The endocrine system is responsible for coordinating and integrating various body functions through the release of hormones. Hormones are chemical messengers that travel through the bloodstream to target organs, where they exert their effects.
Endocrine Glands:
- Pituitary Gland: The “master gland” that secretes hormones that regulate other endocrine glands.
- Thyroid Gland: Regulates metabolism, growth, and development.
- Adrenal Glands: Produce hormones that regulate stress, blood pressure, and metabolism.
- Gonads (Testes and Ovaries): Produce sex hormones.
Hormone Action:
- Hormones bind to specific receptors on target cells.
- Hormone action can be:
- Direct: The hormone directly affects the target cell.
- Indirect: The hormone stimulates the release of a second messenger, which then affects the target cell.
Key Hormones and Their Functions:
- Growth Hormone: Promotes growth and development.
- Thyroid Hormones: Regulate metabolism, growth, and development.
- Cortisol: Regulates stress response and metabolism.
- Insulin and Glucagon: Regulate blood sugar levels.
- Sex Hormones: Control sexual development and reproduction.
Disruptions in the endocrine system can lead to various disorders, such as diabetes, hypothyroidism, and hyperthyroidism.
Exercise
1. Define the following:
(a) Exocrine gland
(b) Endocrine gland
(c) Hormone
Ans :
(a) Exocrine Gland: An exocrine gland is a gland that releases its secretions, such as enzymes or mucus, through ducts to the surface of an organ or outside the body.
(b) Endocrine Gland: An endocrine gland is a gland that secretes hormones directly into the bloodstream, which then travel to target organs or tissues to regulate various bodily functions.
(c) Hormone: A hormone is a chemical messenger produced by endocrine glands that regulates specific physiological processes, including growth, metabolism, reproduction, and mood.
2. Diagrammatically indicate the location of the various endocrine glands in our body.
Ans :
3. List the hormones secreted by the following:
(a) Hypothalamus
(b) Pituitary
(c) Thyroid
(d) Parathyroid
(e) Adrenal
(f) Pancreas
(g) Testis
(h) Ovary
(i) Thymus
(j) Atrium
(k) Kidney
(l) G-l Tract.
Ans :
(a) Hypothalamus
- Releasing hormones: Growth hormone-releasing hormone (GHRH), corticotropin-releasing hormone (CRH), gonadotropin-releasing hormone (GnRH), thyrotropin-releasing hormone (TRH), and growth hormone-inhibiting hormone (GHIH)
- Posterior pituitary hormones: Antidiuretic hormone (ADH) and oxytocin
(b) Pituitary Gland
- Anterior pituitary: Growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin
- Posterior pituitary: Antidiuretic hormone (ADH) and oxytocin
(c) Thyroid
- Thyroid hormones: Thyroxine (T4) and triiodothyronine (T3)
(d) Parathyroid
- Parathyroid hormone (PTH)
(e) Adrenal Glands
- Adrenal cortex: Cortisol, aldosterone, and sex hormones (androgens and estrogens)
- Adrenal medulla: Epinephrine (adrenaline) and norepinephrine
(f) Pancreas
- Insulin
- Glucagon
(g) Testis
- Testosterone
(h) Ovary
- Estrogen
- Progesterone
(i) Thymus
- Thymosin
(j) Atrium (not an endocrine gland)
- Atrial natriuretic peptide (ANP)
(k) Kidney
- Renin (involved in the renin-angiotensin-aldosterone system)
4. Fill in the blanks:
Hormones Target gland
(a) Hypothalamic hormones ………………..
(b) Thyrotrophin (TSH) ………………..
(c) Corticotrophin (ACH) ………………..
(d) Gonadotrophins (LH, FSH) ………………..
(e) Melanotrophin (MSH) ………………..
Ans :
(a) Hypothalamic hormones – Pituitary gland
(b) Thyrotrophin (TSH) – Thyroid gland
(c) Corticotrophin (ACH) – Adrenal cortex
(d) Gonadotrophins (LH, FSH) – Gonads (testes or ovaries)
(e) Melanotrophin (MSH) – Melanocytes in the skin
5. Write short notes on the functions of the following hormones:
(a) Parathyroid hormone (PTH) (b) Thyroid hormones (c) Thymosins
(d) Androgens (e) Estrogens (f) Insulin and Glucagon
Ans :
(a) Parathyroid Hormone (PTH)
- Function: Regulates blood calcium levels.
