Hypothalamus and appetite control Flashcards
What are the boundaries of the thalamus?
Anterior - lamina terminalis
Superior - hypothalamic sulcus
Posterior - tegmentum of the midbrain
Rostral (coronal section) - substantia innominata
Caudal (coronal section) - posterior limb of internal capsule
What hormones are produced by the anterior pituitary (adenohypophysis)?
- growth hormone
- lutenizing hormone
- follicule stimulating hormone
- prolactin
- thyroid stimulating
- adrenocorticotropin hormone
What hormones are released by the posterior pituitary? Where are they produced?
- oxytocin
- vasopressin
- corticotropin releasing hormone
-> supraoptic and paraventricular nuclei in the supraoptic region of the hypothalamus
What is the pathway of the neurohypophysis hormones?
Supraoptic nuclei and paraventricular nuclei produce vasopressin, oxytocin and corticotropin releasing hormone. These hormones are released in the neurohypophysis, where they are then released in to the hypophyseal blood system
What is the pathway of the adenohypophysis hormones?
Hypothalamic neurosecretory cells release hormones in to the hypothalamo-hypophyseal portal system. The hormones then travel to the adenyhypophysis, where they facilitate or inhibit the release of hormones in to the blood stream
What are circumventricular organs?
Circumventricular organs are organs that can monitor and control the level of hormones in the blood. They consist of a specialised BBB, extensive vasculature and sit adjacent to the ventricles.
Why is the adenohypophysis not a circumventricular organ?
The adenohypophysis does not sit adjacent to a ventricle, it does not have a specialised BBB, it does not detect blood hormone levels, and it is not neural in origin (it is epithelial, developing from the oral ectoderm)
What are the three areas responsible for appetite?
Lateral hypothalamic nuclei -> orexigenic (hunger) nuclei, promotes food intake
Ventromedial hypothalamus -> anorexigenic (satiety) nucleus, promotes satiety
Arcuate nucleus -> regulator of orexigenic and anorexigenic neurons
What are the neurons located in the arcuate nucleus?
NPY/AgRP expressing neurons -> orexigenic (promotes hunger)
- activated by ghrelin, inhibited by leptin
POMC/CART expressing neurons -> anorexigenic (promotes satiety)
- activated by leptin, inhibited by NPY neurons
What is leptin, what does it do and where is it produced?
Leptin is an anorexigenic hormone that causes feelings of satiety. It is produced in fatty adipose tissue
What is ghrelin, what does it do and where is it produced?
Ghrelin is an orexigenic hormone, it is produced by the oxyntic cells in the stomach, and it pomotes hunger
How does ghrelin act on the vagus nerve?
Ghrelin synapses to the nodose ganglion of the vagus nerve and sends signals up the nucleus solitarius. The nucleus solitarus cells project to the thalamus, stimulating NPY/AgRP expressing cells in the arcuate nucleus
Where is growth hormone produced?
anterior pituitary by the somatotroph cells
Which hormones regulate growth hormone release? Where are they produced?
Growth hormone releasing hormone (GHRH) - arcuate nucleus
Somatostatin (SST) - periventricular nuclei
