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The Endocrine System - SEM2 > the endocrine system > Flashcards

the endocrine system Flashcards

1
Q

What does hormones include and what do they do?

A

oestrogen, testerone, glucocorticoids, thryoxine, insulin
pass into the bloodstream and act as distant targets

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2
Q

What does neurotransmitters include snd what do they do?

A

noradenaline
acetylcholine
act over small nerve synapses

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3
Q

Where is the hypothalamus located?

A

brain reigon controlling the pituitary gland

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4
Q

What does the pituitary gland do?

A

secretes many different hormones some of which affect other glands

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5
Q

What does the thyroid gland do?

A

affects metabolism among other things

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6
Q

What does the parathyroids do?

A

help regulate level of calcium in the blood

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7
Q

What do adrenal glands do?

A

help trigger the fight or flight response

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8
Q

What does the pancreas do?

A

regulates the level of sugar in the blood

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9
Q

What does the ovary do?

A

secretes female sex hormones

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10
Q

What does the testis do?

A

secretes male sex hormones

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11
Q

What happens with the hypothalamus and pituitary gland?

A

the hypothalamus secretes releasing factors that act on the pituitary gland to stimulate the release of trophic hormones.
hormones/signals, shutting down the production of releasing or/and trophic hormones.
the hypothalamus secretes various hormones that are then transported to the anterior pituitary

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12
Q

What is the hypophyseal portal system?

A

a system of blood vessels connecting the hypothalamus to the anterior pituitary

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13
Q

What are the hormone releasing factors in the hypothalamus?

A

TRH
CRF
GnRH
Prolactin releasing factor
Growth hormone releasing factor
MSH releasing factor

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14
Q

What are the hormones in the anterior pituitary and posterior pituitary?

A

TSH
ACTH
FSH
LH
Prolactin
GH
MSH

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15
Q

What is homrone secretion from the anterior pituitary largely regulated by?

A

hypothalamic releasing factors from the hypothalamus

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16
Q

How is hypothalamic releasing factors to each anterior pituitary get through the blood stream?

A

the hypophyseal portal system

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17
Q

What does the posterior pituitary (neurohyophysis) consist of?

A

largely of nerve terminals of nerve cells which originate in the suparaoptic and paraventricular nuclei of the hypothalamus

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18
Q

What is to occur to the axons of these neurons?

A

to form the hypothalamix hypophyseal tract and terminate in close promixity to the capillaries of the posterior pituitary

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19
Q

What does the peptides do in hormones of the posteroir pituitary?

A

synethesised in the hypothalamic nuclei, pass down those axons into the posterior pituitary, where they are stored and eventually secreted

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20
Q

What happens in the endocrine control of thyroid hormone secretion? - negative feedback

A

hypothalamus (-)
|
thyrotropin releasing hormone (TRH) +
|
anterior pituitary (-)
|
thyroid stimulating hormone (TSH) +
|
throid gland
|
thyroxine

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21
Q

What are the thyroid hormones?

A

TRH - thyroid releasing hormone
TSH - thyroid stimulating hormone
T3 - triiodothyronine hormone
T4 - thyroxine hormone

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22
Q

What is the first step in thyroid hormone biosynthesis?

A

TSH binds to TSH receptor (TSH-R) on the follicular cellls of the thyroid
This increases the prodcution of thyroglobulin (TG) made by the follicular cells
Thyroglobulin is then released into the colloid

23
Q

What is the second step in thyroid hormone biosynthesis?

A

TSH also stimulates the uptake of iodide from the blood into the follicular cell
Iodide uses a Na+ symporter to get into the cell

24
Q

What is the third step of thyroid hormone biosynthesis?

A

TSH also increases the activity of thyroperiodase

25
Q

What happens in the first step to the thyroperoxidase?

A

it is to convert iodine (oxidation as iodide loses electrons to form iodine)

26
Q

What happens at the second step to thyropoxidase?

A

it facilitates the incoporation of iodine onto the tyrosines (Y) of thyroglobulin (iodination)

27
Q

What happens at the third thyroperoxidase?

A

they are also responsible for coupling MIT with DIT (T3) or DIT with DIT (T4)
* endocytosis
* proteases seperate the thyroglobulin /scaffold’ from T4 and T3
* thyroxin ebinding globulin (TBG) transports T4 and T3 to prephial tissues

28
Q

Where is T4 in the body found?

A

mainly in the circulation

29
Q

Where is the T3 in the body found?

A

mainly in the intracellular environment

30
Q

What is within target cells the T4?

A

T4 is converted to T3 which is to interact with a nuclear receptor to regulate gene transcription

31
Q

What is cellular uptake of thyroid hormones done by?

A

transmembrane transporters

32
Q

What is T4 mainly converted to?

A

to T3 by 2 deiodinase (D2) located on the endoplasmic reticulum

33
Q

What does T3 translocate too?

