Introduction to Endocrinology Flashcards
What is a hormone?
A molecule that is released in one part of the body, but regulates the activity of cells in other parts of the body.
What is an endocrine gland?
A gland that produces and secretes hormones into the bloodstream, through which they travel to affect distant targets.
What is an exocrine gland?
A gland which secretes its products into ducts opening onto an epithelium.
Name 8 endocrine organs/glands.
- Hypothalamus
- Pituitary gland
- Thyroid gland
- Parathyroid glands
- Adrenal glands
- Testes
- Ovaries
- Pancreas
Name 4 types of chemical messengers.
- Neurotransmitters
- Hormones
- Neuroendocrine messengers
- Cytokines
What is the difference between a neurotransmitter and a neuroendocrine messenger?
Neurotransmitters are released directly into a synaptic gap, whereas neuroendocrine messengers are released into the blood.
What are the 3 major molecular types of hormones?
- Peptides
- Steroids
- Amines
What molecular type are thyroid hormones and what molecular type do they behave like?
Thyroid hormones are peptides but they behave more like steroids.
What are steroid hormones derived from?
Cholesterol
Describe the onset of action of steroid hormones and why this is.
Onset of action for steroid hormones is longer (hours-days) because steroid hormones are not stored - they need to be synthesised when required.
What are the 4 steps in the synthesis of steroid hormones?
- Hydrolysis of esters and release of cholesterol.
- Conversion of cholesterol to pregnenolone in the mitochondria.
- Processing in the smooth endoplasmic reticulum.
- Diffusion out of the cell.
Once a water-soluble hormone binds to a receptor on the cell surface, what does this activate?
G protein.
After a G protein has been activated by a hormone receptor complex from a water-soluble hormone, what are the next 3 steps? Include examples.
- G protein activates an enzyme e.g. adenylyl cyclase.
- This leads to stimulation or inhibition of a signalling molecule e.g. cAMP.
- This leads to an effect e.g. via activation of protein kinases.
What are the two main types of receptors that water-soluble hormones bind to on the cell membrane?
- G-coupled protein receptors
2. Tyrosine kinase receptors
Which is more common in the endocrine system, positive or negative feedback?
Negative feedback.
In the endocrine system, what is meant by positive feedback?
The output enhances the original stimulus.
In the endocrine system, what is meant by negative feedback?
The output reduces the original stimulus.
What is meant by a tropic hormone?
Tropic hormones are hormones that have other endocrine glands as their target.
What is an effector hormone?
Effector hormones are hormones that directly stimulate target cells to induce effects.
What is meant by ‘resistance’ in the context of endocrinology?
There’s adequate levels of hormone, but a reduced target cell response.
What is Cushing’s syndrome?
Cushing’s syndrome is a hormonal disorder caused by high levels of the hormone cortisol in your body.
List 4 metabolic effects of cortisol.
- Stimulates glucose production in the liver.
- Stimulates the breakdown of fats and proteins.
- Increases plasma concentrations of glucose, amino acids, and fatty acids.
- Decreases muscle mass, maintains muscle function.
List 3 cardiovascular effects of cortisol.
- Maintains blood volume
- Maintains cardiovascular responsiveness to catecholamines.
- Maintains cardiac output.
How does cortisol affect prostaglandin synthesis and the immune system in general?
Cortisol inhibits prostaglandin synthesis and is immunosuppressive.
