Chapter 17 - Heart

Question 1

What are the 3 circulations of the heart and cardiovascular system?

Answer 1

1. Pulmonary - blood flow to the lungs (for oxygenation)
2. Systemic - blood flow throughout the body
3. Coronary - blood flow to the heart

Question 2

Describe the flow of blood into and out of the heart, addressing the 3 circulations.

Answer 2

Superior & Inferior Vena Cava –> R. atrium –> (Tricuspid valve) –> R. ventricle –> (Pulmonary valve) –> Pulmonary arteries –> Lungs [PULMONARY CIRCULATION] –> Pulmonary veins –> L. atrium –> (Mitral valve) –> L. ventricle –> (Aortic valve) –> Aorta

[SYSTEMIC CIRCULATION]
Aorta –> the rest of the body
Blood supply from upper part of the body comes back through superior vena cava
Blood supply from the lower part of the body comes back through the inferior vena cava

[CORONARY CIRCULATION]
Right side:
Aorta –> R. coronary a. –> branches into posterior interventricular a. and marginal artery
—Posterior Interventricular a. –> ventricular walls
—Marginal artery –> walls of r. atrium and r. ventricle
All funneled back to the cardiac veins –> coronary sinus –> right atrium

Left side:
Aorta –> L. coronary a. –> branches into anterior interventricular a. and circumflex a.
—Anterior Interventricular a. –> ventricular walls
—Circumflex a. –> walls of l. atrium and l. ventricle
All funneled back to the cardiac veins –> coronary sinus –> right atrium

Question 3

What are the 3 layers of the heart wall? (Outer –> inner)

Answer 3

1. Epicardium - visceral layer of the serous pericardium
2. Myocardium - cardiac muscle tissue (bulk of the heart)
   - -2 networks (atrial and ventricular)
   - -Intercalated discs with gap junctions
3. Endocardium - simple squamous epithelium and loose connective tissue
   - -Lines the inside of the heart, tendons, and valves

Question 4

How do AV valves differ from semilunar valves?

Answer 4

AV valves:
-Tricuspid valve - 3 cusps
-Mitral (Bicuspid) valve - 2 cusps
»Chordae tendineae - “heart strings”, prevent valves from going into the the atrium , anchor AV valves to ventricles

Semilunar valves:
-Pulmonary valve - 3 cusps
-Aortic valve - 3 cusps
»NO Chordae tendineae

Question 5

What are the jobs of the skeleton of the heart (the fibrous ring between the atria and ventricles)?

Answer 5

Fibrous skeleton - fibrous rings to which the heart valves are attached 
Functions:
-controls heart muscle depolarization
-structure
-anchor site
-insulation

Question 6

Describe the cardiac cycle.

Answer 6

Atrial Systole / Ventricular Diastole
↑ pressure in the atrium
AV valves open / semilunar valves close
Ventricles relax
70% of blood passively flows into the ventricles
Atrium pumps (remaining 30% of) blood into the ventricles

Ventricular Systole / Atrial Diastole
↑ pressure in the ventricles
Semilunar valves open / AV valves close
Chordae tendineae prevents valves from bulging too far into atria
Ventricles pump blood into pulmonary trunk and aorta
Atria relax
Blood flows passively into atria
(↑ pressure in atria…the cycle continues…)

Question 7

Describe the process of heart depolarization starting with the pacemaker and ending with ventricular relaxation.

Answer 7

SA Node - Pacemaker of the ♡
–Creates a spontaneous action potential!
Atrial syncytium conducts impulse through both atria
—Conducting fibers - lead from atria to to AV Node
AV Node - Small and slow transmission of impulse
—Fibers leave AV node via AV bundle, and travel down interventricular septum to Purkinje fibers
Purkinje fibers - Large and fast
—Carry impulse to the apex of the heart (where contraction begins)
Ventricular syncytium receives impulse

Isovolumetric contraction: period of time where ventricular pressure rises just before it exceeds arterial pressure
—Ventricle ejects blood only after pressure is above that of aortic and pulmonary valves

Isovolumetric relaxation: period before the next conduction cycle

Question 8

What are the three stages of ventricular filling?

Answer 8

1. Rapid fill (passive) - first 2/3 (70%) of blood
2. Diastasis - slow filling
3. Atrial Systole (active) - final 1/3 (30%) of blood

Question 9

What are the 3 waves of an electrocardiogram? What does each represent?

Answer 9

P Wave - atrial depolarization (CONTRACTION)
—When the SA Node triggers a cardiac impulse
QRS Wave - ventricular depolarization / atrial –repolarization
—-Greater electrical change (as impulse travels through thick ventricular walls)
T Wave - ventricular repolarization (RELAXATION)

Question 10

What is an ectopic focus?

Answer 10

an excitable group of cells that causes a premature heartbeat outside of the SA node

• –another portion of the heart starts to attempt to control the heartbeat
• –most common ectopic focus is from the AV node

Question 11

When the atria beat too quickly, but in a organized manner

Answer 11

atrial flutter

Question 12

When the atria beat chaotically and irregularly – out of coordination with the ventricles

Answer 12

atrial fibrillation (A-fib)

Question 13

Extra, abnormal heartbeats that begin in one of the heart’s ventricles

Answer 13

premature ventricular contraction (PVC)

Question 14

What are the 3 regulators of heart rate?

Answer 14

1. SA node - pacemaker of the heart
2. AV node - small and slow transmission of impulse down the heart
3. Purkinje fibers - carry impulse to apex of the heart (where contraction begins)