endocrine system
- Communication and regulation of the body
- Works in conjunction with the nervous system
- Glands or specialized cells receive messages and respond by secreting hormones
local regulators
– Small (gases or short polypeptides)
– Non-polar (modified fatty acids)
Hormone (distance) regulators
– Polypeptides
– Steroids
– Amines
How would a gas signaling molecule, like NO, most likely be transmitted between cells?
By diffusing directly through the phospholipid bilayer
hormones can signal many cells at once
endocrine signals travel long distances
Any cells with the proper receptors are targets
where is a water soluble hormone
receptor in plasma membrane
outside of cell
where is lipid soluble hormone
receptor in nucleus or cytoplasm
inside of cell
steroids are lipid soluble hormones
water soluble hormone signaling
– Reception
– Transduction
– Response
how can a water-soluble hormone signal be received and transduced?
G protein coupled receptors, membrane bound receptors
- membrane-bound receptors are coupled to a G-protein complex (has guanine nucleotide) to stimulate a membrane protein, adenylate cyclase, which induce formation of secondary messenger molecules such as cyclic AMP (from ATP)
- secondary messenger activates protein kinases, which transfer phosphate groups to various proteins (phosphorylation)
- ‘activated’ proteins then alter various cellular processes
The α and β receptor both bind epinephrine but produce different cellular responses. Which of the following features do you expect to be similar when comparing these receptors?
their ligand binding sites
digestion is regulated by _____
hormones
negative feedback
the response reduces the initial stimulus
by decreasing hormone signaling, negative feedback regulation prevents excessive pathway activity
positive feedback
reinforces a stimulus, leading to an even greater response
A patient’s pancreatic cells have secretin receptors with defective ligand-binding sites. Which of the following do you expect to observe in the patient?
Low pH in the duodenum
How is a process regulated by positive feedback (like oxytocin signaling) switched off?
External changes resulting in loss of the original stimulus
hormones help maintain _____
homeostasis
Negative Feedback Loops are Common in Maintaining Homeostasis
endocrine disruptors
• A molecule that disrupts normal hormone signaling
– May affect reproduction, development, body homeostasis (diabetes, obesity)
