The Pituitary Gland Flashcards
What are the 2 principle organisers of the endocrine system?
Hypothalamus and the PG
How is the PG connected to the hypothalalmus?
Infundibulum
Pituitary stalk
Is the hypothalamus neuro or endocrine tissue?
Neuro
Where is the hypothalamus located?
Below the thalamus
At the base of the brain `
In which bones does the PG sit?
Sphenoid bone
What are the 2 parts of the PG?
Anterior PG
Posterior PG
What type of tissue is the Posterior PG?
Neuro
What type of tissue is the anterior PG?
Endocrine
What is the posterior PG a continuation of?
The hypothalamus
What are tropic hormones?
Hormones which govern the release of another hormone
What type of hormones does the hypothalamus release?
Neurohormones
Where do the hormones from the hypothalamus travel down to?
Posterior PG
Where are hormones stored in the posterior PG?
In vesicles
Which hormones are released from the anterior PG?
Classic endocrine hormones
What are the 2 forms of hypothalamic hormones?
Tropic
Non-tropic
Where do tropic hormones travel from the hypothalamus?
Secreted into the capillaries traveling to anterior PG- bind to receptors on the anterior PG - govern the release of anterior PG hormones
Where do non-tropic hormones travel from the hypothalamus?
Travel to the posterior PG where they are released into the blood
What type of hormones are all hypothalamic hormones except from dopamine?
Peptides
What are the 5 releasing hypothalamic hormones?
Thyrotrophin Releasing Hormone (TRH) Corticotropin Releasing Hormone (CRH) Growth Hormone Releasing Hormone(GHRH) Gonadotrophin Releasing Hormone (GnRH) Prolactin Releasing Hormone (PRH)
What are the 2 hypothalamic inhibiting hormones?
Growth hormone inhibiting hormone
Dopamine (prolactin inhibiting hormone)
What is the hypophyseal portal system?
Network of tiny vessels which transfer trophic hormones from the hypothalamus to the anterior PG
How is the anterior PG connected to the hypothalamus?
Via the hypophyseal portal system
What % does the anterior and posterior PG make up?
Anterior - 66%
Posterior - 33%
What is the production of anterior PG hormones controlled by?
Hormone release from the hypothalamus
Which hormones are released from the anterior PG?
Thyroid stimulating hormone Adrenocorticotrophic hormone FSH LH Growth hormone Prolactin
Which is the only hormone from the anterior PG to have a direct effect?
Prolactin
What does prolactin stimulate?
Milk production during lactation
What are the 3 integration centres in controlling anterior PG feedback?
Hypothalamus
Anterior PG
Target endocrine tissue
What is a long loop feedback?
When the feedback comes from the endocrine target tissue
What is a short loop feedback?
When the feedback is from the anterior PG to the hypothalamus
What often acts as the negative feedback signal?
The hormone itself
What are the 2 peptide neurohormones released from the posterior PG?
Vasopressin (ADH)
Oxytocin
Where are neurohormones synthesised?
In magnocellular neurons
Where do axons project from the hypothalamus?
Down the infundibulum to the posterior PG
In what ways do oxytocin and vasopressin behave as normal peptide hormones?
They are synthesised in advance
Stored in large vesicles
Target cell surface receptors
What is the main function of ADH/vasopressin?
To regulate water balance
When is vasopressin release triggered?
When there is an increase in plasma osmolarity
Or decrease in plasma volume
What is the action of ADH?
Increases water reabsorption
Increases BP
What is the main function of oxytocin?
Milk ejection
Uterine contraction
When is oxytocin released?
By babies head in contact with the cervix
Suckling of baby on nipple
What is hyposecretion?
Too little hormone secreted
What is hypersecretion?
Too much hormone secreted
What is hyporesponsiveness?
When there is reduced response of the target cell
What is hyperresponsiveness?
Increased response of the target cell
What are primary disorders?
When there is a defect in the cells that secrete the hormone
What are secondary disorders?
When there is too little or too much tropic hormone from the pituitary gland
What are tertiary disorders related to?
Hypothalamic defects