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CEP > Hormone Synthesis and action > Flashcards

Hormone Synthesis and action Flashcards

1
Q

what is the endocrine system?

A
  • a system of ductless glands and cells that secrete hormones
  • regulates many physiological processes
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2
Q

Hypothalamus

A

production of ADH, oxytocin and regulatory hormonea

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3
Q

pineal gland

A

melatonin

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4
Q

parathyroid gland

A
  • posterior surface of thyroid gland

- parathyroid hormone

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5
Q

heart

A

natriuretic peptides: ANP & BNP

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6
Q

kidney

A
  • renin
  • erythropoietin (EPO)
  • calcitrol
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7
Q

adipose tissue

A
  • leptin

- resistin

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8
Q

digestive tract

A

numerous hormones

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9
Q

pancreatic islets

A

insulin, glucagon

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10
Q

gonads

A

testes
- androgens (especially testosterone), inhibin
ovaries
- estrogens, progestins, inhibin

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11
Q

adrenal glands

A

adrenal medulla
- epinephrine, norepinephrine
adrenal cortex
- cortisol, corticosterone, aldosterone, androgens

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12
Q

thymus

A

(undergoes atrophy during adulthood)

thymosins

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13
Q

pituitary gland

A

anterior lobe
- ACTH, TSH, GH, PRL, FSH, LH and MSH
posterior lobe
- release oxytocin and ADH

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14
Q

thyroid gland

A

Thyroxine (t4)
triiodothyronine (t3)
calcitonin (CT)

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15
Q

endocrine glands

A

release secretions into blood directly from cells (ductless glands)

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16
Q

exocrine glands

A

(not part of endocrine sustem)

release their secretions outside the body and may be ducted e.g. gut secretions, sweat glands

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17
Q

mixed glands

A

e.g. pancreas produces digestive juice + insulin, glucagon and somatostatin

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18
Q

chemical coordinator of endocrine system

A

hormone - many different types affecting different specific tissue

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19
Q

chemical coordinator of nervous system

A

neurotransmitter - few types, secreted only onto target tissue

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20
Q

speed of effect of endocrine system

A

generally slow

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21
Q

speed of effect nervous system

A

generally rapid

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22
Q

duration of effect of endocrine system

A

generally long lasting

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23
Q

duration of effect of nervous system

A

generally short lived

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24
Q

localisation of effect of endocrine system

A

secreted into blood therefore widespread

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25
Q

localisation of effect of nervous system

A

secreted onto target cell so effect very localised

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26
Q

neuro-endocrine

A

boundaries become blurred because some hormones are secreted from nerve endings

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27
Q

what is a hormone?

A
  • a substance secreted directly into the blood by specialised cells
  • carries in blood to receptors on target organs (endocrine, autocrine, paracrine)
  • present in only minute concentrations in blood and bind specific receptors in target cells to influence cellular reactions
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28
Q

intracrine system

A

generated by a chemical acting within the same cell

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29
Q

autocrine signals

A

those in which a chemical acts on the same cell

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30
Q

paracrine mechanism

A

chemical communication between neighbouring cells within a tissue or organ

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31
Q

classic endocrine and neuroendocrine signalling mechanism

A

a chemical released by a specialised group of cells into the circulation and acting on a distant target tissue

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32
Q

control of action at a distance

A

stimulus ➡️ gland ➡️ hormone ➡️ target tissue ➡️ action or hormone

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33
Q

what is negative feedback?

A

process by which body senses change and activates mechanism to reduce it (the final product of an endocrine cascade acts to inhibit the release of hormones higher up the cascade)

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34
Q

what is positive feedback?

A

process by which body senses change and activates mechanism to amplify it

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35
Q

endocrine axis

A
  • the target tissue for one hormone may be another endocrine gland (a tropic hormone stimulates another endocrine gland)
  • the functional grouping of endocrine glands
  • faults may occur along this axis
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36
Q

process of hypothalamic-pituitary axis

A

NO - neurons in the hypothalamus secrete
RABBITS - thyrotropin releasing hormone which stimulates cells in the
ALTER - anterior pituitary to secrete
SEXUALLY - thyroid stimulating hormone
EXCITED - TSH binds to epithelial cells in the thyroid gland stimulating
SNAKES - synthesis and secretion of thyroid hormones

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37
Q

negative feedback of hypothalamic - pituitary axis

A

When blood concentrations of thyroid hormones increase above a certain threshold, TRH secreting neurons in the hypothalamus are inhibited and stop secreting TRH

