Anterior Pituitary Gland and Hypothalamic Control Flashcards
Hypothalamic Pituitary system
Major role in co-ordinating entire endocrine system
Pituitary gland = Conductor
Interface between BRAIN and PERIPHERY
organises appropriate hormonal responses to stimuli from higher centres in the brain into:
- changes in external environment
- changes in internal environment
Main Parts of the human brain are?
Forebrain - hypothalamus
Pituitary
Pituitary Gland
sits in the SELLA TURCICA
Comprises of two distinct lobes with different embryological origins
What are the two lobes of the pituitary gland?
ANTERIOR PITUITARY: pink, vascularised tissue. Derived from Rathke’s pouch. contains 5 principle types of secretory cell. Nerve fibres are absent
POSTERIOR PITUITARY: yellowish/brownish tissue. Down growth of neural ectoderm from ventral surface of brain. secretes 2 principle neurohormones
Anterior pituitary contains how many major cells?
THREE:
acidophils
basophils
chromophils
What is hormone secretion from the anterior pituitary like?
Generally pulsatile, fluctuating.
What is the Hypothalamus?
-Regulatory centre form many functions
-Recieve nerve fibres from all areas of the brain
some pathways synapse with hypothalamic PARVOCELLULAR anterior pituitary
-other pathways synapse with magnocellular peptidergic neurones that directly innervate the post. pit.
hypothalamic regulation of anterior pituitary
Communication via: PORTAL SYSTEM
Hypothalamus link with posterior pituitary
Direct NEURAL LINK
Parvocellular Hypothalamic Neurones
5 different cell types, dedicated to controlling a different cell type in the ant. pituitary.
each cell type secretes a specific neuropeptide (HYPOTHALAMIC HORMONE)
neurones terminate in median eminence in close proximity to primary capillary plexus of HYPOPHYSEAL PORTAL SYSTEM
HYPOTHALAMUS:
releasing hormones/releasing factors
Thyrotrophin - releasing hormone (TRH)
Gonadotrophin - releasing hormone (GnRH)
Corticotrophin Releasing hormone(CRH)
Growth hormone releasing hormone(GHRH)
Hypophyseal Portal System
the hypothalamus releases hypothalamic releasing hormone into the blood flow, at the anterior pituitary it causes release of anterior pituitary hormone
Hypothalamic-Pituitary-Adrenal Axis
Negative feedback loop controls cortisone secretion from the adrenal cortex.
Corticotropin Releasing Hormone:CRH released from the hypothalamus
CRH stimulates the release of corticotropin (ACTH) from the Ant. Pituitary
Corticotropin stimulates secretion of cortisol by adrenal cortex.
Adrenal cortex
Cortisol
-> elevated cortisol inhibits release of corticotropin by ant. pit corticotrophins and release of CRH by hypothalamic neurosecretory cells
PANHYPERPITUITARISM
inadequate or absent production of pituitary hormones. frequently the result of other problems that reduce or destroy the function of the pituitary gland.
Panhyperpituitarism - Symptoms
> loss of multiple pituitary endocrine cell types, cause by space occupying, non-functional tumour, or tumour producing only one type of hormone.
