AP - Cardiovascular System I
Chronotropic effects
-produce changes in heart rate. -A negative chronotropic effect decreases heart rate by decreasing the firing rate of the SA node. -A positive chronotropic effect increases heart rate by increasing the firing rate of the SA node.
See diagram of AP
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See diagram on Ca++ role in cardiac muscle contraction
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See diagram on cardiac modulation contraction
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See diagram on leads
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See digram on regulation of cardia output
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See permeability of ion X
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See diagram on cycle, page 11.
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How many chambers?
4 Right atrium, blood is delivered via vena cava Right ventricle, blood is delivered via the right atrium as it moves through the tricuspid valve (atrioventricular -AV- valve). Sends blood to the lungs via the pulmonary loop. Passes through the semilunar valve (pulmonary valve). Returns from lungs to the left atrium. Moves to left ventricle via the left atrium and passes through the bicuspid (mitral) valve. From the left ventricle, it moves to the Aorta via the Aortic valve and goes to the systemic loop.
P wave
Atrial depolarization
The rate of SA node firing is dependent on?
Autonomic Nervous System Parasympathetic nervous system: decrease rate by influencing K+ and C++ channels (K+ up; Ca++ down causes hyper polarization) Sympathetic Nervous System: Increase the rate by opening the "If" and Ca++ channels
Extrinsic regulation of SV
Changes in the contractility of the heart Increase in the intracellular Ca++ Role of Ca++ in the cardiac muscle contraction Effects of sympathetic nerves - increase SNS: increase the rate and extent of Ca++ movement into cytoplasm from SR and outside the cell; more rapid and forceful contraction. Increase rate of removal of Ca++ from cytoplasm: phosphorylation of phospholamaban -> Ca++ - ATPase -> decreased duration of cardiac contraction -> increased relative duration of relaxation. Effects of drugs - Digoxin (digitalis)
The cardiovascular system is?
Closed loop
Energy consumed by heart
Completely depends on production of ATP from the oxidative metabolism of circulating glucose and fatty acids. Oxygen supply is essential Conditions in which energy consumption increases without improving cardiac function: Increase in HR Increase in BP (afterload)
Cardiac Cycle?
Diastole - Ventricular relaxation, ventricular filling Systole - Ventricular contraction, ventricular ejection.
Four layers of the heart?
Epicardium - outer surface of the heart walls, composed of connective tissue and fat, contains main coronary vessels (blood flow for cardiac muscles). Myocardium - Middle muscle layer, composed PRIMARILY of cardiac muscle. Endocardium - Thin layer of endothelial cells. Pericardium - Outside of epicardium, consists of two layers (visceral layer of epicardium and parietal layer), space between two layers is called pericardial space which is utilized to reduce friction during heart beat.
Specialized cardiac cells have?
Few myofibrils and contract weakly.
Purkinje fibers
Fibers in the ventricles that transmit impulses to the right and left ventricles, causing them to contract. Extend from branches of A-V bundle, stimulate muscle fibers in the ventricular walls. The smallest (and final) fibers in the cardiac conduction system. The Purkinje fibers transmit the cardiac impulse to the ventricular muscle.
Inotropic effects
Have to do with the force of the contraction, increased force of contraction has to do with SNS. A negative inotropic decreases force of contraction, a positive inotropic effect increases force of contraction.
Internodal pathways
Interconnect the SA Node with the AV Node, conducts impulses throught to the atrial working cells.
What part of heart pumps to the systemic loop?
Left
Lead III
Left arm (-) and left leg (+)
Diagram of heart
Look over it.
SA node contains?
Pacemaker cells Automatic electrical rythmicity Membrane potential discharges: 55-60mV. Slow leak of Na+ (not same channels) at "rest" is essential for rhythmicity due to the opening of the "If" channels!! Action potential of pacemaker cells triggered by opening of Ca++ channels! ***Look at EKG diagram on page 9
Phases of cardiac action potential
Phase 0: Inward Na+ current (depolarization of membrane) Phase 1: Phase 2: Plateau; A slow inward current of Ca++. Phase 3: Rapid repolarization/increase in outward movement of K+. Phase 4:
ACtion potential is found where in heart?
Purkinje fibers
What part of heart pumps to the pulmonary loop?
Right
Lead I
Right arm (-) and left arm (+)
Lead II
Right arm (-) and left leg (+)
Sequence of electrical impulse travel
SA node (origin of AP in heart) -> Internodal pathways -> AV node -> Bundle of His -> Bundle branches -> Purkinje fibers -> contraction. **Momentary pause (AV node) between atrial contraction and ventricle contraction.
Compare refractory periods in heart vs skeletal muscle
See diagram of refractory period
Regulation of HR
Sympathetic nerves Parasympathetic nerves (dominant regulatory influence). Limitation of changes in HR on CO. Cardiovascular control by the medulla oblongata (see diagram on page 13)
Cardiac output
The amount of blood pumped out by the ventricles in a given period of one minute. Directly related to the heart rate (HR) and the stroke volume (SV): CO = HR x SV
S wave
The downward or negative waveform that follows an R Wave, denotes the completion of ventricular depolarization.
Q wave
The first portion of the QRS complex that is seen with a downward deflection and is usually not obvious on the EKG of the normal heart. Often the first portion of the deflection is positive, signifying no Q wave. This is the beginning of ventricular depolarization.
R wave
The first positive deflection of the QRS Complex after the P wave, denotes continued ventricular depolarization.
AV bundle (bundle of His)
The structure along which the AV node rapidly transmits its signal to the ventricular tissues
Bundle of His
a bundle of modified heart muscle that transmits the cardiac impulse from the atrioventricular node to the ventricles causing them to contract
Pericardium
a double-layered serous membrane that surrounds the heart.
EKG
a graphical recording of the cardiac cycle produced by an electrocardiograph
ECG
a graphical recording of the cardiac cycle produced by an electrocardiograph.
Phonocardiogram
a record of heart sounds. 1st sound - closure of mitral valves 2nd sound - closure of semilunar valves
Tachycardia
abnormally rapid heartbeat >100/min
Bradycardia
abnormally slow heartbeat <60/min
Purkinje fibers
fibers in the ventricles that transmit impulses to the right and left ventricles, causing them to contract.
Sinus node
group of cells in the right atrium where the electrical signal is generated that establishes the heartbeat. (SA node) Pacemaker cells
Bundle branches
part of the conduction system of the heart, the electrical signal travels down the bundle of His results in the ventricles beating at a different rate than the atria also called a heart block.
AV node
picks up electrical impulse from the SA node and causes ventricles to contract, causing blood to move into arteries
Digitalis
strengthens the contraction of the heart muscle, slows the heart rate, and helps eliminate fluid from body tissues. From foxglove.
End-systolic volume
the amount of blood remaining in each ventricle at the end of ventricular contraction, about 60 mL
End-diastolic volume
the volume in the ventricles at the end of ventricular diastole, about 115-130mL in each ventricle.
T wave
ventricular repolarization