Introduction to the Endocrine System Flashcards
What are the major endocrine glands?
→ Hypothalamus → Pituitary → Thyroid → Adrenal cortex → Gonads → Pancreas → Parathyroid glands
What is the function of the hypothalamus?
→ Releases and inhibits hormones
What are the two lobes of the pituitary and what hormones do they secrete?
→ Anterior - trophic hormones (growth)
→ Posterior - oxytocin & vasopressin
What hormones does the thyroid secrete?
→ Thyroxine T4
→ tri-iodothyronine T3
What are the two parts of the adrenal gland and what do they secrete?
→ Cortex - cortisol + aldosterone
→ Medulla - adrenaline/noradrenaline
What hormones do the gonads produce?
→ Estrogens
→ Androgens
→ Progestagens
What hormones does the pancreas secrete?
→ Insulin
→ Glucagon
What hormone does the parathyroid gland release?
→ Parathyroid hormone
What are other hormones that are important?
→ EPO + vit. D (hormone) → ANP, endothelins (CVS) → Melatonin (Pineal gland) → Thymic hormones (thymus) → phosphate (bones) → Leptin (adipose tissue)
What is endocrine signalling?
→ hormones released into circulation and acting on distant target sites
What is paracrine signalling?
→ Hormones released by endocrine cells that act locally on adjacent cells
What is autocrine signalling?
→ Hormones released by a cell which acts on itself
What is intracrine signalling?
→ Conversion of an inactive hormones to an active hormone that acts within that cell
What are the three general functions of hormones?
→ Reproduction, growth and development
→ Maintenance of internal environment
→ Energy production, utilization and storage
What are the hormones involved in reproduction, growth and development?
→ Sex steroids, thyroid hormones, prolactin, growth hormone
What are the hormones involved in maintenance of the internal environment?
→ Aldosterone
→ Parathyroid hormone
→ Vit. D
What are the hormones involved in energy production, utilization and storage?
→ Insulin → Glucagon → Thyroid hormones → Cortisol → Growth hormone
What are protein/peptide hormones?
→ hypothalamic
→ pituitary
→ Insulin, PTH, calcitonin
What are steroid (cholesterol) hormones?
→ Cortisol
→ Aldosterone
→ estrogens
→ Androgens
→ Progestagens
→ Vit. D
What are amino acid derivatives ( tyrosine/tryptophan) hormones?
→Adrenaline
→ Noradrenaline
→ Thyroid hormones
→ Melatonin
WHat are fatty acid derivative hormones?
→ Prostaglandins
→ Thromboxanes
→ Prostacyclins
What are protein and peptide hormones secreted as?
→ Prohormones
Why are there similarities within peptide hormones?
→ Common ancestral gene
How is cholesterol formed?
→ Steroid nucleus
→ Carbon 20 the molecule gets cleaved and the backbone form
What is the half life of protein and peptide hormones and how are they transported?
→ HL : minutes
→ Transport : unbound
What is the half life of tyrosine derivatives and how are they transported?
→ HL: Seconds - Hours
The iodination affects the half life and solubility- thyroid hormones so their t1/2 is hours
→ Transport : Thyroid hormones are bound to plasma proteins
What is the half life of cholesterol derivatives and how are they transported?
→ HL: Hours- days
→ Transport : Bound to plasma proteins
What is the neuroendocrine integration?
→ Nerves
→ Hormones
→ Effector organs
Describe the hypothalamic -pituitary axis?
→ Hypothalamus - releases neurohormones
→ Goes to pituitary gland
→ Pituitary gland releases TSH, FSH, ACTH
→Stimulates the endocrine organs
What does corticotrophin releasing hormone (CRH) stimulate?
→ Released from hypothalamus
→ acts to increase adrenocorticotrophic hormone (ACTH) in the anterior pituitary
What does thyroid releasing hormone stimulate?
→ TRH increases TSH in anterior pituitary
What does GnRH stimulate and where?
→ GnRH from the hypothalamus (gonadotrophin releasing hormone) increases LH and FSH in anterior pituitary
What does dopamine inhibit and where?
→ Dopamine from hypothalamus decreases prolactin in anterior pituitary
What does GHRH stimulate and where?
→ GHRH from hypothalamus (growth hormone releasing hormone) stimulates GH in anterior pituitary
What does GHIH inhibit and where?
→ GHIH from hypothalamus ( growth hormone inhibiting hormone) inhibits GH in anterior pituitary
How does feedback control of hormone synthesis work?
→ Negative feedback
How are hormones released?
→ Pulsatile release → Circadian → Diurnal → Monthly → Annual
What hormone rises when you sleep?
→ Growth hormone
What hormone is independent of the diurnal variation?
→ Cortisol
What are the 4 disorders of the endocrine system?
→ Excess or deficiency
→ Impaired synthesis
→ Transport and metabolism of hormones
→ Resistance to hormone action
What is excess growth hormone called?
→ Acromegaly
Prominent features
What are other diseases that are regulated by cortisol?
→ Addisons - lack
→ Cushings - excess
What does cortisol regulate in the body?
→ Gluconeogenesis
→ Protein mobilization
→ Fat mobilization
→ Anti-inflammatory effects
What is complete resistance to circulating androgens called?
→ Testicular feminization
What is vitamin D resistance called?
→ Rickets
What are magnocellular cells?
in the hypothalamus synthesise and release posterior pituitary hormones
What is the difference between the anterior and posterior pituitary gland?
→ Neuroendocrine neurons in the hypothalamus project axons to the median eminence, at the base of the brain.
→ these neurons can release substances into the small blood vessels that travel directly to the anterior pituitary gland (the hypothalamo-hypophysial portal vessels).
→ The posterior pituitary consists mainly of neuronal projections ( axons ) extending from the supraoptic and paraventricular nuclei of the hypothalamus.
→ These axons release peptide hormones into the capillaries of the hypophyseal circulation.
