chapter 45: hormones and the endocrine system Flashcards
What are hormones?
chemical signals secreted into circulatory system
What are the two systems that coordinate communication throughout the body?
- endocrine system
- nervous system
What is the role of the endocrine system?
it secretes hormones that coordinate slower but longer-acting responses like..
1. reproduction
2. development
3. energy metabolism
4. growth
5. behaviour
What is the role of the nervous system?
convyes high-speed electricl signals along specialized cells called neurons
How does endocrine signalling work?
hormones secreted into extracellular fluids by endocrine cells reach their targets in bloodstream.
this maintains homeostasis, mediates responses to stimuli and regulates growth and development
What are local regulators?
molecules that act over short distances, reaching target cells solely by diffusion
- prostaglandins
What is paracrine signalling?
target cells near the secreting cells
- blood pressure regulation, nervous system function, reproduction
What is autocrine signalling?
target cell is also secreting cell
- blood pressure regulation, nervous system function, reproduction
How does signalling by pheromones work?
- mark trails leading to food
- define territories
- warning of predators
- attracting potential mates
What are the chemical classes of intercellular signalling factors?
- polypeptides - water-soluble
- amines - water-soluble
- steroid hormones - lipid-soluble
What is special about lipid-soluble hormones?
they pass easily through cell membranes whereas water-soluble hormones do not.
What are the protein and amide signalling factors?
- proteins incoded in genes
- insulin: inactive prohormone polypeptide secreted when needed to reduce blood sugar
- growth factors: regulates cell cycle - amine hormones; signalling factors produced from amino acids
What are the lipid signalling factors?
prostaglandins promote fever and inflammation, steroids are derived from cholesterol
What is the cellular response pathway for water-soluble hormones?
- are secreted by exocytosis
- they travel freely in bloodstream
- they bind to cell-surface receptors
What is the cellular response pathway from lipid-soluble hormones?
- they diffuse across cell membranes
2, they travel in the bloodstream bound to transport proteins - they bind to receptors in the cytoplasm or nucleus
- binding initiates signal transduction pathway
- results in gene expression