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BS1060 > Block 6 - Endocrinology > Flashcards

Block 6 - Endocrinology Flashcards

1
Q

Why do cells need to communicate?

A
  • Correct functioning of the body
  • Adapting to the environment
  • Infection
  • Tissue repair
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2
Q

How do cells communicate?

A
  • Human nervous system
  • Hormones
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3
Q

What is endocrinology?

A

The study of biosynthesis, storage, chemistry, biochemical and physiological function of hormones and the cells of the endocrine glands and tissues that secrete them

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4
Q

Hormone definition and 3 exceptions

A

A chemical must be produced by an organ, released in small amounts into the blood and be transported by 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 act on the cell that produced it
- Intracrine hormones: chemicals that act within the cell that produced it without it being released

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5
Q

Differences between the endocrine and nervous systems (list 3)

A

Neuronal - rapid
Endocrine - Slower

Neuronal - Short term effects
Endocrine - Long term effects

Neuronal - Single target organ (eg increased heart rate)
Endocrine - Global effects (eg sexual development, growth, pregnancy)

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6
Q

Explain the autocrine mechanism for cell-to-cell signalling

A

Hormonal signal acts back on the cell or origin or adjacent cells of the same type

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7
Q

Explain the paracrine mechanism for cell-to-cell signalling

A

Hormonal signal carried to an adjacent target cell over a short distance via interstitial fluid

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8
Q

Explain the endocrine mechanism for cell-to-cell signalling

A

Hormonal signal carried to distant target cells via the bloodstream

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9
Q

Explain the neurocrine mechanism for cell-to-cell signalling

A

Hormonal signal that orginates in a neurone, after axonal transport to the bloodstream, is carried to distant target cells

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10
Q

List 3 examples of each:
- Water soluble hormones
- Lipid soluble hormones

A

Water:
- JAK, janus kinases
- ERK, extracellular signal regulated kinase
- GH, growth hormone

Lipid:
- Steriod hormones
- Thyriod hormones
- Vitamin D3

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11
Q

What 3 factors determine hormone levels:

A

1) Rate of production: sysnthesis and secretion, the most highly regulated aspect of hormonal control
2) Rate of delivery: Higher blood flow to a particular organ will deliver more hormone
3) Rate of degradation: Hormones are metabolised and excreted from the body

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12
Q

The endocannabinoid system

A
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13
Q

List 7 cellular roles of calcium

A

1 - Neuromuscular excitability
2 - Coagulation
3 - Synaptic transmission
4 - Second messenger for hormones
5 - Bone formation
6 - Regulation of gene transcription
7 - Coordination of metabolic activity

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14
Q

List 5 cellular roles of phosphate

A

1 - Structure of the membrane phospholipids
2 - Energy metabolism
3 - Protein phosphorylation
4 - Genetic information (DNA/ RNA)
5 - Bone formation

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15
Q

Role of the parathyroid hormone

A

Secreted by the parathyroid glands.
Increases plasma calcium levels
Decreases plasma phosphate levels

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16
Q

The 3 major organs that PTH (parathyroid hormone) targets

A

Bone:
Increases osteoclasts
Increases blood calcium

Kidney:
Increases calcium reabsorbtion
Increases phosphate loss

GI tract:
Increases calcitriol levels which in turn increases calcium and phosphate reabsorbtion

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17
Q

What cells are involved in bone remodelling?

A

Bone - dynamic tissue - 15% of bone mass turns over each year

Coordinated activity of 2 types of cell:
Osteoclasts (OC) and Osteoblasts (OB)

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18
Q

How is bone organised?

A

It is organised in to osteons.

Osteons are circular and are made up of osteocytes, canaliculi, a central canal and lamella.

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19
Q

Fast exchange of calcium between bone and plasma

A

Calcium is moved from the labile pool in the bone fluid into the plasma by means of PTH-activated calcium ion pumps located in the osteocytic-osteoblastic bone membrane

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20
Q

Slow exchange of calcium between bone and plasma

A

Calcium is moved from the stable pool in the mineralised bone into the plasma by means of PTH-induced dissolution of the bone

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21
Q

Activation of vitamin D

A
  • Biologically inactive when first eneters the blood
  • Essential in controlling calcium balance but not as important as PTH for ‘minute to minute’ control (effects are too slow)
  • Lack of vit D leads to rickets (bendy legs)
22
Q

Calcitonin peptide hromone role in body

A

Secreted bu the parafollicilar cells in the thyroid gland.
Secreted in response to high levels of calcium in plasma and in response to gastrointestinal hormones

Decreases plasma calcium levels
Decreases plasma phosphate levels

23
Q

How are levels of calcitonin and parathyroid hormone controlled?

