Endocrine System: Pituitary + Thyroid Gland
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- Created by: Bhickling
- Created on: 21-04-21 09:22
Describe water soluble hormones
- freely soluble in blood plasma
- bind to cell surface receptors
- activate 2nd messenger systems within the cell
- rapid action
- short half life
- most metabolised by liver + excreted by kidneys
- bind to cell surface receptors
- activate 2nd messenger systems within the cell
- rapid action
- short half life
- most metabolised by liver + excreted by kidneys
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Describe lipid soluble hormones
- mostly bind to cytosolic/ nuclear receptors
- protein bound in blood plasma
- protein bound component not physiologically active, acts as reservoir for free hormone
- slower action
- longer half life
- affected by disturbance of blood plasma protein con
- protein bound in blood plasma
- protein bound component not physiologically active, acts as reservoir for free hormone
- slower action
- longer half life
- affected by disturbance of blood plasma protein con
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What are the advantages of carrier proteins?
- hormone reservoir- active free hormone interacts with receptor + become used, new particles detach from transporter protein
- hormone buffer- proteins have remaining hormone binding capacity so can prevent large spikes in hormone concentration
- reduce
- hormone buffer- proteins have remaining hormone binding capacity so can prevent large spikes in hormone concentration
- reduce
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What are the disadvantages of carrier proteins?
- disruptions in blood levels of carrier proteins- decrease of carrier protein = decrease of protein-bound hormones = increase in free hormones
- competition from other substances for carrier proteins e.g. drugs
- competition from other substances for carrier proteins e.g. drugs
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Describe the development of the anterior pituitary
- made up of endocrine cells
- derived from oral ectoderm
- wraps around posterior pituitary
- derived from oral ectoderm
- wraps around posterior pituitary
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Describe the development of the posterior pituitary
- extension of hypothalamus
- derived from neural ectoderm
- cell bodies remain in hypothalamus, axons form stalk of posterior pituitary, nerve endings in posterior lobe
- derived from neural ectoderm
- cell bodies remain in hypothalamus, axons form stalk of posterior pituitary, nerve endings in posterior lobe
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What is the infundibulum?
The stalk that connect the hypothalamus and pituitary
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What does the posterior pituitary do?
- Releases but does NOT synthesise hormones- hormones are synthesised in cells bodies (Paraventricular Nucleus + Supraoptic Nucleus) within hypothalamus
- Hormones = oxytocin + ADH
- Hormones = oxytocin + ADH
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What does the anterior pituitary do?
- Synthesises + releases hormones
- Hormones = FSH, LH, ACTH, TSH, Prolactin, GH
- Hormones = FSH, LH, ACTH, TSH, Prolactin, GH
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Describe the mechanism of ADH release from the posterior pituitary
Increased osmolarity + decreased blood volume stimulates an ADH producing neurone in the hypothalamus.
Vesicles containing ADH travel down the axon into the posterior pituitary + released at the nerve terminal by exocytosis into the bloodstream
Vesicles containing ADH travel down the axon into the posterior pituitary + released at the nerve terminal by exocytosis into the bloodstream
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How do the hypothalamic hormones reach the anterior pituitary?
specialised circulatory system = portal system (2 capillary beds in series
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What is the difference b/w trophic + tropic hormones?
- trophic = regulate growth + development of target organs
- tropic = causes release of another hormone
- tropic = causes release of another hormone
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Describe the intermediate lobe of the pituitary
- embryologically the same as the anterior pituitary
- secretes melanocyte- stimulating hormones (MSH)
- secretes melanocyte- stimulating hormones (MSH)
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Where is the thyroid gland located?
- paired gland
- either side of trachea
- just below larynx
- either side of trachea
- just below larynx
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Describe the relationship b/w the HPA axis + thyroid gland
- neurones in the hypothalamus stimulate TRH (Thyrotropin Releasing Hormone) to be released into the portal system
- causes endocrine cells in the anterior pituitary to release thyrotropin + TSH (thyroid stimulating hormone)
- hormones travel to thyroid g
- causes endocrine cells in the anterior pituitary to release thyrotropin + TSH (thyroid stimulating hormone)
- hormones travel to thyroid g
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Describe the composition of the thyroid gland
made up of mainly spherical epithelial follicular cells that surround a non-cellular filling
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How + where are thyroid hormones produced?
- follicular cells trap iodide via Na/I symporters + oxidised to iodine
- transported into colloid
- follicular cells transport + synthesise substrates needed for thyroid hormone synthesis in colloid
- T3 + T4 are synthesised in the colloid bound to thyro
- transported into colloid
- follicular cells transport + synthesise substrates needed for thyroid hormone synthesis in colloid
- T3 + T4 are synthesised in the colloid bound to thyro
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What is the only known use of iodine in the body?
synthesis of thyroid hormones
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Is there a store of thyroid hormones?
- colloid = thyroid hormone store
- protein bound thyroid hormone in blood
- protein bound thyroid hormone in blood
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How are thyroid hormones regulated?
- secretion of TRH in hypothalamus driven by CNS
- increased concentrations of thyroid hormone in plasma inhibit TSH
- absence of TSH = inactive follicular cells
- increased concentrations of thyroid hormone in plasma inhibit TSH
- absence of TSH = inactive follicular cells
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Explain the role of thyroid hormones in controlling metabolism
- increases metabolic rate in all tissues (except gonads, brain + spleen)
- leads to increase O2 consumption + thermogenesis
- required for normal growth + development
- required for normal development of CNS
- promotes target responsiveness to sympatheti
- leads to increase O2 consumption + thermogenesis
- required for normal growth + development
- required for normal development of CNS
- promotes target responsiveness to sympatheti
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What would happen to the thyroid gland of animals on iodine deficient pastures?
Goitre (enlargement of thyroid gland)
- no synthesis of thyroid hormones
- continual production of TSH
- no synthesis of thyroid hormones
- continual production of TSH
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Other cards in this set
Card 2
Front
Describe lipid soluble hormones
Back
- mostly bind to cytosolic/ nuclear receptors
- protein bound in blood plasma
- protein bound component not physiologically active, acts as reservoir for free hormone
- slower action
- longer half life
- affected by disturbance of blood plasma protein con
- protein bound in blood plasma
- protein bound component not physiologically active, acts as reservoir for free hormone
- slower action
- longer half life
- affected by disturbance of blood plasma protein con
Card 3
Front
What are the advantages of carrier proteins?
Back
Card 4
Front
What are the disadvantages of carrier proteins?
Back
Card 5
Front
Describe the development of the anterior pituitary
Back
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