Physiology

One effect of nicotine is constriction of the terminal bronchioles of the lungs, which increases the resistance of airflow into and out of the lungs.
Second, the irritating effects of the smoke itself cause increased fluid secretion into the bronchial tree, as well as some swelling of the epithelial linings.

Velocity (V) is proportionate to flow (Q) divided by the area of conduit (A).
Therefore, the average velocity of the blood is high in the aorta, declines steadily in the smaller vessels and is the lowest in the capillaries, which have 1000 times the total cross-sectional area of aorta.

No matter a particular sensory pathway is stimulated along its course to the cortex, the conscious sensation produced is referred to the location of the receptor. This principle is called the law of projection.

Metaplasia is the reversible replacement of one differentiated cell type with another mature differentiated cell type, e.g. Barretts esophagus.

Flouride exists in both ionic and bound forms in the plasma with the bound form being present in larger quantity. The unbound or ionic forms vary according to the concentration of fluoride in drinking water. This form is asymmetrically distributed in blood between plasma and the blood cells.

The plasmin proteins contain a euglobulin called plasminogen (or profibrinolysin) which when activated, becomes a substance called plasmin (or fibrinolysin). Plasmin is a proteolytic enzyme that resembles tryspin, the most important proteolytic digestive enzyme of pancreatic secretion.

Merkel cells or discs are expanded tip tactile receptors. They are responsible for giving steady-state that allow one to determine continuous touch of objects against the skin.

Nitric oxide acts through cGMP-dependent protein kinase and not through cAMP. It is a vasodilator important in blood pressure regulation involved penile erection. Neurotransmitter in the brain and peripheral ANS inhibits adhesion activation and aggregation of platelets.

Plasmin, the plasma protein, contains a euglobulin called plasminogen, which when activated, becomes a substance called plasmin (or fibrinolysin). Plasmin is a proteolytic enzyme that resembles trypsin.

Broca’s area is a premotor area concerned with word formation, lying immediately anterior to the primary motor cortex and immediately above the sylvian fissure. This region is called Broca’s area.

Approximate elementary composition of human body (dry weight basis) is as follows:
a. Calcium - 4%b. Phosphorus -2.5%c. Sodium - 0.4%d. Iron - 0.01%e. Iodine - 0.0000.5%f. Chlorine - 0.4%

The primary mechanism of noradrenaline in increasing the blood pressure is by increasing the myocardial contractility.

Advances in the study of electrical activity in nerves include devices like microelectrode, cathode-ray oscilloscope, etc.

1. Calcitonin inhibits bone resorption by direct action on osteoclasts.
2. Calcitonin exerts its calcium-lowering effects by inhibiting bone resorption. This action is direct.
3. Calcitonin inhibits the activity the activity of osteoclasts in vitro.

1. Vitamin C is required for post-translation modification of procollagen polypeptide molecules in collagen synthesis.
2. Vitamin K is required for post-translation of glutamate residues for generation of clotting factors.
3. Synthesis of clotting factors is helped by vitamin K and not by vitamin C.
4. Antioxidant properties are features of vitamin A, vitamin E and vitamin C, but not of vitamin K.

The bone marrow of essentially all bones produces red blood cells until a person is 5 years old. The marrow of the long bones, except for the proximal portion of the humeri and tibiae, becomes quiet and produces no more red blood cells after about an age of 20 years. Beyond this age, most red cells continue to be produced in the marrow of the membranous bones, such as the vertebrae, sternum, ribs and ilia. Even in these bones, the marrow becomes less productive as age increases.

Humoral immunity comprises antibody formation against intracellular pathogens. This is principally mediated by B cells. T cells are involved in the cell-mediated immunity
B cells are precursors of plasma cells. Lifespan of small B cells is less than 1 month.

Breakdown of heme to bilirubin occurs in macrophages of the reticulo-endothelial system.
Major sites of bilirubin production are spleen and other compartments of reticuloendothelial system, which degrade the haemoglobin of injured RBCs. Other sites are liver and bone marrow.