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175 Cards in this Set
- Front
- Back
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what does the endocrine system act with the ns to achieve? |
to coordinate and integrate the activity of body cells |
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how does the nervous system control body actions? |
through nerve impulses |
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how do nerve impulses occur? |
- ns releases neurotransmitters to excite or inhibit nerve, muscle and gland cells - results in milliseconds - brief duration of effects |
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what does the endocrine system do? |
controls body activities by releasing chemical messages called hormones |
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how long do the results of the endocrine system take? |
may take seconds, minutes or hours depending on the hormone |
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do the effects last longer or shorter than ns controls? |
longer |
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he endocrine system affects virtually all body tissues by... |
- altering metabolism - regulating growth and development - regulating reproduction - regulating circadian rhythms - regulate activity of smooth muscle, cardiac muscle, and glands |
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what are endocrine glands? |
small, widely separated glands in the body. They are ductless, well-vascularised glands that secrete hormones into the interstitial fluid. |
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what happens to the hormones that are secreted? |
they move into the blood and travel to virtually all tissues. |
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what does a hormone influence? |
the activity of specific target cells that have the exact receptors for it (lock and key concept) |
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what happens when a hormone binds to the receptor of a target cell |
changes the activity of that target cell |
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name three different types of hormones: |
- local hormones - lipid-soluble hormones - water-soluble hormones |
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name 2 types of local hormones: |
- paracrine hormones - autocrine hormones |
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what do paracrine hormones do? |
activate neighbouring cells |
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give 2 examples of paracrine hormones and their effects: |
- nitric oxide is produced by endothelial cells and promotes relaxation of smooth muscle in blood vessel walls - prostaglandins have many actions including increasing pain and inflammation |
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what do autocrine hormones do? |
activate the cell that produced them |
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where are water-soluble hormones (amino acid based) found? |
circulate freely in the blood |
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how do water-soluble hormones work? |
bind to receptors on cell membrane then alter the activity of intra-cellular enzymes |
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give some examples of water soluble hormones: |
- insulin - the catecholamines: adrenaline, noradrenaline, dopamine |
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why can insulin not be taken orally, it must be injected? |
because water soluble vitamins are destroyed by digestion |
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how do lipid soluble (steroid based) hormones work? |
diffuse into cell through cell membrane, and bind to receptors within the target cell. It then activates genes in cell which results in the formation of new proteins which alter the cell's activity. |
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give some examples of lipid-soluble vitamins: |
- steroid hormones oestrogen, testosterone - thyroid hormones |
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what are lipid-soluble vitamins carried in the blood by? |
transport proteins which prevent them from being active |
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why do lipid-soluble hormones bound to proteins remain in the blood for longer? |
because they are too big for glomerular filtration |
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what are lipid-soluble hormones called that travel freely and independently in the blood? |
free hormones |
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how do free hormones work? |
they bind to receptors in target cells, activating a response. |
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what does the transport protein then release? |
some of the bound hormone to replace the free hormone in the blood. |
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what does this free hormone system provide? |
a reserve of the lipid-soluble hormone |
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are lipid-soluble hormones digested? |
no but they are easily absorbed through the wall of the intestine. |
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so can oestrogen be taken orally? |
yes |
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what is the difference between exocrine glands and endocrine glands? |
exocrine glands secrete their products (eg. sweat, pancreatic enzymes) into ducts. The ducts then carry the secretion to the target site. endocrine glands secrete into interstitial fluid, then diffuse into the blood. |
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which gland is both an endocrine and exocrine gland? |
the pancreas |
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what makes the pancreas an exocrine gland? |
99% of pancreatic cells produce digestive enzymes which move through ducts to the small intestine |
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what makes the pancreas and endocrine gland? |
about 1-2 million tiny pancreatic islets produce glucose-regulating hormone which move into the blood |
