Introduction to endocrinology Flashcards
Hormone definition
A chemical signal released from an endocrine cell to influence the activity if another cell via a receptor
6 endocrine systems
pituitary, thyroid, parathyroid, pancreas, adrenal, gonads
What is the master gland + function
pituitary- controls all of the other endocrine systems
3 different types of endocrine systems
endocrine gland- a well defined collection of endocrine cells
neuroendocrine systems- neurons that release hormones into the blood in the brain and CNS
diffuse endocrine systems- endocrine cells not arranged in glands but dispersed- scattered individually amongst epithelial cells
Three methods of endocrine communication
endocrine- to blood- far acting
paracrine- from one cell to the next
autocrine- automatic feeback loop
What does the speed of endocrine actions depend upon?
rapidity of release, half-life of hormone and rapidity of action
Example of fast response
adrenaline- fight or flight response
Example of intermediate response
insulin- response to a meal
example of slow response
cortisol from fetal adrenal causes the production of surfactant, which lowers the surface tension in alveoli in the lungs
How are hormones released?
in pulses
Explain pulsatile secretion
biochemical phenomenon where chemical products are secreted in a regular pattern
ensures that the delicate homeostatic balance necessary for essential life processes is maintained
Name a specific type of pulsatile secretion
diurnal rhythms
explain diurnal rhythms
processes with 24-hour oscillations that control sleep patterns, such as cortisol
different chemical types of hormone
amino acid derived- adrenaline
polypeptide- insulin
protein- prolactin
glycoprotein- LH
steroids- testosterone
prostaglandins
gaseous mediators- nitrous oxide
Different types of hormone secretion explained
constitutive- hormones that are produced constantly such as cytokines
regulated - respond to a stimulus e.g insulin
key features of regulated secretion
proteins concentrated and stored in secretory vesicles
secretory vesicles stored in cell
vesicles quickly release their contents by exocytosis in response to a stimulus
constitutive secretion
proteins are not concentrated
vesicles are not stored in cell
contents released as they are produced
regulation is by control of transcription
what is the hormones precursor?
prohormones, which are cleaved at dibasic sites
What can one prohormone form?
many different hormones, or many of the same type- due to different dibasic cleavage sites
How are hormones transported in blood?
hydrophilic hormones can circulate freely in plasma
most steroid and thyroid hormones are bound to specific binding proteins in plasma
binding of hormones reduces their clearance and extends their half-life
How are hormones metabolised and excreted?
hormones internalised with their receptor are degraded by lysosomes
steroid hormones degraded in the liver
hydrophilic hormones also lose by excretion through kidneys
Functions of the endocrine system
promote survival of the individual and control processes involved in reproduction
Explain how the endocrine system promotes the survival of the individual
effects development, growth and differentiation
helps in preservation of a stable internal environment
responds to an altered external environment, especially during emergency stress responses
normal concentrations of protein and polypeptide hormones
nanomolar
normal concentrations of steroids
sub-micromolar
which hormones are produced enzymatically as they are needed?
prostaglandins, nitric oxide and angiotensin II