- Action: Increases calcium absorption in the intestines, stimulates bone resorption (breakdown of bone tissue), and increases calcium reabsorption in the kidneys.
(b) Thyroid Hormones (Thyroxine (T4) and Triiodothyronine (T3))
- Function: Regulate metabolism, growth, and development.
- Action: Increase metabolic rate, promote growth and development, and regulate body temperature.
(c) Thymosins
- Function: Stimulate the development of T lymphocytes, which are essential for immune function.
(d) Androgens (e.g., Testosterone)
- Function: Promote male sexual development and characteristics, such as muscle growth, deepening of the voice, and beard growth.
(e) Estrogens (e.g., Estradiol)
- Function: Promote female sexual development and characteristics, such as breast development, menstrual cycles, and pregnancy.
- Also involved in: Bone health and cardiovascular function.
(f) Insulin and Glucagon
- Function: Regulate blood sugar levels.
6. Give example(s) of:
(a) Hyperglycemic hormone and hypoglycemic hormone (b) Hypercalcemic hormone (c) Gonadotrophic hormones (d) Progestational hormone (e) Blood pressure lowering hormone (f) Androgens and estrogens
Ans :
(a) Hyperglycemic Hormone and Hypoglycemic Hormone
- Hyperglycemic hormone: Glucagon, secreted by the alpha cells of the pancreas, raises blood sugar levels.
- Hypoglycemic hormone: Insulin, secreted by the beta cells of the pancreas, lowers blood sugar levels.
(b) Hypercalcemic Hormone
- Parathyroid hormone (PTH)
(c) Gonadotrophic Hormones
- Luteinizing hormone (LH) and follicle-stimulating hormone (FSH), secreted by the anterior pituitary gland, regulate the function of the gonads (testes and ovaries).
(d) Progestational Hormone
- Progesterone, secreted by the ovaries and placenta, is the primary progestational hormone. It is involved in preparing the uterus for pregnancy and maintaining pregnancy.
(e) Blood Pressure Lowering Hormone
- Atrial natriuretic peptide (ANP), secreted by the heart’s atria, helps to lower blood pressure by increasing sodium excretion and reducing blood volume.
(f) Androgens and Estrogens
- Androgens: Male sex hormones, such as testosterone, produced by the testes.
- Estrogens: Female sex hormones, such as estradiol, produced by the ovaries.
7. Which hormonal deficiency is responsible for the following:
(a) Diabetes mellitus (b) Goitre (c) Cretinism
Ans :
(a) Diabetes mellitus is primarily caused by a deficiency or improper function of the hormone insulin.
(b) Goiter is often caused by a deficiency of thyroid hormones, particularly thyroxine (T4).
(c) Cretinism is a condition characterized by stunted growth and mental development in infants and children, and it is typically caused by a severe deficiency of thyroid hormones during early childhood.
8. Briefly mention the mechanism of action of FSH.
Ans :
Follicle-stimulating hormone (FSH) is a gonadotropic hormone secreted by the anterior pituitary gland. Its primary function is to stimulate the growth and development of follicles in the ovaries of females and the seminiferous tubules in the testes of males.
Mechanism of action of FSH:
- Stimulation of Follicular Growth: In females, FSH stimulates the growth and development of ovarian follicles, each containing an egg.
- Estrogen Production: As the follicles grow, they produce increasing amounts of estrogen.
- Negative Feedback: Rising estrogen levels provide negative feedback to the hypothalamus and pituitary gland, reducing the secretion of FSH.
- Ovulation: A surge in LH (another gonadotropin) causes the dominant follicle to ovulate and release an egg.
- Corpus Luteum Formation: The remaining follicular cells develop into the corpus luteum, which produces progesterone to support pregnancy.
9. Match the following :
Column I Column II
(a) T4 (i) Hypothalamus
(b) PTH (ii)Thyroid
(c) GnRH (iii)Pituitary
(d) LH (iv) Parathyroid.
Ans :
(a) T4 – (ii) Thyroid
(b) PTH – (iv) Parathyroid
(c) GnRH – (i) Hypothalamus
(d) LH – (iii) Pituitary
