Cardio Vascular System Fundamentals YouTube Lecture Handouts

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Logo of Cardio Vascular System

Logo of Cardio Vascular System

Image of Calculations of Blood Pressure

Image of Calculations of Blood Pressure



  • Heart &

  • Blood Vessels

    • Arteries

    • Arterioles

    • Capillaries &

    • Veins

Image of Pulmonary Circulation And Systemic Circulation

Image of Pulmonary Circulation and Systemic Circulation

Image of Coronary Arteries of The Heart

Image of Coronary Arteries of the Heart

Functions of CVS

  • To provide pressure head so as to keep blood flowing. Pressure in Lt. Ventricle is up to 120 while in Rt. Atrium it is only about 0 mmHg.

  • To maintain BP during rest as well during various activities

  • Ensures more supply to active tissues

  • During emergencies such as in case of severe hemorrhage

Blood flow to vital organs like brain & heart is maintained, this can be even at the expense of reducing flow to other tissues & at times it can lead to total renal shut down so total anuria

Secondary Functions (Blood)

  • Distribution of metabolites & oxygen

  • Collection of waste products & CO2

  • Thermoregulation

  • Distribution of hormones to the target tissues

Physiological Anatomy of Heart

  • Located in the mediastinal space of thoracic cavity between two lungs.

  • Measures about 12 cm from base to apex and 6 cm anteroposteriorly

  • Weight approx. 300gms in males and 250gms in females

  • Works throughout the life

  • Contracts about one lakh times in a day

  • Pumps about 7200 liters of blood in 24 hrs.

Image of Physiological Anatomy of Heart

Image of Physiological Anatomy of Heart

Image of Right Coronary Artery And Right Coronary Artery

Image of Right Coronary Artery and Right Coronary Artery

Cut Section

  • Four chambered 2 atria & 2 ventricles

  • Atria and ventricles are separated by a fibrous ring and are two separate units

  • Atria are divided by interatrial septum

  • Ventricles are divided by intraventricular septum


  • Atria are thin walled and receive blood

  • Rt atrium from systemic circulation via superior & inferior vena cavae

  • Lt atrium from lungs via pulmonary veins


  • Ventricles are thick walled and serve as pumps

  • Lt ventricle pumps blood in systemic circulation

  • Rt ventricle pumps in pulmonary circulation

Structure of Heart

Image of Structure of Heart

Image of Structure of Heart

Image of Interior of Heart

Image of Interior of Heart

Image of Valves of Heart

Image of Valves of Heart

Valves of Heart

Two types

  • Atrioventricular

    • Mitral

    • Tricuspid

  • Semilunar

    • Aortic

    • Pulmonary

Structure of Valves

Image of Structure of Valves

Image of Structure of Valves

Functions of Valves

  • They open in one direction.

  • Keep circulation unidirectional

  • Prevent backflow of blood.

  • Produce heart sounds which have clinical significance

Wall of the Heart


  • Fibrous

  • Serous

  • Parietal

  • Visceral


  • Specialized tissue of heart

  • Cardiac muscles


Specialized Tissue of Heart

Is made of modified cardiac muscles

Phylogenitically primitive

  • Sinoatrial node (SAN)

  • Interatrial tract (Bachman’s bundle)

  • Internodal fibers: three pathways

  • Ant. pathway of Bachman

  • Middle pathway of Wenckebach

  • Post. Pathway of Thorel

  • Atrioventricular node (AVN)

  • Bundle of His

  • Purkinje fibers

Image of Normal Conduction

Image of Normal Conduction

Histological Features

  • Pace maker is rich in P (pacemaker) cells, which are primitive and less striated

  • P cells are pale, round with few organelles they are connected by gap junctions.

  • P cells are more in SA node and less in AV node

Sino Atrial Node

  • Located near the junction of superior venacava & the rt. atrium

  • Acts as pacemaker because the rate of impulse generation is highest here

Ectopic pacemaker: is pacemaker other than SAN.

