Introduction to Endocrine System

Question 1

There are different types of signalling in the body. The 4 key signalling types that we need to know are:

• paracrine
• neuronal
• autocrine
• endocrine

What is paracrine signalling?

Answer 1

• para = besides/close to

- signalling cell is able to signal cells next to or close to it

Question 2

There are different types of signalling in the body. The 4 key signalling types that we need to know are:

• paracrine
• neuronal
• autocrine
• endocrine

What is neuronal signalling?

Answer 2

• a chemical synapse

- neurotransmitter released at pre to post synapse

Question 3

There are different types of signalling in the body. The 4 key signalling types that we need to know are:

• paracrine
• neuronal
• autocrine
• endocrine

What is autocrine signalling?

Answer 3

• cell releases a signal that binds to itself

Question 4

There are different types of signalling in the body. The 4 key signalling types that we need to know are:

• paracrine
• neuronal
• autocrine
• endocrine

What is endocrine signalling?

Answer 4

• signalling molecules are released and travel in the blood

- bind to target tissue

Question 5

There are different types of signalling in the body. The 4 key signalling types that we need to know are:

• paracrine
• neuronal
• autocrine
• endocrine

Of these which is local and which is systemic?

Answer 5

• local = paracrine, neuronal and autocrine

- systemic = endocrine

Question 6

What is the purpose of a negative feedback loop?

Answer 6

• an inhibitory loop or self-regulating system

- increased output from a system/organ inhibits future production by the system to maintain normal homeostasis

Question 7

What is the purpose of a positive feedback loop?

Answer 7

• as stimulus that causes an ‘non-normal’ physiological response
• release of oxytocin in child birth stimulates contractions in response to baby being born to help with birth

Question 8

Do endocrine glands contain ducts for secretion of their hormones?

Answer 8

• no
• they are ductless
• secrete directly into blood

Question 9

There are lots of endocrine glands. Using the mnemonic below, what are those glands:

Help
Paul
Pick 
The 
Perfect
Toy
And 
Play 
On 
Trains

Answer 9

• Help = Hypothalamus
• Paul = Pineal gland
• Pick = Pituitary
• The =Thyroid
• Perfect = Parathyroid
• Toy = Thymus
• And = adrenal
• Play = pancreas
• On = ovaries
• Trains = testes

Question 10

The pituitary gland is also known as something else, what is this?

Answer 10

• hypo = means lying under

- hypophysis

Question 11

What is the main part of the brain that controls the majority of the pituitary gland secretions?

Answer 11

• hypothalamus

Question 12

There are 2 key parts of the pituitary gland, what are these called?

Answer 12

1 - anterior pituitary

2 - posterior pituitary

Question 13

How are the pituitary and hypothalamus connected?

Answer 13

• pituitary stalk

Question 14

The pituitary gland sits inside the sphenoid bone of the skull, specifically which part of the sphenoid bone?

Answer 14

• sella turcica (pituitary fossa)

- turkish for seat

Question 15

What is acromegaly?

Answer 15

• acro = greek for extremely
• megaly = greek for mega/great
• increased growth hormone release in adults causing bones to increase in size

Question 16

What is gigantism?

Answer 16

• greek for giant
• increased growth hormone release in children prior to bone fusion
• causes abnormal height and bone growth

Question 17

Label the thyroid and parathyroid below:

Answer 17

1 = thyroid gland 
2 = parathyroid glands

Question 18

The thyroid receives the majority of its stimulus from where?

Answer 18

• pituitary gland

Question 19

The thyroid receives the majority of its stimulus from the pituitary gland. What is the main function of the thyroid gland?

Answer 19

• regulation of metabolism

Question 20

The parathyroid are located posteriorly on the thyroid gland. What is the main function of the parathyroid glands?

Answer 20

• regulating plasma calcium concentrations

Question 21

The pancreas has 2 major functions in the body, what are they?

Answer 21

1 = release insulin and glucagon for blood glucose control
2 = release digestive enzymes for digestion

Question 22

The pancreas releases insulin and glucagon, which cells in the pancreas secrete insulin and glucagon?