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how are most hormones released? |
in short bursts with little or no secretion between the bursts |
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how are hormones released from stimulated endocrine glands? |
in more frequent bursts, which increases the concentration in the blood |
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what is the concentration of a hormone in the body also dependent on? |
the speed at which it is inactivated and removed from the body |
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home are hormones degraded or inactivated? |
- some hormones are degraded by enzymes in their target cells. - most hormones travel through the blood and are inactivated by the liver and excreted by the kidneys or in the faeces |
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what can kidney or liver failure lead to? |
built up levels of hormones in the blood |
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what is the synthesis and release of most hormones regulated by? |
negative feedback mechanisms |
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how does the negative feedback work? |
- an internal or external stimulus triggers hormone release - as the levels of a hormone rise it causes target organ effects which then feed back to inhibit further hormone release. |
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what is the result of the negative feedback mechanism? |
blood levels of many hormones vary only within a narrow range |
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what stimulates hormone secretion? |
three types of stimuli trigger endocrine gland production and release of hormones |
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what are the 3 types of stimuli? |
1. signals from the nervous system 2. levels of a chemical in the blood 3. another hormone |
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how do signals from the nervous system stimulate hormone release? |
the sympathetic nervous system sends impulses to stimulate the adrenal medulla to release adrenaline |
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2. how do the levels of a chemical in the blood stimulate release of a hormone? |
some endocrine glands secrete their hormones in direct response to changing levels of critical ions and nutrients |
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give an example of chemical levels stimulating release of a hormone: |
parathyroid glands detect low levels of blood calcium and increase their release of parathyroid hormone |
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what does parathyroid hormone cause? |
causes osteoclasts to resorb more bone and release calcium into the blood |
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how do other hormones stimulate release of hormones? |
many endocrine glands are themselves stimulated by hormones |
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give an example of a hormone released in response to another hormone: |
thyroid stimulating hormone from the anterior pituitary gland stimulates the thyroid gland to produce thyroxine |
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what gland is also known as the "master gland"? |
the pituitary gland |
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why is the pituitary gland also known as the master gland? |
because it secretes hormones and most of these control other endocrine glands |
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describe the size and shape of the pituitary gland: |
size and shape of a pea |
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where is it located? |
lies in a hollow of the sphenoid bone |
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how is it connected to the hypothalamus? |
by a stalk (the infundibulum) |
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what controls the pituitary gland? |
the hypothalamus |
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what does the pituitary gland consist of? |
a larger anterior lobe and a smaller posterior lobe |
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what does the posterior lobe of the pituitary gland receive? |
two ready-made hormones produced in the cell body of neurosecretory cells in the hypothalamus |
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what happens to the hormones? |
they are transported down the axons of the neurosecretory cells to their axon terminals in the posterior pituitary |
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what happens to the 2 hormones then? |
axon terminals in the posterior pituitary store these 2 hormones |
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when is the hormone released? |
when an action potential travels down the axon of the neurosecretory cells |
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what happens to the hormone once released? |
it diffuses into the blood vessels that surround the posterior pituitary gland |
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what are the two hormones? |
oxytocin and antidiuretic hormone |
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what does oxytocin do? |
travels through blood to the breast to stimulate the release of milk from the ducts of the breast. |
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what do nerve impulses do when a baby breast-feeds? |
nerve impulses from the breast travel to the hypothalamus |
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what happens then? |
neurosecretory cells in the hypothalamus send action potentials down their axons to the posterior pituitary. |
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what happens then? |
oxytocin is released from the axon terminals in the posterior pituitary, and it diffuses into the blood vessels. |
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what happens to the oxytocin released? |
travels through the blood to the breast where it stimulates the release of milk from the ducts of the breast. |
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is this a positive or negative feedback cycle? |
positive feedback |
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what stops the cycle? |
