Pituitary gland Flashcards
Hypothalamus is directly connected to pituitary gland via the
infundibulum (pituitary stalk)
Define a non-tropic hormone
One that acts directly on targeted tissues or cells, and not on other endocrine gland to stimulate release of other hormones
Define a trophic hormone
A hormone that governs the release of another hormone from an endocrine gland
Technically speaking, which is a true endocrine gland - anterior or posterior pituitary gland - and why
Anterior pituitary - epithelial origin
Posterior pituitary is just an extension of neural tissue
Name the 2 forms of neurohormones produced by the hypothalamus - including those secreted via the neurohypophysis (posterior pituitary lobe) + describe them
Tropic
-secreted into capillaries from hypothalamus travelling to anterior pituitary to stimulate/inhibit release of AP hormones
Non-tropic
-neurohormones produced in the hypothalamus and travel to posterior pituitary (via axons of hypothalamic neurons) where they are released into blood
Pituitary gland sits in what
Hypophyseal fossa
Pituitary gland divided into
Anterior and posterior pituitary
Hypothalamic communication with the posterior pituitary is…
Hypothalamic communication with the anterior pituitary is…
neural (i.e. nerves)
endocrine
All hormones released by the posterior pituitary are…
neurohormones (from the hypothalamus)
Does the hypothalamus release tropic or non-tropic hormones or both
Both
Does the anterior pituitary release tropic or non-tropic hormones or both
Both
What is the posterior pituitary lobe also known as
neurohypophysis
All tropic hormones released by the hypothalamus are tropic hormones except
dopamine (amine hormone)
What is the hypothalamus-hypophyseal portal system
Network of capillaries which transfer trophic hormones from hypothalamus to anterior pituitary
All hormones released by the posterior pituitary are…
neurohormones (from the hypothalamus)
Posterior pituitary just stores it at its nerve terminals and releases when triggered
What is the hypothalamus-hypophyseal portal system
Network of capillaries which transfer tropic hormones from hypothalamus to anterior pituitary
- Neurons synthesising tropic hormones release them into capillaries of the portal system
- Portal vessels carry the tropic hormones directly to the anterior pituitary
- Endocrine cells release their hormones into the second set of capillaries for distribution to body
(two capillary beds connected IN SERIES)
What is the specific point called where hormones are released from neurosecretory neurons
Median eminence
What is the anterior pituitary lobe also known as
Adenohypophysis
List the 2 neurohormones produced by the hypothalamus and secreted via the neurohypophysis (posterior pituitary lobe)
Vasopressin (aka anti-diuretic hormone (ADH))
Oxytocin
All tropic hormones released by the hypothalamus are peptide hormones except
dopamine (amine hormone)
Neurohormones secreted by the PP are made in the
hypothalamus
Thyrotropin releasing hormone (TRH) released from the hypothalamus stimulates the anterior pituitary to secrete what
Thyroid stimulating hormone (TSH)
List the tropic hormones released by the hypothalamus that stimulate the anterior pituitary
- releasing (5)
- inhibiting (2)
Releasing hormones
- Thyrotropin Releasing Hormone (TRH)
- Corticotropin Releasing Hormone (CRH)
- Growth Hormone Releasing Hormone (GHRH)
- Gonadotropin Releasing Hormone (GnRH)
- Prolactin Releasing Hormone (PRH)
Inhibiting hormones
- Growth Hormone Inhibiting Hormone (GHIH) aka somatostatin
- Dopamine aka Prolactin Inhibiting Hormone (PIH)
List the hormone families (2) and major individual hormones secreted (6) by the adenohypophysis (anterior pituitary lobe)
Tropic
- Thyroid Stimulating Hormone -(TSH)
- Adrenocorticotrophic Hormone (ACTH)
- Follicle Stimulating Hormone (FSH)
- Luteinising Hormone (LH)
- Growth Hormone (GH)
Non-tropic
-Prolactin
Thyroid Stimulating Hormone (TSH) produced by the anterior pituitary is aka
thyrotropin
Adrenocorticotrophic Hormone (ACTH) produced by the anterior pituitary aka
corticotropin
What 2 hormones produced by the anterior pituitary belong to the gonadotropin family
Follicle Stimulating Hormone (FSH)
Luteinising Hormone (LH)
stimulate the gonads
Which hormone secreted by the anterior pituitary is the only one that is not tropic
prolactin
prolactin stimulates what
milk production from the breast during lactation
Hormones themselves can act as a negative feedback signal by
feeds back to inhibit hormone secretion by integrating centres earlier in the reflex
Hormone negative feedback loops can be short or long, what constitutes as a short or long loop
Long loop = feedback from endocrine target organ/tissue
Short loop = feedback from anterior pituitary to hypothalamus
Neurohormones secreted by the posterior pituitary are synthesised by what special kind of neurons which have their cell bodies in the hypothalamus
Magnocellular
does the posterior pituitary release tropic or non-tropic hormones
non-tropic
Define hypo/hyperresponsiveness in terms of endocrine disorders
reduced response of the target cell
-relates to alterations in receptor for hormone
increased response of the target cell
Define a primary endocrine disorder
those in which the defect is in the cells that secrete the hormone, e.g. primary hyperthyroidism
Define a secondary endocrine disorder
those in which there is too little or too much tropic hormone from pituitary, e.g. secondary hyperthyroidism – AP releasing too much TSH
Define a tertiary endocrine disorder
relate to hypothalamic defects, e.g. tertiary hyperthyroidism – hypothalamus releasing too much TRH
What could hyperresponsiveness seen in endocrine disorders be due to
permissive effects, e.g. thyroid hormone ++ adrenaline mediated lipolysis.
