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Week 128 - Endocrinology > Physiology > Flashcards

Physiology Flashcards

1
Q

What are the five types of hormonal signalling pathways?

A 
Endocrine
Neuroendocrine
Paracrine
Autocrine
Intracrine
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2
Q

What is the endocrine pathway?

A

Hormones travel via bloodstream to distant target cells

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3
Q

What is the neuroendocrine pathway?

A

Hormones released by synapse into bloodstream and act on distal target cells

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4
Q

What is the paracrine pathway?

A

Hormones secreted by a cell act on adjacent cells

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5
Q

What is the autocrine pathway?

A

Hormones act on same cell that produced them

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6
Q

What is the intracrine pathway?

A

Hormones work within source cell

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7
Q

What endocrine organs are under control of the hypothalamic-pituitary axis?

A

Thyroid
Adrenal cortex
Gonadal glands

The pituitary trophic hormones stimulate release of glandular hormones which then feedback

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8
Q

Which endocrine organs generally stand alone?

A

Pancreas

Parathyroid glands

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9
Q

What structures make up the thyroid gland?

A

Follicles which consits of:

  • central lumen: stores thyroid hormones
  • follicular cells: surround lumen and secrete T3 and T4 which are made from iodides

Parafollicular C cells: squeezed inbetween follicles which secrete Calcitonin

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10
Q

What hormones do the thryroid gland secrete and what are the secreted in response to?

A

T3: Triiodotyronine
T4: Thyroxine

Secreted in response to TSH which is secreted from the anterior pituitary

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11
Q

How do the thyroid hormones travel in the blood?

A

Carried by Thyroxine Binding Globulin as hydrophobic

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12
Q

What effect do thyroid hormones have?

A

Stimulate increase of metabolism

  • fat and carbohydrate breakdown
  • protein synthesis
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13
Q

What affect does calcitonin have?

A

Decrease Ca2+ levels when high

- increase bone deposition and increased excretion

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14
Q

What hormone does the parathyroid gland produce?

A

Parathyroid hormone (PTH)

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15
Q

What does PTH do?

A

PTH increases plasma Ca2+ and decreased (PO4)2- levels when Ca2+ is low

  • incr. osteoclast activity
  • decr. Ca2+ excretion and increased (PO4)2- excretion
  • incr. vitD production => increased Ca2+ absorption
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16
Q

What are the two layers of the adrenal gland?

A

Adrenal cortex (outer)

  • outer = zona glomerulosa
  • middle = zona fasciculata
  • inner = zona reticularis

Adrenal medulla (inner)

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17
Q

What is the role of the adrenal medulla?

A

Produces catecholamines

  • adrenaline (80%)
  • noradrenaline (20%)
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18
Q

What is the role of the adrenal cortex?

A

Produce steroids

  • glucocordicoids e.g. cortisol
  • mineralocorticoids e.g. aldosterone
  • sex hormones = oestrogen, androgens, progestogens
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19
Q

Which layers secrete what in the adrenal cortex?

A

Zona glomerulosa = mineralocorticoids
Zona fasciculata = glucocorticoids
Zona reticularis = sex hormones

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20
Q

How does the adrenal cortex release mineralocorticoids?

A

In response to stimulation by angiotensin and ACTH

21
Q

What effect does the mineralocorticoid aldosterone have?

A

Increases water and Na+ reabsorption in kidney

22
Q

How does the adrenal cortex release glucocorticoids?

A

Stimulated by ACTH

23
Q

What effect do glucocorticoids, i.e. cortisol have?

A

Stress hormones which can cause rise in blood glucose levels and inhibit immune system

24
Q

What stimulates the release of catecholamines from the adrenal medulla?

A

Preganglionic sympathetic neurones from the hypothalamus

25
Q

What is the endocrine function of the pancreas often referred to as?

A

The islet of langerhans

26
Q

What are the different cell types in the islet of langerhans?

A

alpha cells - secrete glucagon
beta cells - secrete insulin
delta cells - secrete somatostatin

27
Q

What is the role of alpha cells in the pancreas?