removal of the stimulus |
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what else does oxytocin also stimulate? |
contraction of the uterus during labour and breast feeding |
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what does anti-diuretic hormone do? |
- increases blood volume - decreases urine output |
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when is anti-diuretic hormone released? |
when osmoreceptors in the hypothalamus detect an increased concentration of solute in the blood (haemorrhage, diarrhoea, excess sweating) |
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what do the osmoreceptors do when they detect increased concentration of solutes in the blood? |
they transmit excitatory impulses to the neurosecretory cells |
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what do the neurosecretory cells do? |
generate nerve impulses that cause the release of ADH from vesicles in the axon terminals in the posterior pituitary. ADH levels then rise in the blood and travel to the kidney. |
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how many hormones does the anterior pituitary gland produce? |
six hormones |
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what is the release of each anterior pituitary gland hormone stimulated by? |
a releasing hormone from the hypothalamus |
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what can suppress these hormones sometimes? |
inhibiting hormones such as prolactin and growth hormone etc. |
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how does the hypothalamus send its controlling hormones to the anterior pituitary? |
through portal veins |
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what does this stimulate? |
the release of hormones synthesised in the anterior pituitary |
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what does the anterior pituitary gland secrete in response to releasing hormones? |
it secretes hormones into its own capillaries, which empty into the general blood circulation and affect target organs |
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Name the 6 hormones produced by the anterior pituitary: |
1. growth hormone GH 2. thyroid stimulating hormone TSH 3. adrenocorticotropic hormone ACTH 4. Follicle stimulating hormone FSH 5. Luteinizing hormone LH 6. Prolactin |
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what is the function of growth hormone? |
stimulates all body cells to enlarge and divide but its major targets are bone and skeletal muscle. |
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what does it stimulate? |
- epiphyseal plate so long bones lengthen - increase in muscle mass - tissue repair - breakdown of fat and rise in blood glucose (releases a lipid source of energy) |
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how is growth hormone controlled? |
a releasing hormone from the hypothalamus stimulates the anterior pituitary to release GH |
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what does hyposecretion of GH during growth years result in? |
dwarfism |
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what does hypersecretion during childhood result in? |
giantism |
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what does hypersecretion in adulthood result in? |
acromegaly - bones don't increase in length because epiphyseal plates are closed. - bones of hands, feet, cheeks and jaw grow |
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where is the thyroid located? |
just inferior to the larynx |
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what does thyroid stimulating hormone do? |
TSH from the anterior pituitary stimulates the thyroid gland to produce thyroxine |
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what does the thyroid gland contain? |
thryroid follicles |
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what do thyroid follicles do? |
produce thyroxine which is stored in the hollow lumen of the follicle |
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what does thyroxine do? |
increases basal metabolic rate |
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what does the thyroid produce? |
2 iodine-containing hormones |
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what are the two hormones? |
T4 (thyroxine) which contains 4 iodine molecules. then converted to T3 which is more potent and contains 3 iodine molecules |
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what is essential in a diet for synthesis of thyroid hormones? |
adequate iodine |
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how is thryoid hormone transported? |
99% is transported by globulins in the blood and in this form it is inactive |
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what does this mean? |
that very little thyroid hormone is left in the active state |
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function of thyroid hormones? |
- increase the basal metabolic rate - accelerate body growth, particularly nervous and skeletal system - enhance the effects of catecholamines (adrenaline and noradrenaline) |
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what can deficiency of thyroid hormones before birth or during childhood cause? |
severe mental retardation and stunted bone growth (cretinism) |
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what are 2 clinical connections to the thryoid? |
hyperthyroidism and hypothyroidism |
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what is hyperthyroidism? |
over-activity of the thyroid gland causing increased level of thyroxine and increased metabolic rate, rapid pulse, increased bp, increased temp and weight loss |
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what is hypothyroidism? |
causes decreased level of thyroxine and slow heart rate, low body temp, lethargy, weight gain etc. |
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who are these more common in? |
females |
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what can help reduce symptoms? |
oral thyroxine medication reduces symptoms |
