Module 1

Question 1

The heart is composed of three layers:

Answer 1

• The inner layer is the endocardium.
• The middle layer is the myocardium.
• The outer layer is the epicardium.

Question 2

The muscular layers contain specialized

Answer 2

electrical cells of the cardiac conduction system

Question 3

Electrical cells of the cardiac conduction system are responsible for

Answer 3

automaticity, contractility, and conductivity,

Question 4

automaticity, contractility, and conductivity, function together to produce

Answer 4

contractions sequentially.

Question 5

The electrical conduction system of the heart synchronizes

Answer 5

the atria and ventricles to properly empty and fill the ventricles.

Question 6

specialized myocardial conduction cells form

Answer 6

bundles of fibers that spread the action potential to the muscles. This electrical signal contracts the muscles in the atria and ventricles.

Question 7

The action potential has two phases

Answer 7

depolarization (activation) and repolarization (recovery)

Question 8

Specific cellular ion channels open and close during depolarization and repolarization as an

Answer 8

action potential travels throughout the heart

electrolytes (sodium (Na+), potassium (K+), and calcium (Ca2+)) exchange between intracellular /extracellular

Question 9

ions are

Answer 9

polarized charged particles that generate the electrical activity of the action potential.

These electrical currents transmitted to the skin’s surface and recorded using electrodes during an EKG. However, only atrial and ventricular contractions record since other electrical impulses are too small to deliver towards the skin surface.

Question 10

SA node - sinoatrial node

Answer 10

• small oval structure
• located in right atrium
• contains highly specialized cells - able to depolarize without stimulation or discharge.

Question 11

Automaticity

Answer 11

spontaneous depolarization of an action potential.

Question 12

SA node can activate an action potential about

Answer 12

• 70 times or beats per minute,

- considered the primary pacemaker of the heart.

Question 13

The autonomic nervous system can modify the rate of

Answer 13

spontaneous depolarization of the SA node.

Question 14

Stimulation of the sympathetic nervous system during vigorous exercise or excitement does what to the SA node.
While the parasympathetic nervous system during activities such as resting or sleeping does this to the SA node

Answer 14

increases the rate while parasympathetic cause a decrease.

Question 15

Sympathetic and parasympathetic divisions of the ANS have opposite effects on the body and keep the body in

Answer 15

homeostasis

Question 16

Three branches of autonomic nervous system

Answer 16

Sympathetic, parasympathetic, and enteric

Question 17

Parts of the atrial myocardium, the muscle surrounding the AV node, and the His-Purkinje network also have

Answer 17

automaticity and the ability to serve as secondary pacemakers for the heart.

Question 18

The fastest pacemaker, the SA node, determines

Answer 18

the heart rhythm

Question 19

The SA node will reset the secondary pacemakers because

Answer 19

it will depolarize first

Question 20

. The pacemaker rate decreases with

Answer 20

increased distance from the SA node and is slowest in the Purkinje fibers.

Question 21

An escape rhythm occurs when

Answer 21

an ectopic rhythm ( 3 or more ectopic beats produced from an ectopic focus )replaces a normal sinus rhythm.

Question 22

If a secondary pacemaker other than the SA node produces an action potential resulting in myocardial depolarization, that structure is the

Answer 22

ectopic focus and produces ectopic beats

Question 23

An ectopic rhythm occurs if

Answer 23

three or more ectopic beats produce from the ectopic focus.

Question 24

An increased vagal tone causes

Why?

Answer 24

• slower automaticity of the SA node
• slower conduction through the AV node,
• results in a lower heart rate.
• Increased vagal tone activates parasympathetic nervous system
• higher Vagal tone - can relax faster after stress

Question 25

The vagus nerve innervates the heart with

Answer 25

parasympathetic fibers

Question 26

However, an excessive vagal activity could

Answer 26

• inhibit the activity of the SA node
• no impulses are created
• lead to syncope (fainting).
• secondary pacemakers will generate action potentials until the SA node recovers.

Question 27

An action potential is generated and released at the sinoatrial (SA) node then carries the impulse through the heart in the following path:

Answer 27

1. Right atrium
2. Left atrium
3. Atrioventricular (AV) node
   – AV node creates delay before conducting impulse to ventricles - allows atria time to refill with blood before ventricular contraction.
4. Bundle of His (intraventricular septum) - separates into left and right bundle branches.
5. Atria contract, pump simultaneously through tricuspid /mitral valves into right / left ventricles through the right /left bundle branches.
6. The bundle branches continue to separate into Purkinje fibers that extend into the myocardium. The conduction of the Purkinje fibers is very fast, which allows the entire ventricular myocardium to be activated.

Question 28

The myocardial cells contract in response to

Answer 28

activating an action potential.

Question 29

An escape rhythm occurs when

Answer 29

An ectopic rhythm replaces a normal sinus rhythm

Question 30

Normal sinus rhythm

Answer 30

normal sinus rhythm usually accompanies a heart rate of 60 to 100 bpm.

Question 31

Atrial and ventricular tachycardias are the result of

Answer 31

rapid ectopic atrial and ventricular beats.

Question 32

The electrical currents create the EKG waveforms that represent

Answer 32

• Depolarization and repolarization of the heart muscle