Question

1. Review the five steps of the cardiac conduction cycle, including a thorough description of the structures and functions involved with each stage. The four phases of the cardiac cycle should be clearly referenced in the response as well. In addition, review and describe all heart structures that the electrical signals sent by the cardiac conduction cycle passes through (essentially, all heart structures and layers except the connecting blood vessels and the valves), in the approximate order through which the signals pass. (Hint: you’re startingat the right atrium.)

2. You are examining a sample of blood from a healthy individual under the microscope that has already been properly fixed and stained. Provide a review of the morphology and function of the seven blood cells you should see on the slide, including a review of their relative abundance. (I don’t need overly specific numbers, but a sense of how easy it is to find each blood cell is required.) In addition, discuss how your response would change if the sample was from an individual with: 1) sickle-cell disease, 2) leukemia (select a specific variant of your choice), and 3) anemia (select a specific variant of your choice).

3. A freshly minted red blood cell is released from the red bone marrow of the humerus in the right arm, and is provided with the following itinerary of tissues to visit:

   1. a) Report to the apex of the heart.

   2. b) Take a tour of the front of the right knee.

   3. c) Grab some food to go in the jejunum (middle part of the small intestine).

   4. d) Visit the left adrenal gland.

   List and describe all named blood vessels and pertinent structures that the red blood cell will pass through on its trip (arterioles, venules, and capillary beds can be handwaved); it is assumed to start from a small venule feeding directly to the brachial vein. Remember that the trips requires a visit through the pulmonary circuit before and after each of the four steps listed above (the apex of the heart is reached through the coronary circulation).

Answer 1

Cardiac cycle :

It is defined as the sequence of electrical and mechanical events occurring in heart during a single beat

5 steps of cardiac cycle :

1 ) Passive Ventricular filling

2 ) Atrial contraction and emptying

3 ) Isovolumetric contraction

4 ) Ventricular contraction and ejection

5.) Isovolumetric relaxation

4 Phases of Cardiac cycle :

1.) Atrial systole (0.1 seconds)

2.) Atrial diastole (0.7 seconds)

3.) Ventricular systole ( 0.5 seconds)

=> Isovolumetric Contraction

=> Rapid Ejection

=> Reduced Ejection

4.)Ventricular diastole (0.3 seconds)

=> Isovolumetric relaxation

=> Ventricular filling

=> Rapid filling

=> Diastasis

Initiation and Propagation of Cardiac impulse :

Impulse is generated by SinoAtrial node (SA node) situated in Right Atrium

It passes to left atrium via Bachmann's Bundle

The impulse then reaches Atrioventricular node(AV node) situated in the atrioventricular septum

Impulse then reaches Bundle of His (Atrioventricular bundle) which then divides in Left bundle branch and Right bundle branch, inside the interventricular septum

Impulse goes through Purkinje fibres and reaches all of the ventricles.

Ventricular depolrization starts from the left of interventricular septum and reaches the right side and then spreads to the apex of heart.

Then impulse reaches from endocardium to epicardium.

Last structures to be depolarized are posterobasal portion of left ventricle, the pulmonary conus and upper most portion of the septum.

Repolarization occurs in the opposite direction, from epicardium to endocardium

Microscopic examination of Blood :

7 types of blood cells seen :

1.) Red Blood Cells(most plentiful)- orange red circular Biconcave structures about 7.2 microns diameter with a central halo. No nucleus

Functions : Carry oxygen to tissues

2.) Platelets - pink aggregates of tiny cells. Smallest cells of 2 to 4 microns diameter.

Functions : Helps blood to clot

3.) Neutrophils(50-70%)- pale pink with fine pink granules and multilobed nuclei connected by thin strands. 10 to 14 microns in size.

Functions : Fights off Infection

4.) Eosinophils(1-4%) - faint pink with red orange granules and bilobed nuclei connected by thick strand(spectacle shaped). 10 to 14 microns in size.

Functions : Increased in Allergies

5.) Basophils(0-1%) - Blue black granules. Bilobed or trilobed nucleus. 10 to 14 microns in size

Functions : allergy

6.) Lymphocytes(20-40%) - Eccentrically placed large nuclei with scanty clear blue cytoplasm

Functions : Immunity by producing antibodies

7.) Monocytes(2-8%) - 12 to 24 microns. Large cells ground glass appearance of cytoplasm with round nucleus

Functions : Phagocytosis

Questions :

a) Sickle cell disease -

RBC - normocytic normochromic. Sickling of rbcs. Sickle cells, target cells, polychromatophilia

WBC - mildly increased. Shift to left

Platelets - mildy increased

b) Acute Myeloid Leukemia-

RBCs - Normocytic normochromic

WBC - more than 20% myeloblast. Auer rods positive myeloblasts with high N:C ratio and fine chromatin

Platelets - Thrombocytopenia

c) Iron deficiency Anemia-

RBC - microcytic hypochromic. Pencil or cigar shaped cells.

WBC - normal. Eosinophilia

Platelets- normal

Course of red blood cell :

Right humerus

Right brachial Vein

Right Axillary vein

Right Subclavian vein

Inferior vena cava

Coronary artery - Apex of heart

Pulmonary artery - lungs

Pulmonary veins - heart

Aorta - abdominal aorta

Superior mesentric vessels and ceoliac vessels - jejunum

Great saphenous vein - knee joint

Suprarenal vessels - Adrenal gland