Flashcards For NEET Biology - Chemical Coordination and Integration

Acts as an intercellular chemical messenger

Non-nutrient and present in trace amounts

Regulates secretion from anterior pituitary through the hypophyseal portal system

Neurohypophysis is under the direct control

Function- stimulates the synthesis of gonadotrophins from the anterior pituitary

Function- inhibits the secretion of growth hormone (GH) from the anterior pituitary

Secretes- GH, ACTH, TSH, LH, FSH, PRL

Secretes- MSH (melanocyte-stimulating hormone)

Function- MSH regulates pigmentation of the skin

Secretes- oxytocin and vasopressin (ADH)

These hormones are synthesised in the hypothalamus and transported by axon and released by nerve endings

Function- Regulates growth

Gigantism– due to overproduction

Dwarfism– due to under production

Acromegaly– due to overproduction in adults

Function- stimulates the growth of mammary glands and milk production

Function- stimulates the thyroid gland to secrete thyroid hormones

Function- stimulates the adrenal cortex to secrete glucocorticoids (cortisol)

Secreted by- anterior pituitary

Function in males- stimulates the synthesis of androgens

Function in females- induces ovulation and maintenance of corpus luteum

Secreted by- anterior pituitary

Function in males- regulates spermatogenesis with androgens

Function in females- growth and development of ovarian follicles

Function- stimulates contraction of smooth muscles, stimulates contraction of the uterus during childbirth

Oxytocin injection is given to induce labour pain

Function- stimulates reabsorption of water from distal tubules in the kidneys and prevents diuresis

Diabetes Insipidus- decreased synthesis of ADH leading to excessive loss of water from the kidneys

Secretion- melatonin

Function- regulates the sleep-wake cycle, temperature. Also regulates metabolism, pigmentation, immune system and menstrual cycle

Secretion- T₄ (thyroxine) and T₃ from follicular cells, calcitonin from ‘C’ cells

Function- regulation of carbohydrate, fat and protein metabolism, BMR and water and electrolyte balance, regulation of blood calcium level by calcitonin

Cretinism– due to congenital thyroid deficiency causing growth retardation, learning difficulties

Irregular menstrual cycle in adult females

Exophthalmic goitre or Grave’s disease- enlargement of the thyroid gland, increased BMR, weight loss and eyeballs protrude out

Secretion- parathyroid hormone (PTH)

Function- play role in calcium balance with calcitonin. It increases blood calcium level by dissolution from bones, reabsorption from kidneys and absorption from food

Secretion- thymosins

Function- play role in immune system development. Differentiation of T-lymphocytes and production of antibodies

Secretion- glucocorticoids and mineralocorticoids (corticoids) from the adrenal cortex

Epinephrine and norepinephrine (catecholamines) from the adrenal medulla

Middle- zona fasciculata

Inner- zona reticularis

Secretes many hormones called corticoids or steroid hormones

Function- involved in carbohydrate metabolism and water and electrolyte balance

E.g. Cortisol

Function- stimulates gluconeogenesis, proteolysis, lipolysis, RBC production, anti-inflammatory reactions, inhibits cellular uptake and utilisation of amino acids and also helps in maintaining cardiac and kidney functions

E.g. Aldosterone

Function- maintenance of electrolytes, water and blood pressure, stimulates reabsorption of water and Na⁺ ions and excretion of K⁺ and phosphate ions

E.g. Androstenedione (A₄), Dehydroepiandrosterone (DHEA)

Function- weak androgenic activity, play role in the growth of axial, pubic and facial hair during puberty

Secreted by- adrenal medulla during the stress response

Function- induce flight or fight responses, alertness, sweating, increased heartbeat, respiratory rate, breakdown of glycogen, lipids and proteins

Islets of Langerhans secrete two peptide hormones

𝛼-cells- glucagon

β-cells- insulin

Function- increases glucose uptake and utilisation by hepatocytes and adipocytes causing hypoglycemia and also stimulates glycogenesis, i.e. conversion of glucose to glycogen

Function- acts on hepatocytes and induce glycogenolysis, i.e. breakdown of glycogen to glucose and gluconeogenesis leading to hyperglycemia

Secretion- androgens from the Leydig or interstitial cells

E.g. Testosterone

Function- development and maturation of male sex organs, spermatogenesis, secondary sexual characteristics, libido, anabolic effect on carbohydrate and protein metabolism

Secretion- estrogen from follicles and progesterone from corpus luteum

Function- development and maturation of female sex organs, secondary sexual characteristics, progesterone supports pregnancy and milk secretion and alveoli formation

Secreted by- atrial wall

Function- vasodilator, decreases blood pressure

Secreted by- juxtaglomerular (JG) cells of kidneys

Function- stimulates the formation of RBC, i.e. erythropoiesis

Secreted by- G-cells of stomach

Function- stimulates the secretion of HCl and pepsinogen

Secreted by- S-cells of the duodenum

Function- stimulates the secretion of pancreatic bicarbonate

Secreted by- I-cells of the duodenum

Function- stimulates the secretion of bile juice by the gallbladder and pancreatic enzymes

Secreted by- K-cells of the small intestine

Function- inhibits gastric secretion, stimulates insulin secretion

E.g. epidermal growth factor, fibroblast growth factor, etc.

Function- normal cellular growth, repair and regeneration