2. Hypothalamus & Pituitary gland Flashcards
what connects the hypothalamus to the pituitary gland
a stalk called the infundibulum
what type of communication occurs between the hypothalamus and the POSTERIOR pituitary
neural
what type of communication occurs between the hypothalamus and the ANTERIOR pituitary
endocrine
how can the function of the hypothalamus
neuroendocrine - due to both neural and endocrine communication with the pituitary gland
what is neuroendocrine function
when both neural and endocrine hormones are involved - e.g. the hypothalamus = stimulates the anterior pituitary to release endocrine hormones or causes release of neurotransmitters from poster pituitary
where is the hypothalamus located
at the base of the brain below the thalamus
where is the pituitary gland located
in a pocket in the sphenoid bone directly below the hypothalamus
what type of hormone is released from the hypothalamus and posterior pituitary
neurohormones
what type of hormone is released from the anterior pituitary
endocrine hormones
what are the two forms of neurohormones
- tropic
2. non-tropic
define tropic hormones
hormones that govern the release of another hormone
where do all tropic hormones from the hypothalamus travel to and what do they do there
the anterior pituitary where they then governs the release of endocrine hormones - either the stimulation or inhibition
what are the five hypothalamic stimulatory hormones
- Thyrotropin Releasing Hormone (TRH)
- Corticotropin Releasing Hormone (CRH)
- Growth Hormone Releasing Hormone (GHRH)
- Gonadotropin Releasing Hormone (GnRH)
- Prolactin Releasing Hormone (PRH)
what are the 2 hypothalamic inhibitory hormones
- Growth Hormone Inhibiting Hormone (GHIH) aka somatostatin
2. Dopamine aka Prolactin Inhibiting Hormone (PIH)
which is the only hypothalamic tropic hormone that is not a peptide
dopamine - is an amine
what is the hypothalamus-hypophyseal portal system
Network of tiny vessels connected in series which transfer trophic hormones from hypothalamus to anterior pituitary - hormones are released from neurosecretory neurons at the median eminence - very short distance so rapid and dynamic
What are the 6 peptide hormones released from the anterior pituitary gland
- Thyroid Stimulating Hormone (TSH) aka thyrotropin
- Adrenocorticotrophic Hormone (ACTH) aka corticotropin
- Follicle Stimulating Hormone (FSH)
- Luteinising Hormone (LH)
- Growth Hormone (GH)
- Prolactin
all anterior pituitary hormones are tropic except which one
prolactin - directly stimulates milk production from the breast during lactation (ie non-tropic)
all the others control secretion of other endocrine glands and have direct or indirect effects in promoting growth
what is the feedback control for the anterior pituitary
negative feedback control with the hormones themselves acting as the negative feedback - links levels if sequential hormones together and tight maintains plasma levels within the correct range
what are the three integration centres involved in anterior pituitary feedback control
- hypothalamus
- anterior pituitary
- target endocrine cell/organ
what kind of feedback does the anterior pituitary get from the target endocrine cell/organ
long-loop feedback
what kind of feedback does the anterior pituitary send to the hypothalamus
short-loop feedback
what are the two neurohormones stored and released by the posterior pituitary
- vasopressin (aka anti-diuretic hormone ADH)
2. oxytocin
where are the two posterior pituitary neurohormones synthesised
in magnocellular neurons which have their cell bodies in specific areas of the hypothalamus
what are the steps of release of the posterior pituitary neurohormones
- hormone is made and packaged in cell body go magnocellular neutron
- vesicles are transported down the cell
- vesicles containing hormone are stored in terminals posterior pituitary
- hormones are released straight into the blood
vasopressin main function
regulates water balance
vasopressin release triggered by
increase in plasma osmolarity or decrease in plasma volume/blood pressure
vasopressin site and subsequent mode of action
kidney collecting ducts - increased water reabsorption
vascular smooth muscle -
increased blood pressure
oxytocin main function
milk ejection and uterine contraction
oxytocin release triggered by
suckling or labour (baby head against cervix)
oxytocin site and subsequent mode of action
milk duct smooth muscle -
contracts muscle, ejecting milk
uterine smooth muscle -
child birth
what is hyposecretion
too little hormone secreted
what is hyperscretion
too much hormone secreted
what is hyporesponsiveness
reduced response of the target cell - relates to alterations in receptor for hormone, disordered post-receptor events or failure of metabolic activation of hormone, (where this is required for function)
what is hyperresponsiveness
increased response of the target cell - could be due to permissive effects e.g. Thyroid hormone ++ adrenaline mediated lipolysis.
what are primary disorders
where the defect is in the cells that secret the hormone
what are secondary disorders
where there is too little or too much tropic hormone from the pituitary
what are tertiary disorders
relate to hypothalamic defects