38
Q

thyroid action

A

BMR, growth

39
Q

parathyroid action

A

Ca2+ regulation

40
Q

cortisol action

A

glucose regulation, inflammation

41
Q

aldosterone action

A

BP, N’a+ regulation

42
Q

catecholamines action

A

BP, stress

43
Q

oestradiol action

A

menstruation, femininity

44
Q

testosterone action

A

sexual function, masculinity

45
Q

insulin action

A

glucose regulation

46
Q

ANP action

A

Na+ regulation

47
Q

vitamin D action

A

Ca2+ regulation

48
Q

overview of protein and peptide hormones

A
  • most common type of hormone, of amino acids
  • water soluble (hydrophilic) - happy in blood but unable to get through cell membrane (not lipid soluble)
  • performed and stored in membrane bound vesicles ready for release by exocytosis
  • produced by ribosomes (RER) as large precursor molecule - pre-prohormone
49
Q

what is thyrotropin releasing hormone?

A
  • tripeptide, synthesised from a large precursor protein (mol wt ~29000) which contains several copies
50
Q

what does a large precursor allow?

A

structural specificity

51
Q

how to form insulin?

A

preproinsulin ==> proinsulin (cleavage of signal peptide and covalent - S-S bonds formed) + C-peptide ==> insulin
Endoprotease PC2 & PC3 and carboxypeptidase

52
Q

What are common things glycoproteins hormones can have?

A
  • common a subunits

- b subunit which is unique and confers specificity

53
Q

Steroid hormone overview

A
  • all made from cholesterol
  • normally from adrenal glands
  • hormones from adrenal cortex and sex hormones
  • lipid soluble
  • synthesised as required and diffuse out of the cell
  • synthesised in SER from cholesterol derived from diet or from acetate
54
Q

what is the first and rate-limiting step in steroid hormones?

A

cholesterol to pregnenolone

- formed in mitochondrion but moved to endoplasmic reticulum for processing to hormones

55
Q

how are steroid hormone synthesised?

A
  • hydrolysis of esters and release of cholesterol
  • cholesterol to pregnenolone in mitochondria - movement of cholesterol to mitochondrion is regulated by steroid acute regulatory protein (StAR). ACTH regulated StAR activity and processing of cholesterol
  • processing of pregnenolone in SER
  • egress by diffusion or facilitated -
56
Q

3 examples of enzymes within adrenal 3 cortical regions

A

zona glomerulolsa - aldosterone
zona fasciculata - cortisol
zona reticularis - adrenal androgens

57
Q

secretion and excretion of steroid hormones

A
  • newly synthesised steroid hormones are rapidly secreted from the cell with little if any storage
  • increases in secretion reflect accelerated rates of synthesis
  • steroid hormones are eliminated by inactivating metabolic transformations and excretion in urine or bile
58
Q

what are thyroid hormones?

A
  • tyrosine derivatives bound together
  • contain 4 iodine atoms (T4) - less active
  • contain 3 iodine atoms (T3) - active
  • small, non-polar molecules
  • soluble in plasma membranes
59
Q

synthesis of T4 in the thyroid

A
  • from endoplasmic reticulum - thyroglobulin secretion (in thyroid follicular cell)
  • exocytosis in follicle colloid
  • from blood - through Na/I symporter to form I- and Na+, then through pendrin where oxidation changes I- to I0
  • I0 + thyroglobulin (iodination)
  • conjugation
  • endocytosis into thyroid follicular cell
  • proteolysis to thyroxine and triiodothyronine
60
Q

why are steroid and thyroid hormones transported in blood by carrier proteins?

A
  • increase solubility in blood
  • increase half- life
  • create readily accessible reserve in blood
61
Q

what are the types of binding proteins?

A
  • specific binding proteins e.g. thyroid binding globulin (TBG) and cortisol binding globulin (CBG)
  • non specific binding proteins e.g. albumin - loose binding. aldosterone binds to albumin.
  • bound and free hormone are in equilibrium
62
Q

what are the site of action of hormones?

A
  • peptide - cell surface receptors

- steroid - intracellular receptors

63
Q

what are the cellular actions of protein and peptide hormones?

A
  • receptors located on surface of target cell
  • hormone binding activated second messenger cascade
  • ultimately there is phosphorylation of proteins within the cell and the activated proteins bring about a change in cellular function
64
Q

what does chemistry of hormones do?

