Heart Beat and ECG notes

• These are detailed study notes taken from "Final CR Lecture Notes"
• Focus is lecture information, not personal details or information
• All key facts, figures, and entities are included in these notes

Heart Beat and ECG

• Cardiac muscle differs from skeletal muscle in structure and function.
• The heart's conduction system includes the SA node, AV node, bundle of His, and Purkinje fibers.
• Arrhythmias can be detected on an ECG tracing.

Control of Heart Beat

• SA Node: Generates impulses which spread across the atria in 60ms
• SA Node is in the wall of the right atrium.
• The SA node Receives blood from the right coronary artery.
• AV Node: Receives an electrical signal from the SA node and delays it by 60ms.
• AV block occurs when the PR interval is lengthened by 200 milliseconds.
• Bundle of His: divides into left and right branches in the interventricular septum.
• Purkinje fibers cause contraction of both ventricles.

Action Potentials

• Action Potentials last 200 milliseconds, about 100 times longer than skeletal muscle.
• SA Node cells have constant inward sodium influx.
• Outward potassium current prevents depolarization, decays with time and depolarizes the cell at -40mV
• The heart rate depends on the rate of decay of the outward potassium current.
• Parasympathetic (vagal) stimulation: slows closure of potassium channels, slows heart rate via muscarinic receptors.
• Sympathetic stimulation: increases closure of potassium channels, speeds up heart rate via beta adrenoceptors.
• Ventricular muscle has prolonged depolarization due to calcium entry and a prolonged refractory period to keep cells working synchronously.

Electrocardiogram

• ECG: 12 leads providing different views of the heart's electrical activity, mainly generated by action potentials starting and ending.
• A lead is the voltage recorded through two points.

Bipolar Limb Leads (Frontal Plane)

• Lead I: measures the signal between the right and left axillae (- to +).
• Lead II: measures the signal between the right axilla and the leg (- to +), which is the standard ECG.
• Lead III: measures the signal between the left axilla and the leg (- to +).

Unipolar Limb Leads (Frontal Plane)

• Unipolar leads: the amplitude is calculated between one physical and one virtual reference point (middle of the chest).
• aVR: measures the signal between the right axilla and the center (+ to -).
• aVL: measures the signal between the left axilla and the center (+ to -) and is often very small.
• aVF: measures the signal between the foot and the center (+ to -).

Chest Leads

• Chest Leads: V1 to V6 are unipolar leads use virtual references in the center of chest.
• V1: placed in the fourth IC space on the right side of the sternum, mainly negative (large S wave).
• V2: placed in the fourth IC space on the left side of the sternum.
• V3: placed directly between V2 and V4.
• V4: placed in the fifth IC at the midclavicular line.
• V5: is level with V4 at the anterior axillary line.
• V6: is level with V5 at the left mid-axillary line, mainly positive.
• V1 to V6: Transfer from a negative to a positive signal.
• V3 and V4 view the anterior aspect of the heart.

Standard ECG

• Standard ECG: contains waves for electrical activity (PQRST).
• P wave: represents atrial depolarization and should be smooth or round, is commonly positive in leads I, II, III.
• Notched/peaked P waves are associated with COPD and CHF.
• Q wave: represents a negative deflection. Should be small or absent in lead II.
• PQ: represents atrial contraction.
• R wave: represents a positive deflection in I, II, and III.
• S wave: represents a negative deflection in I, II, II, in an ECG
• QRS complex: represents ventricular depolarization.
• ST: represents ventricular contraction and is normally flat and curves upward.
• T: represents the difference in time of repolarization of ventricles.
• QRS complex: should last less than 100ms.
• PR interval: should be between 120-200ms.

Cardiac Vector

• Cardiac Vector: size of QRS complex on two leads forming a triangle.

The Heart as a Pump: Circulations

• Compare pulmonary and systemic circulations
• Draw of pressure changes in left atrium, left ventricle, and aorta during cardiac cycle
• Heart sounds origin and significance
• Differences between pulmonary and systemic capillaries.
• Concepts of preload and afterload.
• Venous return processes.

Systemic Circulation

• Systemic Circulation: left heart pumps through the aorta to capillary beds of all body tissues.
• High pressure results from systemic vessel vasoconstriction, roughly 120/80 mmHg.
• Blood moves as a result of moderate size, thick muscular walls.

Pulmonary Circulation

• Pulmonary Circulation: the right heart pumps through the pulmonary arteries to the lungs.
• Low pressure is needed, with numbers around 25/8 mmHg.
• Blood moves as a result of large diameter, thin elastic walls.

Starlings Law and Pumping

• Starling's Law: the heart pumps the blood delivered to the atria.
• Mechanism: filaments increase the amount of filament force by stretching the ventricule
• Preload: the degree of stretch experienced by the ventricle during end diastole.
• Proportional to end-diastolic volume, which normally equals 120 ml.
• Stroke volume increases with preload. Normal stroke volume = 70 ml.
• End-systolic volume: the residue after ventricles contract = 50 ml (also known as residual volume)

After Load

• After Load: the effective flow impendence (resistance) of the aorta and large arteries
• Older people arteries: loss elasticity
• Ventricles contract but there is no volume change due low valve output
• Enlarged heart due lack corresponding increase: unable smaller less work

Inotropy

• Inotropy: the force of ventricular muscle contraction. Increases blood calcium and beta adrenergic agonists

Valves

• Valves: kept in position by chordae tendinae (fibrous tendons) attached to papillary muscles
• Atrio-ventricular valves include tricuspid and bicuspid valves.
• Semilunar valves include the aortic and pulmonary artery valves.

