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INTRODUCTION TO CVSCELLULAR CARDIACPHYSIOLOGY
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Heart Conducting Tissues
Ventricular Structure & Function
Cardiac Cycle
Cardiac Output
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Cardiac Reflexes
Innervation of Heart
Control of CVS
EKG
Coronary Circulation
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Components of Circulatory SystemCardiovascular System (CVS):
Heart:
Pumps bl push bl through vessels. Blood vessels:
Flow bl from ht to cells & back to the ht.
Lymphatic System: Lymphatic vessels present b/w capillaries. LVs
drain excess interstitial fluid to maintain original bl
volume.
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Cardiovascular System (CVS)Cardiac
(heart)
Vascular- Arteries- Arterioles- Capillaries- Venules- Veins
Right sided:(volume pump)Left sided:(Pressurepump)
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MAIN FUNCTIONS OF THE
CIRCULATORY SYSTEM Transport and distribute essential
substances to the tissues.
Remove metabolic byproducts. Adjustment of oxygen and
nutrient
supply in different physiologic states. Regulation of body
temperature. Humoral communication.
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HISTORY
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h l
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Pressure Drop in the VascularSystem
LARGE ARTERIES
SMALLARTERIES
ARTERIOLES
CAPILLARIESVENULES &VEINS
INSIDE DIAMETERSMALL LARGEARGE
ELASTIC TISSUEMUSCLE
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Distribution of Blood in the
Circulatory System 67% IN THE SYST. VEINS/VENULES 5% IN THE
SYSTEMIC CAPILLARIES
11% IN THE SYSTEMIC ARTERIES 5% IN PULMONARY VEINS
3% IN PULMONARY ARTERIES 4% IN PULMONARY CAPILLARIES 5% IN HEART
ATRIA/VENTRICLES
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Distribution of blood within the circulatory systemat rest:
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Organization in the CirculatorySystem
SERIES ANDPARALLEL CIRCUITS
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Anatomy of the heart: Position:
located behind
sternum.
Hollow, muscular organ.
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Anatomy of the heart Consists of 2 separate pumps that
maintain
unidirectional flow of blood; the Lt & Rt hts.
Lt ht pumps oxygenated blood Systemiccirculation.
Rt ht pumps deoxygenated blood Pulmonary
circulation.
Each pump contains 2 chambers: an atrium & aventricle.
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Chambers of the heart:
2 Atria: thin-walled chambers.
receive bl returning to ht. 2 Ventricles: thicker, muscular
walls. pump blood from heart. each has same capacity
& pumps same volume ofbl in a given period of time.
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Chambers of the heart(continued)Atria & ventricles
areseparated into 2 functional
units by a sheet of fibrousconnective tissue, whichgives
attachment to the
valves.
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Chambers of the heart(continued)Atria & ventricles
areseparated into 2 functional
units by a sheet of fibrousconnective tissue, whichgives
attachment to the
valves.
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Valves of the heart: 2 atrioventricular
(AV) valves:One way valves. Allow bl to flow from
atria into ventricles.Tricuspid (Rt) &
Mitral(Lt).
2 semilunar valves: One way valves. At origin of pulmonary
artery
& aorta.
Pulmonary (Rt) & Aortic(Lt). Open during ventricular
contraction.
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Valves of the heart (continued)Remember: Vs are at entrance
& exit
of each ventricle.
Vs allow bl to flow in only
ONE direction. When AV-vs open, semilunar-
vs close & vice versa.
Opening & closing ofvs occur as a result of
pressdifferences.
AV cusps are held by chordaetendineae to papillary muscles.
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Atrioventricular and Semilunar Valves
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Intra cardiac Circulation:
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Pulmonary and Systemic Circulations Pulmonary circulation:
Bl pumped from RVthrough the lungs & back
to the ht. Systemic circulation:
Oxygen-rich bl pumpedto all organ systems to
supply nutrients. Rate of bl flow throughsystemic circulation =
flowrate through pulmonary
circulation.
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Pulmonary and Systemic Circulations(continued)
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Heart Walls:3 distinct layers1. Endocardium:
the innermost layer of theht.
2. Myocardium:the thickest main layer,consists of cardiac
ms.
3. Pericardium (epicardium):the thin, outer covering orexternal
membrane around
the ht.
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Heart Walls- 3 distinct layers (continued)
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The Cardiac Muscle
Histology & Physiology
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Histology of Cardiacmuscle: Striated. Cylindrical in shape.
Shorter than skeletal muscle. Rich in mitochondria (up to 40% of
cell volume). Branched. Has one nucleus in the center of the cell.
No nerves are involved in the spread of
contraction through the muscle. Adjacent cells are
interconnected endto- end by
intercalated discs.
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Histology of Cardiac muscle:
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Histology of Cardiac muscle(continued)
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Intercalated discs: Contain 2 types of specialized
junctions that permit the
cardiac ms to fx asa syncytium (unit), whichobeys all or none
law.
1. desmosomes2. gap junction
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Intercalated discs(continued)1. desmosomes:
act like rivets & hold cells tightly together.
2. gap junctions: offer little resistance (only 1/400 of
outside
membrane resistance) to the passage of action
potential (easily spread) from one cardiac mscell to adjacent
cells.
allow relatively free diffusion of ions.
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Physiology of cardiac muscle: Cardiac ms tissue forms 2
functional syncytia:
atria, & ventricles.
The ht is composed of 2 major types of cardiacms:
I: Contractile cells.
II: Autorhythmic (or automatic) cells.
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Physiology of cardiac muscle(continued)I: Contractile cells:
Composed of 2 types of ms:a. atrial ms.b. ventricular ms.
Contract when stimulated, in same way as skeletal
ms except for longer duration.
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Physiology of cardiac muscle(continued)I: Contractile cells:
Composed of 2 types of ms:a. atrial ms.b. ventricular ms.
Contract when stimulated, in same way as skeletal
ms except for longer duration.
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II: Autorhythmic (or automatic) cells: Specialized or modified
cardiac ms, that contract
only feebly as they contain few contractile fibrils.
Self-stimulating w/out any external stimulation.
Initiate repetitive action potentials, that exhibit
Pacemaker potentials, rhythmicity & varyingratesof
conduction.
Provide an excitatory system for the ht.
Physiology of cardiac muscle(continued)
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ACTION POTENTIALS FROM DIFFERENTAREAS OF THE HEART
mv0
-80mv
mv0
-80mv
mv0
-80mv
ATRIUM VENTRICLE
SA NODE
time
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ELECTROPHYSIOLOGY OF THE FASTRESPONSE FIBER
t (msec)-80
0
+20
0 300
0
1 2
3
4Cardiac Cell
AMP
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PHASE 0 OF THE FAST FIBER ACTIONPOTENTIAL
hm
Na+
-90mvA
Na+mm
h-65mvB
m
h
Na+
0mvC m
h
Na+D +20mv
Na+m
h+30mvEChemicalGradient
Electrical
Gradient
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OVERVIEW OF SPECIFIC EVENTS IN THEVENTRICULAR ACTION
POTENTIAL
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CONDUCTION OF THE ACTIONPOTENTIAL IN CARDIAC FIBERS
---
----- - ----- --+
+ + + + + + ++ + + ++
FIBER A FIBER B
DEPOLARIZEDZONE POLARIZEDZONE
LOCAL CURRENTS
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