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SL12010 Health and Disease Flashcards > Endocrine Lectures > Flashcards

Endocrine Lectures Flashcards

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1
Q

What are the five types of hormone signalling? Define each type.

A

Intracrine - Hormone signalling within the cell

Autocrine - Hormone secreted and received by same cell

Paracrine - Hormone signalling from cell to adjacent cells via local circulation

Endocrine - Hormone signalling from endocrine gland via general circulation to distant target cells

Neuroendocrine - Hormone signalling from neurosecretory cell via circulation to distant target cells. Initiated by AP.

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2
Q

What is the difference between a neuroendocrine and an endocrine pathway?

A

In a neuroendocrine pathway the hormones are secreted from modified neurosecretory cells instead of a typical endocrine gland.

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3
Q

What is the main output organ of the hypothalamus?

A

The pituitary gland

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4
Q

Define anterior:

A

Describing something towards the front of the body

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5
Q

Define posterior:

A

Describing something towards the back of the body

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6
Q

Describe the general anatomy of the hypothalamic-pituitary axis:

A
  • Hypothalamus located at the base of the brain, with the pituitary gland situated beneath
  • Hypothalamus innervates the posterior pituitary gland with paraventricular nuclei
  • Network of capillaries known as the median eminence located between the two, blood flowing towards the pituitary glands
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7
Q

What type(s) of hormones are secreted by the anterior pituitary gland?

A

Primary and also regulatory hormones

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8
Q

What type(s) of hormones are secreted by the posterior pituitary gland?

A

Primary hormones only

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9
Q

What are the neural connections/functions of the hypothalamus? Divide them based on the corresponding nuclei of the hypothalamus.

A

Paraventricular nucleus:

  • Neuroendocrine secretory role
  • Integrates and controls ANS activity

Suprachiasmatic Nucleus:

  • Receive light input from the retinas to synchronise circadian rhythm
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10
Q

What are the hypothalamic releasing factors?

A

CRF - Corticotropin releasing factor
TRH - Thyrotropin releasing hormone
GHRH - Growth hormone releasing hormone
GnRH - Gonadotropin releasing hormone
PRF - Prolactin releasing factor

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11
Q

What are the hypothalamic inhibiting factors?

A

GHIH - Growth hormone inhibiting hormone
PIH - Prolactin inhibiting hormone
MSH-IH - Melanocyte stimulating hormone inhibiting hormone***

***Don’t need to memorise MSH-IH

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12
Q

What does CRF stand for? Break down the meaning of the name:

A

CRF - Corticotropin releasing factor

Cortico: Relating to the cerebral cortex Tropin: Relating to growth and stimulation

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13
Q

What does TRH stand for? Break down the meaning of the name:

A

TRH - Thryotropin releasing hormone

Thyro: Relating to the thyroid

Tropin: Relating to growth and stimulation

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14
Q

What does GHRH stand for?

A

GHRH - Growth hormone releasing hormone

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15
Q

What does GnRH stand for? Break down the meaning of the name:

A

GnRH - Gonadotropin releasing hormone

Gonado: Relating to the gonads (sexual organs)

Tropin: Relating to growth and stimulation

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16
Q

What does PRF stand for? Break down the meaning of the name:

A

PRF - Prolactin releasing factor

Pro: Promoting
Lactin: Hormone relating to lactation

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17
Q

What does GHIH stand for?

A

GHIH - Growth hormone inhibiting hormone

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18
Q

What does PIH stand for? Break down the meaning of the name:

A

PIH - Prolactin inhibiting hormone

Pro: Promoting
Lactin: Hormone relating to lactation

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19
Q

What is the pars intermedia?

A

The tissue separating the pars nervosa (posterior pituitary) and the pars distalis (anterior pituitary).

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20
Q

What are the pars nervosa and pars distalis?

A

The tissues that make up the posterior and anterior pituitary glands respectively.

