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Endocrine Lectures > Introduction to the Endocrine System Hormones, Receptors and Signalling > Flashcards

Introduction to the Endocrine System Hormones, Receptors and Signalling Flashcards

1
Q

What kinds of glands are in the endocrine system?

A

Ductless

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2
Q

How do glands communicate with each other over a distance?

A

Secretion of hormone into the blood stream and bulk transport to a target site

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3
Q

What is an example of an integrated functional system?

A

Hypothalamus releases CRF that stimulates the anterior pituatru to release ACTH that causes the adrenal cortex to synthesise and release cortisol

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4
Q

How is specificity of signalling achieved?

A

Chemically distinct hormones
Specific receptors for each hormone
Distinct distribution of receptors across target cells

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5
Q

What are the major endocrine organs?

A 
Pineal gland
Hypothalamus
Pituatry gland
Thyroid gland
Parathyroid gland
Thymus
Adrenal glands
Pancreas
Ovary
Testis
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6
Q

What are the 4 chemical natures of hormones?

A

Modified Amino acids
Steroids
Peptides
Proteins

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7
Q

What are some examples of modified amino acids?

A

Adrenaline

Thyroid hormone

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8
Q

What are some examples of steroids?

A

Cortisol
Progesterone
Testosterone

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9
Q

What are some examples of peptides?

A

Anrenocorticotrophic hormone (ACTH)
Anti-diuretic hormone (ADH)
Oxytocin

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10
Q

What is an example of a protein?

A

Insulin

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11
Q

What are all steroid hormones derived from?

A

Cholesterol

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12
Q

What is autocrine signalling?

A

Cell produces signalling molecule that is released into to ECF, these molecules act on the cell itself
(Self-signalling)

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13
Q

What is Paracrine signalling?

A

Cell signals to its close neighbors

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14
Q

What is endocrine signalling?

A

The signalling molecule enters the circulation and signals via molecules transported by the blood to target distant cells

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15
Q

What levels of hormones can affect organ function?

A

Can be very low concentrations

utilises signals which act at an extremely low concentration

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16
Q

If the signal is very scarce, what must be increased?

A

Receptor Affinity

Hormone Potency

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17
Q

What are some examples of where insulin can act?

A

Skeletal Muscle
Adipose tissue
Hepatocytes

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18
Q

How is a biological response brought about?

A

Hormone binds to its cognate receptor which is expressed in a tissue selective manner

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19
Q

What triggers a biological response?

A

Activated receptor engaging in a preferred signal transduction cascade that differs between individual receptors but typically causes amplification of the original signal

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20
Q

Is the speed of onset and duration of a hormone variable?

A

Yes very

seconds to days

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21
Q

How is hormone action terminated?

A

Enzyme mediated metaboloic inactivation in the liver or site of action

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22
Q

What is a complementary action of a group of hormones?

A

Regulates many complex physiological functions on both short and long term scales

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23
Q

What is an example of a complementary action of a group of hormones?

A

Adrenaline, cortisol and glucagon contribute to the response of the body to short term intense exercise enhancing physical performance and preventing potential hypoglycaemia

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24
Q

How does an antagonistic action occur?

A

The balance of opposing influences

25
Q

What 2 hormones have opposing actions that regulates plasma glucose levels?

A

Insulin

Glucagon

26
Q

How are amines made, stores and released?

A

Pre-synthesised
Stored in vesicles
Released in response to stimuli by Ca2+ dependent exocytosis

27
Q

Are amines hydrophilic or hydrophobic?

A

Hydrophillic

28
Q

How are peptides and proteins made, stores and released?

A

Presynthesised from longer precursors
Stored invesicles
Released in response to stimuli by Ca2+ dependent exocytosis

29
Q

Are peptides hydrophillic or hydrophobic?

A

Hydrophyllic

30
Q

How are steroids made, stores and released?

A

Synthesised and secreted upon demand
Stimuli increase:
-Cellular uptake and availlibility of cholesterol
-Rate of conversion of choolesterol to pregnenolone

31
Q

When is cortisol released?

A

Immediately after it is formed

No prestorage or packaging

32
Q

What must occur for a cell to produce a steroid hormone?

A

The cell must initiate synthesis and release the steroid immediately

33
Q

Are steroids hydrophobic or hydrophyllic?

A

Hydrophobic

34
Q

How are steroids transported in blood?

A

Bound to specific transport proteins

35
Q

What is the fraction of steroid that is unbound able to do?

A

Biologically active

Can cross the wall

36
Q

What are 3 steroids that must be carried by circulating carrier proteins?

A

Steroids
Thyroxine
Triiodothyronine

37
Q

What are some functions of carrier proteins?

A

Increase amount transported in blood
Provide a reservoir of hormone
Extends half life of the hormone in the circulation

38
Q

What are 3 important plasma carried proteins?

A

Cortisol-binding globulin (CBG)
Thyroxine-binding globulin (TBG)
Sex steroid-binding globuling (SSBG)

39
Q

What are 2 general carrier proteins?

A

Albumin

Transthyretin

40
Q

What do carrier proteins act as?

A

A buffer and reservoir that helps to maintain relatively constant concentrations of free lipophilic hormone in the blood - equillibrium between free and bound hormone

41
Q

What hormones can cross the capillary wall?

A

Only free hormone

42
Q

What are surges in hormone secretion buffered by?

A

Binding to carriers - free concentration does not rise abruptly

43
Q

How is free hormone removed from plasma?

A

By elimination

44
Q

What is the free hormone that is removed by plasma replaced with?

A

Bound hormone dissociating from carrier proteins

45
Q

What is the primary determinant of plasma concentration?

A

Rate of secretion

46
Q

Describe the pathway in which cortisol is released?

A 
Hypothalamus
Secretes corticotrophin releasing factor (CRF)
Anterior pituitary
Secretes ACTH
Adrenal cortex
Secretes cortisol
47
Q

What is diurnal circadian rhythm?

A

Secretion rate fluctuates (up and down) as a function of time entrained by external cues

48
Q

What important routes can elimination occur by?

A

Metabolism locally
Metabolism by the liver
Excretion by the kidney

49
Q

What is plasma concentration of a hormone equal to?

A

Rate of secretion - rate of elimination

50
Q

What are 3 types of Hormone receptors?

A

G coupled protein receptors
Receptor kinases
Nuclear receptors

51
Q

How are GPCR activated and where are they found?

A

Activater by amines and some proteins and peptides

Found on the cell surface

52
Q

What are receptor kinases activated by and where are they found?

A

Proteins and petides

Found on the cell surface

53
Q

Where are nuclear receptors found?

A

INtracellularly

  • In cytoplasm (class 1)
  • In nucleus
54
Q

What are the 3 classes of nuclear receptors?

A

Class 1 - activated by many steroid hormones, in the absense of activating ligand these are mainly located in the cytoplasm bound to heat shock proteins
Class 2 - activated mostly by lipids, present in the nucleus
Hybrid class - Activated by thyroid hormone and other substances

55
Q

What is constitutive activity?

A

Always active without any signals

56
Q

What kind of receptor is the insulin receptor?

A

Receptor kinases

57
Q

What subunits are present in the insulin receptors?

A

Alpha and Beta subunits

58
Q

What does the binding of insulin to the receptor cause?

A

Autophosphorylation of intracellular tyrosine residues
Recruitment of multiple adapter proteins (IRS1) that are also tyrosine phosphorylated
- binding of Insulin receptor substrate proteins which become phosphorylated
-AKT/Protein Kinase B
-Metabolic effects

Endocrine Lectures (8 decks)

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