Lecture 32 Flashcards
What does the endocrine system act to maintain? How does it do this?
The endocrine system acts to maintain our internal environment (homeostasis) through the usage of hormones.
What are the major endocrine glands?
pineal, hypothalamus, pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, thymus and the testes and ovaries.
What are the four parts of the endocrine system?
The endocrine gland cells, the hormones secreted by those cells, the bloodstream through which the hormones travel and the target cells upon which those hormones act.
What are the two classifications for both water soluble hormones and lipid (fat) soluble hormones (4 in total) and what are the main differences?
Peptides and Catecholamines are water soluble hormones and are made and stored until required, they travel dissolved in blood as blood is largely water.
Steroids and thyroid hormones are lipid soluble hormones and steroids are made from cholesterol as required (rather than stored like water soluble ones), thyroid hormones though are stored until required. Both steroids and thyroid hormones travel in the blood bound to carrier proteins though as they are not water soluble.
How do the water soluble hormones activate responses in cells?
Peptides and Catecholamines will bind to receptors on the cell surface, this binding will cause a shape change which will activate the associated G-protein which in turn will activate adenylyl cyclase which converts ATP into cyclic AMP. This cAMP activates the protein kinase which will then activate the specific enzyme which will then convert the necessary substrate to the product (the cells specific response).
How do Lipid soluble hormones cause responses in cells?
Firstly, steroids and thyroid hormones will arrive near the cell on the carrier protein and dissociate, from there it will diffuse across the cell membrane (as they are lipid soluble) and will bind to receptors inside the cell (intracellular) forming a hormone-receptor complex. This hormone receptor complex acts as a specific transcriptiion factor and causes mRNA production, this mRNA will generate a specific protein via translation and this protein will cause the cells response to the hormone.
What are the relative speeds of the actions of water soluble and lipid soluble hormones?
Water soluble hormones are very fast, milliseconds to minutes. Meanwhile the lipid soluble hormones are much slower, from hours to days.
Why are hormones specific in their target cells?
Hormones can only affect cells which have receptors for them to bind to, hence cells without these receptors are unaffected and as such the hormones target cells are specific.
How do cells become more responsive or less responsive to hormones over time?
Cells will be more responsive to hormones if they have more of that hormones receptors. The body can as such regulate how affective it wants hormones to be via the relative rates of hormone receptor synthesis or degradation, if synthesis is more than degradation than there will be more receptors (up-regulation) and if synthesis is less than degradation there will be less receptors (down-regulation).
Compare the functions of neuronal and endocrine control systems.
Neuronal actions are caused specific wiring of neurons to target cells and have fast transmission speeds, they are good for brief responses but can cause damage if responding to often.
Hormonal actions are the opposite, targeting is wide and instead done by specific receptors on the target cells, it has relatively slow but long lasting action and is good for widespread responses.
What do I mean when i say the neuronal and endocrine systems often work in tandem?
The neuronal system may invoke an instant response in stressful situations but then trigger the endocrine system for follow up responses, this is because the endocrine system cannot function fast enough for unexpected situations, but the neuronal system can, though the neuronal system can’t keep the response up.