  • Some other part discharge at a higher rate

  • Impulse blockage from SAN to AVN

Atrioventricular Node

  • Located at the rt. lower part of the interatrial septum


  • Normally it is the only path of impulse conduction from atria to ventricles

  • Produces A-V delay

A-V Delay

  • Is gap between atrial & ventricular contraction

  • Conduction is slow in different parts of A-V Node because of less number of Gap Junctions. So each succeeding cell is slow to be excited.

  • Normal A-V delay is about 0.13sec.

  • It ensures that Ventricular contraction is always after the Atrial contraction.

Image of Ventricular Septum

Image of Ventricular Septum

Bundle of His & Purkinje fib.

  • Is continuation of AVN. Present on the rt. side of the intraventricular septum

  • Divides into 2 branches

    • Rt. Bundle Branch &

    • Lt. BB

  • Purkinje fib. arise from both branches

Image of Purkinje Fibers

Image of Purkinje Fibers


By both divisions of ANS

  • Sympathetic: from 1 to 5 thoracic seg.

  • Distibited to all parts of heart

  • Parasympathetic: from Vagi

    • Mainly inn. SAN & AVN

    • Lesser extent muscles of atria

    • Even lesser to ventricular muscles or practically no inn. To ventricles

Image of Sympathetic Nerve And Parasympathetic Nerve

Image of Sympathetic Nerve and Parasympathetic Nerve


Innervation of nodes

  • SA Node

  • Parasympathetic—Rt. Vagus

  • Sympathetic-------Rt. sided nerves

  • AV Node

  • Parasympathetic---Lt. Vagus

  • Sympathetic--------Lt sided nerves

Properties of Cardiac Mus

  • Automaticity & Rhythmicity

  • Conductivity

  • Excitability

  • Contractility

  • All or none response

  • Staircase phenomenon

  • Refractory period

  • Tone

Properties of Specialized Tissue

  • Automaticity

  • Rhythmicity

  • Conductivity

Specialized Tissue


Heart can generate its own impulse that is why transplantation is possible

Rate of Impulse Generation

  • SA node---------70-80 per minute

  • AV node---------40-60 “

  • Atrial muscle----40-60 “

  • Ven. muscle-----20-40 “

Image of Specialized Tissue

Image of Specialized Tissue

Automaticity & Rhythmicity

  • Normally impulses are generated automatically & rhythmically

  • It is because of presence of pacemaker potential or prepotential

  • Pacemaker potentials are prominent in SA and AV nodes

Latent Pacemaker

Comes into action when normal pacemaker stops functioning

  • Latent pacemaker are present in the conducting system

  • Atria and ventricles normally have no pacemaker but can discharge when injured

Pacemaker Potential

  • RMP is not stable

  • RMP is -55 to -60 mV

  • Rapid depolarization begins at threshold level -40 mV

  • Depolarization peaks up to +5 mV

  • Then Repolarization begins

  • Normally it goes on throughout the life

Ionic Basis of PP

  • At the beginning of repolarization there is potassium efflux

  • Prepotential caused by opening of T (transient) calcium channels

  • Rest of Depolarization is by opening of L (long lasting) calcium channels

  • Repolarization by potassium efflux

Pacemaker Potential

Image of Pacemaker Action Potential Image - 1

Image of Pacemaker Action Potential Image - 1

Pacemaker Potential

Image of Pacemaker Action Potential Image - 2

Image of Pacemaker Action Potential Image - 2

Effect of ANS

  • Vagal stimulation

  • Membrane becomes hyperpolarized (more negative)