A

the nucleus and binds to the thyroid hormone receptor and complexes with the Retinoid X receptor (RXR-TR heterodimer)

34
Q

What does the complex (RXR-TR) bind too?

A

to the thyroid hormone response element (TRE)
induction of transcription

35
Q

What occurs at the T3 and T4 action?

A

stimulation of metabolism, causing increased oxygen consumption and increased metabolic rate and regulation of growth and development

36
Q

What are the symptoms of hyperthroidsm (thyrotoxicosis)?

A

high metabolic rate, increase in skin temperature, sweating, sensitivity to heat, tremor, tachycardia, increased appetite, weight loss

37
Q

What are the two types of thyroid disorders?

A
  • diffuse toxic goitre (grave’s disease)
  • toxic nodular goitre
38
Q

What is diffuse toxic goitre (graves’ disease)?

A
  • organ specific auto-immune disease
  • thyroid stimulating immunoglobulins directed at the TSH receptor (increasing thyroxine secretion)
  • patient exhibit protruding eyeballs
39
Q

What is toxic nodular goitre caused by?

A

a benign neoplasm or adenoma

40
Q

What is hypothyroidism (myxodema)?

A
  • an auto immune disease which caused low metabolic rate, slow speech , lethargy, bradycardia, sensitivity to the cold, mental impairment and the characteristic thickening of the skin
41
Q

What is hashimoto’s thyroiditis?

A

a chronic autoimmune disease against thyrogloubulin and thyroid tissue

41
Q

What are the steps of the hypothalamic pituitary adrenal axis?

A

hypothalamus
|
CRH
|
anterior pituitary
|
ACTH
|
adrenal cortex
|
corticosteroid

42
Q

In the adrenal cortex, what is aldrosterone?

A
  • tubular reabsorption of Na+ , Cl and K+
  • osmotic retention of H2O; increase in BP
43
Q

What is hydrocortisone (cortisol)?

A
  • controls the metabolism
  • stress response
  • anti-inflammatory
  • immunosupressive
44
Q

What is the regulation of synthesis and secretion of adrenal corticosteriods (the HPA axis)?

A
  • Adrenocorticotrophic hormone (ACTH) stimulates synthesis and
    release of glucocorticoids (e.g. cortisol) from the adrenal cortex
    (zona fasciculata)
  • Corticotrophin-releasing factor (CRF) from the hypothalamus
    regulates ACTH release and is regulated in turn by neural factors
    and negative feedback from plasma glucocorticoids.
  • Mineralocorticoid (aldosterone) release from the adrenal cortex
    (zona glomerulosa) is predominantly controlled by the renin-
    angiotensin system

hypothalamus
|
+ CRF
|
anterior pituitary
|
+ ACTH
|
adrenal cortex
|
endogenous glucocortioids (cortisol)
exogenous glucocorticoids
(prednisolone)

45
Q

What is not under the control of the hypothalamus or pituitary?

A

endocrine tissue

46
Q

What is insulin?

A

a polypeptide hormone (6,000 MW) that is produced in beta cells within the islets of langerhans of the endocrine pancreas

47
Q

What is insulin important in?

A

regulating blood glucose levels and high blood sugar levels stimulate its secretion

48
Q

What happens to insulin once it leaves pancreatic beta cells?

A

insulin and its targets - muscle, liver and fat
1. insulin enters the blood stream
2. insulin binds to insulin receptors on insulin responsive tissue (muscle, liver and far)
3. this facillitates the uptake of glucoses into insulin responsive tissue
4. blood glucose is a consquently lowered

49
Q

What is the insulin a complex of?

A
  • two a- and b- subunits
  • they are held together by disulphide bridges
  • a-subunits are extracellular
  • b-subunits are transmembrane spanning proteins
50
Q

What happens at the insulin receptor - a receptor tyrosine kinase?

A
  1. the a-subunits form the insulin binding site
  2. the intracellular portion of the b-units possess intrinsic tyrosine kinase activity
  3. insulin binding promotes auto-phosphorylation of Tyr residues on the intracellular domains
  4. rapid Tyr phosphorylation of adaptor proteins also occurs
  5. the best charactertised substrate is IRS-1 (insulin receptor substrate-1), which contains 22 tyrosine residues
  6. phosphorylated Tyr residues act as docking sites for a repertoire of signalling of proteins which relay the message from the activated receptor into the cell - such consquences include recruitment of glucose transport channels into the membrane. Occupied receptors aggregate into clusters which are subsquently internalised into vesicles, resulting in down regulation.
    Ulitmately, these receptors are recycled back to the plasma membrane
51
Q

The cellular events triggered by activated insulin receptors have both short and long term actions, what effect is short term actions?

A

the immediate metabolic effects

52
Q

What happens at the insulin receptor activation?

A

it signals via a series of signal transduction proteins , to the nucleus to promote gene expression
* to modulate the synthesis of key enzymes involved in the regulation of blood glucose
* to promote cell growth and division

53
Q
A

The Endocrine System - SEM2 (1 decks)

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