Which one of the following is a function of PGI2?
Which of the following is false as physiological change in pregnancy?
Two identical twins will not have same:
NEET-PG 2019 - Physiology NEET-PG Practice Questions and MCQs
Question 11: Which one of the following is a function of PGI2?
- A. Causes blood vessel constriction and prevents platelet clumping
- B. Causes blood vessel constriction and promotes platelet clumping
- C. Causes blood vessel relaxation and prevents platelet clumping (Correct Answer)
- D. Causes blood vessel relaxation and promotes platelet clumping
Explanation: **Correct Answer: Causes blood vessel relaxation and prevents platelet clumping** ***PGI2 (prostacyclin)*** is a potent **vasodilator** produced by vascular endothelium that causes blood vessel relaxation. It also has a powerful inhibitory effect on **platelet aggregation**, thus preventing platelet clumping and thrombosis. These two functions make PGI2 an important anti-thrombotic mediator in the cardiovascular system. *Incorrect: Causes blood vessel constriction and prevents platelet clumping* - This option is incorrect because PGI2 **relaxes blood vessels** (vasodilation), it does not constrict them. - While it correctly states that PGI2 prevents platelet clumping, its effect on blood vessels is wrongly stated. *Incorrect: Causes blood vessel constriction and promotes platelet clumping* - This statement is entirely incorrect as PGI2's functions are the opposite: **vasodilation** and **inhibition of platelet aggregation**. - **Thromboxane A2 (TXA2)** is an eicosanoid with these described effects (constricts blood vessels and promotes platelet clumping), making it the functional antagonist of PGI2. *Incorrect: Causes blood vessel relaxation and promotes platelet clumping* - While PGI2 does cause **blood vessel relaxation** (vasodilation), it actively **prevents platelet clumping** rather than promoting it. - Promotion of platelet clumping is a function of other substances like **Thromboxane A2 (TXA2)**.
Question 12: Which of the following is false as physiological change in pregnancy?
- A. Increase GFR
- B. Increase total protein (Correct Answer)
- C. Increase cardiac output
- D. Increase plasma volume
Explanation: ***Increase total protein*** - During pregnancy, **plasma volume increases disproportionately more than the increase in red blood cell mass**, leading to hemodilution. - This hemodilution results in a **decrease in the concentration of total plasma proteins and albumin**, making this statement false. *Increase GFR* - **Glomerular filtration rate (GFR) increases significantly** during pregnancy (by 30-50%) due to increased renal plasma flow. - This physiological adaptation helps to clear the increased metabolic waste products produced by both the mother and the fetus. *Increase cardiac output* - **Cardiac output increases by 30-50%** during pregnancy, primarily due to increases in both heart rate and stroke volume. - This increased cardiac output ensures adequate blood supply to the uterus, placenta, and other maternal organs. *Increase plasma volume* - **Plasma volume increases substantially (up to 40-50%)** during pregnancy, starting in the first trimester and continuing until term. - This expansion of plasma volume is crucial for meeting the increased circulatory demands of pregnancy and supporting placental perfusion.
Question 13: Two identical twins will not have same:
- A. DNA
- B. Iris color
- C. Blood group
- D. Fingerprints (Correct Answer)
Explanation: ***Fingerprints*** - **Fingerprints** are unique to each individual, even identical twins, because their formation is influenced by prenatal environmental factors such as **blood flow**, **amniotic fluid pressure**, and **baby's position in the womb**. - These environmental factors affect the development of **dermal ridges** during weeks 6-13 of gestation, leading to distinct patterns. *DNA* - **Identical twins** originate from a single fertilized egg that splits, meaning they share virtually **100% of their DNA**. - While minor epigenetic differences can occur, their core genetic code is the same. *Iris color* - **Iris color** is primarily determined by **genetics**, and since identical twins share the same genetic makeup, they typically have the same (or very similar) **eye color**. - Differences in iris patterns might exist, but the overall color is genetically programmed. *Blood group* - **Blood group** is an inherited trait determined by specific **antigens on red blood cells**, which are encoded by genes. - As identical twins share the same genetic information, they will have the **same blood type**.