Answer 22

• insulin = beta cells

- glucagon = alpha cells

Question 23

What are islets of Langerhans?

Answer 23

• groups of islet cells that secrete insulin and glucagon

Question 24

Which cells in the pancreas secrete gastrointestinal fluids?

Answer 24

• acini cells

Question 25

What are the 3 cells of the islets of langerhans and what do they secrete?

Answer 25

1 - alpha cells = glucagon 2 - beta cells = insulin 3 - delta cells = somatostatin

Question 26

The adrenal glands are located superiorly on the kidneys and have 2 key parts, label them using the labels below: - cortex - medulla

Answer 26

``` 1 = medulla 2 = cortex ```

Question 27

The medulla (centre of the adrenal gland) and the cortex (outer part of the adrenal gland) both secrete hormones. What key hormones do the medulla and cortex secrete?

Answer 27

- medulla = epinephrine (adrenaline) and nora-epinephrine (nora-adrenaline) - cortex = corticosteroids

Question 28

The cortex releases corticosteroids such as cortisol. What are these synthesised from?

Answer 28

- cholesterol | - all have similiar structure to cholesterol

Question 29

The medulla releases epinephrine (adrenaline) and nora-epinephrine (nora-adrenaline). What stimulates the secretion of these hormones?

Answer 29

- sympathetic tone

Question 30

Peptide hormones (also called non-steroidal hormones), as the name suggests are proteins that can be long or short, composed of simple amino acids or secondary, tertiary or quaternary structures. Are they hydrophobic or hydrophilic?

Answer 30

- water loving, so hydrophilic | - able to move freely in the blood without binding to anything

Question 31

Peptide hormones (also called non-steroidal hormones), as the name suggests are proteins that can be long or short, composed of simple amino acids or secondary, tertiary or quaternary structures. They are water loving, so hydrophilic and are able to move freely in the blood without binding to anything. How do they affect their target tissue though?

Answer 31

- hydrophilic so cannot pass plasma membranes | - bind to receptors on cell membrane that cause intracellular cascade

Question 32

Is hormone release via endo or exocytosis?

Answer 32

- exocytosis

Question 33

Hormones can be stored in the cells that release them, beta cells store insulin for example. As this is a peptide (non-steroidal) hormone it can be created through DNA transcription, protein synthesis and then stored in vesicles. What are the hormones stored as in the vesicles?

Answer 33

- prohormones (not already active) | - cleaved by specific enzymes that makes them active just prior to release

Question 34

Steroid hormones that are mainly produced by cholesterol are hydrophilic, meaning they hate water. This means they cannot travel freely in the blood. What must they do to travel in the blood?

Answer 34

- bind to transport proteins

Question 35

Steroid hormones that are mainly produced by cholesterol are hydrophilic, meaning they hate water. This means they cannot travel freely in the blood. They must bind with transport proteins to travel in the blood. How do steroid hormones have an effect on cells?

Answer 35

- able to pass through cell membranes | - bind to receptors inside cell triggering genes to be switched on or off

Question 36

Can steroid hormones be stored in cells?

Answer 36

- no | - but can be synthesises rapidly from cholesterol

Question 37

Tyrosine is an important amino acid in the endocrine system. In relation to neurotransmitters/stress hormones, what is the pathway tyrosine takes to create epinephrine (adrenaline)?

Answer 37

- tyrosine - L-DOPA - dopamine - noradrenaline - adrenaline

Question 38

Tyrosine is an important amino acid in the endocrine system. In relation to the hormones released by the thyroid gland, what is the pathway that tyrosine takes?

Answer 38

- tyrosine - 3-lodo-L-tyrosine - 3-5-lodo-L-tyrosine - 3-5-lodo-L-tyrosine can then be turned into thyroxine (T4) or triiodothyronine (T3)

Question 39

Are peptides (non-steroidal) or steroidal hormones long acting?

Answer 39

- peptides (non-steroidal) = do not need to bind with anything so short acting and short plasma half life - steroidal hormones = need to bind to transport proteins (albumin) so acts as a resevoir meaning it has a long acting and long plasma half life

