Question

The Cardiovascular System Short Answer Figure 11.1 ape Using Figure 11.1, identify the following: 1) The Purkinje fibers are indicated by label 2) The sinoatrial (SA) node is indicated by letter 3) The specific chamber of the heart that is indicated by letter A is called the 4) The atrioventricular (AV) node is indicated by letter 5) The bundle branches are indicated by letter 6) The layer of the heart wall that receives the stimulus from letter E is called the 7) The partition where the bundle branches are located is called the Fill in the blank or provide a short answer: 8) Crushing chest pain caused by oxygen deprivation of the myocardium is called 9) The visceral layer of the serous pericardium is actually the same layer as the while the 10) The two superior receiving chambers of the heart are known as the two inferior discharging chambers of the heart are known as the 11) The valves located between the atria and ventricles are known as the valves 12) The pointed tip of the heart that is directed toward the left hip is called the

Answer 1

1. The Purkinje fibres are indicated by label E.

They take origin from terminal divisions of right and left bundle branch of Bundle of His to penetrate the ventricular wall.

They are larger and thicker than the sino atrial node fibres.

Because of their larger diameter and very high level of permeability of gap junctions at intercalated discs, they transmit the impulses at a fast velocity of 4m/s as compared to the other conducting tissue. this allows almost immediate transmission of cardiac impulse throughout the entire ventricular system.

2. the sino atrial node or SAN is indicated by letter A.

It is located on the posterior aspect of heart at the junction of the superior vena cava and the right atrium.

Its dimensions are 12x2x1mm.

It consists of thin elongated muscle fibres rich in glycogen and mitochondria. these are the P Cells or Pacemaker cells. These cells generate and discharge impulses more rapidly than any other pacemaker tissue in the heart and their rate determines the heart rate. Hence SAN is called Cardiac Pacemaker.

3. the specific chamber of the heart that is indicated by letter A is called the Right Atrium.

The right atrium receives blood from the systemic circulation via the superior and inferior vena cavae.

Serves as capacity function as well as that of contraction.

4. The Atrioventricular node is indicated by the letter B.

it is located posteriorly on the right side of the interatrial septum near the opening of the coronary sinus.

It is innervated by the left vagus nerve, therefore it receives sympathetic nerve supply primarily from left side.

Pathways which conduct impulses from the SAN to the AVN are called internodal atrial pathways. there are 3 bundles:

• Anterior internodal tract of Bachmann
• Middle internodal tract of Wenckebach
• posterior internodal tract of Thorel