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21
Q

What are the structural differences between the pars nervosa and pars distalis? How do these relate to the unique functions of each pituitary gland?

A

The pars nervosa is highly innervated and possesses a more neuronic structure. This relates to the neurosecretory role of the posterior pituitary gland; secreting regulatory hormones produced by the hypothalamus.

The pars distalis is very granular, possessing many secretory granules which support its endocrine functionality as a gland that produces and secretes primary hormones.

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22
Q

Why doesn’t the pars nervosa possess a typical endocrine structure if it secretes hormones?

A

The hormones secreted by the pars nervosa are produced by modified neurosecretory cells in the hypothalamus which innervate the posterior pituitary gland.

Due to this unique setup which involves a lot of innervation. The pars nervosa doesn’t have a typical endocrine structure.

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23
Q

What is the median eminence? Why is it important?

A

A capillary network located between the hypothalamus and the pituitary gland.

It plays a crucial role in the hypothalamic pituitary axis since it allows for hormones secreted by the hypothalamus to almost immediately interface with the pituitary gland before entering systemic circulation.

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24
Q

What are the anterior pituitary hormones? Categorise them.

A

Trophic hormones:

  • Thyroid stimulating hormone
  • Adrenocorticotrophic hormone
  • Follicle stimulating hormone
  • Luteinising hormone

Primary hormones:

