Thursday 12 February 2015

Circulation Notes

Circulation (Notes)
Portal System:
A vein carrying deoxygenated blood from a system of capillaries divides again to form a second capillary system in tissues before returning to the heart. Such a vein is called a portal vein.
Portal vein + Capillary System -----à Portal System.
Eg: Hepatic Portal Vein returns blood from the intestine and breaks into a portal system of capillaries in the liver (hepatic portal system). This allows the liver cells to take up the nutrients from the portal blood brought from the small intestine.
ECG
The recording of electric potential generated by the spread of Cardiac Impulse is called ECG. It is the graphic record of the electric current produced by the excitation of the cardiac muscles. A normal ECG consists of a P wave, a QRS complex and a T wave.
P Wave : Small upward wave that indicates the depolarization of atria. (Spread of impulse from sinus node throughout the atria).
QRS Complex: Ventricular depolarization.
T Wave : Return of ventricles from excited to normal state. (repolarisation).
Importance of Hepatic Portal Circulation :
Blood which comes from alimentary canal contains absorbed food like glucose and amino acids. Excess of glucose is converted into glycogen which is stored in the liver for later use.
When an individual feels the deficiency of food, the glycogen is converted into glucose and transferred to blood stream via hepatic veins.
Also, liver produces proteins which are put into blood circulation.       
Rh (Rhesus) Blood Group:
A protein named Rhesus Antigen is present on the surface of the RBCs in many persons. It was first discovered in the blood of the Rhesus Monkey.
People who have this antigen --à Rh+
Those who do not have -à Rh-
Formation of Rh protein is controlled by a dominant gene, called R.
Incompatibility during blood Transfusion:
Q: First blood transfusion of Rh+ blood to Rh- person causes no harm. Why?
A: Rh- person develops anti Rh factors or antibodies in his/her blood. In the second transfusion, anti Rh factors of Rh- person attacks and destroys the RBCs of the donor.
Incompatibility during Pregnancy
If the father’s blood is Rh+ and the mother’s blood is Rh-, the foetus’s blood will be Rh+. If the Rh- blood of the mother has not earlier come in contact with the Rh+ blood through transfusion, her first child does not suffer. But, the Rh+ blood of the foetus stimulates the formation of anti Rh factors (enough anti Rh factors are not produced in the mother’s blood to harm the foetus).
But, in the subsequent Rh+ fetuses, anti Rh factors of the mother may destroy the foetal RBCs.
This results in the Haemolytic Disease of the Newborn (HDN)- Erythroblastosis foetalis

Wednesday 28 January 2015

Important viva questions

IMPORTANT VIVA QUESTIONS
Q. What are enzymes? Give two most important characteristics of enzymes.
A: Enzymes are biocatalysts that are involved in various metabolic reactions in a living system. All enzymes are proteins chemically, and they remain unchanged at the end of a reaction.
Q. Name the glands from which saliva is produced.
A. 3 pairs of salivary glands: parotid, submaxillary and sublingual.
Q. What is achromic point?
A: It is the time required to digest starch completely by salivary amylase.
Q: What happens to enzyme activity at very high or very low temperature?
A: Enzymes get denatured at high temperature and deactivated at low temperature, as they are proteins in nature.
Q: How are enzymes different from hormones?
A: (i) All enzymes exceptionally are proteins in nature while hormones can either be proteins or amies or lipids.
(ii) Hormones always have a target organ to act while the enzymes don’t.
Q: What are conjugated enzymes?
A: When along with the protein, some other non-protein moiety is also attached to the enzyme, it is known as conjugated enzyme.
Q:  Can a haploid cell divide meiotically?
A: No, since meiosis reduces the chromosome number to half.
Q: What is the significance of crossing over in meiosis?
A: During crossing over in meiosis, exchange of genetic material between non-sister chromatids occurs; as a result, the genotype of the cells is altered. So it results in genetic recombination and finally helps in introducing variations in populations.
Q: What do you mean by the term karyokinesis?
A: Karyokinesis means the division of the nucleus.
Q: What is a meiocyte cell?
A: A cell that is to divide by meiosis is called a meiocyte.
Q: How do you differentiate the chromosomes of mitosis and meiosis?
A: Meiotic chromosomes are comparatively longer and thiner. They show a characteristic beaded appearance by the presence of chromomeres.
Q: From one parent cell, how many daughter cells will be produced after meiosis and mitosis respectively?
A: two cells after mitosis and four cells after meiosis.
Q: At what stage of cell division does nuclear membrane reappear?
A: Telophase
Q: In which stage of cell division chromosomes are seen best?
A: metaphase stage
Q: Name the chemical that can arrest the process of cell division at metaphase stage.
A: Colchicine
Q: What do you mean by cytokinesis?
A: division of the cytoplasm
Q: Why is mitosis termed as equational division and meiosis as reductional division?
A: Mitosis is equational division because the daughter cells formed are identical to the parent cell in all respects. Meiosis is termed as reduction division because the daughter cells formed have half the number of chromosomes as the parent cell.