The Pituitary Gland Flashcards
How is the hypothalamus connected to the pituitary gland ?
Via the infundibulum
What portion of the hypothalamus is connected to the endocrine system?
The anterior pituitary
Where is the pituitary gland located?
The pocket of the sphenoid, directly below the hypothalamus
Where are neurohormones released from?
Posterior Pituitary and Hypothalamus
Where are classic endocrine hormones released?
Anterior Pituitary
Where are tropic and non-tropic hormones released?
The hypothalamus and the anterior pituitary
What are tropic hormones?
Neurohormones secreted into capillaries travelling into the anterior pituitary which govern release of anterior pituitary hormones
What are non-tropic hormones?
Neurohormones produced in hypothalamus and travel to posterior pituitary where they are released into blood
What is the function of tropic hormones?
Bind to receptors on anterior pituitary and stimulate/inhibit release of AP hormones
Name 5 hypothalamic releasing hormones
TRH, CRH, GHRH, GnRH, PRH
Name 2 hypothalamic inhibiting hormones
GHIH and Dopamine
What is the Hypothalamo-Hypophyseal portal system?
A network of tiny vessels which transfer trophic hormones from hypothalamus to anterior pituitary
Where are hormones released within they hypothalamo-hypohyseal portal system?
At the median eminence
What is the origin of anterior pituitary tissue?
Epithelial tissue
What is the origin of posterior pituitary tissue?
Neural tissue
Where is the anterior pituitary connected to?
The hypothalamus via the capillary portal system
Where is the posterior pituitary connected to?
Neural connection to the hypothalamus
How does the hypothalamus control the production of AP hormones?
By releasing or inhibiting trophic hormones that stimulate or inhibit hormone production from the AP
Where does prolactin act and what is its function?
Breast
Results in lactation (Direct)
Where does TSH act and what is its function?
Thyroid
Results in TH release (tropic)
Where does adrenocorticotropic hormone act and what is its function?
Ad. Cortex
Results in Cortisol Release (Tropic)
Where does growth hormone act and what is its function?
Liver
Results as an IGF-1* release (tropic) and tissue metabolism (direct)
Where does FSH and LH act and what are their functions?
Gonads
Regulate reproductive function (direct) and sex hormone release (tropic)
Where does AP feedback control occur?
Hypothalamus, AP and Target Endocrine Cell
What hormones does the PP release?
Vasopressin and Oxytocin
Where are PP hormones synthesised?
Magnocellular Neurons in the hypothalamus
Where do axons of the infundibulum project?
The posterior pituitary
Describe how hormones of the PP synapse?
Terminals end directly on capillaries
What is the main function of ADH?
Regulates water balance
When is ADH released?
When plasma osmolarity or plasma volume/blood pressure is increased
What is the site/mode of action of ADH?
Kidney collecting ducts - increases water reabsorption
Vascular Smooth Muscle - increases blood pressure
What is the main function of oxytocin?
Milk ejection and uterine contraction
When is oxytocin released?
Labour or suckling
What is the site/mode of action of oxytocin?
Milk duct smooth muscle - Contracts muscle and ejects milk
Uterine smooth muscle - child birth
Define hyposecretion?
Too little secreted
Define hypersecretion?
Too much secreted
Define Hyporesponsiveness
Reduced response of target cell. Relates to alteration in hormone receptor, post-receptor disorder or failure of metabolic activation of hormone
Define Hyperresponsiveness
Increased response of target cell. Due to permissive effects
Define a primary disorder
the defect lies within the cell that secretes the hormone
Define a secondary disorder
Where there is too much or too little trophic hormone from pituitary
Define a tertiary disorder
Relates to a hypothalamic defect
What is a trophic hormone?
A hormone which controls the secretion of another hormone
