• The nodal musculature has the ability to generate action potentials without any external stimuli.
• The number of action potentials that could be generated in a minute varies at different parts of the nodal system.
• The SAN can generate the maximum number of action potentials and is responsible for initiating and maintaining the rhythmic contractile activity of the heart.
• Therefore, it is called the pacemaker.

• Platelets, also called thrombocytes, are cell fragments produced from megakaryocytes.
• Platelets can release a variety of substances most of which are involved in the coagulation or clotting of blood.

The hepatic portal vein carries blood from the intestine to the liver before it is delivered to the systemic circulation.

• Prehypertension is when blood pressure values are above normal or optimal levels.
• The World Health Organization classifies prehypertension as:
  Blood pressure reading that measures between 120/80 and 139/89.

Through this streak, cells migrate from the upper layer by the process called gastrulation to form the three germ layers of the embryo proper: the ectoderm, the endoderm, and the mesoderm.The cells that are destined to form the heart are also derived from this mesodermal layer.

The cardiovascular centre is a part of the human brain responsible for the regulation of the rate at which the heart beats through the nervous and endocrine systems. It is found in the medulla oblongata.

(a) When circulating in the bloodstream and inactivated, neutrophils are spherical.
Once activated, they change shape and become more amorphous or amoeba-like and can extend pseudopods as they hunt for antigens.

(b) Eosinophil cells are 12 - 17 µm in diameter - larger than neutrophils, and about 3 times the size of a red blood cell. You can see that eosinophils only have two lobes to their nucleus.

(c) In blood, basophils are round, but the shape changes as they migrate into tissues. They generally have a multilobed nucleus and no evidence of nucleoli.
Basophils also have an abundance of condensed chromatin around the periphery of the nucleus.

(d) Monocytes are the largest type of white blood cells and can be up to 20µm in diameter.
They have a large eccentrically placed nucleus, which is kidney bean-shaped. They have abundant cytoplasm and some fine pink/purple granules in the cytoplasm.

(e) Lymphocytes can look like monocytes, except that lymphocytes do not have a kidney-bean shaped nucleus, and lymphocytes are usually smaller.
They have a small spherical nucleus and have abundant dark staining condensed chromatin. Not much cytoplasm can be seen, and it is basophilic (pale blue/purple staining).

The pericardium is the protective covering of the heart. The pericardium is made of different layers to perform different functions.
The layer of heart pericardium which checks its overstretching and overfilling as well as protects the heart from mechanical injury is fibrous pericardium.

Prothrombin plays a crucial role in blood coagulation and vitamin K is essential for blood clotting.
Vitamin K is necessary for the synthesis of prothrombin in the liver.

A special case of Rh incompatibility (mismatching) has been observed between the Rh^-ve blood of a pregnant mother with Rh^+ve blood of the foetus.

• In ECG, P-Wave represents depolarization of atria.
• The QRS complex represents the depolarization of ventricles.
• T-wave represents repolarization of ventricles i.e., returns from excited to the normal state.
• Reduction in the size of T-wave i.e., if the T-Wave represents the insufficient supply of Oxygen i.e. coronary ischemia.
• Hence,
  (a) – (iv)
  (b) – (i)
  (c) – (ii)
  (d) – (iii)

During long hours of standing still swelling of feet is observe due to accumulation of blood in the lower limb, due to gravitation effect. This can be corrected by a jerk or wriggle of legs to restart circulation properly.

Lymph is the extracellular fluid that contains WBC’s and plasma. Lymph flows in the lymphatic system and finally drains into veins. Lymph is known as the middle man of our body.

• The arteries carry blood from the heart to all over body parts. Hence, statement (i) is correct.
• The vessels which carry blood from the heart to the lungs is the pulmonary artery but it carries deoxygenated blood. Hence, statement (ii) is correct.

Angina pectoris is the sensation of chest pain, pressure or squeezing or pain in the centre of the chest. These symptoms are often mistaken by indigestion.

• WBCs are relatively lesser in number which averages 6000-8000 mm^-3 of blood.
• A healthy adult man has, on average, 5 million to 5.5 millions RBCs mm^–3 of blood.
• Blood normally contains 1,500,00-3,500,00 platelets mm^–3.

During an injury, the blood platelets release thromboplastin which converts plasma protein prothrombin into thrombin in the presence of calcium ions. Thrombin then converts soluble plasma protein fibrinogen into fibrin which forms a meshwork by trapping red blood cells, thus forming a clot.

Hypertension can cause a number of effects on the functioning of different vital functions but hypertension does not associate with hypoglycemia and diabetes insipidus.

• Vitamin D status is associated with increased risk of hypertension (6–9), randomized controlled trials (RCTs) have provided little support for the beneficial effect of vitamin D supplementation on blood pressure (10–13).
• Role of Hyperglycemia in the Vascular Abnormalities Associated with Diabetes and Hypertension. Chronic hyperglycemia may exacerbate the vascular disease associated with diabetes mellitus and hypertension. 
• Patients who develop hypertension (diastolic pressure, 90 mm Hg) on oral contraceptives should stop taking the pills immediately, and should be considered to have estrogen-induced hypertension. They should never again receive estrogen-containing oral pills, although they can try pills containing the only progestogen.

The nucleus is absent in mature sieve tube cells and mammalian erythrocytes. Sieve tube is described as the cells of the phloem tissue present in vascular plants. Their function is to translocate and distribute the food material to different parts of the plants. The nucleus of the sieve tube fragmented and disappeared.

On the other side, the mammalian erythrocytes are also known as red blood cells and a major component of the blood. They are formed in the bone marrow. During the process of formation of erythrocytes, the nucleus and mitochondria disappear and are converted to the mature erythrocyte. They possess a red coloured pigment which is known as haemoglobin. Erythrocytes are unable to multiply because they lack a nucleus, and they can survive for 100-120 days.

All statements are correct as the ECG pattern describes all the abnormalities in the heart.