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endocrine Flashcards

1
Q

By which two pathways can proteins be secreted?

Hint - the two ways all drama starts (1) c → m, n, p and (2) e →

A

‒ direct pathway: proteins moved from cytosol → mitochondria, nuclei and peroxisomes
‒ secretory pathway: proteins moved from ER

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2
Q

What are the two types of protein secretion?

Hint - all over the place “c” and controlled “r”

A
  1. constitutive secretion → all cells + continual exporting of some substances e.g. ECM proteins
  2. regulated secretion → specialised secretory cells (e.g. pancreatic acinar cells) release stored substances in response to signal
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3
Q

What route is taken during protein secretion?

Hint - p → e → ga → final destination

A

proteins → ER → golgi apparatus → final destination (lysosomes, endosomes, ER and PM)

(process of travel to golgi can involve early endosome and then late one)

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4
Q

What is translocation?

Hint - from one jail to another

A

process by whichproteinsmove between cellular compartments

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5
Q

Are all secretory pathways simple?

A

no, some can be pretty complex

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6
Q

How much of a pancreatic cell is endocrine and exocrine and in what percentages do cells of the islets of Langerhans secrete each hormone?

A
  • 99% exocrine (secretory acini & associated ducts) and 1% endocrine
  • islets of Langerhans located w/in pancreas tail:
    • insulin-secreting β-cells (60-70%)
    • glucagon-secreting α-cells (15-20%)
    • somatostatin secreted by δ-cells (5-10%); identical to hormone hypothalamus secretes
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7
Q

Describe protein secretion in pancreatic acinar cells.

(Hint - protein is frozen and then re-heated, ogen and digestive ones, collectively called what in pancreas “z”, PA cells have lots of which loopy structure, sec granules and ordered what?)

A
  • unusual as most protein is synthesised and secreted before it can be stored
  • mainly digestive enzymes (trypsinogen and chymotrypsinogen) → produced as inactive precursors (e.g. trypsinogen → trypsin)
  • in pancreatic cells → collectively known as zymogen (active form)
  • pancreatic acinar cells have lots of RER, large secretory granules and ordered cytoplasmic structures
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8
Q

What are the six stages of secretion of proteins in cells?

(Hint - (1) initiation (2) synthesis segregation (3) processing (4) golgi apparatus (5) secretory zymogen vesicles (6) exocytosis of protein)

A
  1. initiation of protein synthesis → secretory proteins synthesised by ribosomes attached to ER
  2. synthesis segregated from cytosolic proteins
    → mRNA determines whether protein synthesis takes place in cytosol OR RER
  3. processing → in ER + golgi apparatus, both major sites of glycosylation (=addition of oligosaccharide molecules) to form glycoproteins
    - most lumen proteins in ER = glycoproteins + cytosolic proteins = not glycosylated
  4. golgi apparatus → shows polarity with cis-face near ER where vesicles bring proteins IN + trans-face facing PM - vesicles bud from ER + contents fuse with golgi membrane
  5. secretory (zymogen) vesicles - budded from GA, stored in cytoplasm, released by exocytosis as needed
  6. exocytosis – fusion of membrane-bound vesicles with PM releasing contents outside cell → triggered by external signal (i.e. hormone or NT)
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9
Q

Describe the recognition system for proteins coding (for secretion, fitting into the PM, lysosomes etc…) which determines whether protein synthesis takes place in the cytosol or SER.

(Hint - signal sequence is in the 6s = SRP + R bind once signal made → stops p. synthesis until R + ER attached → secreted proteins ER → lumen → signal peptide removed)

A
  • proteins contain signal sequence in mRNA (16-26 AAs long)
  • signal recognition protein (cytoplasm) binds to ribosome once signal made → stops protein synthesis until ribosome attaches to ER → process resumes → secreted proteins cross ER membrane to lumen as their synthesized → signal peptide removed in ER lumen
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10
Q

Describe protein processing in the ribosomal endoplasmic reticulum.

