The pituitary gland Flashcards
What is a hormone?
A messenger carried from the organ where they are produced to the organ whcih they affect by means of the bloodstream
What is the difference between a peptide and a steroid (synthesis)
Peptide is synthesised as prohormones which required further processing (in inactive form)
Steroid is synthesised from cholestrol
What is the difference between a peptide and a steroid (storage)
Peptide it is stored in vesicles (regulatory secretion)
Steroid it is released immediately
What is the difference between a peptide and a steroid (receptors)
Peptide binds to receptors on cell membrane and transduce signal using 2nd messenger systems
Steroid bind to intracellular receptors to change gene expression regularly
Diagram of the pituitary
What are hypothalamic parvocellular neurons
Regulate anterior pituitary functions
Short, terminate on median eminence
Release hypothalamic factors into capillary plexus in median eminence
Hypothalamic regulatory factors carried by portal circulation to anterior pituitary
Diagram of anterior pituitary
What are the steps of the hypothalamo-pituitary portal system
Axon terminals of hypothalamic neurosecretory cells release hormones
Travel through portal system through leaky blood vessels
Arrive in anterior pituitary hormones
Either release or inhibit from anterior pituitary
Hormones leave via blood
What are smatotrophns
Growth hormone (somatotrophin)
What are lactotophs
Prolactin
What are thyrotrophs
Thyroid stimulatin ghormone (TSH)/ thyrotrophin
What are gonadotrophs
Luteinising hormone (LH)
Follicle stimulating hormone (FSH)
What are corticotrophs
Adrenocorticotrophic hormone (ACTH or corticotrophin)
What hormone triggers the release of growth hormone
Growth hormone releasing hormone
(Inhibitory) somatostatin
What hormone triggers the inhibition of prolactin
Dopamine
What hormone triggers the release of thyroid stimulating hormone
Thyrotropin releasing hormone
What hormone triggers the release of LH and FSH
Gonadotrophin releasing hormone
What hormone triggers the release of ACTH
Corticotrophin releasing hormone
Main target cells of anterior pituitary hormones
What is a bitemporal hemianopia
Peripheral vision is inhibited, cannot see outer view
Prevents sensory information from the lateral visual fields
How does the neuroendocrine reflex arc of mild production work
Mechanical stimulation of nipple and surrounding area affects afferent pathways
Inhibit dopmaine release in hypothalamus
Less dopamine in hypothalamic-pituitary portal means less inhibition of anterior pituitary lactotrophs
Increase plasma prolactin increase milk secretion
What are the mechanisms of growth hormone
Can travel to liver to stimulate liver to produce IGF-1 and IGF-2
Can travel straight towards body tissues
What is acromegaly
Excess growth hormone
Coarsening of facial features
Macroglossia
Prominent nose
Increase hand and feet
Sweatiness/headache
Why does acromegaly not affect height
Because the epiphyseal plates have already been fused which stops someone from growing
How is the posterior pituitary gland different from anterior
Posterior is anatomically continous, continous neural tissues
What are the hypothalamic magnocellular neurons of AVP called
Supraoptic
What are the nuclei of oxytocin called
Paraventircular
What are the hormones produced in the posterior pituitary
Arginine vasopressin (Anti diuretic hormone)
Oxytocin
What is the action of vasopressin
Stimulation of water reabsorption in the renal collecting duct which concentrates urine
V2 receptors in the kidney
Also a vasoconstrictor via V1 receptors
Stimulates adrenocorticotropic hormone
What does oxytocin do
Cause contraction of myometrial cells and myoepithelial cells
What are the roles of lactin and oxytocin for breastfeeding
Prolactin is responsible for milk storage and secretion
Oxytocin is responsible for ejection
Summary of anterior and posterior pituitary hormones
What anterior pituitary hromones typically target glands
Prolactin
LH
FSH
ACTH
TSH
What is the difference between a peptide and a steroid (travel)
Peptide travels free in blood
Steroid bound to proteins
What are the anterior pituitary glands and posterior pituitary glands known as
Adenohypophysis
Neurohypophysis