  • Growth hormone
  • Prolactin
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25
Which of the pituitary gland secretes regulatory hormones?
The anterior pituitary gland
26
Which pituitary gland is innervated by the hypothalamus?
The posterior pituitary gland
27
What hormones are secreted by the posterior pituitary gland?
- ADH - Oxytocin
28
What structure are hypothalamo-pituitary portal vessels a part of?
The median eminence
29
State the neuroendocrine pathway of GnRH: (Hyp, pit, target organ)
GnRH secreted by the hypothalamus, triggering secretion of LH and FSH by the pituitary, which proceed to stimulate the gonads.
30
State the neuroendocrine pathway of TRH: (Hyp, pit, target organ)
TRH secreted by the hypothalamus, triggering secretion of TSH by the pituitary, which stimulates the thyroid.
31
State the neuroendocrine pathway of CRF: (Hyp, pit, target organ)
CRF secreted by the hypothalamus, triggering secretion of ACTH by the pituitary, which stimulates the adrenal glands.
32
State the neuroendocrine pathway of GHRH: (Hyp, pit, target organ)
GHRH secreted by the hypothalamus, triggering secretion of GH by the pituitary, which increases growth in tissues throughout the body.
33
State the neuroendocrine pathway of SRIF/GHIH: (Hyp, pit, target organ)
GHIH secreted by the hypothalamus, inhibiting secretion of GH by the pituitary, thereby decreasing growth in tissues throughout the body.
34
State the neuroendocrine pathway of PRF: (Hyp, pit, target organ)
PRF secreted by the hypothalamus, triggering secretion of PRF by the pituitary gland, which stimulates the breasts to increase lactation.
35
State the neuroendocrine pathway of PIH: (Hyp, pit, target organ)
PIH secreted by the hypothalamus, inhibiting secretion of prolactin, thereby causing the breasts to decrease lactation.
36
Describe the mechanism for feedback control of the hypothalamic-pituitary axis:
Negative feedback loops exist from the lover levels to the higher levels of the axis. In this way, hormones secreted by the target gland reduce secretion of the related hormones from the anterior pituitary and the hypothalamus. Secretion of the relative pituitary hormone will also decrease secretion of the releasing hormone by the hypothalamus.
37
Summarise the effects of growth hormone on the body:
- Increase cell size, number and differentiation - Stimulate protein synthesis - Stimulate fat utilisation - Alter carbohydrate metabolism
38
By stimulating fat utilisation, how is GH increasing growth?
By increasing fat utilisation, more energy is available from the hydrolysis of triglycerides in fat cells. This energy can be used in order for cells to synthesise proteins and undergo mitosis in order for the body to grow.
39
What does IGF stand for? Where do they come from? What triggers their secretion?
- IGF: Insulin-like growth factor - They are secreted by the liver - Secreted in response to growth hormone
40
In what ways does GH influence protein synthesis?
- Increases AA uptake - Increases protein translation - Increases protein transcription
41
Why must GH increase amino acid uptake in order to increase protein synthesis?
A greater supply of amino acids are required in order to facilitate the increased protein synthesis.
42
What is meant by GH having both direct and indirect effects?
Growth hormone binds to cells throughout the body, stimulating growth. It also binds to the liver, causing the release of IGF-1 and 2, which goes on to bind to cells in order to stimulate growth.
43
What are the direct effects of GH?
- Metabolic effects - Increased protein synthesis - Increased fat breakdown - Increased blood glucose
44
What are the indirect effects of GH?
- Growth effects - Increased cell size, number and differentiation - Increased protein synthesis - Increased bone growth
45
What are some of the main factors that influence GH secretion? (Accept three of the below)
- Sleep - Exercise - Stress - Fasting - Blood glucose
46
Name two conditions associated with growth hormone deficits:
- Dwarfism - Accelerated aging
47
Name two conditions associated with growth hormone excess:
- Gigantism - Acromegaly
48
Describe the overall structure of the thyroid gland:
The thyroid gland is split into two lobes. The thyroid is deeply vascularised, with its circulation stemming from the jugular veins and carotid arteries.
49
Describe the histology of the thyroid gland:
Comprised of thyroid follicles which store thyroglobulin in their cavities. Lined with follicle cells. In between the follicles are C cells and capillaries.
50
Why is iodine intake so important for healthy endocrine function?
Iodine is essential in the synthesis of thyroid hormones which play a vital role in endocrine function.
51
Where does thyroid hormone synthesis occurs?
Occurs in the centre of the thyroid follicles.
52
What is MIT? What does it stand for?
Mono-iodotyrosine; it is a precursor to the thyroid hormones.
53
What is DIT? What does it stand for?
Di-iodotyrosine; it is a precursor to the thyroid hormones.
54
How is T3 synthesised?
DIT+MIT = T3
55
How is T4 synthesised?
DIT+DIT = T4
56
How are MIT and DIT synthesised?
Iodine is added to tyrosine in successive steps to synthesise MIT then DIT.
57
State the steps involved in the synthesis and release of thyroid hormones:
- Cells accumulate iodide and iodinate tyrosine residues - Iodinated thyroglobulin enters lumen via exocytosis - Stored thyroglobulin re-enters follicle cells via endocytosis - Lysosomal enzymes release T3 and T4
