Lecture 9

Question 1

Tachycardia

Answer 1

Fast heart rate of over 100 beats/min at rest; caused by increased body temperature, stimulation of the heart by sympathetic nerves, or toxic conditions of the heart

Question 2

Endogenous Tachycardia

Answer 2

Due to exercise; heart rate increases, cardiac output increases, and filling time is reduced but stroke-volume does not fall

Question 3

Pathological Tachycardia

Answer 3

Due to an “illness”; heart rate increases and cardiac output decreases

Question 4

Bradycardia

Answer 4

Slow heart rate of less than 60 beats/min at rest; caused by an athletic heart, vagal stimulation, or extremely sensitive carotid baroreceptors in carotid sinus syndrome

Question 5

Spillover Signals

Answer 5

Come from medullary respiratory centers into vasomotor center during inspiratory and expiratory respiratory cycles; signals alternately increase and decrease number of impulses transmitted through the sympathetic and vagus nerves to the heart

Question 6

Sinoatrial Block Characteristics

Answer 6

Sudden cessation of P waves, resultant standstill of atria, ventricles pick up a new rhythm, usually originating in the AV node; rate of QRS is slowed but not otherwise altered

Question 7

Atrioventricular Block Caused By…

Answer 7

Ischemia of AV node or AV bundle fibers through coronary insufficiency, compression of AV bundle by scar tissue or calcified portions of the heart, inflammation of the AV node or bundle, or extreme stimulation of the heart by the vagus nerves

Question 8

First Degree Incomplete AV Block

Answer 8

Normal P-R interval of .16s that increases in length with slower heartbeat and decreases with faster heartbeats; when P-R interval is prolonged patient has first degree incomplete AV block

Question 9

Second Degree Incomplete AV Block

Answer 9

P-R interval increases to .25 to .45s; atrial P wave is present but QRS-T wave may be missing, resulting in dropped beats of the ventricle; 2:1 rhythm or other variations may develop

Question 10

Complete Atrioventricular Block

Answer 10

Ventricles establish their own signal (usually the AV node); no relation between the rate of the P waves and the rate of the QRS-T complexes; duration of the block is highly variable; ventricles may stop beating for 5-30 seconds and often times patients will faint due to lack of blood to the brain

Question 11

Ventricular Escape

Answer 11

Resumption of the ventricular beat after they stop beating

Question 12

Stokes-Adams Syndrome

Answer 12

Periodic fainting spells after complete AV block occurs

Question 13

Partial Intraventricular Block

Answer 13

Also called “electrical alternans”; alternation in the amplitude of P waves, QRS complexes, or T waves

Question 14

Premature Contractions

Answer 14

Contractions occur before they should, usually the result of ectopic foci, such as:
Local ischemic areas
Calcified plaques
Irritation of the conduction system or nodes

Question 15

Paroxysmal Tachycardia

Answer 15

Heart becomes rapid in paroxysms; paroxysm begins suddenly and lasts for a few seconds, minutes, hours, or longer and then suddenly ends; pacemaker of the heart instantly shifts back to the sinus node

Question 16

Fibrillation

Answer 16

Twitching of individual muscle fibers in the atria or ventricles and also in recently denervated skeletal muscle fibers

Question 17

Causes of Atrial Fibrillation

Answer 17

Enlargement of the atria due to valve lesions or inadequate emptying of the ventricles causing blood to back up in the atria