Animal, Plant Hormonal Coordination: The endocrine or hormonal system relies on chemical messengers called hormones.
A hormone is a chemical substance produced in small quantities by endocrine glands and carried to the target organs by the blood stream where it produces a response.
TYPES OF GLANDS AND HORMONES SECRETED, WHERE SECRETED, FUNCTIONS, EFFECTS OF OVER SECRETION AND UNDER SECRETION
1. PITUITARY GLAND: Pituitary gland also called master gland because of its considerable influence over others.
LOCATION: Fore brain
FUNCTIONS: Production of several hormones, such as growth hormones, thyroid stimulating hormone, gonado trophic hormones and anti-duretic hormone.
2. THYROID GLAND
LOCATION: Neck region
FUNCTIONS: Controls body metabolism, growth and metamorphosis
OVER SECRETION: Hypothyroidism, associated with nervousness irritability, increased heart beat, weight loss and bulging eyes.
UNDER SECRETION: Hypothyroidism associated with goitre, cretinism in children (mental and physical retardation): overweight.
3. PANCREAS (ISLET OF LANGERHAUS)
LOCATION: Between the stomach and the small intestine.
FUNCTION: Production of insulin which stimulates the liver to remove excess blood sugar by converting into glycogen.
OVER SECRETION: Blood sugar falls below normal
UNDER SECRETION: Diabetes mellitus or sugar diabetes
4. ADRENAL GLAND
LOCATION: On top of each kidney
FUNCTION: Production of adrenaline (emergency hormone) which prepares the body for fight.
OVER SECRETION: Over anxiety and excitement, hypertension and increase blood sugar.
UNDER SECRETION: Fatigue, lack of energy, weakness and sluggishness.
SITE OF PRODUCTION: Shoot and root apices
i) Promotes growth / elongation of stem.
ii) Stimulates development of lateral and adventitious root
iii) Promote ripening of fruits.
iv) Includes cell differentiation.
v) Causes apical dominance.
vi) Control tropism
MODERN APPLICATION OF AUXINS
i) Synthetic auxins are used to regulate the growth of economic plants.
ii) Certain auxins are used for parthenocarpy i.e. production of fruits in unpollinated flowers.
iii) Auxins aid are used to induce ripening in fruits.
iv) Auxins aid dormancy in some crops e.g. yam potatoes etc.
v) Auxins are used to promote root growth in stem cutting.
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