Lecture #32 - What are hormones and how do they work? Flashcards Preview

HUBS191 - Module #3 - Endocrine System > Lecture #32 - What are hormones and how do they work? > Flashcards

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1

Define the endocrine system

Regulates internal environment by secreting hormones that travel through the bloodstream to target areas

 

-Maintianing e.g. glucose, Ca2+ levels in a healthy range

-Endocrine releases hormone that affect organs

-Long distance regulators bc they travel

2

What're the major endocrine glands? (7 covered in this course)

1. Hypothalamus - interacts with pituitary; related to release of hormone

2. Pituitary

4. Thyroid gland

5. Parathyroid gland

6. Adrenal glands

7. Pancreas - blood glucose level regulates (glucagon etc)

3

Endocrine system consists of? (4)

1. Endocrine gland cells that secrete.....

2. Hormones (chemical messengers) which are.....

3. Carried in the blood stream to....

4. The target cells upon which they act

-these target cells are a long way away thus called long distance regulators 

4

What're hormones?

Hormones are chemical messengers produced in one location and transported to a second location (target cells) where they exert their effects 

5

Functional classification of hormones

Water-soluble hormones:

1. Chemical classification?

2. Storage?

3. Transport? 

Lipid (fat)-soluble hormones:

1. Chemical classification?

2. Storage?

3. Transport? 

Water-soluble hormones:

1. Chemical classification?

-Peptides (75% of hormomes)

-Catecholamines 

 

2. Storage?

-Made and stored until required (released by exocytosis)

-Produced in gland cells and stored in vesicles 

 

3. Transport? 

-Travel dissolved in the blood

-Hydrophilic - blood good solvent so travel in blood

-Released when needed

 

 

Lipid (fat)-soluble hormones:

1. Chemical classification?

-Steroids

-Thyroid hormones

 

2. Storage?

-steroids made from cholesterol as required (not stored - gland cells don't store - water-soluble get stored, not these

-thyroid hormones made in thyroid cells, stored until required

 

 

3. Transport?

-travel in the blood bound to a protein (carrier protein) 

-Hydrophobic; can't get dissolved in blood so need carrier proteins - binds to this & transported

6

Examples of water and lipid (4 peptide, 2 catecholamines, 5 steroids and 1 thyroid)

Water:

Peptide = oxytocin, insulin, growth hormone, glucagon

Catecholamines = norepinephrine, epinephrine

 

Lipid:

Steroids = cortisol, aldosterone, testosterone, estrogen/estradiol and progesterone

Thyroid = thyroxine 

7

Cellular response to receptor activation: Water-soluble hormones

Seven steps - what are they?

1. Water-soluble hormone binds to cell surface receptor

2. Hormone binding allows activation of associated G-protein

3. G-protein activates adenylyl cyclase

4. Adenylyl cyclase converts ATP to cyclic AMP (cAMP)

5. cAMP activates protein kinase

6. Protein kinase activates specific enzyme

7. Enzyme converts specific substrate to product (cell’s specific response) 

 

The hormone can't just enter through the membrane bc it's hydrophilic so it goes to binding site on target cell (e.g. plane goes to dock). It locks onto receptor protein and the receptor protein changes chape - activates protein inside cell that's attahed to it. This then activates other proteins and effect is seen. 

Domino effect - the actual hormone doesn't do anything 

1. Bind

2. Receptor changes conformation

3. G-protein

4. Adenyl cyclase

5. Protein kinase phosphorylates the enzyme that will mediate the effect

8

Epinephrine 

1. The hormone epinephrine has ______ effects in _______ the body’s response to _____-_____ ______

2. Epinephrine binds to ________ on the plasma membrane of _______ cells 

3. This triggers the release of _____ _______ that activate _______ and result in the release of _______ into the bloodstream 

 

1. The hormone epinephrine has multiple effects in mediating the body’s response to short-term stress

2. Epinephrine binds to receptors on the plasma membrane of liver cells

3. This triggers the release of messenger molecules that activate enzymes and result in the release of glucose into the bloodstream 

 

-Water soluble can't actually enter the cell 

-Release of glucose bc that's what we use for fight or flight

9

Lipid-solube hormones: Steroid & thyroid hormones

Also has 7 steps

1. Lipid-soluble hormone dissociates from carrier protein

2. Hormone diffuses across cell membrane

3. Hormone binds to INTRACELLULAR receptor

4. Hormone-receptor complex acts as a specific transcription factor

5. New mRNA is generated

6. New protein is generated by translation of mRNA

7. New protein mediates cell’s specific response (SLOW PROCESS) 

 

