CBSE Questions for Class 11 Medical Biology Chemical Coordination And Integration Quiz 12 - MCQExams.com

• When blood calcium levels drop, the parathyroid gland secretes parathyroid hormone. 
• This hormone works to raise blood calcium levels by stimulating osteoclasts to break down bone and release calcium into the bloodstream. 
• PTH also signals kidneys to conserve calcium by reducing the amount excreted in the urine. 

• In presence of parathyroid hormone, bones will give up their calcium in an attempt to increase the blood level of calcium.  
• Under the influence of parathyroid hormone, the bones will continue to release their calcium into the blood at a rate, which is too high, resulting in high blood calcium levels. 

$$\textbf{Correct option:D}$$ 

$$\textbf{Solution:}$$

Corticoid are steroid hormones which are fat soluble and secreted from different endocrine glands.

$$\textbf{Option (A)}$$

$$\bullet$$ Adenocorticotropin hormone from anterior pituitary stimulates the adrenal cortex to secrete three types of corticoid mineralocorticoid aldosterone that maintains the sodium homeostasis in the body,glucocorticoid cortisol that regulates sugar metabolism and sex corticoid such as androgens and estrogens that are involved with the development of sexual characters in human.

$$\textbf{Option (B)}$$

$$\bullet$$ The primary gonads in males are a pair of testes that secretes testosterone and in females they are a pair of ovaries which secretes estrogens. These are steroid hormones that promotes the growth and development of secondary sexual characters and organs,production and maturation of gametes.

$$\textbf{Option (C)}$$

$$\bullet$$ Placenta is a temporary endocrine gland that secretes Human chorionic gonadotropin which promotes the secretion of progesterone in order to maintain the uterine contraction and lining at the time of pregnancy.Human placental lactogen is a growth stimulating hormone that mobilizes fatty acids from the maternal depots to the increasing needs of the fetus for this substance.Placental progesterone and Estrogen helps in the development of the uterine wall and growth of mammary glands.

$$\textbf{Hence, the correct option is (D)}$$

• Cyclic GMP is a cyclic nucleotide, Guanosine 3', 5' cyclic monophosphate or cGMP. It functions as a second messenger in certain cells including those of intestinal linings, heart, blood vessels, brain and the collecting ducts of the kidneys. 
• The cGMP is produced by guanylate cyclase. In mammals, guanylate cyclase is activated by the binding of the hormone atrial natriuretic factor or ANF, which is released by cells in the atrium of the heart when increased blood volume stretches the atrium. Carried in the blood to the kidney, 
• ANF activates guanylate cyclase in cells of the collecting ducts, and the resulting rise in cGMP triggers increased renal excretion of sodium and consequently of water.
• Water loss reduces the blood volume, countering the stimulus that initially led to ANF secretion. Vascular smooth muscles also have an ANF receptor- guanylate cyclase, upon binding to the receptor, ANF causes vessel relaxation (i.e., vasodilation) which reduces the blood pressure.

$$\textbf{Correct option:D}$$ 

$$\textbf{Solution:}$$

$$\textbf{Option (A)}$$

$$\bullet$$ Neural gland is a glandular mass in ascidians that is ituated in close proximity to nerve ganglion and is homologous with the pituitary body of vertebrates.The neural gland complex is interpreted as an organ of blood volume regulation.

$$\textbf{Option (B)}$$

$$\bullet$$ Pharyngeal gill pouch are formed during embryogenesis in vertebrates on the endodermal side between the pharyngeal arches.

$$\textbf{Option (C)}$$

$$\bullet$$ Nerve cord is a unique feature found in Chordates and is a site for attachment of the skeletal muscles which helps in coordinating the functions of the body.

$$\textbf{Option (D)}$$

$$\bullet$$ The endostyle is a pharyngeal organ of urochordates, cephalochordates, and primitive vertebrates. This organ has iodine-concentrating and iodine-metabolism activities, and therefore the endostyle is considered to be similar to thyroid gland.

$$\textbf{Hence, the correct option is (D)}$$