Cardiac Overview

Question 1

Name the path of blood through the pulmonary circuit starting at the superior and inferior vena cava

Answer 1

• superior/inferior vena cava
• right atrium
• tricuspid valve (right AV valve)
• right ventricle
• pulmonary valve
• pulmonary artery
  -pulmonary capillaries (on alveoli)
  -pulmonary vein
• left atrium
• mitral valve (bicuspid)
• left ventricle
• aortic valve
• aorta

Question 2

What are the two types of Myocardial cells?

Answer 2

• Contractile (Cardiomyocytes)
• Nodal and Conducting

Question 3

Nodal and Conducting Cells characteristics

Answer 3

• self excitable (ability to generate action potentials)
• minimal actin and myosin

Question 4

What is the threshold for a nodal cell to conduct an action potential?

Answer 4

-40mV

Question 5

Charge of the cell during 1)Depolarization and 2)Repolarization

Answer 5

Depolarization - cell is more positive than RMP
Repolarization - returns back to RMP

Question 6

Main differences between action potentials in a neuron vs a nodal cell

Answer 6

1. Neuron AP is generated and conducted much faster
2. In depolarization of a neuron - Na+ rushes in
   In depolarization of a myocardial nodal cell - Na rushes in but then right when repolarization starts, Ca rushes in to hold contraction for a bit

Question 7

What is considered to be the pacemaker of the heart?

Answer 7

SA Node (Sinoatrial node)
- in right atrium
- fastest to excite = generation of APs

Question 8

What is the conducting system path for action propagation through the heart?

Answer 8

1) SA Node –> Atrial Muscle –> AV Node –> Bundle of His –> Left and Right bundle branches –> Purkinje fibres –> Ventricular Muscle

Question 9

What is occurring in the heart during each phase of the PQRST cycle?

Answer 9

P - Atrial Depolarization
QRS - Ventricular depolarization
T - Ventricular repolarization