L27 & 28: Endocrine System Flashcards
What is the difference between the mediator molecules in the nervous system and the mediator molecules in the endocrine system?
Nervous system uses neurotransmitters that are released locally in response to impulses.
Endocrine system uses hormones delivered to tissues throughout the body by blood.
What is the difference between the site of mediator action in the nervous system and endocrine system?
Nervous system: Close to site of release at the synapse. Binds to the receptors on the post synaptic membrane.
Endocrine system: Far from the site of release. Binds to receptors on or in target cells.
What is the difference between the types of target cells in the nervous and endocrine systems?
Nervous: Targets muscle cells (all 3 types), gland cells, and neurones.
Endocrine: Targets all cells in the body.
What is the difference between the time to onset of action in nervous and endocrine systems?
Nervous: Milliseconds
Endocrine: Hours or days
What is the difference between duration of action in nervous and endocrine systems?
Nervous: Milliseconds
Endocrine: Seconds to days
Define “hormone”
A mediator molecule that is released in one part of the body but regulates the activity of cells in other parts of the body.
Roughly how may hormones do we produce?
30
True or false: Some mediators can act as a neurotransmitter and a hormone
True. e.g. Noradrenaline
Complete the sentence:
“Homones work by ____?____.”
Hormones work by…binding to specific receptors on target cells.
Which type of gland produces hormones?
Endocrine
Fill in the gaps:
Most hormones enter __1__ and then the __2__.
1) interstitial fluid
2) blood stream
What does interstitial mean?
Refers to something being between two structures.
Which of the following is not exclusively an endocrine gland?
A) Thyroid
B) Pituitary
C) Pineal
D) Thymus
D) Thymus
It contains cells that secrete hormones, but is not exclusively an endocrine gland.
What are the 5 major endocrine glands?
1) Pineal
2) Pituitary
3) Thyroid
4) Parathyroid
5) Adrenal
Hormones travelling in the blood will pass all cells, but they will only affect certain cell types. Why is this?
Hormones bind to specific receptors, not all cell will have these receptors
What are the 2 chemical classes of hormones?
1) Lipid soluble
2) Water soluble
What are the 3 types of lipid-soluble hormones?
1) Steroid hormones
2) Thyroid hormones (T3 & T4)
3) Gas (Nitric Oxide, NO)
Name the steroid hormones (7 total) and where they are secreted (4 sites).
Adrenal cortex: Aldosterone, cortisol, and androgens.
Kidneys: Calcitriol
Testes: Testosterone
Ovaries: Oestrogens and progesterone
What are the 2 thyroid hormones?
T3 (triiodothyronine) and T4 (thyroxine)
What hormone is secreted by the endothelial cells lining the blood vessels?
Nitric Oxide (NO)
What are the three types of water-soluble hormones?
1) Amines
2) Peptides and proteins
3) Eicosanoid hormones
Which type of hormone is derived by decarboxylation of amino acids?
Amine hormones (these are water-soluble)
E.g. histamine & serotonin
Protaglandins and leukotrienes are examples of what type of hormone?
Eicosanoid hormones (these are water-soluble)
ADH & oxytocin are examples of what type of hormone?
Peptide/protein hormones
True or false: Water soluble hormones tend to bind to a transporter in the blood?
False. They tend to pass through in a free form
Which type(s) of hormone tend to bind to a transport protein in the plasma?
Steroid and thyroid hormones tend to bind to a transport protein to circulate in the plasma.
Why do steroid and thyroid hormones tend to bind to a transport protein?
1) Soluble
2) Stop/slow filtration by kidneys
3) Act as a hormone reserve
How does a hormone reserve work?
0.1-10% of the hormone molecules are free, as they leave the bound hormones take their place.
Which are typically longer lasting, circulating or local hormones?
Circulating
Do lipid-soluble hormones bind inside or outside the cell?
Inside the cell
What can cells do about the number of receptors when hormone levels are high?
Receptor numbers can be down-regulated.
What can cells do about the number of receptors when hormone levels are low?
Receptor numbers can be up-regulated.
How are cell-hormone receptors up-regulated?
Ribosomes make more of the protein receptors, Golgi apparatus sends to the membrane.