A

Secrete glucagon which makes the liver increase its secretion of glucose via increased glycogenolysis and reduced gluconeogenesis

28
Q

What is the role of beta cells in the pancreas?

A

Secrete insulin which increases hepatic glycogen production and tissue glucose uptake

29
Q

What is the role of delta cells in the pancreas?

A

Secrete somatostatin which inhibits the secretion of gastric acid

30
Q

How do insulin and glucagon work together?

A

Work antagonistically in response to blood glucose levels

31
Q

What are the different types of hormones differentiating by structure?

A

Peptides & proteins

Amino acid derivatives = amine hormones

Steroid hormones

Fatty acid derivatives = eicosanoids

32
Q

Describe the structure of a peptide/protein hormone

A

Largest class
- GH, prolactin, insulin, ACTH, LH, FSH, PTH

Largest hormones
- range from 3 AAs to 100s of AAs

Often produced as pro-hormones which are cleaved into active hormones

Water soluble

33
Q

Describe the process associated with producing pro-hormones?

A

Gene translated via mRNA into ‘preprohormone’
- Modified in ER to include carbohydrates

  • ‘pre’ section acts as signal, targeting molecule to golgi bodies where it is removed forming pro hormone
  • Prohormone packaged into secretory vescicles
    [] Hormone may be cleaved to active form before of after secretion
34
Q

Describe the structure of an amine hormone

A

Derived from tyrosine
- 2 families derived
[] catecholamines
[] Thyroid hormones

35
Q

Describe the structure of steroid hormones

A

Derived from cholesterol

Lipid soluble / not water soluble

May be converted to active form inside target cells
e.g. androgens converted to oestrogen in brain

36
Q

Where are steroid hormones produced?

A

Adrenals
Gonads
Placenta

37
Q

Describe the types of steroid hormones.

A

Glucocorticoids

  • Control carbohydrate metabolism
  • Modulate inflammatory response
  • Respond to stress

Mineralocorticoids
- Control salt balance and BP

Sex steroids
- e.g. androgens, oestrogens, progestogens

38
Q

Describe the structure of eicosanoid hormones

A 
Fatty acid derivatives derived from polyunsaturated FAs
Groups include:
 - Prostaglandins
 - Prostacyclins
 - Leukotrienes
 - Thromboxanes
39
Q

What are the different types of hormones differentiating by solubility?

A

Water soluble hormones

Lipid soluble hormones

40
Q

Describe the characteristics of water soluble hormones

A

Fast acting

Often have multiple effects on target cells due to second messengers

41
Q

Describe the mechanism of action of water soluble hormones

A

Bind to receptors on target cell surface

Receptor mediates release of second messenger inside cell
- second messengers include cAMP, cGMP, arachidonic acid, phosphoinostil, tyrosine kinase
[] messenger has multiple effects on cell function

42
Q

Describe the characteristics of lipid soluble hormones

A

Slow acting - must diffuse through cell membrane to nucleus then wait for protein production

Often have more specific antigens

43
Q

Describe the mechanism of action of lipid soluble hormones

A

Able to diffuse through lipid cell membrane

Bind to nuclear membrane receptors with which the form complex

Complex has effect on DNA transcription, eventually leading to production of new protein

44
Q

List the forms of hormonal control

A

Sensing and signalling

Neural control

Chronotropic control

Pulsatile control

45
Q

What is the key component of neural control?

A

Neural input to hypothalamus stimluates releasing factor secretions which in turn stimulate pituitary hormone secretion

46
Q

What is the key component of chronotropic control?

A

Hormones released in response to rhythms

e.g. diurnal, circadian, seasonal

47
Q

What is the key component of pulsatile control?

A

Hormones released due to pulses in releasing factors

48
Q

Describe the different types of hormone feedback.

A 
Negative feedback (most common)
 - high levels of releasing factors cause release of hormones, which then decrease the amount of releasing factors
Positive feedback (rare)
 - the enhancing or amplification of an effect by its own influence on the process which gives rise to it

Week 128 - Endocrinology (6 decks)

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