Endocrine System

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  • Created by: gec114
  • Created on: 20-04-16 16:58
Secreted from endocrine glands. They are chemical messengers that affect specific target cells. They circulate in the blood stream and regulate body processes. Generally target cells far away from site of production.
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Neuroendocrine system
nerves release substances into the blood stream for activation of distant targets.
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Specialized cells release hormones that circulate within the blood stream to initiate activity in distant target cells.
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Hormones are released by one cell and are effective on the neighbouring cells. e.g. during blood clotting.
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A cell releases hormones which are then effective on that same cell.
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Specialized cells release substances into ducts which are directly connected to the external environment. (body is modeled like a doughnut so gut is external)
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Hydrophilic hormones
Soluble in water but not fat. Can travel independently in the blood but cannot enter the cell. Receptor in the cell membrane which activates a messenger cascade which can amplify the signal. PEPTIDES
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Hydrophobic hormones
Soluble in fat but not water. Need carrier molecules to travel in the blood but can easily diffuse into the cell. Receptors are in the cytoplasm or nucleus. Stimulate/modify transcription. The receptor is switched off by cellular enzymes. STERIODS
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Inputs that Control Hormone Secretion
->Change in plasma concentration of minerals or organic nutrients -> neurotransmitter release from nerve cell. -> Trophic hormones
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Control of Hormone Inactivation
-> Enzymes in the liver and blood destroy hormones -> receptor-hormone complex is destroyed by the cell.
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too little hormone : -> primary - gland doesnt produce enough ->secondary - gland doesnt recieve enough tropic hormone
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too much hormone: ->primary - gland produces too much hormone -> secondary - excessive stimulation of the gland by its tropic hormone.
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reduced responsiveness in target cells
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increased responsiveness in target cells
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Hypothalmic-pituitary axis
The hyperthalamus and pituitary gland secrete a range of hormones. they are connected by the pituitary stalk.
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Posterior lobe
Part of the pituitary gland. Hormones are synthesized in cell bodies in the hypothalamus and these terminate in the posterior lobe. Here it is packed into vesicles and stored in the neuron terminals. Upon stimulation they are released into the blood.
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Hormones of the Posterior lobe
OXYTOCIN-delivery of milk, contraction of uterine smooth muscle. VASOPRESSIN -constricts blood vessels (increases blood pressure), acts in the kidney to reduce water loss through the urine.
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Anterior lobe
Part of the pituitary gland. Neuro-secretory cells in the hypothalamus secrete hypophysiotropic hormones in to the hypothalamo-pituiitary portal to the anterior lobe. Stimulates further hormone release.
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growth hormone releasing hormone. Stimulating the release of human growth hormone from the anterior lobe.
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growth hormone inhibiting hormone. Inhibiting for the anterior lobe
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Thyrotopin releasing hormone. Stimulates FSH release from the anterior lobe
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Gonadotropin releasing hormone. Stimulates the release of Luteinising hormone from the anterior lobe.
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dopamine. inhibiting for the anterior lobe, prolactin is released.
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Corticotropin releasing hormone. Stimulating for the anterior lobe. releases adrenocorticotrophic hormone.
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Stress hormone. Has an anti-growth effect where in extreme situations the bone is broken down and growth hormone secretion is inhibited.
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Hormones for sexual development and reproduction
GnRH, FSH, LH. the concentrations of these in the body vary greatly depending on what stage of life you are in.
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Effects of testosterone in males
spermatogenesis, sex drive, bone growth, negative feedback means the hypothalamous reduces GnRH secretion also the anterior pituitary reduces LH secretion.
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Located in the neck and has two lateral lobes. It contains thyroid follicles surrounded by follicular cells which secrete thyroglobullin. Thyroid cells have iodine pumps in their membranes (hormone production requires iodine)
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Thyroid hormones
THR -> thyrotropin releasing hormone, THS -> thyroid stimulating hormone, T3 and T4
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thyroid hormone level above normal. Causes a rapid, irregular heart beat; sweating; nervousness and excitability; muscle weakness and fatigue; weight loss.
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Graves disease
spontaneous formation of antibodies which imitate TSH and continuously stimulate the thyroid. The thyroid behaves as if TSH levels are high when the thyroid output is inhibiting TSH release. Failure in the feedback loop.
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thyroid hormone level below normal. In adults it causes muscle weakness; slow heart; weight gain. In children it leads to dwarfism and mental retardation.
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Adrenal gland
Has an outer region (CORTEX) which produces steroid hormones and an inner region (MEDULLA) which produces amine hormones.
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Medullary hormones
Tyrosine based. Mainly adrenalin and nor-adrenalin, Their function is to respond to stress and emergencines. flight or fight.
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Coritcal hormones
Androgens- sex hormones, important for puberty, all oestrogen comes from the conversion of adrenal androgens; Aldostrone- sodium and potassium regulation in the kidney; Cortisol - related to stress, immune system development and organic metabolism.
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control water, sodium and potassium levels, regulates levels leaving through the kidney. Main example is aldosterone. stimulates reabsorption of Na+ in the kidney and absorption in the salisa, perspiratoin and gut. Na+ pumping activity is enhaned
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Gluocorticoids (cortisol)
stressors increase levels of ACTH released leading to increased cortisol. leads to: metabolic effects- ensures energy is available; enhanced effect adrenaline - increases blood pressure; decreased immune response; grossly defincient response = death
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Adrenocorticotrophic hormone. Released from the pituatory gland.
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Metabolic effects of cortisol
stimulates gluconeogenesis (formation of glucose from amino acids); protein catabolism (breaking down protein sources e.g. muscles) to mobilise amino acids; promotes mobilisation of fatty acids into the plasma from adipose tissue
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Control of cortisol level
negative feedback. corticotrophin releasing hormonne (CRH) and ACTH cause the production and release of cortisol.
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Chromaffin cells
in the medulla. secrete 80% adrenaline and 20% nor-adrenaline into local capillaries. activated by sympathetic fibres. In stress situations catecholamines which increases blood pressure etc. enforces fight/flight but lasts longer.
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Islets of Langerhams
Found in the pancreas. alpha cells - glucagon (raise blood glucose) beta cells- insulin (reduces blood glucose) delta cells - somatostatin (inhibits secretion of insuling, glycagon and gut hormones) F cells.
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stimulus - high blood glucose. strong negative feedback. increases glucose uptake by the muscles where it is stored as glycogen is not used. glucose uptaken by liver and stored. promotes conversion of glucose to fatty acids and fat storage.
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stimulus - low blood glucose. targets the liver. stimulates: breakdown of gycogen to glucose, synthesis of glucose from amino acids, release of glucose form the liver.
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Calcuim homeostasis
too much- suppressed neuromuscular excitability, cardiac arrhythmia. too little - nureomuscular excitability. regulated by: parathyroid hormone (PTH), calcitrol (stimulates the intestinal absorption of Ca2+), Calcitonin (inhibits osteoclasts,)
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Parathyroid hormone.
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lowers Ca2+ levels, weaker than PTH. reduces activity and production of osteoclasts. Only important in childhood.
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Card 2


nerves release substances into the blood stream for activation of distant targets.


Neuroendocrine system

Card 3


Specialized cells release hormones that circulate within the blood stream to initiate activity in distant target cells.


Preview of the back of card 3

Card 4


Hormones are released by one cell and are effective on the neighbouring cells. e.g. during blood clotting.


Preview of the back of card 4

Card 5


A cell releases hormones which are then effective on that same cell.


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