How are cell-hormone receptors down-regulated?
Receptor-mediated endocytosis. The receptors are pulled back into the cell.
How are hormones T3 & T4 made?
By attaching iodine to tyrosine
Do white blood cells and T-cells work by circulating or local hormones?
Local - including autocrine action
Why can the same hormone and receptor produce different effects in different cell types?
The receptors may be the same, but the signalling molecules inside the cells are different. Therefore the action is different.
Which of the following is NOT a lipid-soluble hormone?
A) Aldosterone
B) T4
C) Insulin
D) NO
C) Insulin
T helper cells release the hormone interleukin 2, causing the t-helper cells to proliferate. What is this an example of?
A) Autocrine action
B) Paracrine action
C) Endocrine action
D) Exocrine action
A) Autocrine action
Which of the following is NOT part of the endocrine system?
A) Thalamus
B) Heart
C) Small Intestine
D) Pineal Gland
A) Thalamus
Regarding hormones mechanism of action, which of the following is correct?
A) cAMP is a second messenger for lipid soluble hormones
B) Peptide hormones directly regulate mRNA synthesis
C) Cholesterol based hormones work through phosphorylation amplification cascades
D) Phosphodiesterases inactive peptide hormone signalling
D) Phosphodiesterases inactive peptide hormone signalling
Which is not a feature of hormone signalling?
A) Slow onset
B) Only regulates muscles and glands
C) Diffuse, systemic effect
D) Prolonged effect
B) Only regulates muscles and glands
Transport proteins do not help lipid hormones to:
A) Circulate in the plasma for longer
B) Avoid filtration by kidney
C) Be stored as a reserve
D) Bind to their receptors
D) Bind to their receptors
True or false:
After binding to their receptors, hormones trigger mechanisms of synthesis, degradation, motility changes, secretion, electrical impulses etc.
True.
What does insulin stimulate in liver cells? What does it stimulate in adipose cells?
Liver cells: glycogen synthesis
Adipose cells: triglyceride synthesis
The same hormone can trigger a different mechanism, depending on the responding molecules in the cell.
What are the four steps of lipid-soluble hormone action?
1) Lipid-soluble hormone diffuses into target cell cell
2) Activated receptor-hormone complex alters gene expression
3) Newly formed mRNA directs synthesis of specific proteins on ribosomes
4) New proteins alter cell’s activity
Are lipid-soluble hormones slower or quicker than water soluble?
Lipid-soluble hormones are slower, because they require the formation of new mRNA and then a protein. The process can take 24 hours.
What are the 5 stages of water-soluble hormone action?
1) Water-soluble hormone (first messenger) binds to it’s receptor, activating G protein, which activates adenylate cyclase.
2) Activated adenylate cyclase converts ATP to cAMP (second messenger)
3) cAMP serves as a second messenger to activate protein kinases
4) Activated protein kinases phosphorylate cellular proteins
5) Millions of phosphorylated proteins cause reactions that produce physiological responses
True or false: Water soluble hormones act quicker than lipid-soluble hormones.
True. Water-soluble hormones trigger a quick cascade of action to phosphorylate existing proteins; whereas lipid-soluble hormones trigger the production of new proteins.
How can hormone responses be controlled?
Drugs can inhibit key steps.
e.g. Viagra (phosphodiesterase) inactivates cAMP, preventing the activation of protein kinases.
Fill in the gap:
FSH and oestrogen are an example of __?__ hormones.
Synergistic
Fill in the gap:
Insulin and glucagon are an example of __?__ hormones.
Antagonistic
What is a permissive hormone?
A hormone that works to enhance the response to another hormone. May increase receptor density or promote enzyme activation required for signalling.
Describe the relationship between adrenaline and T3/T4.
Adrenaline is a weak stimulator of lipolysis, but is greatly elevated by T3 and T4.
True or false:
Hormones are released in short bursts.
True
Fill in the gaps:
Endocrine tissue can be __1__/__2__ to control the rate of hormone __3__ (regulated by __4__ and __5__ systems and __6__ of the blood)
1) stimulated
2) inhibited
3) release
4) nervous
5) endocrine
6) chemical composition