(Hint - protein has SRP → allows protein + ER receptor binding → protein contact with ER translocation channel on ER membrane → SRP released + recycled → polypeptide chain through trans. channel into lumen)

A

‒ protein contains signal recognition particle which allows it to attach to receptors of ER membrane
‒ protein can then make contact with translocation channel on ER membrane
‒ here, SRP is released and recycled; growing polypeptide chain moves through translocation channel into ER lumen

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11
Q

What is the endoplasmic reticulum and its central role in the biosynthesis of transmembrane proteins (plasma membrane), lipids (mitochondria), lumen proteins (lysosomes) and secreted proteins (ECM)?

(Hint - what is ER and how much space does it occupy? ER and main proteins)

A
  • highly convoluted single membrane inside cell
  • generally >½ of total cell plasma membrane → space inside lumen which is >10% of cell volume and has regulated entry
  • ER has a central role in the biosynthesis of transmembrane proteins
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12
Q

Which modifications occur in the Golgi apparatus?

Hint - G ‘adding sugar to the end’, C + P, S

A

‒ completes glycosylation
‒ protein solutions become condensed and packaged
‒ segregates proteins according to final destination e.g. secretory proteins to storage vesicles

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13
Q

What is the endocrine system made up of and what is the primary function of endocrine cells?

A
  • consists of cells, tissues and organs that secrete hormones
  • glands (ductless) are secrete hormones which are transported via interstitial fluid and blood throughout body
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14
Q

What are each of endocrine glands and what do they secrete?

Hint - PATPPOT

A
  • pituitary gland → FSH, LH, ADH, growth hormone, oxytocin, prolactin (breast milk-production)
  • adrenal gland → adrenaline, cortisol (FOF and stress)
  • thyroid gland → thyroxin
  • parathyroid gland
  • pineal gland → melatonin (biological clock)
  • (endocrine) pancreas → insulin + glucagon
  • ovaries → oestrogen and progesterone
  • testes → testosterone
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15
Q

How is the endocrine system involved in homeostasis?

Hint - regulation of gdrb

A

• regulates:

  • growth
  • development
  • reproduction
  • blood pressure
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16
Q

What are hormones and how do they work?

A
  • chemical messengers classified as a peptide, steroid or amine → discrete glands and tissues
  • enter bloodstream → dispersed throughout the body
  • exert effects on target cells with specific high-affinity receptors
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17
Q

Endocrine cells secrete hormones - which endocrine cells are gathered together to form a specialised gland and which form discreet clusters in another specialised organ?

(Hint - the discreet clusters are reproductive and within panc.)

A

cells gathered together to form specialised organ/gland

  • adrenal
  • pituitary
  • pineal

form discreet clusters in another specialised organ

  • ovary
  • testis
  • pancreas
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18
Q

In which three ways can hormones be classed and what is each type derived from?

A
  • each class differs in its biosynthetic pathway
    1. peptides + proteins → hormones synthesised from AAs
    2. steroids → cholesterol-derivatives
    3. amines → tyrosine-derivatives
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19
Q

What are hormones synthesised and secreted by? Give examples of steroid hormones.

(Hint - agcp - stress hormone, sex hormones etc…)

A
  • adrenal cortex
  • gonads
  • corpus luteum
  • placenta
  • i.e. cortisol, aldosterone, oestradiol, estriol, progesterone, testosterone and 1,25 dihydroxycholecalciferols
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20
Q

How is hormone secretion regulated?

Hint - mechanisms

A

by neural or (positive/negative) feedback mechanisms

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21
Q

Give an example of hormonal +VE feedback.

Hint - not oxytocin but another female o hormone in your teens - O → F + L → ovulation + more o secretion

A
  • during follicular phase of menstrual cycle, ovaries secrete oestrogen
  • oestrogen acts on anterior pituitary to release FSH and LH
  • have two effects on ovaries: ovulation + stimulation of oestrogen secretion → causes more oestrogen secretions

(see notes for diagram)

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22
Q

Describe the pituitary gland.

A

‒ multifunctional gland → secretes many hormones
‒ activate peripheral endocrine cells in → adrenal gland, thyroid gland, testis and ovary
‒ bean-shaped, under the brain linked by the pituitary stalk and anatomically divided into anterior and posterior sections

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23
Q

What is the hypothalamus and which four hormones does it release and inhibit?

