Introduction to Endocrine Systems

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  • Created by: LBCW0502
  • Created on: 24-09-19 09:28
State the glands in the endocrine system and function (11) -1
Testis (testosterone), parathyroids (regulate Ca level in blood), hypothalamus (controls pituitary), pineal (melatonin, circadian rhythm), pituitary (hormones), thyroid (metabolism), ovary (oestrogen/progesterone), adrenal glands (fight/flight)
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State the glands in the endocrine system and function (11) - 2
Pancreas (regulates level of sugar in the blood)
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What are the functions of the endocrine system (4)? -1
Development (proliferation, growth, differentiation, organogenesis). Reproduction (sexual maturation/behaviour, maintenance of pregnancy, lactation), metabolism (carbohydrate, energy storage, metabolic rate, temperature)
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What are the functions of the endocrine system (4)? -2
Homeostasis (water balance, salt levels, blood volume, pressure)
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Outline how the endocrine system works? (1)
Hormones (messenger molecules). Alter specific structure/activity of target cell by binding to specific hormone receptors (stimulate DNA synthesis, affect transcription/translation of mRNAs, affect channel proteins/enzymes by modifying shape).
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Outline how the endocrine system works? (2)
Help the body to maintain a constant internal environment (homeostasis)
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What is a hormone? (1)
A substance secreted by cells of endocrine glands/tissues that regulates the activity of other cells in the body
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What is a hormone? (2)
Hormones are released into the bloodstream, transported to their distant target tissues in the blood and act on target tissues through specific receptor. Different target tissues express receptors for different hormones
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What are the three types of hormones?
Amino acid derivatives (structurally related to amino acids e.g. noradrenaline). Peptides (short/long chains of amino acids e.g. oxytocin, insulin). Lipid derivatives (from cholesterol/steroid,arachidonic acid/eicosanoids, testosterone/progesterone)
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Amino acid derived hormones are based on which two amino acids?
Tyrosine or tryptophan
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Give examples of amino acid derived hormones based on tyrosine (2)
Thyroid hormones e.g. T3 and T4 both produced by the thyroid glands. Catecholamines e.g. adrenaline, noradrenaline, dopamine
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Give an example of an amino acid derived hormone based on tryptophan
Melatonin, produced by the pineal gland
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Describe the interaction of amino acid derived hormones with hormone receptors (1)
All but thyroid hormones bind to cell membrane receptors. Binds to GPCRs, activation of second messenger (e.g. cAMP, cGMP, Ca2+) in cytoplasm to trigger hormone response
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Describe the interaction of amino acid derived hormones with hormone receptors (2)
Thyroid hormones cross the plasma membrane (via transport protein or diffusion). Binds to intracellular (cytoplasmic) receptors, triggers transcription/mRNA production. Binds to receptors at mitochondria (increase ATP production)
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Give examples of peptide hormones
Oxytocin, ADH, polypeptides (insulin, GH), glycoproteins (LH, FSH, TSH)
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Describe the regulated secretion of peptide hormones (1)
Cell stores hormone in secretory granules and releases them in bursts when stimulated (e.g. insulin). Synthesis (preprohormone - prohormone), packaging (prohormone - hormone), storage (hormone), secretion (hormone/pro fragments)
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Describe the regulated secretion of peptide hormones (2)
Insulin - rise the blood glucose levels, stimulates pancreatic beta islet cells to secrete insulin, binds to insulin receptors to open glucose channel. Glucose enters cell (metabolism), ATP generated binds to ATP sensitive channel
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Describe the regulated secretion of peptide hormones (3)
Causes depolarisation of membrane, voltage gated Ca 2+ channels open, Ca 2+ influx, stimulates exocytosis (release of hormones from vesicles). Regulation ensures there are not too high/low levels of insulin being released (prevent hypoglycaemia)
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Describe the constitutive secretion of peptide hormones (1)
Cell doesn't store hormone but secretes it from secretory vesicles as it is synthesised (e.g. FSH)
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Describe the constitutive secretion of peptide hormones (2)
Hydrophilic, interact with cell membrane receptors. Insulin - binds to insulin receptor, cascade reaction, beta subunit tyrosine kinase activation, RAS complex, actions on DNA/RNA (gene expression/growth)
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Describe the constitutive secretion of peptide hormones (2)
IRS and effects on synthesis of key enzymes. Alteration in pattern of phosphorylation of key enzymes and effects on kinases and phosphatases . Results in utilisation of glucose, increased glucose uptake, glycogen formation (decrease blood glucose)
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Give examples of hormones derived from cholesterol
Cholesterol can be converted to pregnenolone - progesterone - either cortisol or androstendione. Androstendione can be converted to testosterone and then to estradiol-17b
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State features of a steroid secreting cell
SER (subsequent conversions). Lipid droplets (cholesterol stores). Mitochondria (initial conversion to pregnenolone)
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Describe the interaction of lipid derived hormones with hormone receptors (1)
Lipophilic (cross plasma membrane and enter cell). Hormones bind to intracellular (cytoplasmic) receptors. Regulate gene transcription by binding to hormone response elements in DNA
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Describe the interaction of lipid derived hormones with hormone receptors (2)