-Carrier protein - releases hormone as it gets closer to target cell

-Hormone inside cell binds to receptor which is the transcription factor (floating around or in nucleus) 

-Transcription factor bines to promotor gene involved in that hormone response 

1. Hormone travels

2. Enters nucleus

3. Transcription

4. mRNA

5. Protein

-Much slower effect (hours or days)

-Millisecond to minutes for water soluble to show effect 

 

10

Steroid hormone effects in cells 

-Diffuses into cell

-HRE is the specific element for element for transcription factor for specific gene/promotor (Idek)

-If you want big response, increase no. of receptors so regulate the no. of receptors 

11

Comparison of water-soluble & lipid-soluble hormones 

 

Water-soluble hormones

1. Chemical classification?

2. Storage?

3. Transport?

4. Receptors

5. Mechanism of action

6. Speed of response

 

Lipid (fat)-soluble hormones

1. Chemical classification?

2. Storage?

3. Transport?

4. Receptors

5. Mechanism of action

6. Speed of response

Water-soluble hormones

1. Chemical classification?

-Peptides (75% of hormones)

-Catecholamines 

 

2. Storage?

-Stored until required (released by exocytosis)

 

3. Transport?

-Dissolved in blood

 

4. Receptors

-Cell surface

-Initiate cascade to make cyclocamP (?)

 

5. Mechanism of action

-via 2nd messengers

 

6. Speed of response

-Milliseconds to minutes 

 

Lipid (fat)-soluble hormones

1. Chemical classification?

-Steroids 

-Thyroid hormone

 

2. Storage?

-Steroids made from cholestrol as required (not stored)

-Thyroid hormones made in thyroid cells, stored until required 

 

3. Transport?

-Bound to carrier protein

 

4. Receptors

-Intracellular receptors (cytoplasm or nucleus) 

-Get into cell w/ diffusion (water don't come in)

 

5. Mechanism of action

-Alter gene transcription

 

6. Speed of response

-Hours to days

12

Specificity of hormone action

1. Hormone can only affect cells with......

2. What's a receptor?

1. A hormone can only affect cells with speicific receptors for that hormone

2. Receptor is a protein in the cell membrane or inside the cell) - shape is specific 

 

-One cell can express more than one receptor; one cell can respond to more than one hormone

13

Regulation of target cell sensitivity

1. Sensitivity of a target cell to any particular hormone depends on the ____ __ ______ expressed for that hormone

2. Receptors are constantly _____ and ______ to ensure _______

3. Provides a method to change ____ _____ when needed

4. Synthesis > Degradation ----> ?

5. Synthesis < Degradation ----> ?

1. Sensitivity of a target cell to any particular hormone depends on the number of receptors expressed for that hormone

2. Receptors are constantly degraded and synthesized to ensure efficiency

3. Provides a method to change receptor number when needed

4. Synthesis > Degradation ----> Up- regulation

5. Synthesis < Degradation -----> Down- regulation 

 

-If want a big response, increase receptors so regulate no. of receptors

-Cells get rid of receptors so response to hormone decreases - body can modulate how effective hormone is 

14

Comparison of endocrine and neural control systems 

  • Neuronal; basic overview?
    • Targeting achieved by ______?
    • Fastest transmission speed to.....?
      • When conditions are changing rapidly, response delay can lead to.......?
    • Good for ______ responses

 

  • Hormonal; basic overview?
    • Targeting by......?
    • Relatively _____, but ____ _____ action
    • Good for ______ and ______ responses

 

Comparison of endocrine and neural control systems 

 

  • Neuronal; action potentials in axons and neurotransmitter release at synapse 
    • Targeting achieved by specific "wiring"
    • Fastest transmission speed to minimise response delays
      • When condictions are changing rapidly, response delay can lead to tissue damage and to instability of control
    • Good for brief responses

-Only useful for fast, quick responses

-Can't go on for long time

-Pulse sent down axon; neurotrans doesn't have to travel very far (just over post synaptic gap) so post synap cell activated real fast

 

  • Hormonal; hormones released into blood
    • Targeting by expression of specific receptors on target cells
    • Relatively slow, but long lasting action
    • Good for widespread and sustained responses

-Long lasting; can't with neuronal bc keep firing will result in tissue damage 

-Minutes still longer than synapse bc hormones need to go from different point in body - not just synaptic cleft 

-Nervous system will initially quikcly fire response and then hormone comes in and does its job