Electrophysiology of the Heart

Question 1

What two types of cells does the heart have?

Answer 1

electrical

mechanical

Question 2

What do electrical cells do?

Answer 2

initiate and conduct impulses

Question 3

What do mechanical cells do?

Answer 3

contract in response to electrical stimulation

Question 4

Why are electrical cells arranged in a specific pattern?

Answer 4

to control the flow of electrical impulses from the atria to the ventricles in a coordinated fashion (referred to as the conducting system)

Question 5

What is an electrical impulse?

Answer 5

the result of cells changing chemically. this change come from the sodium potassium pump at the cellular level changing the electrical balance of the cell

Question 6

What is automaticity?

Answer 6

cellular ability to repeat impulse without an external signal

Question 7

What is the dominant controller or pacemaker of the conduction system?

Answer 7

SA node

Question 8

What is a pacemaker?

Answer 8

a cluster of electrical cells that rhythmically repeats electrical impulses that travel down the conducting system

Question 9

T/F: the conducting system has more than one built-in pacemaker but the dominant one controls the heart

Answer 9

true

Question 10

What is the inherent rate of the SA node?

Answer 10

60-100

Question 11

What is the inherent rate of the AV junction?

Answer 11

40-60

Question 12

What is the inherent rate of the ventricle (purkinje fibers)?

Answer 12

20-40

Question 13

What is the escape mechanism?

Answer 13

when the dominant pacemaker fails and the next one in line takes over. it will pace the heart at its inherent rate

Question 14

What is the irritability mechanism?

Answer 14

any clump of heart cells that can become irritable and become a pacemaker, and take control of the heart from the SA node

Question 15

What is the heart influenced by?

Answer 15

autonomic nervous system (both sympathetic and parasympathetic systems)

Question 16

How does the sympathetic system affect the heart?

Answer 16

• directly influences the entire heart (SA node, AV junction, every heart cell)
• it increases irritability (increased rate and force of contraction)

Question 17

How does the parasympathetic system affect the heart?

Answer 17

decreases irritability (decreases rate and force of contraction)

Question 18

T/F: the heart does not need electrical stimulation before mechanical contraction

Answer 18

false; electrical stimulation must occur before mechanical contraction

Question 19

T/F: electrical activity can occur without mechanical contraction

Answer 19

true

Question 20

What should you assess for mechanical activity?

Answer 20

• pulse
• blood pressure
• cardiac output

Question 21

What should you asses for electrical activity?

Answer 21

ECG (electrical impulses that reach the surface of the body)