E.g. testosterone stimulates production of structural proteins in skeletal muscle fibres - increase in muscle size and strength
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What are the two types of hormone receptors?
Cell membrane receptors. Intracellular receptors
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What makes a cell a target cell?
A cell is a target cell because it has a specific receptor for the hormone
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What are the three types of domains for cell membrane receptors? (1)
Extracellular domains (residues on outside of cell, interact with hormone). Transmembrane domains (hydrophobic stretches of amino acids, found in lipid bilayer, anchor receptor in membrane)
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What are the three types of domains for cell membrane receptors? (2)
Intracellular/cytoplasmic domains (parts of receptor within cytoplasm, respond to hormone binding by activating second messengers, open ion channels or activated enzymes)
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Describe features of cell membrane receptors (1)
Enzyme linked receptors/catalytic receptor. Binding of extracellular ligand causes enzymatic activity on intracellular domain e.g. insulin receptor - tyrosine kinase receptor
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Describe features of cell membrane receptors (2)
GPCRs, coupled to G-proteins, can be excitatory (+) or inhibitory (-), involves second messengers e.g glucagon-like peptide 1 receptor (target)
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Describe features of intracellular receptors (1)
Located either in the cell cytoplasm or nucleus. E.g. hydrophobic steroids bound to plasma proteins carriers, only unbound hormones can diffuse into the target cell. Steroid hormone receptors in cytoplasm/nucleus
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Describe features of intracellular receptors (2)
Receptor-hormone complex binds to DNA, activated/represses one or more genes. Translation produces new proteins for cell processes. Some steroid hormones also bind to membrane receptors that use second messengers to create rapid cellular responses
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What is homeostasis?
Maintaining a constant internal environment
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Describe the feedback control of hormone secretion (1)
External stimulus activates endocrine cell (stimulus specific to endocrine cell type). Endocrine cell release hormone into blood (hormones rapidly cleared from circulation by liver/kidney). Target tissue responds (tissue specific)
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Describe the feedback control of hormone secretion (2)
Response reduces stimulus (negative feedback control loop ensures homeostasis)
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Describe how insulin secretion from pancreatic beta cells results in a negative feedback control loop
Increase plasma glucose concentration (stimulus). Insulin released from b cells. Increased insulin secretion/plasma insulin concentration. Actions of insulin at target cell (transport glucose from plasma to IC space). Response reduces stimulus
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What is the difference between negative and positive feedback?
(Hormone secretion is regulated by feedback loops). Negative feedback (response counteracts stimulus shutting off response loop). Positive feedback (response reinforces stimulus sending parameter farther from set point)
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Give an example of positive feedback
Child birth - oxytocin causes contractions (outside factor required to shut off feedback cycle)
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Give an example of negative feedback
TSH produced T3/T4 (negatively affects TSH production)
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Outline features of a long feedback loop
Process (stimulus, hypothalamus, trophic hormone, anterior pituitary, tropic hormone, endocrine gland, hormone, target tissue, response). Presence of hormone secreted by endocrine gland sends signal to hypothalamus to turn off feedback loop
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Outline features of a short feedback loop
Process (stimulus, hypothalamus, trophic hormone, anterior pituitary, tropic hormone, endocrine gland, hormone, target tissue, response). Presence of tropic hormone secreted by anterior pituitary sends signal to hypothalamus (turn off feedback loop)
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Give an example of a long negative feedback feedback loop
Process (hypothalamus, CRH, anterior pituitary, ACTH, adrenal cortex, cortisol, target tissue, response). Long (cortisol sends signal to prevent CRH and ACTH being secreted)
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Outline the homeostatic controls (1)
Organism in homeostasis (external change e.g. obesity or internal change e.g. insufficient secretion of insulin). Internal change results in loss of homeostasis. Organism attempts to compensate (failure/illness/disease, compensation/wellness)
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Outline the homeostatic controls (2)
Successful compensation (homeostasis established). Failure to compensate (pathophysiology - illness, death)
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What are the disorders of endocrine systems? (1)
Excess secretion of a hormone (e.g. acromegaly, giantism, too much GH, Cushing's syndrome, too much cortisol). Deficient secretion of a hormone (type 1 diabetes/no insulin, Addison's disease, adrenal cortisol deficiency, thyroid deficiency)
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What are the disorders of endocrine systems? (2)
Failure to respond to a hormone (e.g. type 2 diabetes, insulin resistance, GH receptor defects)
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Card 2

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State the glands in the endocrine system and function (11) - 2

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Pancreas (regulates level of sugar in the blood)

Card 3

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What are the functions of the endocrine system (4)? -1

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Preview of the front of card 3

Card 4

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What are the functions of the endocrine system (4)? -2

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Card 5

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Outline how the endocrine system works? (1)

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