5.4 Hormonal Communication Flashcards
Define endocrine system
A communication system that uses hormones as signalling molecules
Define hormones
- Molecules (proteins or steroids) that are released by endocrine glands directly into the blood
- They act as messengers
Define target cells
- cells that possess a specific receptor on their plasma membrane
- Many similar cells together form a target tissue
Define adrenal cortex
The outer layer of the adrenal gland
Define adrenal gland
One of a pair of glands lying above the kidneys
-release adrenaline and a number of other hormones (corticoids such as aldosterone)
Define adrenaline
A hormone released from the adrenal glands
-stimulates the body to prepare for fight to flight
Define adrenal medulla
The inner layer of the adrenal gland
Define beta cells
Cells found in the islets of Langerhans that secrete the hormone insulin
Define glucagon
a hormone that causes an increase in blood glucose concentration
Define insulin
the hormone, released from the pancreas, that causes blood glucose levels to go down
Define diabetes mellitus
A condition in which blood glucose concentrations cannot be controlled effectively
Define stem cells
Unspecialised cells that have potential to develop into any type of cell
What type of glands are endocrine glands
Ductless, hormones are released directly into the capillary
Example of non steroid hormones
- Adrenaline
- Insulin
- Glucagon
Examples of steroid hormones
- oestrogen
- testosterone
Describe steroid hormones
- lipid soluble (can go through plasma membrane)
- can get to cells nucleus
- can affect DNA
Describe non-steroid hormone
- cannot pass through membrane
- known as first messenger
What do many non steroid hormones act via?
G protein in the membrane
-activates an effector molecule
What is a common effector molecule?
- adenyl cyclase
- converts ATP to cyclic AMP and cAMP is the second messenger
What may a second messenger do?
- Act directly on another protein
- Initiate a cascade of enzyme controlled reactions
Three layers of adrenal cortex
- Zona glomerulosa - outermost layer (secretes mineralocorticoids)
- Zona fasciculata - secretes glucocorticoids
- Zona reticularis - secretes molecules that make sex hormones
Example of mineralocorticoids
Aldosterone
Example of glucocorticoids
Cortisol
What hormones are derived from cholesterol
Steroid hormones produced in 3 zones