ECE 501 Introduction to BME

ECE 501 Introduction to BMEECE 501Dr. Hang

Part IV Bioinstrumentation ElectrocardiogramECE 501Dr. Hang

ECE 501Dr. HangNumber of deaths for leading causes of death in US (2004)* Heart disease: 654,092 Cancer: 550,270 Stroke (cerebrovascular diseases): 150,147 Chronic lower respiratory diseases: 123,884 Accidents (unintentional injuries): 108,694 Diabetes: 72,815 Alzheimer's disease: 65,829 Influenza/Pneumonia: 61,472 Nephritis, nephrotic syndrome, and nephrosis: 42,762 Septicemia: 33,464* http://www.cdc.gov/nchs/fastats/lcod.htmIntroduction

ECE 501Dr. Hang Physiology Instrumentation

Medicine Introduction

ECE 501Dr. HangPhysiologyWhat is the Heart?

The heart is a very specialized muscle that pumps blood through the body, transporting oxygen, carbon dioxide, nutrients and waste. The heart is located in the middle of the chest, between the lungs. Its bottom is tipped to the left.

ECE 501Dr. HangPhysiologyThe Heart as a Pump The heart is like two pumps: one pumping blood into the body and one pumping blood out of the body. The heart is about as big as two clenched fists put together. The heart pumps blood in beats.

ECE 501Dr. HangPhysiologyThe Hard Work of the Heart

ECE 501Dr. HangPhysiologyAnatomy of the Heart

ECE 501Dr. HangPhysiologyHeart Chambers

Atrium is a chamber that pumps blood into the heart.

Ventricle is a chamber that pumps blood out of the heart.

The atria and the ventricles regulate blood flow by pumping blood in and out of the heart.

ECE 501Dr. HangPhysiologyHeart Chambers

ECE 501Dr. HangPhysiology

Heart Valves There are four valves in the heart. These are unidirectional valves that allow blood flow in only one direction.

They prevent blood from flowing back to the chamber that it has just left.


Heart Valves


Heart Valves

The tricuspid valve and the mitral valve are also called A-V valves, because they separate an atrium from a ventricle. The pulmonary valve and the aortic valve are also called arterial valves, because they separate a ventricle from an artery.


Arteries and Veins

Artery is a blood vessel that delivers blood out of the heart. The two arteries of the heart are connected to ventricles.

Vein is a blood vessel that delivers blood into the heart. The two veins of the heart are connected to atria.


Arteries and Veins


Pulmonary Circulation


Systemic Circulation


Blood Vessels


Diffusion

The exchange of molecules between cells and blood occurs at the capillary level.

Capillaries are very small blood vessels with very thin walls.

Oxygen and nutrients diffuse from the blood into the cell and carbon dioxide and waste diffuse from the cell into the blood.

ECE 501Dr. HangPhysiologyThe Cardiac Cycle: Phase I

ECE 501Dr. HangPhysiologyThe Cardiac Cycle: Phase II

ECE 501Dr. HangPhysiologyThe Cardiac Cycle: Phase III

ECE 501Dr. HangPhysiologyThe Cardiac Cycle: Phase IV

ECE 501Dr. HangPhysiologyThe Cardiac Cycle: Phase V

ECE 501Dr. HangPhysiologyThe Cardiac Cycle: Phase VI

ECE 501Dr. HangPhysiologyThe Cardiac Cycle: Phase VII

ECE 501Dr. HangPhysiologyMuscle Types: Skeletal Muscle

Fast-twitching

Voluntary control

Gets tired

Arms, legs etc.

ECE 501Dr. HangPhysiologyMuscle Types: Smooth Muscle

Slow-twitching

Involuntary control

Does not get tired

Stomach, bladder, blood vessels etc.

ECE 501Dr. HangPhysiologyResting Membrane Potential

ECE 501Dr. HangPhysiologyResting Membrane PotentialGoldman Equation

ECE 501Dr. HangPhysiologyAction Potential

Once the cell is electrically stimulated (typically by an electric current from an adjacent cell), it begins a sequence of actions involving the influx and efflux of multiple cations and anions that together produce the action potential of the cell, propagating the electrical stimulation to the cells that lie adjacent to it

ECE 501Dr. HangPhysiologyAction Potential: Phase 4

Phase 4 is the resting membrane potential. This is the period that the cell remains in until it is stimulated by an external electrical stimulus (typically an adjacent cell).


Phase 0 is the rapid depolarization phase. The slope of phase 0 is determined by the maximum rate of depolarization of the cell and is known. This phase is due to opening of the fast Na+ channels and the subsequent rapid increase in the membrane conductance to Na+ and a rapid influx of ionic current in the form of Na+ ions into the cell.


Phase 1 of the action potential occurs with the closure of the fast Na+ channels. The transient net outward current causing the small downward deflection of the action potential is due to the movement of K+ and Cl- ions.


This "plateau" phase of the cardiac action potential is sustained by a balance between inward movement of Ca2+ through calcium channels and outward movement of K+ through the potassium channels


During phase 3 of the action potential, the Ca2+ channels close, while the K+ channels are still open. This ensures a net outward current, corresponding to negative change in membrane potential, This net outward, positive current (equal to loss of positive charge from the cell) causes the cell to repolarize.

ECE 501Dr. HangPhysiologyElectrical Circuit of the Heart

ECE 501Dr. HangPhysiologyThe S-A node

The S-A Node is the most important element in the electrical circuit of the heart.

It starts the cardiac cycle by periodically generating action potentials without any external stimulation. (Therefore, it is said to be autorhythmic.)

It is also known as the pacemaker of the heart.

ECE 501Dr. HangPhysiologyThe A-V node

The atrioventricular node periodically receives action potentials via the junctional fibers.

The most important function of the A-V node is to regulate the timing of the ventricular contraction by delaying the action potentials.

The delayed action potentials are spread over the ventricles to cause a contraction

ECE 501Dr. HangPhysiologyThe Electrical Cycle

ECE 501Dr. HangPhysiologyThe Electrocardiogram

The electrocardiogram (ECG) is a standardized way to measure and display the electrical activity of the heart.

Physicians can diagnose problems with the heart by analyzing its ECG and comparing it to the ECG of a healthy heart.

ECE 501Dr. HangPhysiologyECG Waves

ECE 501Dr. HangPhysiologyECG Intervals

ECE 501 Introduction to BME

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