A

determines its mode of action

65
Q

what are endocrine disorders?

A
  • overproduction of a hormone
  • underproduction of a hormone
  • non-functional receptors that cause target cells to become insensitive to hormones
66
Q

excess endocrine disorders

A
  • often caused by tumours
  • or exogenous administration of hormones
  • treatment = surgical removal of part of gland
67
Q

deficient endocrine disorders

A

primary - primary organ inadequate, tropic hormone - feedback
secondary - tropic hormone deficient
- autoimmune organ destruction most common cause
treatment = replacement therapy (orally absorbed, long half-life e.g. steroid (corticosteroid), thyroid (thyroxine) hormones/ injections e.g. GH, insulin - peptide hormones. otherwise degraded in GI tract)

68
Q

growth hormone

A

deficiency - growth hormone deficient (dwarfism - proportionate)
excess - gigantism (children), acromegaly (adults)

69
Q

antidiuretic

A

deficiency - diabetes insipidus

excess - hypervolaemia (SIADH)

70
Q

thyroid

A

deficiency - hypothyroidism (1/2/3), hashimoto’s thyroiditis (1), congenital hypothyroidism (iodine deficiency)
excess - hyperthyroidism (Graves disease)

71
Q

parathyroid

A

deficiency - hypoparathyroidism - tetany

excess - hyperthyroidism (1/2/3) bone resorption

72
Q

insulin

A

deficiency - diabetes mellitus

excess - coma

73
Q

cortisol

A

deficiency - adrenal insufficiency (addisons disease)

excess - cushings syndrome

74
Q

aldosterone

A

deficiency - hypoaldosteronism

excess - 1: aldosteronism (Conn’s), 2: aldosteronism

75
Q

why would blood flow to endocrine glands change?

A
  • endocrine glands work in tandem to the blood flow in order to transport hormones around the body
  • aging may change this : less of a hormone = less blood flow
  • stress - more adrenaline = higher blood flow
76
Q

what is the embryologic origin of the thyroid gland?

A
  • the primitive pharynx - median thyroid and neural crest - rudimentary lateral thyroid
  • develops near base of neck and descends in week 7
  • week 10 : can develop thyroglossal duct cyst if not descended properly
77
Q

Simple lateral cross section of thyroid gland (top to bottom)

A
  • thyroid cartilage
  • cricoid cartilage
  • thyroid gland
  • trachea
78
Q

cross section of thyroid gland (outside in)

A
  • sternocleidomastoid muscle
  • strap muscles
  • thyroid lobes
  • trachea
  • oesophagus
    also includes internal jugular vein and internal carotid artery
79
Q

what triggers release of T3 & T4?

A
  • triggered by hypothalamus releasing in thyrotropin- releasing hormone which stimulates pituitary gland to produce TSH
80
Q

which nerves, vessels and structures are at risk during a thyroidectomy?

A
  • vagus nerve - regulation of internal organ functions e.g. digestion
  • external branch of superior laryngeal nerve - inner ages the cricothyroid muscle (CTM) to promote lengthening and thinning of vocal cord and therefore pitch
  • inferior laryngeal nerve - main motor nerve of intrinsic laryngeal muscles and provides sensory innervation to larynx
81
Q

what is the embryological origin of parathyroid glands?

A

From pharyngeal pouches

82
Q

what cells are in parathyroid glands?

A
  • chief cells

- oxyphil cells

83
Q

what hormone is secreted by parathyroid glands?

A

low calcium levels trigger the release of the parathormone

84
Q

what are the consequences of removal of parathyroid glands?

A
  • blood calcium levels drop, leading to confusion, depression, forgetfulness, stiff/achy muscles
  • would need to take calcium supplements
  • hyperplasia - cells don’t increase but glands get bigger
85
Q

at what vertebral levels do adrenal glands lie?

A

12th thoracic - above and slightly medial to kidneys within renal fascia

86
Q

what produces mineralcorticoids?

A

zona glomerulosa

87
Q

what produces glucocorticoids?

A

zona fasciculata

88
Q

what produces sex hormones?

A

zona reticularis

89
Q

what does central adrenal medulla produce?

A

epinephrine and norepinephrine

90
Q

how might the pancreas be damaged ?

A
  • chronic pancreatitis - inflammation
  • heavy alcohol use
  • high levels of calcium/fats in blood
  • medications
  • autoimmune conditions

CEP (9 decks)

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