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1800-102-2727i. Exocrine Glands:
ii. Endocrine Glands:
iii. Heterocrine glands:
Classification of hormones:
1. Amino acid derivatives: Adrenaline, noradrenaline, thyroid hormones (iodothyronines)
2. Steroid: These hormones are not water-soluble, for example, Testosterone, Progesterone, Oestrogen and Corticosteroids.
3. Glycoprotein hormones: Gonadotropins i.e., FSH, LH and ICSH.
4. Peptide hormones: Calcitonin, all hypothalamic hormones, Glucagon, insulin, Oxytocin, ADH (Anti Diuretic Hormone), MSH (Melanocyte Stimulating Hormone), ACTH, parathormone.
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1. Endocrine hormones:
2. Local hormones:
a. Autocrine hormones:
b. Paracrine hormones:
c. Pheromones:
Enzyme | Hormone | |
---|---|---|
1 | Always proteinaceous | Maybe proteinaceous, or steroid. |
2 | High molecular weight | Low molecular weight |
3 | They may act at the site where they are produced or carried to another site by some duct | They are produced at one site and are passed by blood to another site for action |
4 | Acts slowly, but increases the rate of reaction | Accelerate or retard a specific reaction. May act slowly or quick |
5 | Catalyze reversible reaction | Hormone controlled reactions are not reversible |
6 | Are not used up in reactions | Are used up in reaction |
Vitamins | Hormone | |
---|---|---|
1 | Taken along with food from outside. Rarely synthesized in the body | Some are synthesized by endocrine glands, while others by neurosecretory cells. |
2 | Simple organic compounds like amines, esters, organic acids etc. | These are steroids or proteinous or amino acid derivatives. |
3 | These generally act as coenzymes or constituents of coenzymes for enzyme action. | These are excitatory or inhibitory in action. They never act as coenzymes |
4 | Vitamins have catalytic action. | Hormones directly influence gene expressions. |
5 | Their deficiency (avitaminosis) causes specific deficiency diseases. | Their deficiency and overproduction cause metabolic disorders |
6 | Are not used up in reactions | Are used up in reaction |
Q1. What are hormones ?
Ans: Hormones are non-nutrient chemicals that act as intracellular messengers and are produced in trace amounts.
Q2. What are pheromones ?
Ans: Pheromones are chemicals that act as hormones outside the body of the individual. These affect the behaviour of the individual receiving them. Generally, these are secreted as sexual responses but they can also induce other behavioural changes in the animals. Eg., Bombykol (released by female Bombyx mori or silkworm to attract males).
Q3. Which was the first discovered hormone?
Ans: Secretin
Q4. What are local hormones ?
Ans: Local hormones are signalling molecules that do not circulate within the bloodstream. Examples: prostaglandins, angiotensin, neurotensin, nitric oxide, kinins, histamine, serotonin etc. They can be classified into three categories:
1. Autocrine hormones
2. Paracrine hormones
3. Pheromones
Q5. What are the three types of glands on the basis of ducts?
Ans: There are 3 types of glands present in the body:
a. Exocrine glands
b. Endocrine glands
c. Heterocrine glands
Q6. Define heterocrine gland with example?
Ans: Heterocrine glands contain both exocrine and endocrine glands, the first secreting through ducts and the second directly into the bloodstream. Example - Pancreas.