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how can we ensure level of medication is correct? |
regular blood tests to check levels of free T3 and T4 |
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when is adrenocorticotrophic hormone released? |
when a person is physically stressed eg. hypoglycaemia, pain, injury |
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how is this hormone released? |
-hypothalamus releases adrenocorticotropin releasing hormone. - that then goes to the anterior pituitary. - anterior pituitary releases adrenocorticotropic hormone. - that goes to the adrenal cortex. - adrenal cortex releases cortisol |
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what does cortisol do? |
it is a glucocorticoid which under normal circumstances helps maintain: - blood glucose levels - vasoconstriction to ensure bp homeostasis - raise glucose levels - enhance sympathetic ns - anti-inflammatory effect but depresses the immune system and slows tissue repair and wound healing |
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when are dramatically higher levels of cortisol released? |
during stress involving haemorrhage, infection or physical/emotional trauma |
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how does cortisol raise blood glucose levels? |
through gluconeogenesis |
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how does it raise levels of fatty acids and amino acids in the blood? |
breakdown of proteins and lipids |
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who is cortisol prescribed to often? |
organ transplant patients to avoid organ rejection |
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what does follicle stimulating hormone do in females? |
- initiates development of oocytes in the ovarian follicles - stimulates the production of oestrogen |
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what does follicle stimulating hormone do in males? |
stimulates the testes to produce sperm |
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what does luteinizing hormone do in females? |
stimulates the production of oestrogen and progesterone in the ovaries |
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what does luteinizing hormone do in males? |
stimulates the testes to produce testosterone |
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what does prolactin do? |
- initiates and maintains milk production |
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what happens towards the end of pregnancy? |
prolactin levels rise dramatically |
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what produces adrenaline? |
adrenal medulla |
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what hormones regulate calcium levels? |
parathyroid hormone, calcitriol and calcitonin |
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what regulates blood glucose levels? |
insulin and glucagon |
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what regulates circadian rhythm? |
melatonin |
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where is aldosterone produced? |
adrenal cortex |
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when is adrenaline released? |
under stressful situations and exercise - fight or flight response |
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what do adrenaline and noradrenaline intensify? |
sympathetic nervous impulses: - increase rate and force of heart contraction - increase cardiac output - increase bp - increase blood flow to heart, liver and skeletal muscle - dilate airways - increase blood glucose levels |
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what is parathyroid hormone the main hormone for? |
controlling blood calcium level |
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what is precise control of calcium levels essential for? |
- transmission of nerve impulses - muscle contraction - blood clotting |
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what are the 3 main functions of parathyroid hormone? |
1. stimulates osteoclasts to resorb bone and raise blood calcium 2. enhances reabsorption of calcium by the kidneys 3. activates vit D to become calcitriol which is needed to absorb calcium from food |
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what produces calcitonin? |
parafollicular cells in the thyroid gland |
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what does calcitonin do? |
lowers blood calcium levels |
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how does it do this? |
- inhibits osteoclast activity - stimulates deposit of calcium into the bone |
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how is calcium absorbed from the GI tract? |
under the influence of calcitriol |
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how much calcium is absorbed and what happens to the rest? |
30-50% of dietary calcium is absorbed, the remainder is excreted in faeces |
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locations of calcium? |
- 99% stored in bone - 1% intracellular calcium - 0.1% extracellular calcium |
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how is calcium excreted? |
by the kidneys |
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vitamin D is classed as a ____________ but functions as a ________________ |
vitamin, hormone |
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describe synthesis of vitamin D: |
- modified cholesterol molecules in skin are exposed to UV converting them to inactive vit D. - vit D (inactive) also gained from diet - inactive vit d transported by the blood to the kidney. - converted by the kidney to calcitriol, the most active form of vit d. |
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function of calcitriol (active vitamin D): |
sustains normal levels of calcium and phosphate by: - increasing their absorption from the intestine. - enhances the actions of PTH which resorbs bone. |
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what are the two main regulators of glucose? |
insulin and glucagon |
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where are these two hormones produced? |
in the pancreatic islets |
