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bs1060 > endocrinology > Flashcards

endocrinology Flashcards

1
Q

what is endocrinology?

A

Endocrinology is the study of hormones and how they affect your body.
-the original 1902 definition that, to be classified as a hormone, a chemical must be produced by an organ, be released (in small amounts) into the blood, and be transported by the blood to a distant organ to exert its specific function Exceptions Paracrine hormones- Chemical communication between cells within the same Tissue or organ Autocrine hormones- Chemicals that acts on the cell that produced it Intracrine hormones- Chemicals that acts within the cell that produced it without being released

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2
Q

what is the endocrine system?

A

numerous glands, all in different parts of the body, which secrete hormones directly into the blood rather than into a duct system
-One hormone may have several effects on different target organs
-One target organ may be affected by more than one hormone
-Defined by the types of receptors expressed on/in cells

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3
Q

how are glands made

A

-derived from epithelial cells and are specialised for secretion

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4
Q

common features between endocrine system and nervous system

A

-Respond to changes in diet, environmental, chemical or physical inputs
-Release signalling molecules via exocytosis Neurones and endocrine cells (e.g. adrenal medulla) calcium is involved.
-can be depolarized- release noradrenaline/adrenaline

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5
Q

difference between neuronal or endocrine system

A

neuronal is a quick process whereas the endocrine system is slower to get to the site of action.
-neuronal system is short terms. ACTH is usually broken down from the synaptic cleft to prevent unwanted side effects whereas the endocrine system is long-term.
-neuronal= single target organ e.g. increased heart rate whereas the endocrine system has global effects e.g. sexual development or pregnancy

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6
Q

mechanisms for cell to cell signalling via hormones.

A

-autocrine= hormonal signal acts back on the cell of origin or adjacent cells of the same type..
-paracrine= Hormonal signal carried to an adjacent target cell over a short distance via interstitial fluid
-endocrine=Hormonal signal carried to distant target cells via the bloodstream
-neurocrine=Hormonal signal originates in a neurone and after axonal transport to the bloodstream, is carried to distant target cells

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7
Q

water soluable hormones actions

A

-binds to the receptor of the cell
-activates adenylate cyclase to convert ATP into cAMP.
-cAMP activates protein kinases
-protein kinases phosphorylate cellular proteins
-phosphorylated protein cause reactions that produced= physiological responses

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8
Q

lipid soluble hormone action

A

-diffuse straight into the cell
-activated recoptor-hormone complex alters gene expression
-newly formed mRNA directs synthesis of specific proteins on ribosomes
-new protein alters cell activity

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9
Q

what factors determine hormone levels?

A

-Rate of production: Synthesis & secretion, the most highly regulated aspect of hormonal control
-Rate of delivery: Higher blood flow to a particular organ will deliver more hormone
-Rate of degradation: Hormones are metabolized and excreted from the body

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10
Q

parathyroid hormone

A
  • produced by principal cells
    -increases plasma calcium levels and decreases plasma phosphate levels
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11
Q

parathroid hormone targets

A

-the bones=removes calcium from the bones and puts it into the blood= increase calcium concentration in the blood
-kidney= causes an increase in calcium reabsorption and increases phosphate loss
-gastrointestinal tract =increases the level of vitamin D which reacts with the intestine to stimulate the absorption of calcium and phosphate

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12
Q

how is the bone able to be a dynamic tissue

A
  • contain osteoclasts and osteoblasts cells to allow remodelling of bone
    -osteoclasts=take out calcium and phosphate from the bone when required and into the bloodstream
    -osteoblasts= put back calcium and phosphate to make fresh bone
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13
Q

activation of vitamin D

A

-biologically inactive when first enters the blood
-becomes active in the kidneys
-lack of vitamin D leads to rickets as it is essential in controlling calcium balance

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14
Q

calcitonin

A

-Peptide hormone produced by the parafollicular cells of the thyroid gland
- Secreted in response to high level of plasma Ca2+ and also in response to gastrointestinal hormones (e.g. gastrin)
-decreases calcium levels and phosphate levels

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15
Q

how does calcium control levels of calcitonin and parathyroid hormones via negative feedback

A

-high levels of calcium in blood stimulates thyroid glands parafollicular cells to release more CT
-this promotes the movement of blood calcium into the bone matrix thus decreasing calcium levels
-low levels of calcium in the blood stimulates principal cells to release PTH.
-PTH promotes the release of calcium from bone matrix into blood and slows the loss of calcium in the urine thus increases calcium levels
-PTCH also stimulates the kidney to release calcitriol which stimulates increased absorption of calcium from foods which increases blood calcium levels

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16
Q

link between the endocrine and nervous systems

A

The hypothalamus and pituitary gland form a complex functional unit that serves as the major link

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17
Q

pituitary gland

A

-anterior pituitary gland= the front of the gland and the posterior pituitary gland = the bavk of the gland
-physically connected to the hypothalamus which is at the top

18
Q

neurocrine functions of the posterior pituitary

A
  • neurosecretory cells release ADH/oxytocin
    -they are transported down neurones into posterior pituitary
    -released directly into the circulation
    -oxytocin=uterine contractions and milk secretion
    -ADH= water homeostasis
19
Q

neurocrine functions of the anterior pituitary glands

A

-7 different Trophic hormones produced by the hypothalamus
-released directly into circulation
-acts on endocrine cells in the anterior pituitary
-endocrine cells secrete hormones
-hormones interact with target cells/tissues

