Endocrine Flashcards
what is the endocrine system?
a group of glands that secrete (release) hormones in the circulatory system in response to specific signals
what do hormones regulate?
- homeostasis
- energy metabolism
- growth and development
- reproduction
- behaviour
what is a peptide hormone?
composed of a chain of amino acids
- hydrophilic (not able to diffuse across the membrane)
what are steroid hormones?
derived from cholesterol
- hydrophobic (can diffuse across membranes)
what are amine hormones?
amino acid derivatives (tyrosine and tryptophan)
- not defined whether hydrophobic or hydrophilic
what are the two types of amino hormones?
catecolamines and thyroid derivatives
how is peptide hormones stored and released?
stored in secretory vesicles and release the cell by exocytosis
- dissolved in plasma
- receptor is on the cell membrane
how are steroid hormones stored and released?
- synthesised on demand from precursors
- released by diffusion
- bound to carrier proteins in blood
- receptors present in cytoplasm or nucleus
how are catecholamines stored and released?
- made in advance, stored in secretory vesicles
- released by exocytosis
- dissolved in plasma
- receptors on cell membrane
how are thyroid hormones stored and released?
- made in advance, pre-cursor stored in secretory vesicles
- released from transport proteins
- bound to carrier proteins in the blood
what do steroid hormones modulate?
gene transcription
what factors control secretion of hormones?
- concentration of ions or nutrients in plasma
- environmental changes
- neuronal activity
- other releasing hormones by hypothalamus and pituitary gland
what hormones does the hypothalamus produce?
releasing and inhibiting hormones which act on the pituitary glands
what is the anterior pituitary?
able to produce hormones
what is the posterior pituitary?
doesn’t produce hormones but releases them
what hormones enter the capillaries in posterior pituitary?
oxytocin and ADH (released from axon terminal)
how do hormones released from the hypothalamus enter the anterior pituitary and how does this affect release?
They move through the portal veins and either stimulate or inhibit hormone release
what does a 3-hormone sequence do?
- facilitates signal amplification, from a small number of neurons in the hypothalamus to a large peripheral hormonal signal
- allows different types of hormonal feedback regulation
what is the master endocrine gland?
pituitary gland - releases many different hormones
