located?
7. What is the medical significance of the anastamoses in the coronary arterial system?
8. Why do the coronary arteries carry a greater blood flow during ventricular diastole than they do during ventricular systole?
9. What are the three major veins that empty into the coronary sinus?
QUIZ
CARDIAC CONDUCTION SYSTEM and CARDIAC MUSCLE
OBJECTIVES: Describe the nerve supply to the heart
Describe the internal electrical system of the heart
Describe the unique structural and metabolic characterisitic of cardiac muscle
Explain the nature and functional significance of the intercellular junctions between cardiac muscle cells
INTRO
Heart contracts at regular intervals (obviously) Typically 75bpm
Invertebrates (clames, crabs, insects, etc) have heartbeat triggered by a pacemaker in the nervous system
Vertebrates (us) is myogenic Signal originates within the heart itself
NERVE SUPPLY TO THE HEART
Heart has its own pacemaker, but it does receives sympathetic and parasympathetic nerves, modifying the heart rate and contraction strength
Sympathetic stimulation may raise HR to 230 bpm.
Parasympathetic stimulation can slow the HR as low as 20 bpm, or even stop for a few seconds.
NERVE SUPPLY TO THE HEART
Sympathetic pathway originates w.neurons in the lower cervical/upper thoracic spinal cord
Efferent fibers from these neurons pass from the spinal cord to the sympathetic chain and travel up the chain to the 3 cervical ganglia
Cardiac nerves arise from these ganglia, and lead to the myocardium, increasing force of contraction
NERVE SUPPLY TO THE HEART
NERVE SUPPLY TO THE HEART
Some fibers innervate the atria
Sympathetic fibers to the coronary arteries dilate them and increase coronary blood flow to the coronary arteries during exercise
Parasympathetic pathway to the heart is through the vagus nerves
RIGHT VAGUS nerve innervates mainly an electrical center of the heart – SA node
LEFT VAGUS nerve innervates the AV node
Ventricles receive little or no vagal stimulation
Vagus nerve slows the heartbeat. W.o this influence, the average resting HR would be 100 bpm Steady firing of the vagus nerve, VAGAL TONE, holds resting HR down to 70-80 bpm
IN SHORT – Sympathetic nerves do NOT make the heart beat, they only MODIFY it.
CONDUCTION ANIMATION
http://en.wikipedia.org/wiki/File:ECG_Principle_fast.gif
Fig. 19.12-1Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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SA node fires.
Purkinje fibers
Atrioventricularbundle
Atrioventricularnode
Sinoatrial node(pacemaker)
Right atrium
Bundlebranches
Leftatrium
Purkinjefibers
Fig. 19.12-2Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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1
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SA node fires.
Excitation spreads throughatrial myocardium.
Purkinje fibers
Atrioventricularbundle
Atrioventricularnode
Sinoatrial node(pacemaker)
Right atrium
Bundlebranches
Leftatrium
Purkinjefibers
Fig. 19.12-3Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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SA node fires.
Excitation spreads throughatrial myocardium.
AV node fires.
Purkinje fibers
Atrioventricularbundle
Atrioventricularnode
Sinoatrial node(pacemaker)
Right atrium
Bundlebranches
Leftatrium
Purkinjefibers
Fig. 19.12-4Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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SA node fires.
Excitation spreads throughatrial myocardium.
AV node fires.
Excitation spreads down AVbundle.
Purkinje fibers
Atrioventricularbundle
Atrioventricularnode
Sinoatrial node(pacemaker)
Right atrium
Bundlebranches
Leftatrium
Purkinjefibers
Fig. 19.12Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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SA node fires.
Excitation spreads throughatrial myocardium.
AV node fires.
Excitation spreads down AVbundle.
Purkinje fibers distributeexcitation throughventricular myocardium.
Purkinje fibers
Atrioventricularbundle
Atrioventricularnode
Sinoatrial node(pacemaker)
Right atrium
Bundlebranches
Leftatrium
Purkinjefibers
Fig. 19.13Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Pacemakerpotential
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Threshold
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 19.14-2
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Voltage-gated Na+ channels open.
Na+ inflow depolarizes the membraneand triggers the opening of still more Na+channels, creating a positive feedbackcycle and a rapidly rising membrane voltage.
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Myocardialcontraction
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 19.14-3
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Voltage-gated Na+ channels open.
Na+ inflow depolarizes the membraneand triggers the opening of still more Na+channels, creating a positive feedbackcycle and a rapidly rising membrane voltage.
Na+ channels close when the celldepolarizes, and the voltage peaks atnearly +30 mV.
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Absoluterefractory
period
Myocardialcontraction
Actionpotential
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 19.14-4
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Voltage-gated Na+ channels open.
