18 Overview of endocrine system Flashcards
what is the endocrine system
a group of glands that secrete hormones into the circulatory system in response to their specific signals
what does the circulatory system do
carry the hormones to their target organs
what do target cells/organs express
specific hormone receptors that allow them to respond to hormones
what do exocrine glands do
secrete their products via. duct into some other location in the body
what do hormones regulate
- homeostasis
- energy metabolism
- growth and development
- reproduction
- behaviour
what are peptide hormones made up of
a chain of amino acids (short peptides and proteins)
peptide and protein hormones are same thing
can peptide hormones diffuse across membrane
no because they are hydrophilic
what are steroids hormones derived from
cholesterol
can steroid hormones diffuse across the membrane
yes as they are lipophilic
what are amine hormones derived from
amino acids (tyrosine and tryptophan)
how are steroid hormones transported
since its not very soluble its bound to specific proteins in the circulation
how do steroid hormones leave the cell
steroid hormones are lipophilic and leaves the cell by diffusion
secretion of steroid hormone is enhanced by increasing its synthesis (not stored)
how do peptide hormones travel in blood
freely as they are hydrophilic
where are peptide hormones stored
in secretory vesicles
what do the secretory vesicles do to release the peptide hormone
they fuse with the plasma membrane to release the hormone into the blood (exocytosis)
what does secretion and transport of amine hormones depend on
the specific amine hormone
transport and secretion of catecholamines
leave by exocytosis
dissolve in plasma
secretion and transport of amine hormones
leave by transporter proteins
travel bound to carrier proteins
where are peptide hormone receptors found
at the plasma membrane of the target cell
where are steroid hormone receptors found
in the target cell
where are amine hormone receptors found
either in the cell or on the membrane, depends on hormone
what do steroid hormones do
bind to intracellular receptors and modulate gene transcription
steps of steroid hormones modulating gene transcription
- steroid enters cell
- steroid binds to receptor
- steroid-receptor complex enters nucleus and modulates gene transcription
do amine hormones act via cell surface or intracellular receptors and what do they do
catecholamines
cell surface receptor
activation of second messenger systems
thyroid hormones
nuclear receptor
gene transcription
what factors control secretion of hormones
- ion or nutrient conc in plasma
- environmental changes
- neuronal activity
- other ‘releasing’ hormones
what regulates release from the pituitary gland
the hypothalamus
what does the hypothalamus receive signals from
essentially all areas of the CNS
what does the hypothalamus produce
releasing and inhibiting hormones which act on the pituitary gland
what is a key link between the nervous system and endocrine system
the hypothalamus
what is the pituitary gland
the master endocrine gland that releases many different hormones
divided into anterior and posterior pituitary
what do axons from hypothalamic neurons enter
the posterior pituitary
what hormones are released from posterior pituitary axon terminals and what happens to them
oxytocin and ADH
enter the capillaries in the posterior pituitary and are then released into circulation
does the posterior pituitary synthesis hormones
NO they just release them, they are synthesised in the hypothalamus
what do hormones released from the hypothalamus move through in the anterior pituitary
through portal veins
what do hypothalamic hormones stimulate or inhibit
hormone release from cells in the anterior pituitary
where do hormones released from the anterior pituitary go
to the general circulation
what do some anterior pituitary hormones control
the secretion of hormones from other endocrine glands
where are hormones released from anterior pituitary glands synthesised
in the anterior pituitary
example of 3 hormone sequence
- hypothalamus released THR
- THR causes anterior pituitary to release TSH
- TSH causes thyroid gland to release thyroid hormones
what does a 3 hormone sequence facilitate
signal amplification from a small number of neurons in the hypothalamus to a large peripheral hormone signal
what does a 3 hormone sequence allow for
different types of hormone feedback regulation
what is the secretion of a hormone related to
the requirement for the biological response produced by that hormone
what happens once there is enough hormone produced for a biological reponse to happen
hormone secretion is stopped to prevent an over-response
what is a characteristic feature of the endocrine system
the presence of feedback loops that regulate secretion of the hormones
can the biological response to a hormone directly feed back to the gland that secretes the hormone
yes
can the hormone itself exert feedback regulation
yes
