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43 Cards in this Set

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What are the organs considered to be part of the classical endocrine system?
-hypothalamus
-pituitary gland
-thyroid gland
-parathyroid glands
-thymus
-adrenal glands
-pancreas
-ovaries (female)
-testis (male)
What are hormones?
-they are biochemical substances that exert a physiological effect
-they are messengers secreted into blood or body fluids to target organ/cell
What are the four ways that hormones work?
-exocrine
-paracrine
-endocrine
-autocrine
How do exocrine hormones work?
secreted externally or into a duct, affect distant targets
How do paracrine hormones work?
secreted by one cell, acts on an adjacent cell in the same tissue. affects cells of a different type.
How do endocrine glands work?
secreted internally
How do autocrine hormones work?
factor acts on the same cell (itself), a cell of the same type.
What is the HPT Axis?
hypothalamic-pituitary-target organ
-to control protein synthesis is to control cell metabolism, intra/intercellular transport, F&E balance, growth & development, reproduction.
For a hormone to have an action it must first interact with a what?
receptor
What is receptor up-regulation?
when there is a low hormone concentration it causes the cell to increase the number & sensitivity of receptors
What is receptor down-regulation?
when there is a high hormone concentration is causes the cell to decrease the number & sensitivity of receptors
What are the characteristics of water soluble hormones?
large, high molecular weight molecules that cannot readily pass through the cell membrane.
How do water soluble hormones interact with the cell?
they activate the receptors on the plasma membrane (PM)
What are the characteristics of lipid soluble hormones?
-bound to plasma proteins
-fat soluble
-freely dissolve through lipid bi-layer of the PM
-steroids
How do most lipid‐soluble hormones regulate protein synthesis?
at the level of RNA transcription
Describe negative feedback.
-most common method of hormonal control
-rising level of hormone will feed back to the source glad to shut down further production
Describe positive feedback.
-a mechanism in which hormone stimulates the production of more hormone until a physiologic action occurs (ie. menstrual cycle & male ejaculation)
Why do hormones go bad?
-failure of feedback mechanism
-hyporesponsiveness
-hyposecretion
-hypersecretion
-target cell may fail to respond
What is primary gland failure?
-gland fails
-inadequate hormone produced
-blood level of gland secreted hormone is too low
-tropic hormones are high
What would tropic vs. peripheral hormone levels be with primary gland failure?
-tropic hormones are high
-peripheral hormones are low
What is secondary gland failure?
-hypothalamus/pituitary fails to stimulate tropic hormone
What would tropic vs. peripheral hormone levels be with secondary gland failure?
-tropic hormones are low
-peripheral hormones are low
Growth hormone equals what?
somatotropin
What does GH do physiologically?
stimulates nutrient metabolism & tissue growth
What is GH target organ?
liver
What does the thyroid gland secrete?
-T3 (3 atoms of iodine)
-T4 (4 atoms of iodine)
-structurally they are similar but T4 is more potent
What is the function of thyroid hormone?
-stimulation of energy production
-stimulation of the heart & inotropic/chronotropic
-promotion of growth & development of the brain & other nervous system components and the development of skeletal mm.
How does the HP Axis apply to the thyroid?
-hypothalamus
-TRH (releasing hormone)
-anterior pituitary
-TSH
-thyroid gland
-T3, T4, thyroglobulin
What is necessary for T3/T4 production?
iodine
What hormone is secreted from zona glomerulosa?
aldosterone
What hormones are secreted from zona fasicularis?
glucocorticoid = cortisol
What hormone is secreted from zona retucularis?
adrenal androgen
What are the three zones/layers of the adrenal cortex?
-zona glomerulosa
-zona fascularis
-zona retucularis
Reminder: What is secreted from the adrenal medulla?
epinepherine
What is important to remember about glucocorticoids and mineralocorticoids?
glucocorticoids can sometimes fill the receptor of a mineralcorticoid. they are basically a "good enough" fit for each other.
What are the physiologic effects of cortisol?
-anti-inflammatory: inhibits activity of phospholipase A2, thus reducing LT, PG production
*decreased capillary permeability of WBC
*decreases immune system function
-metabolic effects
*raises blood glucose for immediate use
*glucogenesis from AA's
*increased appetite
What are the main functions of cortisol?
-increase blood sugar
-suppress the immune system
-aid in fat, protein & carbohydrate metabolism
How do the adrenal glands fit into the HP Axis?
-hypothalamus is stimulated (stress, infection, pain, sleep, trauma)
-hypothalamus releases corticotropin-releasing hormone (CRH)
-CRH acts on the anterior pituitary
-ACTH is released and acts on adrenal cortex
-adrenal cortex releases cortisol
-cortisol acts on target organ(s)
Why is cortisol secretion critical for survival?
-it is critical to balance stress in the body.
-without cortisol the body will not balance to homeostasis during stressors.
-cortisol helps protect from damaging effects of stress by suppressing inflammation/immunity
How many parathyroid glands are there?
four
What do the parathyroid glands do?
-regulate Ca++
-parathyroid hormone (PTH) acts on bones & renal tubules to cause increase in Ca++ levels
What is the function of PTH?
-increase osteoclast activity
-increase release of Ca++ from bone matrix to ECF
-increase renal Ca++ reabsorption
-activates vitamin D
What is the function of calcitonin?
it is the antagonist of PTH (does the opposite)