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Physiology Flashcards

1
Q

Communication between glands and other tissues occurs by the secretion of _____ ?

A

Hormones

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2
Q

What is a hormone?

A

A chemical messenger
Signalling molecule produced by endocrine glands
They activate specific receptors

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3
Q

Autocrine hormone

A

Hormone acts on the same cell that produced it

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4
Q

Paracrine hormone

A

Hormone acts on target cells nearby

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5
Q

Endocrine hormone

A

Hormone is distributed in the blood circulation and binds to distant target cells

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6
Q

Hormones involved during short term intense exercise?

A

Adrenaline
Cortisol
Glucagon

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7
Q

Hormones involved during long term for normal growth?

A

GH
Insulin
IGF-1
Sex hormones

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8
Q

What is the function of insulin?

A

Lowers plasma glucose levels and stimulates the uptake of glucose into muscle and adipose tissue where it is stored as glycogen

  • inhibits hepatic glycogenolysis
  • inhibits gluconeogenesis
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9
Q

What is the function of glucagon?

A

Raises plasma glucose levels

  • stimulates hepatic glycogenolysis
  • stimulates gluconeogenesis
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10
Q

Are steroid hormones pre-synthesised or synthesised on demand?

A

Synthesised on demand

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11
Q

What are steroid hormones derived from?

A

Cholesterol

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12
Q

What is the function of carrier proteins?

A

To transport insoluble molecules
They increase the amount of hormones transported in the blood
(eg steroids, T4, T3)

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13
Q

Specific carrier proteins: CBP

A

Binds cortisol in a selective manner

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14
Q

Specific carrier proteins: TBG

A

Binds T4 in a selective manner

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15
Q

Specific carrier proteins: SSBG

A

Binds testosterone and oestradiol

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16
Q

General carrier proteins (2)

A

Albumin

Transthyretin

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17
Q

What is the aim of negative feedback

A

To maintain plasma concentration at a set level

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18
Q

Are hormones secreted at the same rate throughout the day?

A

No

  • there is a diurinal rhythm
  • the secretion rate fluctuates depending on the time of day
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19
Q

Where does hormone elimination occur?

A

Metabolised by the liver

Excreted by the kidney

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20
Q

Name the 3 types of hormone receptor

A

GPCR
Receptor tyrosine kinase
Nuclear receptors

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21
Q

GPCR

A

Dissociation of the G protein complex from the GPCR causes the conversion of GDP -> GTP

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22
Q

Examples of GPCR

A

TSH receptor (thyroid stimulating hormone)

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23
Q

Examples of receptor tyrosine kinase

A

Insulin receptor

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24
Q

Pancreatic islets: function of beta cells?

