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