Cardiac Physiology

Question 1

What is the conduction system?

Answer 1

specialized muscle cells (myocytes) produce and transmit electrical impulses to create contraction and relaxation

Question 2

What are myocytes?

Answer 2

specialized muscle cells

Question 3

What are the components of the conduction system?

Answer 3

SA node, AV node, bundle of HIS, Purkinjie fibers

Question 4

What is the SA node?

Answer 4

aka sinoatrial node
located at border of SVC and RA
‘Pacemaker of heart’
beats 60-100bpm
causes atria to contract
P wave on EKG

Question 5

What is the AV node?

Answer 5

aka atrioventricular node
receives impulse from SA node
‘back up pacemaker’
lets ventricles fill

Question 6

What is the bundle of HIS?

Answer 6

located at base of IVS
receives impulse from AV node
divided AV bundle branches

Question 7

What are the Purkinjie fibers?

Answer 7

located at apex of heart
curves with each ventricle
carries impulse through ventricle walls
continuation of bundle branches

Question 8

What causes depolarization?

Answer 8

stimulation of cardiac muscle cells

Question 9

Where does contraction of the heart start?

Answer 9

starts from inside to outside, starts at apex and moves to base

Question 10

What does the SNS do?

Answer 10

increases HR and contraction
fibers attach to SA and AV nodes via Vagus nerve

Question 11

What does the PNS do?

Answer 11

decreases HR and force of contraction
attached to SA node
derived from vagal cardiac nerves

Question 12

What is an EKG?

Answer 12

recording of electrical activity of the heart, consists of P, QRS, T waves

Question 12

What does the P wave represent?

Answer 12

depolarization of atria, atrial systole

Question 12

What does the T wave represent?

Answer 12

repolarization of ventricles, ventricular diastole

Question 12

What does the QRS complex represent?

Answer 12

depolarization of ventricles, ventricular systole

Question 13

What is the cardiac cycle?

Answer 13

the timing from beginning of one heart beat to the next

Question 14

What are the components of pulmonary circulation?

Answer 14

RV, PA and branches, pulmonary capillaries, pulmonary veins

Question 15

What are the components of systemic circulation?

Answer 15

LV, aorta, systemic capillaries, cerebral, abdominal and peripheral veins, SVC, IVC

Question 16

What is sinus bradycardia?

Answer 16

slow HR, less than 60 bpm, occurs during sleep or in trained athletes

Question 17

What is sinus tachycardia?

Answer 17

regular but rapid HR, 100-140 bpm, occurs with exercise

Question 18

What are premature atrial contractions (PAC)?

Answer 18

when the atria beat early, often felt as palpitations, QRS waves are close together and loss of P wave

Question 19

What are premature ventricular contractions (PVC)?

Answer 19

when the heart beat originates in ventricles, very common, results in wide QRS complexes, felt as palpitations

Question 20

What is ventricular tachycardia (V-Tach)?

Answer 20

when several ventricular beats occur in a row, ventricles are not able to fill completely with blood, results in wide QRS complexes

Question 21

What is ventricular fibrillation?

Answer 21

rapid, chaotic beating of ventricles that can disrupt hearts pumping action, no QRS complexes, LETHAL rhythm

Question 22

What is asystole?

Answer 22

without systolic beat, ventricular standstill, occurs when heart stops beating

Question 23

What is a pacemaker?

Answer 23

pulse generator consisting of electronic circuitry and battery, releases impulse when it does not sense intrinsic heart beat