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Insulin, the dominant hormone of the ________ state, ____________ blood glucose levels |
fed, lowers |
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when is insulin production increased? |
when blood glucose levels are high |
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glucagon, the dominant hormone of the __________ state, _________ the blood glucose levels |
fasted, raises |
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when is glucagon production increased? |
when blood glucose levels are low |
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what controls the release of insulin and glucagon? |
glucose levels in the blood |
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is it normal to have high levels of insulin and glucagon at the same time? |
no |
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blood glucose is lowered by... |
insulin |
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blood glucose is raised by... |
- glucagon - adrenaline - growth hormone - cortisol |
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why does adrenaline raise blood glucose levels? |
so that glucose is available for an emergency |
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how does growth hormone increase blood glucose levels? |
by stimulating lipolysis so that lipids are available for growth leaving glucose to be available for the brain |
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why does cortisol increase blood glucose levels? |
so that additional glucose is available to deal with stress situations |
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melatonin is an __________ _____________ |
amine hormone |
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what secretes melatonin? |
the pineal gland |
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where is the pineal gland located? |
attached to the roof of the 3rd ventricle |
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what does melatonin contribute to? |
the natural body clock |
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when are levels of melatonin highest and lowest? |
- peak levels at night causing drowsiness - low level before waking - lowest levels at noon |
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what suppresses melatonin secretion? |
bright light |
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who is levels higher in? |
children |
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some __________ helps us meet ___________ in life |
stress, challenges |
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what are stressors? |
heat, cold, environmental poisons, bacterial toxins, heavy bleeding, or a strong emotional reaction |
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what do homeostatic stress mechanisms do? |
attempt to counteract stress, it is controlled by the hypothalamus in 3 stages |
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what are the 3 stages? |
1. initial fight-or-flight response 2. slower resistance reaction 3. exhaustion |
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what initiates the fight or flight response? |
nerve impulses from the hypothalamus to the ANS |
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what does the fight or flight response do to the body? |
•Quickly provides large amounts of glucose& oxygen to brain,skeletal muscles & heart •Non-essential functions digestive,urinary & reproductive functions are inhibited. –Reducedblood flow to kidneys stimulates rennin AAS to produce aldosterone to raise BP |
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what initiates the resistance reaction? |
hypothalamic hormones for a longer lasting response |
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what do these hormones stimulate? |
•These hormones stimulate the productionof ACTH,GH & TSH bythe anterior pituitary.& |
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what do the actions of these hormones do? |
•The actions of these hormones help thebody continuefighting stressors longafter the fight-or-flight response dissipates. –Theheart pounds long after danger is removed. •Usually this helps us through a stressfulperiod until life returns to normal. |
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when does exhaustion occur? |
•Occasionally the resistance stage failsto combat the stressor & the body moves into the stage of exhaustion. |
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what does prolonged exposure to high levels of cortisol and other hormones do? |
•Prolonged exposure to highlevels of cortisol &other hormones involved in the resistance reaction causes wasting of muscle ,suppression of the immune system, ulceration of the gastrointestinal tract,& failure of the pancreatic beta cells which produce insulin. |
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what are people under stress at greater risk of? |
developing chronic disease or dying prematurely |
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age related changes.. |
•Most endocrine organs operate smoothlyuntil old age when •Growthhormone decreases allowingmuscle atrophy •Thyroid gland decreases production of thyroidhormones –Decreasein metabolic rate –Increasein body fat |
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cont.. |
•PTH rises possibly due to lower calciumdiet –Osteoporosis& fractures may result •Adrenal cortex produces less aldosterone& cortisol •Adrenal medulla continues to producenormal levels of adrenaline |
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cont... |
•Pancreas releases insulin more slowly& cells are not as responsive to insulin(insulin resistance)
–Bloodglucose levels increase more quickly after eating & are slower to return tonormal•Ovaries become unresponsive to FSH &LH so decreaseoestrogen production –Osteoporosis –Highblood cholesterol & atherosclerosis |
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cont.. |
•Testosteronelevels decline buteffects aren’t apparent until very old age. –Spermcan still be produced in normal numbers but there is higher numbers of abnormalsperm & decreased motility •Reducedfertility |
