pituitary gland Flashcards
hormone actions on whole body level
Regulation and integration of :
- Ionic and fluid balance
- Energy balance (metabolism)
- Coping with the environment
- Growth and development
- Reproduction
hormone actions on cellular level :
Regulation of :
- Cell division
- Differentiation
- Death (apoptosis)
- Motility
- Secretion
- Nutrient uptake
hormone actions on molecluar level:
Hormone receptor is within the cell nucleus therefore effect on :
- Regulation of
- Gene transcription
- Protein synthesis & degradation
- Enzyme activity
- Protein conformation
- Protein:protein interactions
what are autocrine hormones
hormones that act on the same organ they are produced by
cell produces a hormone but is also influenced by that hormone
what are paracrine hormones?
- adjacent or near to
- hormone that has an effect on neighbouring cells
what are endocrine hormones?
hormones in circulation
act on far off organs
What is the significance of hormones which are bound to a plasma protein in circulation??
- effective as the hormone is not immediately excreted
- stays in circulation for longer
- glomerulus does not allow large proteins to pass through
fill
how does endocrine feedback work?
- Sensory receptors gather external/internal information
- Integrated by neurons of CNS
- Hormone produced
- nervous system and endocrine system are tightly integrated
- hypothalamus bridges both systems
- with anterior pituitary
- hypothalamus bridges both systems
location of pituitary gland
small structure at base of brain
- lies inferior to the hypothalamus with the optic chiasm between
optic chiasm = crossing of optic nerves
what does the pituitary gland do
- which releases hormones that, in turn,
- controls the activity of the body’s other hormone glands
structure of the pituitary gland
Anterior lobe (pars distalis)
- Portal blood vessels connect pituitary and hypothalamic capillary beds
- Connected to hypothalamus by series of bleed vessels
Posterior lobe (pars nervosa)
- Nerve fibres originate in the hypothalamus and transport hormones to posterior pituitary
- Series of nerve fibres which transport hormone
- Hormones travel within a nerve fibre
what hormones does the posterior pituitary release?
where are they produced?
oxytocin
vasopressin
both produced in hypothalamus
role of oxytocin
- controls milk release from lactating breast
- controls uterine contraction at onset of labour
- essential for childbirth
role of vasopressin
- anti-diuretic hormone (ADH)
- acts on kidneys to reaborb water
Regulates blood osmolarity and urine output
Needed if dehydrated or haemorrhaging as we don’t want to lose plasma volume
when are hormones from the posterior pituitary gland released?
in response to nerve impulses
hormones come down nerve axons
action potentials release hormones into the capillary bed and out into circulation
how does the interaction of oxytocin with its receptors lead to a response to the stimuli?
- suckling -> nerve impulses
- hypothalamus produces oxytocin
- oxytocin released by posterior pituitary gland
- binds to receptors
- actives secondary messengers
- raises level of intracellular calcium in myoepithelial cells of the mammary gland
- myoepithelial cells contract forcing milk into ducts
describe the neuro-endocrine reflex with vasopressin
- increased plasma osmolarity stimulates osmoreceptors in hypothalamus
- dehydration
- hypothalamus and posterior pituitary release vasopressin
- water selectively reabsorbed in distal tubules and collecting ducts of kidney
- action of aquaporins
- urine becomes more concentrated and urine volume decreases = decreased plasma osmolarity
name an inhibitor of ADH from the posterior pituitary
alcohol
what hormones does the anterior pituitary secrete?
what are their target organs?
- Growth Hormone
- Prolactin
- Adenocorticotropic hormone (ACTH)
- Stimulates the adrenal cortex
- Thyroid stimulating hormone (TSH)
- Follicle stimulating hormone (FSH)
- Stimulates the ovaries & testes
- Luteinising hormone (LH)
- Stimulates the ovaries & testes
what cells in the anterior pituitary release which hormones?
What are ‘releasing hormones’?
- Stay within private circulation of the hypothalamus and anterior pituitary
- Stimulate release of anterior pituitary hormone
what releasing hormones are able to stimulate or inhibit anterior pituitary hormones?
- GH has a inhibitory and stimulatory hormone from the hypothalamus
- SS and SHRH
- Prolactin
- Has no stimulatory but has inhibitory
- DA
- E.g. if not breastfeeding
- Has high levels of dopamine in circulation to suppress prolactin (milk production)
- Dopamine antagonists
- Suppress dopamine function
- Will produce milk
differences between the posterior and anterior lobe of the pituitary gland
Posterior lobe
- Connects hypothalamus by nerve fibres
- 2 hormones
Anterior lobe
- Releasing hormones produced in hypothalamus
- Travel through private network of vessels
- Stimulate release of anterior pituitary hormones
