ENDOCRINE SYSTEM
Chemical coordination: Slow, prolonged process of communicating information through body by
chemicals (hormones), secreted by endocrine glands
Hormone: Organic substance (protein/steroid) secreted by endocrine gland and carried in
bloodstream to target organ to regulate metabolic reactions.
Target Organ: Specific cells that respond to a given hormone and have receptor sites for that
hormone.
Endocrine gland: Vascular, ductless gland that secretes hormones carried in bloodstream to target
organs
• Exocrine gland: Secretions carried in ducts eg. liver, salivary glands
• Endocrine gland: No ducts; secretions carried in bloodstream to target organs eg. adrenal glands
Endocrine glands in the body:
, 1) Hypothalamus:
Part of brain, above pituitary gland. Secretes ADH (Anti-diuretic hormone)
• Osmoreceptors in blood vessels of hypothalamus detect increase in osmolarity (low water levels)
of blood
• Hypothalamus responds & releases ADH
• Helps to conserve water if body is dehydrated; causes more water to be reabsorbed into blood
from kidney (less water lost as urine)
2) Pituitary gland - 'master gland':
• Chemical co-ordinator of other endocrine glands
• Attached to hypothalamus by a short stalk
• Secretes:
- TSH (thyroid stimulating hormine): Stimulates thyroid to secrete thyroxin
- FSH (follicle stimulating hormone): Stimulates oogenesis in ovary & spermatogenesis in testis
- LH (luteinizing hormone): Stimulates ovulation from ovary & formation of corpus luteum
- Prolactin: Stimulates production of milk in mammary glands after birth
- ACTH (adrenocarticotropic hormone): Stimulates adrenal cortex to secrete cortisone and
aldosterone
- ICSH (interstitial cell stimulating hormone): Stimulates testis to secrete testosterone
- GH/STH (growth hormone/somatotrophic hormone): Promotes skeletal & muscular growth
Growth disorders:
• Hypersecretion: over secretion of hormone
• Hyposecretion: under secretion of hormone
• In prepubertal children:
- Hypersecretion of GH: Gigantism (caused by tumour in pituitary)
- Hyposecretion of GH: Pituitary dwarfism (can be treated with STH - synthetic growth hormone)
Chemical coordination: Slow, prolonged process of communicating information through body by
chemicals (hormones), secreted by endocrine glands
Hormone: Organic substance (protein/steroid) secreted by endocrine gland and carried in
bloodstream to target organ to regulate metabolic reactions.
Target Organ: Specific cells that respond to a given hormone and have receptor sites for that
hormone.
Endocrine gland: Vascular, ductless gland that secretes hormones carried in bloodstream to target
organs
• Exocrine gland: Secretions carried in ducts eg. liver, salivary glands
• Endocrine gland: No ducts; secretions carried in bloodstream to target organs eg. adrenal glands
Endocrine glands in the body:
, 1) Hypothalamus:
Part of brain, above pituitary gland. Secretes ADH (Anti-diuretic hormone)
• Osmoreceptors in blood vessels of hypothalamus detect increase in osmolarity (low water levels)
of blood
• Hypothalamus responds & releases ADH
• Helps to conserve water if body is dehydrated; causes more water to be reabsorbed into blood
from kidney (less water lost as urine)
2) Pituitary gland - 'master gland':
• Chemical co-ordinator of other endocrine glands
• Attached to hypothalamus by a short stalk
• Secretes:
- TSH (thyroid stimulating hormine): Stimulates thyroid to secrete thyroxin
- FSH (follicle stimulating hormone): Stimulates oogenesis in ovary & spermatogenesis in testis
- LH (luteinizing hormone): Stimulates ovulation from ovary & formation of corpus luteum
- Prolactin: Stimulates production of milk in mammary glands after birth
- ACTH (adrenocarticotropic hormone): Stimulates adrenal cortex to secrete cortisone and
aldosterone
- ICSH (interstitial cell stimulating hormone): Stimulates testis to secrete testosterone
- GH/STH (growth hormone/somatotrophic hormone): Promotes skeletal & muscular growth
Growth disorders:
• Hypersecretion: over secretion of hormone
• Hyposecretion: under secretion of hormone
• In prepubertal children:
- Hypersecretion of GH: Gigantism (caused by tumour in pituitary)
- Hyposecretion of GH: Pituitary dwarfism (can be treated with STH - synthetic growth hormone)