(Hint - links endo and NS → all of the weirdly-named hormones ending in H - ggtc)

A
  • small region of brain below thalamus and the major link between nervous and endocrine systems
  • releasing and inhibiting hormones:
    • corticotropin releasing hormone (CRH)
    • thyrotropin releasing hormone (TRH)
    • growth hormone releasing hormone (GHRH)
    • gonadotropin-releasing hormone (GnRH)
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24
Q

What type of gland is the hypothalamus and how is it anatomically divided?

A
  • multifunctional gland → secretes large number of hormones
  • activate peripheral endocrine cells → adrenal, thyroid, testes and ovaries
  • anatomically divided into anterior and posterior
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25
Q

Describe the negative feedback control of the pituitary gland.

(Hint - reg. hormone from hyp. → hormone from A pituitary → hormone from e gland → hormone sends signal back to hyp. → production stopped → cascade finished)

A

regulatory hormones are released in hypothalamus → anterior pituitary gland secretes a hormone → affects endocrine gland (secretes hormone) → hormone acts + sends a signal back to initial hypothalamus → stop production of regulatory hormones → cascade stops

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26
Q

For each cell type of the anterior pituitary, state the hormone(s) secreted, its effects and the syndrome associated with its over-production:

a) somatotrophs
b) lactotrophs
c) corticotrophs
d) gonadotrophs
e) thyrotrophs

A

a) growth hormone (GH):
• effects → promotes growth of bone and muscle, promotes protein synthesis + fat metabolism, decreases carbohydrate metabolism
• syndrome → gigantism
b) prolactin
• effects → stimulates mammary gland development, pregnancy stimulates milk production
• syndrome → infertility (males)
c) adrenocorticotropic hormone (ACTH)
• effects → stimulates synthesis + secretion of adrenal cortical hormones
• syndrome → cushing’s syndrome
d) FSH
• effects → sperm-production (M) and stimulates growth of ovarian follicle and ovulation (F)
• syndrome → hypogonadism
AND LH
• effects: secretion of testosterone, development of interstitial testis tissue (M) and stimulates development of corpus luteum, release of oocyte, production of oestrogen and progesterone (F)
• syndrome → hypogonadism
e) Thyroid-stimulating hormone (TSH)
• effects → stimulates growth of thyroid epithelial cells
and the release of thyroid hormones
• syndrome → hyperthyroidism

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27
Q

What are anterior pituitary hormones classed as and which two steps does their synthesis include?

A

• a peptide/polypeptide
• steps:
- transcription - DNA → mRNA
- translation - mRNA → final hormone

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28
Q

In which three ways can hormones be seen in the body?

Hint - acting, hiding, or moving → s+s, t, b+e

A
  • synthesis and storage
  • transport
  • binding and effects
29
Q

What are the 3 histological parts of pituitary epithelial tissue?

(Hint - p. distant, p. trabs, p. interm.)

A
  • pars distalis
  • pars trabecula
  • pars intermedia
30
Q

Which two hormones does the pituitary release?

Hint - the positive feedback “o” and water hormone “a”

A
  • antidiuretic hormone (ADH) → decrease water loss by the kidneys
  • oxytocin → promotes contraction of smooth muscle in the uterus and myoepithelial cells in the breast
31
Q

Where is the pineal gland located and what is it composed of?

(Hint - two cells types are “pin…cytes” for sleeping melon hormone and “g… cells” on neuronal system)

A
  • under brain
  • composed of lobules of two types of specialised cells:
    • pinealocytes – neurone-like cells, produce melatonin
    • glial cells – bipolar, elongated cells that run between nests of pinealocytes → indistinct unless stained
32
Q

What is the function of melatonin and the link between melatonin and ageing?

A
  • secretion of melatonin by the pineal gland is responsive to light and regulates seasonal change in the body
  • secretion decreases with aging – this triggers changes throughout the endocrine system
33
Q

Describe the thyroid gland.

Hint - two parts, affects all and two main hormones by epithelia

A
  • bilobed, with thyroid hormones synthesised and secreted by epithelial thyroid cells → affects all bodily organ systems
  • two active hormones T3 and T4 → synthesised by follicular epithelial cells
34
Q

What are the hormones in the thyroid glands and what is their function?

