Week 3- Pituitary Gland Flashcards
What are the 2 main hormones?
Peptide and steroid
What are peptide hormones synthesized as?
Prohormones
What are steroid hormones synthesized as?
A series of reactions from cholesterol
How are peptide hormones stored?
In vesicles
How are steroid hormones stored?
They aren’t, they get released immediately
What tissue does the anterior pituitary gland contain?
Glandular (NOT neural)
What 5 types of endocrine cells make up the anterior pituitary?
Somatotrophs Lactotrophs Corticotrophs Thyrotrophs Gonadotrophs
What hormone do somatotrophs release?
Growth hormone (somatotropin)
What hormone do lactotrophs release?
Prolactin
What hormone do thyrotrophs release?
Thyroid stimulating hormone
What hormone do gonadotropes release release?
LH/FSH
What hormone do corticotrophs release?
ACTH (adrenocorticotrophic hormone)
What is the releasing component of the growth hormone?
Growth hormone releasing hormone
What is the inhibiting component of the growth hormone?
Somatostatin
What is the inhibiting component of prolactin?
Dopamine
What is the releasing component of TSH?
Thyrotropin releasing hormone
What is the releasing component of LH/FSH?
Gonadotrophin releasing hormone
What is the releasing component of ACTH?
Corticotrophin releasing hormone and Argenine vasopressin
Where are growth hormone receptors found?
Liver, muscle and skeleton
Where are prolactin receptors found?
Breast
Where are thyrotropin receptors found?
Thyroid
Where are gonadotrophin receptors found?
Testes for men
Ovaries for women
Where are corticotrophin receptors found?
Adrenal glands
What is bitemporal hemianopia?
Loss of temporal part of visual field due to a pituitary tumor squashing the optic chiasm
What does reduced dopamine do in reference to milk production?
More prolactin is produced so milk is produced
What does binding of growth hormone to liver receptors stimulate the production of?
Insulin-like growth factor (IGF 1 is the main one but also IGF 2)
What are the 2 mechanisms of action of growth hormone?
- Binding directly to receptors in muscles/skeleton
2. Binding to liver receptors causing production of IGF
What is the condition where there is excess growth hormone in children? Describe the symptoms
Gigantism- child grows very tall
What is the condition where there is excess growth hormone in adults? Describe the symptoms
Acromegaly- bigger nose, tongue, feet, hands etc (small changes over time)
What are the 2 posterior pituitary hormones?
Arginine vasopressin (AVP aka anti diuretic hormone) Oxytocin
What does vasopressin do?
Stimulation of water reabsorption in collecting duct, concentrating urine
Which receptor does vasopressin work through? Where is the receptor found?
V2 receptor in kidney collecting duct
What are the 2 main physiological actions of oxytocin?
- In the delivery of the baby (uterus at parturition causes contraction of myometrial cells)
- In milk ejection (causes contraction of myoepithelial cells in the breast during lactation)
How do peptide hormones act on receptors?
Receptors are found on the cell membrane and transduce signal using 2nd messenger systems
How do steroid hormones act on receptors?
They bind to intracellular receptors and directly change gene expression
What is a hormone?
A chemical messenger that is carried from the organ where it’s produced to the organ it affects by the bloodstream
How are hormones carried from place to place?
Bloodstream
What are the 5 components of the anterior pituitary gland?
Optic chiasm Pars tuberalis Pars intermedia Pars distalis Sella turcica of the sphenoid bone
What are the 5 complements of the posterior pituitary gland?
Hypothalamus Mammillary body Pars nervosa Infundibulum Median eminence
What neurons regulate anterior pituitary function?
Hypothalamic parvocellular neurones
What do hypothalamic parvocellular neurons do and where do they terminate?
They terminate in the median eminence and release hypothalamic releasing/inhibitory factors into the capillary plexus of the median eminence. These factors are carried by portal circulation to the anterior pituitary
What is the anterior pituitary gland regulated by and via what system?
Hypothalamic releasing/inhibiting factors via the hypohyseal pituitary portal system
Describe how the hypothalamo-pituitary system works
Axon terminals of neurosecretpry cells release hormones (RHs and IHs) into the hypothalamo-pituitary portal system
RHs and IHs travel in the portal system to the anterior pituitary
They stimulate or inhibit the release of hormones from anterior pituitary cells
Anterior pituitary hormones leave the gland via blood
Where is the optic chiasm found?
Right on top of the pituitary gland
Where is dopamine released from?
Dopaminergenic neurons
What is the posterior pituitary a continuation of?
The hypothalamus
Where do hypothalamic magnocellular neurons originate?
In the supraoptic and paraventricular hypothalamic nuclei
Describe the regulation of the posterior pituitary gland
2 sets of hypothalamic neurosecretory cells produce AVP and oxytocin and transport the, to the posterior pituitary
Excitation of magnocellular neurons stimulates the release of AVP or oxytocin into the posterior pituitary where they diffuse into blood capillaries
What is the action of vasopressin via V1 receptor?
A vasoconstrictor that stimulates ACTH release from anterior pituitary
What does oxytocin do in the milk production pathway and via what pathway is it released?
Mechanical stimulation of the nipple causing oxytocin release via ascending sensory pathways, increase of plasma oxytocin increases milk ejection in mammary glands
What is the difference in action of prolactin vs oxytocin in regards to lactation
Prolactin: stimulates milk production
Oxytocin: stimulates milk ejection
What is the alternative name for the anterior pituitary?
Adenohypophysis
What is an alternative name for the posterior pituitary gland?
Neurohypophysis
What is the stalk like process that connects the hypothalamus and the pituitary?
Infundibulum
What is the peptide precursor to ACTH?
Proopiomelanocortin
What is the source of inhibitory or stimulatory signals that affect the pituitary?
Hypothalamus
Usually what is the cause of acromegaly?
Pituitary adenoma