20
Q

trophic hormones

A
  • hormone that controls the release of another hormone in the target tissue
    e.g. growth hormones, thyroid stimulating hormones, LH or FSH etc…
    refer back to lecture slides for pictures
21
Q

hormonal effect of cells

A
  • hyperplasia= growth hormones can stimulate cells to reproduce faster and produce more cells
    -hypertrophy= increases in cell size
    -atrophy= decrease in cell size and number
    -necrosis or apoptosis
22
Q

growth hormone

A

-produced in the anterior pituitary
-has a signal peptide that must be cleaved off before proper folding
-effects mainly exerted indirectly via insulin-like growth factors
-liver and thee skeletal muscles usually are the ones to respond to growth hormone and produce and secrete IGF.

23
Q

growth hormone essential for normal growth during childhood and teenage years

A

-GH stimulates long bone growth
-Increases length prior to epiphyseal closure
-increases width after epiphyseal closure
-IGFs stimulate both bone and cartilage growth

In adults
-GH and IGFs help maintain muscle and bone mass and promote healing and tissue repair as well as modulating metabolism and body composition

24
Q

hormonal regulation of growth hormone secretion

A

-controlled via the hypothalamus
-GHRH(growth hormone releasing hormone )=increases growth hormone secretion
-somatostation= decreases growth hormone secretion

25
Q

long loop negative feedback

A

-Mediated by IGFs( insulin -like growth factors)
when there is a high level of GF
-Inhibit the release of GHRH
-Inhibit the action of GHRH in the anterior pituitary
-Stimulates the release of somatostatin

26
Q

short loop negative feedback

A

when GH hormone level rises
-Mediated by GH itself via stimulation of somatostatin release

27
Q

what factors are growth hormone secretion influenced by?

A
  • regulated metabolically by glucose and free fatty acids
    -↓ in glucose or fatty acid leads to ↑ in GHsecretion
    -↑ in glucose or free fatty acid leads to ↓ in GH secretion
    -Fasting ↑ GH secretion
  • Obesity ↓ GH secretion
    -CNS regulates GH secretion via inputs into the hypothalamus effecting GHRH and somatostatin levels:
    -surge in GH secretion after onset of deep sleep
    -Light sleep (Rapid Eye Movement (REM) sleep) ↓ GH secretion
    -Stress (e.g. trauma, surgery, fever) ↑ GH secretion
  • Exercise ↑ GH secretion
28
Q

growth hormone deficiency

A
  • results in pituitary dwarfism and can be fixed with growth hormone replacement therapy
29
Q

excess growth hormone

A

-gigantism. bonds are able to continue extend because ethicidal plates dont close.
- in adulthood=acromegaly
= large hands,feet and lower jaw as the bones cant extend so become wider

30
Q

insulin like growth factors (IGF)

A

IGFs act through IGF receptors (distinct from GH receptors) to modulate
- Cell growth (Hypertrophy)
- Increases in cell numbers (Hyperplasia)
- Increase in the rate of protein synthesis
-Increase in the rate of lipolysis in adipose tissue (fat)
-Decrease glucose uptake The actions of IGFs can be paracrine and autocrine as well as endocrine

31
Q

histology of thyroid tissues

A
  • Follicular cells arranged in spheres called thyroid follicles.
    -Follicles filled with colloid, a deposit thyroglobulin
    -Colloid is “extracellular “even though it is inside the follicle
32
Q

thyroid hormone structure

A

iodine is added to thyroid until
-can be mono,di,trio,dixodo,tetraiododothryronin(thyroxine) (is formed= 4 iodine attached

33
Q

synthesis of thyroid hormones

A

-iodine is absorbed via our diet into the blood
-NA/I symporter system transfers iodide and sodium the thyroglobulin cells into colloid mixture via pendrin
-oxidation occurs iodide into iodine
-then iodination occurs where iodide is added to tyrosine
-conjugation process occurs adding the molecules together to form hormones
-endocytosis
-proteolysis

34
Q

roles of thyroid peroxidase

A

-produces iodine at a faster rate. adds peroxide to iodide to form idodine
-adds iodine molecules on to tyrosine and does the conjugation reaction

35
Q

why does the thyroid gland secrete both T3 hormone and T4

A

-They have different biological activity.
- we release 90% more T4 than T3
-T3 has greater avtivity

36
Q

regulation of thyroid hormone secretion via a negative feedback loop

A

-refer back to lecture photo

37
Q

What is thyroid stimulating hormone

A

TSH is a glycoprotein hormone composed of 2 non-covalently bound subunits (a and b).
-The a subunit is also present in FSH and LH.
-b subunit provides unique biological activity.

38
Q

What roles does thyroid stimulating hormone play in the thyroid?

A

-increases Thyroglobulin (TG)iodination
-Increases DIT/MIT conjugation
-Promotes TG endocytosis
-increases TG proteolysis
-Stimulates T3/T4 secretion

39
Q

mechanism of thyroid receptor action

A

-thyroid hormone released(T3 or T4)
- enters the cell membrane and binds to the receptor on the nucleus.
-removes the co repressor and requites co activators
-activation of gene transcription
-increase protein expression

40
Q

biological actions of thyroid hormones

A
  • metabolism
    -growth and development

bs1060 (11 decks)

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