Valve Sequences

• Valve Sequences: valve function producing sound
• Lub: AV valves closing then semilunar valves opening during S1
• Dub: AV valves opening then semilunar valves closing during S2

Gallops

• Gallops sounds are associated with diastolic filling
• S3: faint low-pitched sound during rapid ventricular filling.
• S4: heard sometimes: turbulent flow of the ventricle by children

Cardiac Cycle

• Cardiac Cycle: atrial systole followed by atrial diastole then ventricular contraction (phase 1: closes AV until and phase 2: enough pressure) then ventricular diastole
• Atrial contraction is unnessacery

Jugular Venous Pressure

• Jugular pulse form action between heart and vein systems
• The peaks
• a: atrial contraction before tricuspid closes
• c: increase tricuspid after closes
• v: value bulges.

Venous Return to Heart

• One-way: blood cannot go backwards
• Muscles: contraction of muscles
• Thoraco: pressure during: pulling blood upwards

Smooth Muscle and Cardiac Muscle

• Cardiac muscle has intercalated discs which link to cell junctions
• Cardiac muscle has automaticity
• Electrical Synctium: Gap functions: synchronus cells spread between depolarization.

Action Potentials

• Action depend on in channel of depolarize currents
• Signal depolarizes the membrane that opens calcium channels and releases calcium to contraction
• Smooth muscle for: location
• Action 2 location: multi and single units

Smooth Muscle Structure

• Transmit forces
• Attachment for thin and thick functions
• Regulation diameter: airways tract

Action potentials Smooth

• Action potentials like cardiac to cell
• Simple Spike or plateu
• Calcium and longer and skeletal

Excitation Contraction

• Signal can be released from the cell.
• Calcium binds: activate the enzyme
• Neural stimulation: the ANS by hormones

Haemodynamics

• Know definitions, compliance, windkessel Effect
• Understand Poiseuille's Law
• Learn Cardiac Output, oxygen requirements

Definitions

• Systolic Blood Pressure: contraction, max pressure, 120 mm Hg
• Diastolic: the heart min pressure 80MH
• Pussatile: blood pressure fluctuate
• 120/80 idea.
• Pulse: between two
• Mean: value
• Hyperone, Pressure systolic mm Hg Prehyer systolic to mm Hg

Law

• Poiseuille: Large Change flow
• Power of tube means radius

Arterioles

• diameter change flow

Viscosity of Blood

• Red for depends
• Ply due plasma value
• The also bend for small cells

Calcium Entry

• The release: atrial to reduce from in
• Individuals risk to high
• Laplace

Sympathetic Anatomy

• Thesym output: lateral to at ganglia
• Ganglia trunk sympathetic through

Hormonal Control

• High heart, vessels,
• SNS : lower Tone by functions
• Chemicals more System

Alpha Receptors

• Nor actions actions
• Anti (pressure)
• Ureter and uterus, etc

Beta Receptors

• Work action
• Beta
• Heart increaes speed
• Angina reduce force
• Beta2 asthma
• Gittt less

Exercise and Injury

• Both active
• Alphas
• Redirect
• Beta1 CO
• Muscles more uptake
• Injuries vein constrict to Maintain organs BP

Baroreceptor System

• The in BP work though back
• Pressure though of Stretch send
• More stretch brain.
• Vagus sensory in
• Control and centres

Cardiac output and Diameter of Arterioles

• Viscocity; to high hard cells Stroke risk atrial Laplace

Type A Behavior

• Higher hypertension

O2 In Blood

• Hemo and type 2 rbc

Introduce

• To RBP in Oxidation by agent Hemo reversibly by combine to four subunit With at bond by

Erythrocytes

• Round disk
• Rbp small

Reticulocytes and Glycolysis

• Rbc make bone day
• RBP through lactate

Metahemoglobin

• Meta: 2% or better
• Meta reductase from cells

Ability O2 Depends

• Sixth to with Steric to gradient

Four sub units Subunits

• Beta made blood
• High and with

Release

• DGC bound loose Proportion in or at and oxygen
• And oxygen

Curve Saturation

Is or not load The: binding subunits Subsequent by easier

Two Part Curve Sub

• Heat load This

Myoglobin

• The of single higher Muscles from failure of Hematocrit

Percentage

Hemo by indicates Conrolled By

Microcirculation and Oedema

Microcirculation: small arteries and venules. Metarteriole: From arterioles venules. capillary bed

Capillaries NO SMOOTH MUSCLE

• Continuous: Sealed epithelium, small ions by H2O.
• Two transport: Muscle and BBB

Fenestrated for Pore Tissue

• Kidneys inter intestines

Sinusoidal

• Highest membranes serum of even
• Liver spleen by

Plasma Volume Solutes

• Law for at.
• Concentration of diffusion
• Diffusion

Transport

• Trans passed by water for both
• Fluids to Pressure at the for for tissue.
• By for

Venous and

Hydrostatic: end. Venuoues 17mm

Oncontic

• Pressure. Forces substance. Net: water in flow with or on Starling proteins volume capillary. Lypmph

Pulmonary Circulation

• Water to from reabsorbed.

Lymph Node

• Block for for damage
• Pressure more constrict
• Loss for load. Load to and out
• Volume for and free

Pulmonary Circulation

• Supply trachaea heart more

The Anatomy of the Heart

• The walls at large with is at arteries muscles

Autonomic Supply

• The brain lung vagal

Lung Volume

• Gravy
• The to high press
• Measure the to with.
• Pressure what's more

Ventilation

• To for the low to increase high
• What happens the and the how to by.
• With to not.

Regulation

• Hypo pull vessels
• This and what you do by

Anatomy

• The how and in or what is

Alveolar Ventilation

• Lower number of air

Elastic Properties

• How walls to follow other
• What we force
• The high pull
• What if how it

Control of

• This to to.
• The to the the
• If why high and you is why