Zoology MCQs for NEET — Practice Questions with Answers

Cortisol and catecholamines (such as adrenaline and noradrenaline) are directly involved in cardiovascular activity. Cortisol helps regulate blood pressure and cardiovascular function, while catecholamines increase heart rate and blood pressure during stress responses. Insulin (o1), progesterone (o2), and oestrogen (o4) do not have direct roles in cardiovascular activity.

Estradiol is not a peptide/protein hormone. It is a steroid hormone, which belongs to the class of estrogens. On the other hand, Glucagon, Insulin, and FSH (Follicle Stimulating Hormone) are peptide/protein hormones.

Glucagon and insulin both require secondary messengers for their action. Glucagon uses cAMP as a secondary messenger, while insulin uses a signaling pathway involving insulin receptors and subsequent secondary messengers like PI3K and Akt.

Delta cells, also known as D cells, in the pancreas secrete somatostatin. Somatostatin acts to inhibit the release of both insulin and glucagon.

The ovaries secrete several hormones, including estrogen and relaxin. Estrogen is primarily responsible for the development of female secondary sexual characteristics and the regulation of the menstrual cycle. Relaxin is involved in the relaxation of the pelvic ligaments and cervix during childbirth.

The correct matching pairs are: (p-iii) Thymosin is involved in the differentiation of lymphocytes; (q-i) Glucocorticoids suppress the immune response; (r-iv) Deficiency of Iodine (Id₂d) leads to less BMR (Basal Metabolic Rate); (s-ii) Estrogen is associated with a high-pitched voice.

The hormones involved in carbohydrate metabolism include insulin, glucagon, glucocorticoids, and epinephrine. Insulin lowers blood glucose levels by promoting the uptake of glucose into cells. Glucagon increases blood glucose levels by stimulating the conversion of glycogen to glucose in the liver. Glucocorticoids, such as cortisol, promote gluconeogenesis, and epinephrine increases blood glucose levels by stimulating glycogenolysis.

The thyroid gland plays a crucial role in regulating the body's basal metabolic rate (BMR). It produces hormones such as thyroxine (T4) and triiodothyronine (T3), which regulate the rate of oxidation in cells and hence ATP production. Therefore, any irregularities in the thyroid gland can indeed alter the BMR. Since statement y explains why statement x is true, option o1 is correct.

Under stress conditions, the body's 'fight or flight' response is activated, which is controlled by the adrenal medulla. This leads to the secretion of adrenaline (epinephrine) and noradrenaline (norepinephrine), which among other things, cause body hairs to stand up (a phenomenon called piloerection). Therefore, statement x is correct. However, statement y is incorrect because the secretion from the adrenal medulla increases under stress, not stops. Hence, option o3 is correct.