58
What is the purpose of thyroglobulin in thyroid hormone synthesis?
It is a precursor to T3 and T4 used as a store for tyrosine residues.
59
In what ways does TSH influence the synthesis and release of thyroid hormones?
- Regulates iodide pump expression - Regulates expression of thyroid peroxidase - Stimulates endocytosis and lysosymal digestion
60
What hormones are involved in the regulation of thyroid hormone secretion? What are their functions?
- TRH, secreted by the hypothalamus, triggers TSH secretion - TSH, secreted by the pituitary gland, increases iodine uptake and T3/T4 synthesis - Somatostatin, secreted by the hypothalamus, inhibits TSH secretion - Cortisol, secreted by the pituitary gland, inhibits TRH secretion - GH, secreted by the pituitary gland, inhibits TRH secretion
61
Which of the two thyroid hormones is associated with most of the physiological effects (which is more biologically active)?
T3, aka tri-iodothyronine
62
Summarise the effects of TSH
- Increases iodine uptake - Increases TH synthesis - Increases thyroglibulin internalisation and breakdown
63
Summarise the effects of thyroid hormones on the body:
- Stimulate protein carbohydrate and lipid metabolism - Regulates energy metabolism (affecting body temperature) - Regulates nervous, cardiovascular, musculo-skeletal and reproductive systems
64
Summarise the mechanism for TH reception in cells:
- TH binds to mitochondrial receptors, increasing ATP production - TH binds to nuclear receptors, increasing expression of certain genes
65
How do thyroid hormones increase ATP production?
THs bind to mitochondrial receptors, stimulating mitochondria to increase ATP production
66
How do thyroid hormones increase transcription?
Tis bind to nuclear receptors, increasing expression of specific genes.
67
What is another name for tyrosine receptor element (TRE)?
Tyrosine receptor kinase (TRK)
68
What does BMR stand for?
Basal metabolic rate
69
In what way do thyroid hormones affect BMR? Over what time span does this effect occur?
Thyroid hormones increase the basal metabolic rate. To reach peak effect, this takes approximately 10 days.
70
Explain how thyroid hormones affect BMR:
- TH binds to TH receptors on the nucleus and mitochondria - Increases expression of Na+/K+ ATPase and rate of ATP production Overall, increases heat production, thereby increase BMR
71
Explain how thyroid hormones affect protein metabolism:
The effect of TH on protein metabolism is dose-dependent. At high concentrations: - Increased protease synthesis - Thereby increasing protein breakdown and energy expenditure - Increasing BMR At low concentrations: - Increased cell protein synthesis - Thereby facilitating tissue growth
72
How does increased protein metabolism increase energy expenditure
Since the process is anabolic, energy is required to break down proteins.
73
Explain how TH stimulates carbohydrate metabolism:
The effect of TH on carbohydrate metabolism is dose dependent. At higher concentrations: - TH increases enzyme synthesis - Enzymes produced increase glycogenolysis, increase glucose uptake and increase gluconeogenesis - Thereby increasing blood sugar At lower concentrations: - TH increases insulin associated enzyme synthesis - Thereby increasing glycogenesis
74
Explain how TH stimulates fat metabolism:
- TH binds to nuclear receptors - Increasing lipase and lipoprotein receptor expression By increasing lipoprotein receptor expression, there is increased bile and cholesterol secretion, decreasing plasma cholesterol. By increasing lipase synthesis, lipid metabolism increases. Thereby increasing plasma FFAs.
75
Summarise the overall physiological effects of TH on the body:
Body weight - Decreased weight, increased appetite Cardiovascular - Increased blood flow Respiration - Increased respiratory (depth and rate) GI tract - Increased secretions and motility CNS - Increased activity Muscle - Increased tension and contractile force
76
What are the main/most noticed effects of hyperthyroidism? What does this suggest about the body's metabolism?
- Decreased body weight - Heat intolerance - Nervousness - Irritability All of these effects are associated with increased metabolism.
77
What are the main/most noticed effects of hypothyroidism?
- Increased body weight - Cold intolerance - Mental sluggishness - Fatigue - Somnolence All of these symptoms are associated with decreased metabolism.
78
Explain why people with hypothyroidism are intolerant of the cold:
- Cell activity decreases during hypothyroidism - Decreased cell activity decreases BMR - Thus, less heat is produced, making the body colder - As a result the body is more sensitive to the cold
79
Explain why people with hyperthyroidism are intolerant of heat:
- Cell activity increases during hyperthyroidism - Increased cell activity raises BMR - Thus, more heat is produced making the body hotter - As a result, the body is more sensitive to heat
80
What are the two main signs of hyperthyroidism?
- Bulging of the eyes (exophthalmos) - Swelling of the thyroid (goitre)
81
Why is goitre a sign of both hypo and hyper thyroidism?
When underactive (hypo), not enough TH is released causing the colloid to swell with thyroglobulin. When overactive (hyper), too much TH is released causing the colloid to shrink but the surrounding epithelial cells to adapt and enlarge.
82

SL12010 Health and Disease Flashcards (18 decks)

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