A

Via a negative feedback loop:
1) High levels of calcium in blood stimulates production of CT
2) CT promotes movement of blood Ca2+ into bone matrix, decreasing blood Ca2+ level
3) Low levels of Ca2+ in blood stimulates the production of more PTH
4) PTH promotes the release of calcium into the blood and slows loss of calcium in urine thus increasing calcium level
5) back to 1) and PTH also stimulates the kidneys to release calcitriol
6) Calcitriol stimulates increased calcium absorbtion from foods which increases blood calcium level - back to 1)

24
Q

List 8 physiological processes regulated by the hypothalamus and pituitary gland

A

1) Body growth
2) Reproduction
3) Adrenal gland function
4) Water homeostasis
5) Milk secretion
6) Metabolism
7) Thyroid gland function
8) Puberty

25
Q

Where are the hypothalamus and pituitary gland located in relation to one another?

A

Pituitary gland sits beneath the hypothalamus ina socket of bone called the sella turcica.

They are physically connected - the hypothalamus drops down through the infundibulum to form the posterior pituitary.

26
Q

What are the names of the two parts of the pituitary gland?

A

Anterior pituitary gland - Adenohypophysis
Posterior pituitary glad - Neurohypophysis

27
Q

Explain neurocrine function of the posterior pitutary and list the two hormones it secretes

A
  • ADH (antidiuretic hormone) or vasopressin/ oxytocin are produced by hypothalamus
  • Transported down neurones in to posterior pituitary
  • Released directly into circulation

Oxytocin
Uterine contractions
Milk secretion

ADH
Water homeostasis

28
Q

Explain the role of the hypothalamic-pituitary portal system and the anterior pituitary in endocrine function

A

7 different TROPHIC hormones are produced by the hypothalamus
- Released directly into circulation
- Act on endocrine cells in the anterior pituitary
- Endocrine cells secrete hormones
- Hormones interact with target cells/ tissues

29
Q

List the 7 trophic hormones (and define trophic hormone)

A

Trophic hormones - controls the release of another hormone in the target tissue

  • releasing hormone ) inhibiting hormone

1 - TRH, Thyrotropjin releasing hormone
2 - PRH, Prolactin releasing hormone
3) PIH, Prolactin release-inhibiting hormone
4 - CRH, Corticotrophin releasing hormone
5 - GnRH, Gonadotropin releasing hormone
6 - GHRH, Growth hormone releasing hormone
7) SS, Somatostatin (or GHIH)

30
Q

What 6 main hormones does the anterior pituitary secrete?

A

1 - TSH, Thyroid stimulating hormone
2 - ACTH, Adrenocorticoptrophic hormone
3 - GH, Growth hormone
4 - PRL, Prolactin
5 - LH, Lutenising hormone
6 - FSH, Follicle stimulating hormone

31
Q

Explain growth hormone’s function and role in the body

A

Regulates postnatal growth

Produced in the anterior pituitary:
Stimulated by GHRH, Growth hormone releasing hormone
Inhibited by SS, Somatostatin

Growth-promoting effects mainly indirect via insulin-like growth factors (IGFs or Somatomedins)

GH cells of the liver and skeletal msucle produce and secrete IGFs

32
Q

Regulation of growth hormone

A

Long loop negative feedback:
Mediated by IGFs
- inhibits the release of GHRH
- inhibits the action of GHRH in the anterior pituitary
- stimulates the release of SS

Short loop negative feedback:
Mediated by GH itself via stimulation of SS release

33
Q

CNS regulation of GH

A

CNS regulates GH secretion via inputs into the hypothalamus effecting GHRH and SS levels.

  • Surge in GH secretion after onset of deep sleep
  • Light sleep (REM) lowers GH secretion
  • Stress (eg. trauma, surgery, fever) increases GH secretion
  • Exercise increases GH secretion
34
Q

Impact of metabollic process on GH regulation

A
  • Decrease in glucose of fatty acids leads to an increase in GH secretion
  • Fasting increases GH secretion
  • Obesity decreases GH secretion
35
Q

List 2 roles of GH in childhood and 4 roles of GH in adulthood

A

Childhood:
- GH stimulates long bone growth (inc in length prior to epiphyseal closure and inc in width after)
- IGFs stimulate both bone and cartilage growth

Adulthood:
- maintain muscle and bone mass
- promote healing and tissue repair
- modulating metabolism
- modulating body composition

36
Q

What 5 things do IGFs modulate?

