Lecture 13: Endocrine Major Glands and Hormones Flashcards
What is the endocrine system? what is Paracrine? Autocrine? Neuroendocrine? Gland?
Endocrine: refers to a hormone that is
-Produced and decorated w/in the body could be via blood
-Opposite of exocrine which is secreted outside body (mammary gland, lumen of digestive tract etc)
-Acts at a distance from the release site
Paracrine:acts on nearby cells (locally)
Autocrine: acts on its own secreting cells
Neuroendocrine: Synthesized by nervous tissue and carried in the blood (neurotransmitter in blood)
Gland: cluster of cells organized for synthesis/release of compound
-Glands can be endocrine or exocrine
What are hormones?
-Regulatory chemicals produced in an endocrine gland or scattered cells, secreted into the blood and carried to its target cell that respond by altering its metabolism
-Involved in maintaining homeostasis (slower and long lasting effect)
-Subjected to tight regulation by feedback from target organs
-Regulation of hormones synthesis and mode of action differ greatly based on their structure (biochemical structure)
What kind of control is involved in the endocrine system?
Feedback loops: cyclic systems (loops) that control the amount of hormone released
Mainly Negative feed back: to maintain homeostasis
Occasionally positive: Want to get out of cycle, so brings the body out of range to achieve specific action (ovulation)
What is the first structural classification of hormones?
Steroid hormones: Lipid soluble
-Stepwise conversion of cholesterol by multiple enzymes
-Lipid-soluble= leave production cells and enter target organ by diffusion through the membrane (hard to travel in blood bc you have to be water soluble so needs a carrier in blood, but if you are water soluble need receptor to allow you in/out of membrane when entering or leaving the blood)
What is the second structural classification of hormones?
Peptides, proteins, glycoproteins water sol
-Chains of AA: the sequences determines the primary structure and nature
-DNA goes through transcription, then mRNA goes through translation to become a protein and then its further modified to glycosylation or phosphorylation
-Genetic code=3 base sequences code for 1 AA
-Glycosylation =carbohydrate chains attached
-Phosphorlation =phosphate group attached
-Modified, packaged in the E.R and Golgi
-Secreted by exocytosis (controlled release, active process)
What is the third structural classification of hormones?
Amino Acid derivatives water sol (thyroid hormones, catecholamines):
-Generally derived from tyrosine and tryptophan (depends on modification)
-ex dopamin, norepinephrin, epinephrin can be considered a group of neurotransmitter
What is the fourth structural classification of hormones?
Fatty acid derivatives to eicosanoids (prostaglandins) lipid soluble
-Derived from cell membrane phospholipids (arachidonic acid)
-Produced locally, have mainly autocrine, paracrine effects
-ex prostaglandins, prostacyclins, thromboxanes
What are some of the major endocrine glands?
-Pineal gland
-Hypothalamus
-Pituitary
-Parathyroid glands
-Thyroid gland
-Pancreas
-Liver
-Adrenal gland
-Kidney
-Ovary
-Placenta
-Testes
-Adipose tissue
-Stomach wall
-Small intestine
-Skin
Explain the role of the pineal gland and why it’s important.
-on the roof of the 3rd ventricle, encapsulated by meninges
-Secretes melatonin (synthesis based on enzymes)
-Under the indirect influence of the hypothalamic circadian centre
-Major role during sleep patterns and recognition of seasons
-Melatonin secretion is stimulated during dark phases
-Signal goes from eye, through NS to pineal gland (mammals)
Explain the role of the gastrointestinal (stomach and small intestine) tract and what hormones they secrete.
Stomach
-Stomach wall secretes the hormone gastrin which stimulates acid secretion locally (food coming in and need more acid gastrin will help)
Small intestine
-Secretes secretin which stimulates the pancreas
-secretes Cholecystokinin which stimulates pancreas and gall bladder
-secretes gastric inhibitory peptide (GIP) which inhibits stomach activity
Explain the role of the kidneys and what hormones they secrete.
-Secrete renin which increases aldosterone secretion by adrenal cortex
-Erythropoietin which increases production of red blood cells in bone marrow
Explain the role of adipose tissue and what hormones they secrete.
-Adipocytes release leptin and other adipokins
-Leptin receptors can be found in the hypothalamus
-Give info about energy storage status
-Regulates appetite
