CBSE Class 11 Biology Chemical Coordination and Integration Assignments

Short Answer Type Questions

Question. Write any four characteristic features of hormones.

Answer. (i) Hormones are intercellular chemical messengers. (ii) They have low molecular weight. (iii) They are effective in low concentration. (iv) They may accelerate or retard the specific reactions.

Question. (a) What is intermedin?
(b) (i) Name the smallest endocrine gland of human body.
(ii) Name the hormone secreted by it.

Answer. (a) Intermedin is a substance secreted by the pars intermedia of pituitary gland. (b) (i) Pituitary is the smallest endocrine gland of human body. (ii) Hormones of pituitary gland are growth hormone (GH), prolactin, TSH, ACTH, oxytocin, antidiuretic hormone, FSH, and LH.

Question. Which two hormones regulate blood calcium levels? Briefly describe the feedback mechanism.

Answer. Calcitonin and parathormone regulate blood calcium levels. Calcitonin is secreted when blood calcium levels are high. It lowers the calcium levels by decreasing mobilisation of Ca2+ from bones and prevents Ca2+ reabsorption in nephrons. Parathormone (PTH) is secreted in response to fall in blood calcium level. The release of parathormone increases blood calcium to normal by drawing calcium from bones into the plasma, by increasing calcium absorption in the digestive tract and by reducing loss of calcium in the urine. PTH has an effect that opposes the effect of calcitonin.

Question. (a) Name the hormone which lowers the blood sugar level.
(b) From where that hormone is secreted?
(c) Describe functions of insulin.

Answer. (a) Insulin is the hormone which lowers the blood sugar level. (b) Insulin is secreted from the b-cells of islets of Langerhans of pancreas. (c) (i) It lowers blood glucose levels by stimulating the deposition of glycogen granules in the liver and muscles. (ii) It increases the glucose entry through the plasma membrane. (iii) Insulin increases protein synthesis by incorporation of amino acids into peptides. (iv) It helps in the deposition of fat in adipose tissue from glucose.

Question. Mention the chemical nature of animal hormones and give their examples.

Answer. Chemical nature of animal hormones – (i) Protein nature – TSH, ACTH, FSH (ii) Steroid nature – Testosterone, estrogen (iii) Amino nature – Thyroxine, Epinephrine (iv) Polypeptide nature – ADH, Oxytocin

Question. Write short notes on the functions of the following hormones :
(a) Thymosin
(b) Androgen
(c) Estrogen
(d) Insulin and Glucagon.

Answer. (a) Thymosin is secreted by thymus. It accelerates cell division, stimulates the development and differentiation of T-lymphocytes and also hastens attainment of sexual maturity. (b) Androgens are secreted by testis. They stimulate the development of male reproductive system, formation of sperms, development of male accessory sex characters and also determines the male sexual behaviour and the sex urge. (c) Estrogens are secreted by ovaries. It stimulates the female reproductive tract to grow to full size and become functional, differentiation of ova and development of accessory sex characters. (d) Insulin is secreted by the b-cells of the pancreas. It lowers blood glucose level, and promotes synthesis of proteins and fats. Glycogen is secreted by the a-cells of the pancreas. It increases the level of glucose in the blood.

Question. Mention the name and source of the hormone which regulates the following:
(a) Heart beat and blood pressure
(b) Maturation of Graafian follicle
(c) Milk secretion
(d) Secretion of growth hormone
(e) Lowers the level of calcium ion in blood

Answer. The name and source of the hormones are given in the table: 

Long Answer Type Questions

Question. Hypothalamus is a super master endocrine gland. Elaborate.

Answer. Hypothalamus is a super master endocrine gland as it secretes hormones that regulate the synthesis and secretion of pituitary gland which is a master gland. The hypothalamus is connected to the anterior lobe of pituitary gland by hypophysial portal veins, however, it is connected to the posterior lobe of pituitary gland mainly by axons of neurosecretory cells. The hormones produced by hypothalamus are of two types, the releasing hormones (which stimulate the secretion of pituitary hormones) and the inhibiting hormones (which inhibit secretions of pituitary hormones). The hormones secreted by hypothalamus are summarised below: (i) Adrenocorticotropic Releasing Hormone (ARH) or Corticotropin Releasing Hormone – It stimulates the anterior lobe of pituitary gland to secrete its adrenocorticotropic hormone (ACTH). (ii) Thyrotropin Releasing Hormone (TRH) – It stimulates the anterior lobe of pituitary gland to secrete its thyroid stimulating hormone (TSH) or thyrotropin. (iii) Growth Hormone-Releasing Hormone (GHRH) – It stimulates the anterior lobe of pituitary gland to release its growth hormone (GH) or somatotrophin. (iv) Growth Hormone-Inhibitory Hormone (GHIH) – This hormone is also called somatostatin (SS). It inhibits the secretion of growth hormone from the anterior lobe of pituitary gland. (v) Gonadotropin Releasing Hormone (GnRH)- It stimulates the anterior lobe of pituitary gland to secrete two gonadotropic hormones : Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH)). (vi) Prolactin Releasing hormone (PRH) – It stimulates the anterior lobe of the pituitary gland to secrete its prolactin hormone. (vii) Prolactin Inhibitory Hormone (PIH) – It inhibits the secretion of prolactin from the anterior lobe of pituitary gland. (viii) MSH Releasing Hormone (MSHRH) – It stimulates the intermediate lobe of pituitary gland to secrete its melanocyte stimulating hormone (MSH). (ix) MSH Inhibitory Hormone (MSHIH) – It inhibits the secretion of melanocyte stimulating hormone from the intermediate lobe of pituitary gland.