Question 40

There are 3 classes of hormone receptors, what are they?

Answer 40

1 - tyrosine kinase receptors 2 - G-protein coupled receptor 3 -Steroid hormone receptors

Question 41

There are 3 classes of hormone receptors: 1 - tyrosine kinase receptors 2 - G-protein coupled receptor 3 -Steroid hormone receptors Which are peptide (non-steroidal) and steroid hormones?

Answer 41

- peptide (non-steroidal) = tyrosine kinase receptors and G-protein coupled receptor - steroidal = steroid hormone receptors

Question 42

What is the pathway for the GPCR Gaq?

Answer 42

- Phospholipase C activation cleaves PIP2 - PIP2 cleavage into DAG and IP3 - Ca2+ influx, cAMP activation leading to protein phosphorylation

Question 43

What is the pathway for a tyrosine kinase receptor (TKR)?

Answer 43

- TKR = a membrane bound protein dimer - hormone binds to receptor - results in auto-phosphorylation at tyrosine residues inside the cell - further phosphorylation of intracellular proteins and biochemical cascade

Question 44

Steroid hormones can directly enter cells. Reorganise the order below of how steroid hormones, are able to exert its effects on the cell? - enters through cell membrane due to small size and hydrophobic nature - cell undergoes transcription and protein synthesis - HRC enters the nucleus and cytoplasmic receptor aspect of the HRC binds to DNA - steroid hormone binds with cytoplasmic receptor forming hormone receptor complex (HRC) - HRC binds to specific parts of DNA and genes can be turned on or off

Answer 44

1 - enters through cell membrane due to small size and hydrophobic nature 2 - steroid hormone binds with cytoplasmic receptor forming hormone receptor complex (HRC) 3 - HRC enters the nucleus and cytoplasmic recpeotr aspect of the HRC binds to DNA 4 - HRC binding to genes is able to turn genes on or off 5 - cell undergoes transcription and protein synthesis

Question 45

The thyroid gland comes under the control of the hypothalamus and the anterior pituitary gland. What does the hypothalamus release to stimulate the pituitary gland, and then what does the pituitary gland secrete to stimulate the thyroid gland?

Answer 45

- hypothalamus secretes - thyrotropin-releasing hormone (TRH) - pituitary gland secretes - thyroid stimulating hormone (TSH)

Question 46

The thyroid gland comes under the control of the hypothalamus and the anterior pituitary gland resulting in the follow secretions: - hypothalamus secretes - thyrotropin-releasing hormone (TRH) - pituitary gland secretes - thyroid stimulating hormone (TSH) Once TSH stimulates the thyroid gland to secrete triiodothyronine (T3) and thyroxine (T4). How do the levels of T3 and T4 regulate the thyroid gland?

Answer 46

- increased T3 and T4 in blood bind to pituitary gland | - act as a negative feedback loop to inhibit secretion of TSH

Question 47

The thyroid gland comes under the control of the hypothalamus and the anterior pituitary gland resulting in the follow secretions: - hypothalamus secretes - thyrotropin-releasing hormone (TRH) - pituitary gland secretes - thyroid stimulating hormone (TSH) In addition to triiodothyronine (T3) and thyroxine (T4) being released from the thyroid and binding to the pituitary gland causing a negative feedback loop and inhibiting TSH, what else can T4 do?

Answer 47

- T4 binds to target cells (metabolism) | - target cells then signal pituitary gland and hypothalamus to inhibit TRH and TSH secretion

Question 48

What is the pathway of the hypothalamus-pituitary-adreanl (HPA) axis?

Answer 48

- hypothalamus secretes corticotropin releasing hormone (CRH) - CRH binds to anterior pituitary gland causing release of adrenocorticotropic hormone (ACTH) - ACTH is released into blood and binds to adrenal cortex - adrenal cortex releases glucocorticoids (cortisol)

Question 49

Once glucocorticoids (cortisol) have been released from the adrenal glands as part of the hypothalamus-pituitary-axis (HPA) axis, how are glucocorticoids involved in a negative feedback loop?

Answer 49

- glucocorticoids bind to pituitary gland and hypothalamus, inhibits further release of glucocorticoids