(Hint - for the numbered ones its the reason why you put on weight/can’t put it on with thyroid problems, c hormone to do with c homeostasis)

A
  • thyroxine (T4) and triiodothyronine (T3) = metabolism

- calcitonin = calcium homeostasis

35
Q

Summarise the histology of the thyroid gland.

Hint - C → T, PF cells → C and cuboidal epithelia

A
  • composed of follicles = hollow spheres of cuboidal epithelial cells
  • lumen filled with colloid (contains hormone thyroglobulin)
  • surrounding each follicle is a BM enclosing parafollicular (C-cells) → secrete calcitonin
36
Q

How does underactive and overactive thyroid link to colloid and why does goiter occur?

(Hint - to do with colloid and T4 cells where more T4 means faster metabolism, too much secretion because of iodine)

A
  • underactive thyroid → increased colloid + decrease in T4, flattened cells
  • overactive thyroid → decreased colloid + overproduction of T4, tall cells
  • enlarged thyroid gland/goiter → thyroid hyposecretion due to iodine insufficiency
37
Q

Describe the parathyroid gland.

Hint - two cells types → a general and an oxy

A
  • embedded in P surface of thyroid + separated by dense capsular fibres of thyroid
  • secrete parathyroid hormone (PTH) → Ca homeostasis
  • contain two cell populations:
    • chief cells (secrete PTH)
    • oxyphils – larger than chief cells, rare before puberty, unknown function
38
Q

What are most common endocrine abnormalities due to and what will this affect?

(Hint - gcbnc)

A 
- disturbances of thyroid hormones - will affect →
• growth
• CNS
• BMR (metabolic rate)
• nutrient metabolism 
• CV system
39
Q

What is Graves’ disease and why does it occur?

Hint - autoimmune, lose weight, more TSIs, stimulated thyroid gland + breakdown of gland

A
  • autoimmune disease which is the most common form of hyperthyroidism
  • increased circulating levels of thyroid-stimulating immunoglobulins (antibodies to TSH receptors on thyroid follicular cells)
  • antibodies stimulate thyroid gland → increasing secretion of thyroid hormone + hypertrophy of gland

(exophthalmos - bulging eyes)

40
Q

State the diagnosis, symptoms and treatment for hyperthyroidism.

(Hint - diagnosis based on two hormones, symptoms → weight, HR, throat, treatment → drugs or surgery)

A
  • diagnosis → symptom-based and measurement of increased T3 and T4 levels
  • symptoms → weight loss, rapid HR due to up-regulation of β1 receptors in heart, presence of goiter (enlarged thyroid gland)
  • treatment → administration of drugs which inhibit synthesis of thyroid hormones (i.e. carbimazole), surgical removal of gland
41
Q

State the most common cause, effect, diagnosis, symptoms and treatment for hypothyroidism.

(Hint - self-caused, effects → hair loss, throat, cold, periods, weight, diagnosis → less of two hormones, treatment → replacement of mian hormone of higher number)

A
  • most common cause → autoimmune destruction of thyroid gland (thyroiditis) so antibodies destroy gland/block thyroid hormone synthesis
  • effects on body → hair loss, fatigue, feeling cold, goiter, menstrual changes, weight gain
  • diagnosis → symptom-based and decreased T3 and T4 levels
  • symptoms → weight gain, decreased HR, periorbital, menstrual dysfunction
  • treatment → thyroid HRT (usually T4 (Thyroxine))
42
Q

What does the central core and outer rim of the pancreas consist of and in which 3 ways do pancreatic cells communicate with each other?

(Hint - junctions between cells called g. junctions, venous blood, islets have different types of nerones)

A
  • central core contains mostly β cells
  • with α-cells distributed around outer rim
    1. gap junctions connect α cells to β cells which permit rapid cell-to-cell communication
    2. venous blood from one cell bathers the other cell type
    3. islets are innervated by adrenergic, cholinergic and peptide neurons
43
Q

Where are adrenal glands located and what does each part of the adrenal cortex secrete?

(Hint - GFR with the outside most male, middle stress-related, inside the most mineral-related)

A
  • secretes steroid hormones i.e. cholesterol → 3 distinct zones:
    • zona reticularis → pale brown → secrete mineralocorticoids like aldosterone
    • zona fasciculata → glucocorticoids → cortisol and corticosterone
    • zona glomerulus → smallest → androgens like DHEA + androstenedione
44
Q

What is the structure of an embryological foetus/neonate?

