Introduction to Endocrine System Flashcards
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?
- para = besides/close to
- signalling cell is able to signal cells next to or close to it
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?
- a chemical synapse
- neurotransmitter released at pre to post synapse
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?
- cell releases a signal that binds to itself
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?
- signalling molecules are released and travel in the blood
- bind to target tissue
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?
- local = paracrine, neuronal and autocrine
- systemic = endocrine
What is the purpose of a negative feedback loop?
- an inhibitory loop or self-regulating system
- increased output from a system/organ inhibits future production by the system to maintain normal homeostasis
What is the purpose of a positive feedback loop?
- 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
Do endocrine glands contain ducts for secretion of their hormones?
- no
- they are ductless
- secrete directly into blood
There are lots of endocrine glands. Using the mnemonic below, what are those glands:
Help Paul Pick The Perfect Toy And Play On Trains
- Help = Hypothalamus
- Paul = Pineal gland
- Pick = Pituitary
- The =Thyroid
- Perfect = Parathyroid
- Toy = Thymus
- And = adrenal
- Play = pancreas
- On = ovaries
- Trains = testes
The pituitary gland is also known as something else, what is this?
- hypo = means lying under
- hypophysis
What is the main part of the brain that controls the majority of the pituitary gland secretions?
- hypothalamus
There are 2 key parts of the pituitary gland, what are these called?
1 - anterior pituitary
2 - posterior pituitary
How are the pituitary and hypothalamus connected?
- pituitary stalk
The pituitary gland sits inside the sphenoid bone of the skull, specifically which part of the sphenoid bone?
- sella turcica (pituitary fossa)
- turkish for seat
What is acromegaly?
- acro = greek for extremely
- megaly = greek for mega/great
- increased growth hormone release in adults causing bones to increase in size
What is gigantism?
- greek for giant
- increased growth hormone release in children prior to bone fusion
- causes abnormal height and bone growth
Label the thyroid and parathyroid below:
1 = thyroid gland 2 = parathyroid glands
The thyroid receives the majority of its stimulus from where?
- pituitary gland
The thyroid receives the majority of its stimulus from the pituitary gland. What is the main function of the thyroid gland?
- regulation of metabolism
The parathyroid are located posteriorly on the thyroid gland. What is the main function of the parathyroid glands?
- regulating plasma calcium concentrations
The pancreas has 2 major functions in the body, what are they?
1 = release insulin and glucagon for blood glucose control 2 = release digestive enzymes for digestion
The pancreas releases insulin and glucagon, which cells in the pancreas secrete insulin and glucagon?
- insulin = beta cells
- glucagon = alpha cells
What are islets of Langerhans?
- groups of islet cells that secrete insulin and glucagon
Which cells in the pancreas secrete gastrointestinal fluids?
- acini cells
What are the 3 cells of the islets of langerhans and what do they secrete?
1 - alpha cells = glucagon
2 - beta cells = insulin
3 - delta cells = somatostatin
The adrenal glands are located superiorly on the kidneys and have 2 key parts, label them using the labels below:
- cortex
- medulla
1 = medulla 2 = cortex
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?
- medulla = epinephrine (adrenaline) and nora-epinephrine (nora-adrenaline)
- cortex = corticosteroids
The cortex releases corticosteroids such as cortisol. What are these synthesised from?
- cholesterol
- all have similiar structure to cholesterol
The medulla releases epinephrine (adrenaline) and nora-epinephrine (nora-adrenaline). What stimulates the secretion of these hormones?
- sympathetic tone
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?
- water loving, so hydrophilic
- able to move freely in the blood without binding to anything
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?
- hydrophilic so cannot pass plasma membranes
- bind to receptors on cell membrane that cause intracellular cascade
Is hormone release via endo or exocytosis?
- exocytosis
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?
- prohormones (not already active)
- cleaved by specific enzymes that makes them active just prior to release
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?
- bind to transport proteins
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?
- able to pass through cell membranes
- bind to receptors inside cell triggering genes to be switched on or off
Can steroid hormones be stored in cells?
- no
- but can be synthesises rapidly from cholesterol
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)?
- tyrosine
- L-DOPA
- dopamine
- noradrenaline
- adrenaline
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?
- 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)
Are peptides (non-steroidal) or steroidal hormones long acting?
- 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
There are 3 classes of hormone receptors, what are they?
1 - tyrosine kinase receptors
2 - G-protein coupled receptor
3 -Steroid hormone receptors
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?
- peptide (non-steroidal) = tyrosine kinase receptors and G-protein coupled receptor
- steroidal = steroid hormone receptors
What is the pathway for the GPCR Gaq?
- Phospholipase C activation cleaves PIP2
- PIP2 cleavage into DAG and IP3
- Ca2+ influx, cAMP activation leading to protein phosphorylation
What is the pathway for a tyrosine kinase receptor (TKR)?
- 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
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
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
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?
- hypothalamus secretes - thyrotropin-releasing hormone (TRH)
- pituitary gland secretes - thyroid stimulating hormone (TSH)
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?
- increased T3 and T4 in blood bind to pituitary gland
- act as a negative feedback loop to inhibit secretion of TSH
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?
- T4 binds to target cells (metabolism)
- target cells then signal pituitary gland and hypothalamus to inhibit TRH and TSH secretion
What is the pathway of the hypothalamus-pituitary-adreanl (HPA) axis?
- 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)
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?
- glucocorticoids bind to pituitary gland and hypothalamus, inhibits further release of glucocorticoids
