131207
| Question | Answer |
| Functions of the endocrine system | Communication system, vital to homeostasis, regulates long term processes, cells release secretions into extra-cellular fluid, controlled by negative feedback |
| Glands involved | Hypothalamus, pituitary gland, pineal gland, thyroid gland, parathyroid glands, thymus gland, adrenal glands, |
| Primary organs involved | Pancreas, ovaries, testes |
| Secondary organs/glands involved | Heart, thymus, kidneys, adipose tissue, gonads, digestive tract |
| Methods of stimulation | Neural (nerve fibres), hormonal (primary and secondary), hormonal (presence of products in blood) |
| Hormones- key facts | Released into bloodstream for transportation, can alter metabolism (locally or body-wide), calls have specific receptors for each hormone, aim to preserve homeostasis |
| Three groups of hormones | Amino acid derivatives, peptide hormones, lipid derivatives |
| Recycling of hormones | Remain functional for <1 hour, diffuse out of bloodstream and bind to cells, broken down or absorbed by liver and kidneys, broken down by enzymes in plasma and interstitial fluid |
| Changes hormones make within cells | Identity, activities, quantities |
| Cell membrane receptors | Needed for hormones which aren't limited soluble so cannot cross the membrane (adrenaline, peptide hormones etc), receptor proteins on the outer surface, these are first messengers |
| First/second messengers | First messengers lead to second, may act as enzyme activators, inhibitors or cofactors, can change rates of metabolic reactions |
| Important second messengers | Cyclic-AMP (cAMP), cyclic-GMP (cGMP), calcium ions (these are broken down very quickly) |
| Intra-cellular receptors | For hormones which are lipid soluble, receptor proteins on the inner surface of the membrane, commonly involved with DNA and genetic activity |
| Intra-cellular receptors | For hormones which are lipid soluble, receptor proteins on the inner surface of the membrane, commonly involved with DNA and genetic activity |
| Types of negative feedback | Directly- changes in extracellular fluid, indirectly- through hypothalamus |
| Three ways in which the hypothalamus controls the system | Controls the release of adrenal medulla through nerve stimulation, acts as a gland to release ADH and oxytocin into the bloodstream, secretes regulatory hormones to be transported to endocrine cells |
| Pituitary gland- key facts | Regulates many of the endocrine organs, releases 9 different peptide hormones, uses cAMP as a 2nd messenger, divided into anterior and posterior sections |
| Thyroid gland- key facts | Lies anterior to the larynx, consists of two lobes, connected by the isthmus |
| Parathyroid gland- key facts | Regulates blood calcium levels, parathyroid hormone raises calcium ion levels, speeds bone breakdown and slows kidney loss, |
| Adrenal glands- key facts | Lies superior to each kidney, divided into adrenal cortex and adrenal medulla, produces hormones that adjust metabolic rate (corticosteroids) |
| Pineal gland- key facts | Lies posterior of the third ventricle of the brain, synthesizes melatonin |
| Pancreas- key facts | Lies between the stomach and small intestine, contains islets of Langerhans and exocrine cells, responsible for insulin (beta cells) and glucagon (alpha cells) |
| Testes- key facts | Produce androgens in interstitial cells, secretes inhibin (supports differentiation and matures sperm) in nurse cells |
| Ovaries- key facts | Produce estrogen, follicle cells release progesterone and reorganize into corpus luteum after ovulation |
| Secondary organs- intestines | Secrete hormones to control digestion |
| Secondary organs- kidneys | Secrete three hormones e.g. EPO |
| Secondary organs- heart | Specialised muscle cells secrete ANP to lower blood volume or pressure |
| Secondary organs- thymus | Secretes thymosins to control immune system defenses |
| Secondary organs- adipose tissue (fat) | Secretes leptin to control appetite and resistin to reduce insulin response |
| Three phases of the stress response | Alarm phase (fight or flight), resistance phase (long term metabolic adjustments), exhaustion phase (collapse of vital systems) |
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