Introduction to the Endocrine System

Question 1

What does the endocrine system consist of

Answer 1

Ductless endocrine glands occurring at numerous locations in the body

Question 2

How is communication achieved between glands and other tissues

Answer 2

By secretion of a hormone into the blood stream and transport to a target site

Question 3

In what 3 ways is specificity of signalling achieved

Answer 3

1. Chemically distinct hormones
2. Specific receptors for wach hormone
3. Distinct distribution of receptors across target cells

Question 4

Name the 3 endocrines in the brain

Answer 4

Pineal
Hypotahlamus
Pituitary

Question 5

Name the 2 endocrines in the Neck

Answer 5

Parthyroid

Thyroid

Question 6

Name the 2 endocrines in the abdomen

Answer 6

Adrenal gland and pancreas

Question 7

Name the 3 other endocrines depending on the sex of the patient

Answer 7

Testes
Ovaries
Placenta in pregnant females

Question 8

Name the 6 overall functions of the endocrine system

Answer 8

1. Regulation of nutrient metabolism and H2O and electrolyte balance
2. Enabling changes to stress
3. Promoting growth and development
4. Controlling reproduction
5. Regulating red blood cell production
6. Controlling and integrating the activities of the cardiovascular and digestive systems (co-operation with the autonomic nervous system)

Question 9

What is cortisol

Answer 9

A chronic stress hormone

Question 10

What are the 3 main classes of hormones

Answer 10

Glycoproteins and peptides
Steroids
Tyrosine and tryptophan derivatives

Question 11

What are the most diverse class of hormones

Answer 11

Glycoproteins and peptides

Question 12

Give two examples of hormones in the proteins and peptide class

Answer 12

Oxytocin and insulin

Question 13

What are steroid hormones derived from

Answer 13

Cholesterol

Question 14

Give 2 examples of steroid hormones

Answer 14

Cortisol and testosterone

Question 15

Give 3 examples of Tyrosine and tryptophan derivatives

Answer 15

Adrenaline (epinephrine)
Thyroid hormones
Melatonin

Question 16

How are amines synthesised, stored and released

Answer 16

Pre synthesised
Stored in vesicles and released in response to stimuli by Calcium dependent exocytosis
They are hydrophilic and are transported mainly “free” in plasma

Question 17

How are peptides and proteins synthesised, stored and released

Answer 17

Pre-synthesised usually from a longer precursor, stored in vesicles, released in response to stimuli by Ca2+ dependent exocytosis

Question 18

How are peptides transported

Answer 18

They are hydrophilic and are mainly “free” in the plasma

Question 19

How are steroid synthesised and stored?

Answer 19

They are synthesised and secreted on demand

Question 20

What is the rate limiting step in sterois

Answer 20

Rate of conversion of cholesterol to pregnenolone

Question 21

How are steroids released and transported

Answer 21

Steroids are hydrophobic and are transported in plasma main young to plasma proteins - only free is biologically active

Question 22

Describe the solubility of steroids and thyroxine in plasma

Answer 22

Relatively insoluble

Question 23

What do carrier proteins do

Answer 23

Increase the amount transported in blood and prevent rapid excretion by preventing filtration at the kidney

Question 24

What are some of the specific carrier proteins

Answer 24

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

Question 25

What does CBG do

Answer 25

Binds cortisol in a selective manner (also some aldosterone

Question 26

What does TBG do

Answer 26

binds thryoxine (T4) selectively (also some triiodothyronine (T3)

Question 27

What does SSBG do

Answer 27

Binds mainly testosterone and estradiol

Question 28

What are some of the general carrier proteins

Answer 28

Albumin and Transtyhyretin

Question 29

What does albumin do

Answer 29

Binds many steroids and thyroxine

Question 30

What does Transthyretin do

Answer 30

Binds thyroxine and some steroids

Question 31

Describe the solubility of proteins and peptides in plasma

Answer 31

The are soluble

Question 32

Why do proteins and peptides not require carrier proteins for transport

Answer 32

Due to their soluble nature in plasma

Question 33

What do carrier proteins act as

Answer 33

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

Question 34

What type of hormones can cross the capillary wall to activate receptors in target tissues

Answer 34

Free hormones

Question 35

What are surges in hormone secretion buffered by

Answer 35

Binding to carriers - free concentration does not rise abruptly

Question 36

A free hormone removed from plasma by elimination is replaced by what

Answer 36

Bound hormone dissociating from carrier protein

Question 37

What is the primary determinant of plasma concentration

Answer 37

Rate of secretion

Question 38

Secretion is subect to several controls. What are the 2 main controls

Answer 38

Negative feedback Neuroendrocrine Diurnal (circadian) rhythm

Question 39

What does negative feedback play a role in

Answer 39

Maintains plasma concentration at a set level

Question 40

Where are the 2 main centres for regulating negative feedback control

Answer 40

Hypothalamus and anterior pituitary

Question 41

What does the hypothalamus secrete

Answer 41

Corticotropin-releasing hormone

Question 42

What does the anterior pituitary secrete

Answer 42

Adrenocorticotropic homrone

Question 43

What does the adrenal cortex secrete

Answer 43

Cortisol

Question 44

What does neuroendocrine play a roll in

Answer 44

Elicits a sudden burst in secretion to meet a specific stimulus

Question 45

What is an example of a neuroendocrine control of hormones

Answer 45

Stress

Question 46

What is the Diurnal rhythm

Answer 46

Secretion rate fluctuates (up and down) as a function of time - entrained to external cues (e.g. night / day)

Question 47

Elimination occurs by several routes - what are the 2 most important

Answer 47

Generally metabolism by the liver and excretion by the kidney are the most important.

Question 48

How long does it take for amines e.g. adrenaline to be eliminated

Answer 48

Seconds

Question 49

How long does it take for proteins and peptides to be eliminated

Answer 49

Minutes

Question 50

How long does it take for steroids and thyroid hormones to be eliminated

Answer 50

Hours to days

Question 51

Why doe steroids take much longer to be eliminated

Answer 51

Due to the extensive protein binding

Question 52

When are the testosterone level highest

Answer 52

In the morning

Question 53

When should testosterone levels be tested

Answer 53

First thing in the morning

Question 54

What are the 3 structural and functionally distinct types of hormone receptors

Answer 54

G-protein coupled (GPCR) Receptor kinases Nuclear receptors

Question 55

How are G protein coupled receptors activated

Answer 55

By amines and some proteins/peptides

Question 56

Major signalling pathways involve coupling to what GPCRs

Answer 56

Gs, Gi or Gq

Question 57

How are receptor kinases activated

Answer 57

by some proteins/ peptides

Question 58

What are nuclear receptors subdivided into

Answer 58

Class 1, class 2 and a hybrid class

Question 59

What are the cell surface receptors

Answer 59

GPCR and Receptor kinases

Question 60

What are the intracellular receptors

Answer 60

Nuclear receptors

Question 61

What is a class 1 nuclear receptor

Answer 61

Activated by any steroid hormones - in the absence of activating ligand these are mainly located in the cytoplasm bound to inhibitory heart shock proteins (HSP) - they move to the nucleus when activated

Question 62

What are the class 2 nuclear receptors

Answer 62

Activated mostly by lipids - constitutively present in the nucleus

Question 63

What are the hybrid class of nuclear receptors

Answer 63

Activated by thyroid hormone (T3) and other substances - similar in function to class 1