Chemical Coordination and Control MCQs for NEET — Zoology Questions with Answers

Though not explicitly stated as 'why' trace amounts are effective in a single sentence, the text explains that hormones 'act as intercellular messengers and are produced in trace amounts' and 'produce their effects on target tissues by binding to specific proteins called hormone receptors... Hormone-Receptor complex formation leads to certain biochemical changes in the target tissue.' This binding and subsequent biochemical cascade allows even trace amounts to have a significant effect.

Under the classification based on chemical nature, NCERT lists '(ii) steroids (e.g., cortisol, testosterone, estradiol and progesterone).'

The NCERT states: 'Hormones which interact with intracellular receptors (e.g., steroid hormones, iodothyronines, etc.) mostly regulate gene expression or chromosome function by the interaction of hormone-receptor complex with the genome.'

As per the NCERT text, 'the atrial wall of our heart secretes a very important peptide hormone called atrial natriuretic factor (ANF), which decreases blood pressure.'

The NCERT states, 'When blood pressure is increased, ANF is secreted which causes dilation of the blood vessels. This reduces the blood pressure.' ANF directly lowers blood pressure.

According to the NCERT, 'The juxtaglomerular cells of kidney produce a peptide hormone called erythropoietin which stimulates erythropoiesis (formation of RBC).'

The NCERT excerpt states, 'Gastrin acts on the gastric glands and stimulates the secretion of hydrochloric acid and pepsinogen.'

Erythropoietin stimulates erythropoiesis (formation of RBC) as mentioned in the NCERT text. A deficiency would lead to reduced RBC formation.

The NCERT states, 'Secretin acts on the exocrine pancreas and stimulates secretion of water and bicarbonate ions.'

As per the NCERT text, 'CCK acts on both pancreas and gall bladder and stimulates the secretion of pancreatic enzymes and bile juice, respectively.'