Hypothalamus Flashcards
• Where is the hypothalamus located?
At the floor of the third ventricle, beneath the thalamus
• Where do the ventricles arise from?
A series of expansions of the neural tube
• Where is the pars nervosa?
In the posterior pituitary gland (neurohypophysis)
• How does the pituitary gland form?
Downward evagination of third ventricle forms the posterior pituitary lobe
Evagination of oral ectoderm forms anterior and intermediate pituitary lobes
• What are the three main sources on inputs to the hypothalamus?
Descending neural afferents, ascending neural afferents, from the blood
• What is the biological clock?
Suprachiasmatic nucleus (SCN) in the hypothalamus
• What are circadian, ultradian & infradian rhythms?
Circadian rhythm – a biological process with 24 hour endogenous rhythmicity
Ultradian rhythm – occurring more frequently than every 24 hours
Infradian rhythm – at intervals longer than every 24 hours (oestrus cycle)
• What is a healthy change in circadian rhythm if a morning an evening sample is taken?
Healthy if decreases by 30%
• What are the main functional inputs to the hypothalamus?
Direct sensing via receptors, indirect via blood (humoral), indirect via nerves
• What are the main hypothalamic nuclei?
Paraventricular (PVN), supraoptic (SON), suprachiasmatic (SCN), arcuate (AN)
• Which area of the hypothalamus responds to cold?
Posterior hypothalamus, initiates peripheral vasoconstriction & shivering
• How does the hypothalamus respond to an increase in blood osmolarity?
ADH released from supraoptic nucleus
• What centres respond to glucose levels?
Satiety centre – high glucose levels, appetite centre – low glucose levels
• What are the major outputs from the hypothalamus?
Endocrine, secretory neurons (posterior pituitary gland), neurohormones
• Where do secretory, inhibitory and stimulatory hormones act?
Secretory – posterior pituitary, inhibitory and stimulatory – anterior pituitary