Hint - outside is thickest and the most external layer says disappears after baby is born

A
  • cortex is largest layer

- 4th external layer → involutes after birth

45
Q

Where is the adrenal medulla located and what does each part of it secrete?

(Hint - literally just secretes the two stress hormones)

A
  • 20% of tissue → cells have polyhedral shape and arranged in clumps, cords, columns and surrounded by rich network capillaries
  • cells → large pale staining nuclei and fine granular cytoplasm
  • neuroectodermal origin → derived from the neural crest
  • secretes → epinephrine and norepinephrine
46
Q

What is Cushing’s syndrome and what are its causes and possible treatment?

(Hint - too much glucs, too much stress hormone “c” from adrenal cortex or from drugs, stop by inhibiting the source of the problem)

A
  • causes → result of chronic excess of glucocorticoids (overproduction of cortisol by adrenal cortex/from administration of pharmacological glucocorticoids i.e. steroids)
  • treatment → medication to block steroid hormone biosynthesis (ketoconazole)
47
Q

Via which molecules can we sense receptors to recognise specific extracellular stimuli?

(Hint - h-n-a/p agents-o (smells) - m for growth- j agents/p for adj. cells)

A

‒ hormones
‒ NTs
‒ autocrine + paracrine agents
‒ odours
‒ molecules that regulate growth/differentiation
‒ proteins outside of adjacent cells (juxtacrine agents)

48
Q

What are the three main routes for receptor-based signals?

Hint - two main signal systems and then local produce

A

1) nervous system
2) endocrine system (hormones)
3) locally-produced factors

49
Q

Which type of receptors do we get in the endocrine system and how does it coordinate responses?

(Hint - inside/outside cells → (1) distance from targets, (2) bloodstream, (3) travelling to body cells but only some respond)

A
  • extracellular or intracellular receptors
    1) secreting endocrine cells are far away from target cells
    2) hormone released in blood stream
    3) travel to all body cells – but only those cells with specific receptors will respond
50
Q

What are hormones and what can they be produced by?

A
  • slow-acting molecules which regulate homeostasis and gradual changes
  • produced by:
    • endocrine cells
    • some nerves (neurohormones)
    • non-endocrine cells (e.g. glucagon by intestine cells)
51
Q

State the 2 main types of hormone and how they act on cells.

A

1) enter cell and bind to intracellular receptors e.g. steroid hormones (androgens + oestrogens)
2) bind to receptors on plasma membrane – it cannot enter the cell so acts via secondary messenger e.g. protein hormones (insulin)

NB: lipid-soluble hormones can enter the cell whereas non-lipid-soluble hormone bind to receptors on the surface of target cells

52
Q

What are the stages of the hormone pathway for the hormone secretin?

(Hint - (1) HCl (2) blood (3) pancreas juice)

A
  1. secretin produced by presence of HCl
  2. secretin carried by blood
  3. secretin brought by the blood stimulates formation of pancreatic juice
53
Q

Describe cellular signalling and how it works.

Hint - p + c but always end p

A
  • cells primarily detect chemical + physical signals

- at the receptor, physical signals → converted to chemical signals (e.g. rhodopsin signalling)

54
Q

A few receptors respond directly to physical input. In which two ways this can be done? Give an example of each.

(Hint - by a pushing stimulus and then a heat/pain stimulus, for rhod: GP → cGMP protein → cGMP → pdrase → pdrase + cGMP reducing conc.)

A
  • pressure → sensed on channels
    • e.g. – Rhodopsin signalling – chemical signals → G-protein activation → cGMP protein → cGMP → phosphodiesterase → PDE hydrolyses cGMP reducing its conc.
  • heat/pain → sensed on ion channels
    • e.g. – heat – physical signals
55
Q

What are secondary messengers, what are the 2 types and how do they work?

(Hint - the classic and then the 2+ ion + adenyl cyclase)

A
  • binding of hormone to cell surface receptor - types:
    1) cAMP (cyclic AMP)
    2) Ca2+
  • adenyl cyclase converts ATP to cAMP
    • effects of cAMP
    • cascade effect
    • amplification
56
Q

What is cholera caused by and what does it result in?

