Cardiac Conduction System Terms
Cardiac Conduction System: A system of specialized non-contractile cardiac muscle cells
without sarcomeres which conduct electrical impulses that stimulate the heart to beat
(contractile muscle cells).
Functional Syncytium: mass of merging cells that function as a unit
SA Node: 1) Spontaneously depolarizes. 2) Pacemaker of the heart. 3) located in Right
Atrium.4) Simultaneously contract Atria. 5) NA+ channels always open
AV Node: Cluster of cells between the atria and ventricle. 2) .1 second delay from receiving AP
till it transmits it to the ventricles.
Bundle of His: AV bundle in which the AP travels through to reach the ventricles Bundle
Branches: electrical signal travels from AV bundle travel through these brancheslocated in the
interventricular septum
Purkinji Fibers: Arise from the bundle branches at the bottom of the heart.They branch
extensively and deliver the AP to the contractile cells of the ventricles.
ECG
electrocardiograph: Records electrical impulses of the myocardium as they pass through the
heart wall into the surrounding tissue.
P wave: in an ECG corresponds to depolarization of the atrial fibers (leads to contraction
QRS Complex: in ECG corresponding to depolarization of ventricals
T wave: ventricular repolarization
Atrial repolarization: occurs at the same time as QRS complex, not usually evident
PR Interval: Starts at the beginning of the P wave and ends at the beginning of the
QRS complex. When delay happens
Normal PR interval: 0.12-0.20 seconds
Ventricles filling: Q-R
Ventricles emptying: R-S
Fibrillation: chaotic, irregular contractions of the heart, as in atrial or ventricular fibrillation
Ventricular fibrillation: breakdown of conduction system resulting in no blood being pumped to
the pulmonary or systemic circuits, followed by death if not reversed. Defibrillator: an
electronic device that administers an electric shock of preset voltage to the heart through the
chest wall in an attempt to restore the normal rhythm of the heart during ventricular fibrillation
causes of 3rd degree heart block (most severe)(AKA complete heart block):
Cardiac infection, coronary artery disease, & chronic, long-term hypertension
ECG , 3rd degree Indications: More P waves than QRS complexes
Bradycardia between 40 - 60bpm: Have favorable prognosis
Bradycardia of less than 40bpm: Develope ventricular systole
Ventricular Tachycardia: Heart rate higher than 100bpm, and QRS complex typically longer than
0.12 sec.
Ventricular Tachycardia Symptoms: Dizziness, fainting, shortness of breath.
Sinus Bradycardia: When the SA node fires at a rate of less than 60 beats per minute.
The P wave and the QRS complex are normal.
, Sinus Bradycardia symptoms: dizziness, fainting, being extremely tired, and shortness of
breath.
Na+ channels of cardiac pacemaker cells: always open
Denervate: raise in heart rate
Cardiac output: Volume of blood the heart pumps in one minute. Stroke Volume X Heart Rate
Stroke Volume: The volume of blood pumped out by a ventricle with each heartbeat
Normal cardiac output range: 5L/min resting to 20L/min during exercise Extrinsic factors
affecting Cardiac output: Input on the heart from autonomic nervous system and
endocrine system
Intrinsic factors affecting Cardiac Output: Affect of preload and afterload on the heart
Preload: degree of stretch of the cardiac muscle fibers at the end of diastole End-diastolic
volume: amount of blood collected in ventricle during diastole.
Afterload: resistance to left ventricular ejectionDichrotich
Dicrotic notch: brief rise in aortic pressure caused by back flow of blood rebounding off
semilunar valves
Dicrotic wave: The secondary & smaller upstroke after the primary wave caused by the recoil of
the artery to the pressure generated by left ventricular systole.
The Blood Terms
Blood: Type of connective tissue consisting of plasma (approx. 46-63%) and formed elements
(approx. 47-54%).
Formed Elements: Composed of: Erythrocytes (red blood cells or RBC); Leukocytes (white blood
cells or WBC); Platelets
Erythrocytes: Red blood cells (RBCs). Sacs of hemoglobin molecules that transport the bulk of
oxygen carried in the blood. Contain at least 50 dif't surface antigens on their external surfaces.
Have no organelles or a nucleus and rely exclusively on fermentation to produce ATP.
Luekocytes: Known as white blood cells (WBCs), there are five kinds in two groups:
granulocytes & agranulocytes
Granulocytes: Leukocytes characterized by the presence of granules in the cytoplasm.
Three different kinds.
Neutrophil: Leukocyte with a multi-lobed nucleus. Most prevalent leukocyte in the blood,
composing approximately 50-70% of leukocytes. They phagocytize bacteria in the blood.
Eosinophil: Leukocyte with bi-lobed nucleus and large, reddish cytoplasmic granules. Composes
approx. 2-4% of leukocytes in the blood. Play a role in countering parasitic worms and in
allergies and asthma.
Basophil: Least abundant leukocyte (approx. .5-1% of total). Large U/S shaped nucleus, but
mostly hidden by large coarse granules (usually appear purple) and about the size of a
neutrophil. Mediates inflammatory response and discharges several chemicals, including
histamine, in response.
Agranulocyte: Group of leukocytes (WBCs) that contain no obvious, visible granules.
Found in the bloodstream, but most abundant in lymphoid tissue.
Lymphocyte: Smallest leukocyte, it's about the same size as a RBC. Large nucleus takes up most
of the space with a small sliver of cytoplasm around the edge. Plays a role in immune system
response. About 25% of the WBC population.
Monocyte: Largest leukocyte, about 2x the size of RBCs. Kidney-shaped nucleus.
Becomes an active phagocyte (macrophage) once it makes its way to the tissues. Fibrinogen: a
protein present in blood plasma (clothing)
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller anyiamgeorge19. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $12.99. You're not tied to anything after your purchase.