A

Secrete insulin

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25
Pancreatic islets: function of alpha cells?
Secrete glucagon
26
Pancreatic islets: function of delta cells?
Secrete somatostatin
27
Which energy source are you using when you are running for 4 seconds?
ATP
28
Which energy source are you using when you are running for 15 seconds?
Phosphocreatanine
29
Which energy source are you using when you are running for 4 mins?
Free circulating glucose
30
Which energy source are you using when you are running for 77 mins?
Glycogen stores
31
Which energy source are you using when you are running for 3 days?
Fat stores
32
Cellular structure of the thyroid gland
Contains a large follicle Layer of follicular cells around the follicle Colloid in the centre
33
What does the colloid store?
Thyroglobulin | Thyroid hormone which is attached to thyroglobulin
34
What do parafollicular cells secrete?
Calcitonin
35
Synthesis of thyroid hormones
Iodine is taken up by follicular cells Iodine makes its way into the colloid and combines with thyroglobulin tyrosine residues This forms MIT (monoiodotyrosine) and DIT (diiodotyrosine) and eventually produces thyroid hormones (T3 and T4)
36
2 x DIT = T3 or T4?
T4 (thyroxine)
37
(1 x MIT) + (1 x DIT) = T3 or T4?
T3 (triiodothyronine)
38
Storage of thyroid hormones
In the colloid of the thyroid gland
39
Which substance is required for the synthesis of thyroid hormones?
Iodine
40
What happens to thyroid hormone production if the patient is iodine deficient?
There is no production of thyroid hormones
41
Thyroxine (T4)
The main thyroid hormone | Mainly found bound to plasma proteins
42
Do you measure free (unbound) or bound thyroid hormone levels?
Free levels are measured as this is the biologically active form It is only the free hormones that are available to the tissues
43
Tri-iodothyronine (T3)
Produced mainly by the de-ionisation of T4 | Mainly found bound to plasma proteins
44
Which thyroid hormone is more potent and why; T3 or T4?
T3 | - more rapid onset of action
45
Thyroid hormone regulation pathway
Hypothalamus releases TRH --> Stimulates the anterior pituitary gland to release TSH (thyrotropin) --> thyroid gland releases thyroid hormones (T3, T4)
46
What happens to the thyroid hormone regulation pathway when too much thyroid hormone is produced?
Negative feedback occurs | Less TRH is produced, so less TSH, so less thyroid hormones released
47
What happens to the thyroid hormone regulation pathway when not enough thyroid hormone is produced?
Positive feedback occurs | More TRH is produced, so more TSH, so more thyroid hormones released
48
Relationship between cold temperatures and thyroid hormone production
increased thyroid hormone production
49
Relationship between stress and thyroid hormone production
decreased thyroid hormone production
50
Thyroid hormone levels are highest at night - true or false?
True | - and lowest at the morning
51
D-iodinase type 1 (D1)
Converts T4 -> T3 | Found in the liver and kidney
52
D-iodinase type 2 (D2)
Converts T4 -> T3 in the tissues
53
D-iodinase type 3 (D3)
Found in foetal tissue, placenta, brain
54
What do the 4 parathyroid glands secrete?
Para thyroid hormone (PTH)
55
How does TSH allow the release of thyroid hormones?
TSH binds to TSH receptor (GPCR) on the surface of thyroid follicular cells. The production of cAMP increases the production of thyroid hormones
56
How do you measure thyroid hormone function?
By measuring TSH levels Normal TSH = normal thyroid function Increased TSH = Hypothyroid Decreased TSH = Hyperthyroid
57
Increased TBG levels
Increased amount of 'bound' thyroid hormone, but less 'unbound' thyroid hormone - therefore there is less thyroid hormone available to the tissues
58
Which type of receptor is the thyroid hormone receptor
Nuclear receptor When T3 is present, mRNA can be produced When T3 is not present, mRNA cannot be produced
59
Which 2 glands make up the adrenal gland?
Cortex (outer layer) | Medulla (inner layer)
60
Adrenal cortex; 3 sub-sections
Zona glomerulosa - secretes mineralocorticoids eg aldosterone, controlled by RAS system Zona fasciculata - secretes glucocorticoids eg cortisol, controlled by anterior pituitary (ACTH) Zona reticularis - secretes adrenal androgens, controlled by anterior pituitary (ACTH)
61
Adrenal medulla; what does it contain?
Contains chromaffin cells, stored and secretes catecholamines (adrenaline, noradrenaline)
62
Where are the adrenal glands located?
On top of the kidneys
63
Can hormones secreted from the cortex be stored in the cortex or are they synthesised on demand?
Synthesised on demand
64
When is the RAS pathway activated?
When there is a decrease in BP
65
What is the RAS system
Leads to the release of aldosterone in order to increase BP
66
Hypothalamus-pituitary-adrenal axis
Hypothalamus releases CRH --> anterior pituitary gland releases ACTH --> Stimulates the adrenal cortex to release cortisol
67
What happens to the hypothalamus-pituitary-adrenal axis when too much cortisol is produced?
Negative feedback loop | Hypothalamus releases less CRH, anterior pituitary releases less ACTH, this results in less cortisol release
68
When is the best time to measure cortisol levels?
Early morning | - excess cortisol builds up during the night as there is no secretion of cortisol during the night
69
What is cortisol?
Stress hormone | Provides a quick source of energy
70
What is prolactin?
It acts on breast tissue and when active it allows lactation
71
Which cells secrete prolactin?
Lacotroph cells of the anterior pituitary
72
Why is prolactin different from the other anterior pituitary hormones?
It is under INHIBITION (instead of stimulation) by dopamine in the hypothalamus
73
Prolactin pathway
Hypothalamus releases dopamine --> | this inhibits the anterior pituitary from releasing prolactin
74
What happens in the prolactin pathway when dopamine is not released from the hypothalamus?
Anterior pituitary can release prolactin --> | stimulates the mammary glands to lactate
75
What causes raised prolactin levels?
Pregnancy, breast feeding Dopamine antagonists eg metochlopramide Tumour Hypothyroidism
76
Growth hormone pathway
Hypothalamus releases GHRH --> Anterior pituitary gland releases GH --> this stimulates the release of IGF-1 from liver
77
Growth hormone functions
Decreases abdominal fat Increases muscle mass, stamina Improves cardiac function - decreases cholesterol
78
"trophic" hormones - definition
Hormones which act on other endocrine glands
79
Hormones in the posterior pituitary gland? (2)
Oxytocin Vasopressin (ADH) - produced in the hypothalamus - stored in the posterior pituitary gland
80
What investigations do you use to assess posterior pituitary gland function?
U&E's | Plasma/urine osmolality
81
Dynamic pituitary function tests - suppression test
Carried out if the patient is producing too much hormone in order to try and suppress the hormone production - hormone level should come down following the suppression test
82
What is implied if the hormone suppression test doesn't work?
Suggests there is a tumour which is producing too much hormone
83
Dynamic pituitary function tests - stimulation test
Carried out if the patient isn't producing enough hormone in order to try and stimulate the hormone production - hormone level should increase following the stimulation test
84
Examples of hormone stimulation tests
Synacthen test
85
What is the synacthen test
Synthetic ACTH is given to the adrenal gland to see if there is normal secretion of cortisol
86
What happens to the thyroid gland during pregnancy?
It expands which results in increased thyroid hormone production

Endocrine SOH (25 decks)

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