Introduction to the Endocrine system

Question 1

What are some criteria for an endocrine hormone?

Answer 1

travels in the blood
target organ distal to site of synthesis
secreted from cells, tissues or glands

Question 2

Give an example of a fast and a slow response endocrine hormone

Answer 2

fast eg adrenaline

slow eg growth hormone

Question 3

What is a paracrine hormone? + example

Answer 3

Acts local to site of synthesis

histamine

Question 4

What is an autocrine hormone? + example

Answer 4

Act on/in the same cell that synthesises it

cytokine

Question 5

What is an exocrine hormone? + example

Answer 5

Released from exocrine glands via ducts

GI tract eg saliva, bile

Question 6

What 2 systems control all body function?

Answer 6

nervous and endocrine

Question 7

What must be present for a hormone to have an effect on a tissue?

Answer 7

Presence of specific receptors

Question 8

What is a neurotransmitter?

Answer 8

released from presynaptic neuron and travels across cleft and acts locally

Question 9

What is an example of a long term phenomena which includes the co-operation of nervous and endocrine systems?

Answer 9

growth

Question 10

What is the neuroendocrine hormones? + example

Answer 10

Nerves release hormones into the blood

hypothalamic-posterior pituitary axis

Question 11

Why is the response of hormones highly specific?

Answer 11

Only act on target cells with receptors

Question 12

Does a hormone have 1 or more than 1 target sites and effects?

Answer 12

more than 1 effect on different target cells

Question 13

What is the broad function of hormones and neurotransmitters?

Answer 13

Bring about changes in activity of target cells and tissues (increase/decrease activity)

Question 14

What systems is endocrine function embedded into?

Answer 14

reproductive, renal, GI

Question 15

What diffuse systems of glands is endocrine function in its own right?

Answer 15

thyroid, adrenal + pituitary glands, hypothalamus

Question 16

Do you require large or small concentrations of hormones to bring about their effect?

Answer 16

very small - pico Molar

Question 17

How is hormone action often terminated?

Answer 17

negative feedback loops

metabolised

Question 18

What are the 3 classes of hormones?

Answer 18

peptide/protein
steroid
amine

Question 19

What is the most common class of hormone?

Answer 19

peptide

Question 20

What are peptide hormones composed of?

Answer 20

chains of amino acids

Question 21

What are all steroid hormones derived from?

Answer 21

cholesterol

Question 22

What 2 amino acids are amine hormones derived from?

Answer 22

tryptophan - melatonin

tyrosine

Question 23

Are peptide hormones synthesised on demand or premade?

Answer 23

premade and stored in vesicles

Question 24

What produces the preprohormone and state its size and activity

Answer 24

ribosomes
large
inactive

Question 25

How is the prehormone made?

Answer 25

preprohormone is cleaved in RER | still inactive

Question 26

What happens to prehormone?

Answer 26

Packaged into vesicles at Golgi apparatus with proteolytic enzymes

Question 27

What do the proteolytic enzymes break the prehormone into?

Answer 27

active hormone | inactive fragment

Question 28

What is meant by co-secretion?

Answer 28

Active hormone and inactive fragments released from vesicle into the blood

Question 29

Give an example of when measuring inactive fragments can be important clinically

Answer 29

c peptide with insulin | measures ENDOGENOUS insulin, independent of any synthetic function

Question 30

Are peptide hormones hydrophilic or hydrophobic?

Answer 30

hydrophilic (lipophobic)

Question 31

How do peptide hormones cross the cell membrane?

Answer 31

membrane bound receptors on target cells

Question 32

Do peptide hormones have slow or fast responses?

Answer 32

fast

Question 33

2 membrane bound receptors used with peptide hormones

Answer 33

GPCR | tyrosine kinase linked signalling pathways

Question 34

How do GPCR work?

Answer 34

activate 2nd messengers - rapid response

Question 35

How do Tyrosine kinase linked receptors work?

Answer 35

alter gene expression - slower, longer lasting

Question 36

Why are steroid hormones made as they are needed?

Answer 36

highly lipophilic | cannot be retained in lipid membrane

Question 37

How are steroid hormones transported in the blood

Answer 37

bound to carrier proteins eg albumin

Question 38

2 advantages of having steroid hormones bound to carrier proteins

Answer 38

increases half life | protects from enzymatic degredation

Question 39

4 organs producing steroid hormones and what they produce

Answer 39

gonads - sex hormones placenta - hCG and sex hormones adrenal cortex - corticosteroids kidney - vitamin D3

Question 40

How is the specific steroid hormone determined and how is this important with the effects of excess steroids

Answer 40

different enzymes | common ancestry

Question 41

Where are steroid hormone receptors located?

Answer 41

in cells as lipophilic | cytoplasmic or nuclear

Question 42

What is meant by the genomic effect of steroid hormones? What is the knock on effect of this?

Answer 42

activate or repress gene function | protein synthesis

Question 43

What is the difference in response if the steroid hormones bind to cell surface receptors?

Answer 43

rapid response

Question 44

3 examples of amine hormones

Answer 44

dopamine epinephrine norepinephrine

Question 45

Are amine hormones lipophilic or lipophobic?

Answer 45

lipophobic - like peptide hormones

Question 46

Only amine hormone derived from tryptophan

Answer 46

melatonin

Question 47

What hormones do thyroid hormones act like?

Answer 47

steroid hormones

Question 48

What is the physiologically important fraction of lipophilic hormones?

Answer 48

free unbound

Question 49

Is free or complex hormones favoured? what is this ratio in health?

Answer 49

complexed | constant

Question 50

What does the law of mass action say?

Answer 50

free hormone is constant | as it leaves plasma more is released from carriers

Question 51

total plasma [hormone] =

Answer 51

free hormone + complexed hormone

Question 52

What organ excretes and what organ metabolises hormones?

Answer 52

kidneys | liver

Question 53

Why are peptide/amine hormones easily excreted?

Answer 53

short half-life | soluble in water

Question 54

Why do steroid and thyroid hormones take hours to excrete?

Answer 54

protein bound

Question 55

3 ways that hormone secretion can be controlled

Answer 55

negative feedback loop neural feedback loop multiple control mechanisms

Question 56

What adaptions will be made in response to low and high hormone concentration?

Answer 56

low - increase number of receptors = upregulation increase sensitivity high - opposite = downregulate

Question 57

What is meant by a permissive effect?

Answer 57

the presence of 1 hormone enhances the effect of another

Question 58

Give an example of a permissive effect

Answer 58

Thyroid and epinephrine with lipolysis | TH increases synthesis for epinephrine receptors on adipocytes

Question 59

Why may 24 hour monitoring of hormones be required?

Answer 59

They are released in short bursts and concentration varies widely single values misleading