Lehigh Valley Wellness Center
Articles & Forms

Review of Cardiovascular
Anatomy & Physiology

The heart is a cone shaped muscular organ located in the chest behind the sternum in the mediastinal cavity between the lungs and in front of the spine. The heart is approximately the size of a fist.

The heart’s wall (Pericardium) is made up of three layers:

A skeleton of connective tissue called the fibrous pericardium surrounds the heart and acts a tough protective sac.


The right and left ventricles are the pumping chambers of the heart.


Coronary Circulation

The heart needs an adequate supply of blood to survive. The coronary arteries which lie on the surface of the heart supply the heart muscle with blood and oxygen.

  • Left coronary artery originates off the aorta and supplies blood to the right atrium, the right ventricle, and part of the inferior/posterior surfaces of the left ventricle. The Bundle of His, the AV node and the SA node receive blood from this artery.
  • The left coronary artery runs along the surface of the left atrium where it splits into the anterior descending and the left circumflex arteries.
  • The left anterior descending artery supplies blood to the anterior wall of the ventricle, the interventricular septum, the right bundle branch and the left anterior fascicle of the left bundle branch.
  • The circumflex artery supplies oxygenated blood to the lateral walls of the left ventricle and to the left atrium. The circumflex also supplies blood to the left posterior fascicle of the left bundle branch. This artery circles around the left ventricle and provides blood to the ventricle’s posterior portion.
  • When two or more arteries supply the same region they usually connect through anastomoses junctions that provide alternative routes of blood flow. These alternate routes of blood are called collateral circulation and provide blood capillaries that directly feed the heart muscle. Collateral circulation becomes so strong that even if major coronary arteries become clogged with plaque collateral circulation can continue to supply blood to the heart.

    Transmission of Electrical Impulses

    The heart can’t pump unless an electrical stimulus occurs first. Generation and transmission of electrical impulses depend on the automaticity, excitability, conductivity and contractility of cardiac cells.
  • Automaticity refers to a cell’s ability to initiate an impulse. Pacemaker cells possess this ability.
  • Excitability results from ion shifts across the cell membrane and indicates how well a cell responds to an electrical stimulus.
  • Conductivity is the ability of a cell to transmit an electrical impulse to another cardiac cell. Contractility refers to how well the cell contracts after receiving a stimulus.
  • As impulses are transmitted cardiac cells undergo cycles of depolarization and repolarization.
  • Polarized - cardiac cells are at rest meaning - no electrical activity takes place
  • Resting potential – cell membranes separate different concentrations of ions such as sodium and potassium and create a more negative charge inside the cell.
  • Cell depolarization (action potential) - a stimulus causes the ions to cross the cell membrane.
  • Repolarization – electrical charges within the cell reverse and return to normal. The cell attempts to return to its resting state.
  • ------------------------------------------------------------------------------

    Cycles of depolarization-repolarization This cycle consists of 5 phases 0-4.

  • 0 – cell receives an impulse from a neighboring cell and is depolarized
  • 1 - Early rapid repolarization (resting phase)
  • 2 - Plateau phase period of slow repolarization
  • 3 - Rapid repolarization phase During the last half of this phase the cell is in the relative refractory period, a very strong stimulus can depolarize it. During phases 1,2 and the beginning of phase 3 the cell is in its absolute refractory period. No stimulus can excite the cell.
  • 4 – Resting phase of the action potential. By the end of phase 4 the cell is ready for another stimulus. Once depolarization and repolarization occur the resulting electrical impulse travels through the heart along a pathway called the conduction system Impulses travel SA node
  • ------------------------------------------------------------------------------

  • Internodal tracts and Bachmann’s bundle to the AV node, responsible for delaying the impulses that reach it. The nodal tissue itself has no pacemaker ability, but the tissue around it (junctional tissue) has pacemaker ability. 40-60 times a minute. This delay allows the ventricles to complete their filling phase as the atria contract. Also allows the cardiac muscle to contract to it’s fullest for peak cardiac output.
  • Bundle of HIS, the Bundle branches - Resumes the rapid conduction of the impulse through the ventricles. The bundle divides into the right and left branches.
  • Purkenjie Fibers - Network of nervous tissue that extends through the ventricles. Can serve as a pacemaker at a rate of 20-40 times a minute.

  • Contact Us Today!

    Louise Diehl, RN, MSN, ND, ACNS-BC, NP-C
    Nurse Practitioner - Owner
    Doctor of Naturopathy

    Phone: 908-213-8808
    Fax: 908-213-8898

    Lehigh Valley Wellness Center
    101 Coventry Drive
    Phillipsburg, NJ 08865

    E-mail: info@lehighvalleywellnesscenter.com

    Healing - Divorce, separataion & abandoned love - by Louise Diehl

    A Country Divided - by Louise Diehl

    Informative Links

    Healthy Eating Tips

    High-fructose corn syrup

    Home - Meet Louise - What is Naturopathy? - Publication Guidelines - Articles & Forms - Contact
    Copyright © Lehigh Valley Wellness Center — All Rights Reserved Worldwide
    Webmaster Deb Phillips: deb.phillips@web-design-lehighvalley.com - Deb Phillips Web Design

    Information contained within this website is for use by health care professionals
    and NOT to be used by anyone in the place of contacting their healthcare provider.