Na+ inflow depolarizes the membraneand triggers the opening of still more Na+channels, creating a positive feedbackcycle and a rapidly rising membrane voltage.
Na+ channels close when the celldepolarizes, and the voltage peaks atnearly +30 mV.
Ca2+ entering through slow Ca2+
channels prolongs depolarization ofmembrane, creating a plateau. Plateau fallsslightly because of some K+ leakage, but mostK+ channels remain closed until end ofplateau.
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Time (seconds)
.15
Absoluterefractory
period
Myocardialcontraction
Actionpotential
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 19.14
0
Voltage-gated Na+ channels open.
Na+ inflow depolarizes the membraneand triggers the opening of still more Na+channels, creating a positive feedbackcycle and a rapidly rising membrane voltage.
Na+ channels close when the celldepolarizes, and the voltage peaks atnearly +30 mV.
Ca2+ entering through slow Ca2+
channels prolongs depolarization ofmembrane, creating a plateau. Plateau fallsslightly because of some K+ leakage, but mostK+ channels remain closed until end ofplateau.
Ca2+ channels close and Ca2+ is transportedout of cell. K+ channels open, and rapid K+
outflow returns membrane to its restingpotential.
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4
5
Mem
bra
ne p
ote
nti
al
(mV
)
0
+20
–20
–40
–60
–80
Plateau
Myocardialrelaxation
.30
Time (seconds)
.15
Absoluterefractory
period
Myocardialcontraction
Actionpotential
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 19.15a
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
0.8 second
Fig. 19.15bCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
0Mil
livo
lts
R R
QS
+1
–1
Atriacontract
Ventriclescontract
Atriacontract
Ventriclescontract
STsegment
PQsegment
QRS interval
T waveP wave
PRinterval
QTinterval
Fig. 19.15Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
0Mil
livo
lts
R R
QS
0.8 second
+1
–1
Atriacontract
Ventriclescontract
Atriacontract
Ventriclescontract
STsegment
PQsegment
QRS interval
T waveP wave
PRinterval
QTinterval
Absolute versus Relative Refractory
Fig. 19.16-1Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
P
Wave ofdepolarization
Wave ofrepolarization
Atria begin depolarizing.
Key
Fig. 19.16-2Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
2
P
P
Wave ofdepolarizationWave ofrepolarization
Atria begin depolarizing.
Atrial depolarization complete.
Key
Fig. 19.16-3Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
2
Q
R
P
P
P
3
Wave ofdepolarizationWave ofrepolarization
Atria begin depolarizing.
Atrial depolarization complete.
Ventricular depolarization begins at apex andprogresses superiorly as atria repolarize.
Key
Fig. 19.16-4Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1 4
2
SQ
R
P
Q
R
P
P
P
3
Wave ofdepolarizationWave ofrepolarization
Atria begin depolarizing.
Atrial depolarization complete.
Ventricular depolarization begins at apex andprogresses superiorly as atria repolarize.
Ventricular depolarization complete.
Key
Fig. 19.16-5Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
5
1 4
2
T
SQ
R
P
SQ
R
P
Q
R
P
P
P
3
Wave ofdepolarizationWave ofrepolarization
Atria begin depolarizing.
Atrial depolarization complete.
Ventricular depolarization begins at apex andprogresses superiorly as atria repolarize.
Ventricular repolarization begins at apex andprogresses superiorly.
Ventricular depolarization complete.
Key
Fig. 19.16Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
5
6
1 4
2
T
SQ
R
P
T
SQ
R
P
SQ
R
P
Q
R
P
P
P
3
Wave ofdepolarizationWave ofrepolarization
Atria begin depolarizing.
Atrial depolarization complete.
Ventricular depolarization begins at apex andprogresses superiorly as atria repolarize.
Ventricular repolarization complete; heart isready for the next cycle.
Ventricular repolarization begins at apex andprogresses superiorly.
Ventricular depolarization complete.
Key
So why does this matter?
Table 19.1
SOURCES
http://legacy.owensboro.kctcs.edu/gcaplan/anat2/notes/APIINotes5%20Anatomy%20of%20the%20Heart.htm
http://www.nhlbi.nih.gov/health/health-topics/images/pericarditis.jpg
http://o.quizlet.com/i/MYYoBudMtF4Nd4VX8VXZ5w_m.jpg
http://stevegallik.org/sites/histologyolm.stevegallik.org/images/heartwall.gif
Saladin, K. “Anatomy and Physiology: The Unity of Form and Function.”4th ed. Philadelphia. McGraw Hill Publishing.
http://www.unm.edu/~jimmy/refractory_periods.jpg