  • Slope of prepotential decreases

  • Acetylcholine increases potassium conductance

  • Firing rate hence HR decreases

  • Strong stimulation can stop heart

Image of Extended Vagus Stimulation

Image of Extended Vagus Stimulation

Vagal Escape

  • Vagal stimulation by tetanising current

  • Slowing of heart

  • After some time heart starts beating even if the stimulation is continued

  • It is called Idioventricular Rhythm

Sympathetic Stimulation

Results in

  • Rapid fall in repolarization

  • No change in RMP

  • Beta1 receptors stimulated

  • Mediated via cAMP



Image of Extended Sympathetic Nerve Stimulation

Image of Extended Sympathetic Nerve Stimulation


Tissue and Its Rate of Conduction. (M/S)

  • SAN

  • Atrial muscles

  • AVN

  • Bundle of His

  • Purkinje system

  • Ven. Muscles

Pathway of Impulse

Image of Pathway of Impulse

Image of Pathway of Impulse

Last to Depolarize

  • Poster basal region of left ventricle

  • Pulmonary conus

  • Upper portion of interventricular septum

Time Required

Image of Endocardial To Epicardial Surface

Image of Endocardial to Epicardial Surface

Specialized Tissue

Heart as Specialized Tissue

Heart as Specialized Tissue

Cardiac Muscle

  • Are involuntary

  • There are two functional units

    • Atrial syncytium

    • Ventricular syncytium

Types of Muscles

Image of Types of Muscles

Image of Types of Muscles

Cardiac Muscle


  • Size Length----- 80µm Width---- 15µm

  • Fibers are striated

  • Branching and anastomosis present

  • Nucleus is central

Image of Cardiac Muscle

Image of Cardiac Muscle

Intercalated Disc

  • Present at the junction of two cells

  • Intercalated disks 0.5 to 1µ in thickness

  • Desmosomes ensure tight junctions

  • Gap junctions help in fast conduction

Image of Intercalated Disc

Image of Intercalated Disc

Sarcotubular System

  • Sarcoplasmic reticulum less developed as compare to skeletal muscles

  • “T” tubules and “L” tubules present

  • “T”-tubules are wider

  • One triad per sarcomere

  • Triads are at Z lines

  • Dyads are often seen

  • Dyads have “T” tubule and one cistern of “L” tubule



Image of Calcium In Muscle Contraction

Image of Calcium in Muscle Contraction

Image of Sarcoplasmic Reticulum Less

Image of Sarcoplasmic Reticulum Less

Properties of Cardiac Muscles

  • Excitability

  • Automaticity & Rhythmicity

  • Contractility

  • Conductivity

  • All or none law

  • Staircase phenomenon

  • Fatigue


Shows following changes

  • Electrical changes

  • Ionic changes

  • Mechanical changes

  • Metabolic changes

Electrical Changes

Table of Electrical Changes
Table of Electrical Changes




Rapid depolarization


Rapid repolarization




Slow depolarization



Image of Cardiac Myocyte Action Potential

Image of Cardiac Myocyte Action Potential

Ionic Changes

Table of Ionic Changes
Table of Ionic Changes




Na influx


Na channels closed & K efflux


Ca influx


K efflux





  • All or none Law

  • Staircase phenomenon

  • Refractory period

Cardiac Muscles Do Not Fatigue

Following reasons:

  • Aerobic metabolism so lactic acid does not accumulate

  • Rich blood & O2 supply

  • Mitochondria in plenty


  • Basic mechanism similar to skeletal muscle contraction

  • Depends more on extracellular Ca++ level

  • Isotonic as well as isometric

Characteristics of Contraction

Refractory period is long

  • Absolute RP (.20 to .30 sec.)

  • Relative RP (.05 sec.)

  • Because of long refractory period muscle cannot be Tetanized


Image of Electrical Activity

Image of Electrical Activity

Metabolic Changes

  • Mainly aerobic

  • Normally only 1% anaerobic

  • During hypoxia up to 10% anaerobic

Energy Sources

  • Fat--------------------- 60%

  • Carb.------------------ 35%

  • Ketones & A.A.------- 5%

Contractility in Heart


  • Heterometric regulation

    • Frank- Starlings Law of heart

  • Homometric regulation

    • by Autonomic Nervous System

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