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The Endocrine System > Introduction to the Physiology and Pharmacology of the Endocrine System > Flashcards

Introduction to the Physiology and Pharmacology of the Endocrine System Flashcards

1
Q

The endocrine system essentially consists of many ___________ glands

A

The endocrine system essentially consists of many ductless glands

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2
Q

How is the specificity of signalling achieved in the endocrine system?

A
  1. Chemically distinct hormones
  2. Specific receptors
  3. Distinct distribution of receptors across target cells
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3
Q

Why is specificity of signalling required in the endocrine system?

A

Hormones in the blood stream can reach any tissue

(and only “need” to act on certain tissues)

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4
Q

What are the 4 main secretion types from endocrine glands?

A
  1. Modified amino acids
  2. Steroids
  3. Peptides
  4. Proteins
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5
Q

Give an example of a modified amino acid secretion from an endocrine gland?

A
  1. Adrenaline
  2. Thyroxine (T4)
  3. Triiodothyronine (T3)
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6
Q

Give an example of a steroid hormone

A
  1. Cortisol
  2. Progesterone
  3. Testosterone
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7
Q

What do all steroid hormones originate from?

A

Cholesterol

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8
Q

Give an example of a peptide hormone

A
  1. Adrenocorticotropic hormone (ACTH)
  2. Anti-diuretic hormone (ADH)
  3. Oxytocin
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9
Q

Peptide hormines come from _________ ___________ proteins

A

Peptide hormines come from larger precursor proteins

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10
Q

Give an example of a protein hormone

A

Insulin

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11
Q

What are the 7 main endocrine organs?

A
  1. Pituitary gland
  2. Thyroid gland
  3. Parathyroid glands
  4. Adrenal glands
  5. Pancreas
  6. Ovary
  7. Testis
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12
Q

What is autocrine signalling?

A

When a cell is both the originator and recipient of the signal

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13
Q

What is paracrine signalling?

A

Signalling molecules travel short distances by diffusion and act on cells close by

(they do not enter systemic circulation)

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14
Q

What is endocrine signalling?

A

Hormone is released into the circulation and reaches the target organ this way

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15
Q

Hormones can only function in one of the following three ways, autocrine, paracrine or endocrine. True or false?

A

False

(hormones can function in more than 1 way)

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16
Q

Why do receptors for endocrine hormones have very high affinity for hormone?

A

Organ function is regulated at very low hormone concentrations

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17
Q

Endocrine hormones have high ________

A

Endocrine hormones have high potency

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18
Q

Due to the scarcity of the endocrine hormone signal, what does the target cell do to combat this?

A

Signal transduction pathways amplify the original signal

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19
Q

The onset and duration of hormone action is fairly consistent.

True or false?

A

False

It is highly variable froms seconds to days

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20
Q

The onset and duration of hormone action depends on deactivation of enzyme, but which two locations does this mainly occur at?

A
  1. Enzyme mediated deactivation in the liver
  2. Deactivation at the site of action
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21
Q

Which two categories of functions can hormones have?

A
  1. Complementary
  2. Antagonistic
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22
Q

Are amines either presynthesised or synthesised and secreted on demand?

A

Presynthesised

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23
Q

When would amines be released?

A

In response to stimuli by Ca2+ dependent exocytosis

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24
Q

What are the three key characteristics of amines?

A
  1. Small
  2. Water soluble
  3. Released on demand
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25
Q

Are peptides and proteins either presynthesised or synthesised and secreted on demand?

A

Presynthesised

26
Q

When would peptides and proteins be released?

A

In response to Ca2+ dependent mechanisms

27
Q

In terms of peptides and protein hormones, what is the general term given to enzymes which alter the precursor to the mature hormone?

A

Convertases

28
Q

Cholesterol is converted to steroid hormones via which intermediate?

A

Pregnenolone

29
Q

Are steroids either presynthesised or synthesised and secreted on demand?

A

Synthesised and secreted on demand

30
Q

How do steroid hormones travel in the plasma and why?

A

Via steroid binding proteins

They are very sparingly soluble in water (mostly hydrophobic)

31
Q

What three things do carrier proteins (for steroid hormones) allow?

A
  1. More hormone to be transported in blood
  2. Provides a reservoir of hormone
  3. Extends hormone half life
32
Q

Why do carrier proteins increase the half life of steroid hormones?

A

The protein prevents kidney filtration into the urine

33
Q

Which carrier protein will bind cortisol and some aldosterone?

A

Cortisol-binding globulin

34
Q

Which carrier protein will bind thyroxine and triiodothyronine?

A

Thyroxine-binding globulin

35
Q

Which carrier protein will bind testosterone and some oestradiol?