Hint - microbiology vc and leads to fluid loss via faeces and cardiac shock if untreated

A
  • caused by → bacteria vibrio cholerae

- results in → severe diarrhoea and litres of fluid lost in hours - leads to shock and death if fluid isn’t replaced

57
Q

State the mechanism of action for cholera.

(Hint - bacteria in body produces toxin in gut cells → toxin + GP of adenyl cyclase → adenyl cyclase increases cAMP → cAMP increases ac. transport of ions by intestine cells → increased Na of gut hence water into gut)

A
  1. bacteria enters body and produces cholera toxin which enters gut cells
  2. toxin covalently binds to G-protein controlling adenyl cyclase activity
  3. ↑ adenyl cyclase activity therefore ↑ cAMP
  4. ↑ active transport of ions by intestinal cells
  5. ↑ Na into gut and by process of osmosis ↑ water into gut
58
Q

What is paracrine communication? give an example.

Hint - ‘para’ and straight to the point

A
  • cell releases signalling molecule into the immediate environment and binds to neighbouring cells
  • has an immediate effect on them e.g. somatostatin to pancreatic cells to inhibit insulin secretion
59
Q

What is autocrine communication? give an example.

A
  • cell releases a regulatory molecule which is bound by its own receptors → positive feedback to the cell itself
  • e.g. insulin-like growth factor (IGF)
60
Q

What is intracrine communication? give an example.

Hint - within the cell

A
  • NOT intercellular communication – intracellular signalling (between different parts of the same cell)
  • i.e. organelles → the molecules don’t leave cell
61
Q

Steroid hormones are non-polar, lipid-soluble and can cross the plasma membrane. How do steroid receptors allow and what do they affect?

(Hint - can hormone come into cell and what can it affect?)

A
  • allows entry of steroid hormones

- affect regulation of gene expression

62
Q

What does an inhibitor of steroid receptors block?

Hint - to do with DNA

A

the receptor from binding to DNA until the hormone is present

63
Q

What are the three functional domains of a steroid receptor?

Hint - two different molecules binding and an additional other-cell-binding domain

A
  1. hormone-binding domain
  2. DNA-binding domain
  3. domain that interacts with co-activators to affect gene expression
64
Q

What are the three types of membrane-receptor types and how does each one work?

(Hint - channel, enzyme and GP where a GP has 2 components)

A
  1. channel-linked → ion channel that opens in response to a ligand
  2. enzymatic → receptor is an enzyme which is activated by the ligand
  3. G-protein-coupled → where G-protein = protein + GTP
65
Q

State the stages in membrane-receptor binding to an enzyme/hormone with a G-protein.

(Hint - G-protein + receptor → effecter protein → second messenger → response)

A
  1. G-protein switched on by receptor
  2. G-protein activates an effecter protein (normally an enzyme)
  3. effector protein produces a second messenger (e.g. adenylyl cyclase produce cAMP)
  4. second messenger generates response to original stimuli

(see notes for diagrams)

66
Q

What are receptor tyrosine kinases and how do they work? provide an example.

(Hint - membrane receptor + ligands → dimers + auto → add a P to try on protein → i.e. blood sugar example)

A
  • membrane receptor
  • when ligand binds – receptor is activated by dimerization + autophosphorylation
  • activated receptor adds a phosphate to tyrosine on a response protein
  • e.g. insulin receptor
67
Q

What is a kinase cascade and how does it work? provide an example.

(Hint - subsequent phosphorylation of PKs → multiplies signals for response → i.e. maps)

A
  • series of protein kinases which phosphorylate each other in succession
  • amplifies signal → a few signal molecules can elicit large cellular response
  • e.g. Mitogen-activated protein (MAP) kinases are activated by kinase cascades
68
Q

What is the nervous system?

A

large interconnected network which receives sensory info from inside and outside body

69
Q

What are the six stages in the mechanism of nervous system signalling via neurotransmitters (NT)?

(Hint - first stimuli at d, electrically setting up, release, binding, effect, inactivation)

A
  1. stimulation at dendrites
  2. alteration in electrical properties of plasma membrane
  3. rapid release of stored NT
  4. NT binds to receptor on target cell surface
  5. NT has effect on target cell
  6. NT inactivated

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