A
  • Cell growth (hypertrophy)
  • Increases in cell numbers (hyperplasia)
  • Increase in the rate of protein sysnthesis
  • Increase in the rate of lipolysis in adipose tissue (fat)
  • Decrease glucose uptake

Can be paracrine, autocrine and endocrine.

37
Q

Which hormones other than GH influence growth and what effect do they have?

A

Insulin - enhances somatic growth, interacts with IGF receptors

Thyroid hormones - Promote CNS development and enhance GH secretion

Androgens - Accelerate pubertal growth spurt, increase muscle mass, promote closure of epiphyseal plates

Oestrogens - Decrease somatic growth, promote closure of epiphyseal plates

Glucocorticoids - Inhibit somatic growth

38
Q

What does the thyroid gland comprise of?

A

2 lobes - thyroid gland and the parathyroid gland
Joined by isthmus
Bow-tie shape and location

39
Q

Explain the histology of thyroid tissue

A

Follicular cells arranged in spheres called thyroid follicles
Follicles are filled with a deposit of thyroglobulin called colloid
Colloid is inside the follicle but still considered ‘extracellular’

40
Q

How does iodine enter the body through diet?

A

Iodine can be consumed in dairy products, grains, meat, eggs and vegetables although the highest would be found in iodised salt.

It is converted to iodide and absorbed in the small intestine.
Once in the bloodstream it is absorbed into the thyroid gland and converted into thyroid hormones.

41
Q

Which hormones make up T3, Triiodothyronine?

A

MIT, Monoiodotyrosine
DIT, Diiodotyrosine

42
Q

Which hormones make up T4, Tetraiodothryronine?

A

2 molecules of DIT, Diiodotyrosine

43
Q

What role does thyroid stimulating hormone play in the thyroid?

A

1) Increases Thyroglobulin (TG) iodination
2) Increases DIT/MIT conjugation
3) Promotes TG endocytosis
4) Increases TG proteolysis
5) Stimulates T3/T4 secretion

44
Q

Roles of Thyroid Peroxidase (TPO) in the producation of thyroid hormones

A

Converting iodide into iodine
Converting tyrosine into diiodotyrosine and then to thyroxine

45
Q

What are the main actions of thyroid hormones?

A

Increases Basal metabolic rate and heat production
- increases the number and sixe of mitochondria
- stimulates the synthesis of enzymes in the respiratory chain

Stimulation of metabolic pathways
- catabolic pathways are generallu stimulated more than anabolic
- Effects depend of the level of thyroid hormone (low = stim of glucose to glycogen | high = stim of glycogen to glucose

Sympathomimetic effects
- increases target cell response to catecholamines by increasing receptor number on target cells

46
Q

Explain two tissue specific effects of thyroid hormones

A

Cardiovascular system:
Increases heart’s responsiveness to catecholamines
- inc in cardiac output (heart rate and force of contraction)
- inc in peripheral vasodilation to carry extra heat to body surface.

Nervous system:
Essential for both development and adult function
- increases mylination of nerves and the development of neurons

47
Q

What is a goitre and when does it occur?

A

An enlarged thyroid gland.

May accompany either hypo- or hyperthyroidism.

Develops when the thyroid gland is overstimulated.

48
Q

Explain the 3 causes of hypothyroidism and how it affects the plasma concentrations of relavent hormones.

A
  • Primary failure of the thyroid gland; decrease in T3 and T4, increase in TSH; goitre present
  • Secondary to hypothalamic or anterior pituitary failure (TSH or TRH deficiency); decrease in T3 and T4, decrease in TRH and/or TSH; no goitre present
  • Lack of dietary iodine; decrease in T3 and T4, increase in TSH; goitre present
49
Q

Explain the 3 causes of hyperthyroidism and how it affects the plasma concentrations of relavent hormones.

A
  • Abnormal presence of TSI (thyroid stimulating immunoglobulin) AKA Graves’ disease; increase in T3 and T4, decrease in TSH; goitre present
  • Secondary to excess hypothalamic or anterior pituitary secretion; Increase in T3 and T4, increase in TRH and/or TSH; goitre present
  • Hypersecreting thyroid tumor; increase in T3 and T4, decrease in TSH; no goitre present
50
Q

What is Hashimoto’s disease?

A

A common thyroid gland autoimmune disease.
5x more common in women than men

Causes production of an antibody that blocks the TSH receptor on follicle cells
Destruction of thyroid follicles

Treatment: oral thyroid hormones

BS1060 (10 decks)

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