A

Sex steroid-binding globulin

36
Q

Which general carrier binding protein is associated with steroids and thyroxine?

37
Q

Which general carrier protein is associated with thyroxine and some steroids?

A

Transthyretin

38
Q

In surges of steroid hormone production, why do hormone levels not immediately skyrocket?

A

Carrier proteins act as a buffer

They mop up excess proteins and maintain an equilibrium between free and bound hormone

39
Q

The rate of hormone secretion is ultimately dependent on what?

A

Plasma concentration of hormone

40
Q

Hormones function in a negative/postive feedback loop?

41
Q

Using cortisol as an example, what are the steps which ensure cortisol is secreted from the adrenal cortex?

A
  1. Low cortisol levels (or stress requiring cortisol)
  2. Hypothalamus releases corticotropin-releasing hormone
  3. Corticotropin-releasing hormone acts on the anterior pituitary
  4. Anterior potuitary secretes adrenocorticotropic hormone (ACTH)
  5. ACTH acts on the adrenal cortex
  6. Adrenal cortex secretes cortisol
42
Q

In the control of cortisol secretion pathway, what is the short range inhibition loop?

A

High cortisol levels act on the anterior pituitary preventing ACTH hormone production

This prevents further cortisol production

43
Q

In the control of cortisol secretion pathway, what is the long range inhibition loop?

A

High cortisol levels act on the hypothalamus preventing corticotropin-releasing hormone from being secreted

This prevents cortisol production further down the pathway

44
Q

The secretion rate of certain hormones fluctuates with certain times in the day (ambient light level), what is the term given to this rhythm?

A

Diurnal (Circardian) rhythm

45
Q

The plasma concentration of a hormone is dependent on which two things?

A
  1. Rate of secretion/production
  2. Rate of elimination
46
Q

What are the 3 classes of hormone receptors?

A
  1. G-protein coupled receptors
  2. Receptor kinases
  3. Nuclear receptors
47
Q

Which types of hormones will generally utilise G-protein coupled receptors?

A

Amines

Some proteins and peptides

48
Q

What are the three classes of nuclear receptors?

A
  1. Those activated by steroid hormones
  2. Those activated by lipids
  3. Those with hybrid activation
49
Q

Nuclear receptors which are activated by steroid hormones are always in the nucleus.

True or false?

A

False

They are mainly located in the cytoplasm and move to the nucleus when activated

50
Q

Nuclear receptors which are activated by lipids are always found in the nucleus.

True or false?

51
Q

What is the receptor for insulin?

A

A receptor kinase

52
Q

What is the receptor kinase for insulin comprised of?

A

Alpha and beta subunits

(2 of each)

53
Q

What happens when insulin binds to its receptor kinase?

A
  1. Conformational change
  2. Autophosphorylation occurs at the beta subunits
  3. Insulin receptor protein subunits are subsequently phosphorylated
  4. These carry out cell actions
54
Q

What is a G-protein and what is it comprised of?

A

Guanine nucleotide binding protein

3 subunits (alpha, beta and gamma)

55
Q

How do steroid molecules enter cells?

A

Diffusion

(they are lipophilic)

56
Q

How can steroid hormones influence the transcription of certain proteins?

A
  1. They diffuse into cells
  2. Bind to intracellular receptors, displacing inhibitory heat shock proteins (HSPs)
  3. The receptor/steroid complex forms a dimer and enters the nucleus
  4. It binds to hormone response elements in DNA
  5. Transcription of certain genes is influenced
  6. Mediator protein levels are influenced
57
Q

Name a hormone which can act on a G-protein coupled receptor

A
  1. Angiotensin II
  2. Gonadotrophin releasing hormone
  3. Thyrotropin releasing hormone
58
Q

When a G-protein coupled receptor and Gq is activated, what does the Gq act on and what is the effect?

A

Acts on phospholipase C

Starts the conversion of phosphatidylinositol (4,5) bisphosphate (PIP2) to the soluble messenger molecule inositol (1,4,5) trisphosphate (IP3).

59
Q

Once IP3 is produced, what occurs within a cell?

A
  1. IP3 binds to IP3 receptors of the endoplasmic reticulum
  2. This causes calcium release
  3. This initiates a cellular response e.g. muscle contraction
60
Q

What is DAG, how is it produced and what is its function?

A

Diacylglycerol

  1. It is also produced by phospholipase C when it is activated
  2. It stays in the membrane and recruits protein kinase C from the cytosol
  3. The action of protein kinase C leads to phosphorylation of serine/threonine residues in target proteins
  4. This results in different cellular effects

The Endocrine System (35 decks)

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