55.1 Functions of the Hypothalamus Flashcards
What are examples of the functions of the hypothalamus?
- Endocrine
- Autonomic
- Survival functions (eating, sleep, sexual behaviour, aggression)
What are the different hypothalamic nuclei?
What are the roles of the hypothalamic nuclei?
Homeostasis, rhythms, development (e.g. puberty), metabolism, control of ANS, and endocrine system control
How is the circuitry of the hypothalamus different to other brain areas?
- There are both neural and extensive non-neural interconnections
- Interconnections are bidirectional (besides a few exceptions like retinal input)
Which systems is the hypothalamus interconnected with?
- Limbic circuits
- Sensory and autonomic circuits
- Neurohumoral systems: Pituitary gland, circumventricular organs
What do the connections to the pituitary gland and circumventricular organs allow?
Monitoring of plasma levels of hormones, metabolites, and plasma osmolarity
How do hypothalamic neurons connect to the anterior posterior pituitary gland?
Secrete releasing factors into primary capillary plexus in the median eminence
Travel via hypothalamic-hypophyseal portal vessels to anterior pit
How do hypothalamic neurons connect to the posterior pituitary gland?
Directly travel down into posterior pit
Secrete vasopressin/oxy into blood supply
What are the circumventricular organs and their role?
Structures in the brain with extensive and highly permeable capillaries (no BBB)
Either sensory or secretory
In contact with CSF and blood so permit communication between CNS and peripheral blood
What are examples of sensory circumventricular organs?
Area postrema
Subfornical organ (SFO)
Organum vasculosum of Lamina terminalis (OVLT)
What are examples of secretory circumventricular organs?
Pituitary gland
Median eminence
Pineal gland
How does the hypothalamus control metabolism?
- Appetite control - leptin, insulin etc signalling
- Thyroid (T3) action
- Glucose sensing
- Amino acid sensing
What is the role of the hypothalamus in growth?
Releases GHRH to stimulate GH release
Releases somatostatin to inhibit GH release
(GH stimulates IGF-1 release from liver)
What is the role of the hypothalamus in triggering puberty?
Kisspeptin activates GnRH neurons to start releasing GnRH in 90 min pulses
Causes FSH and LH release from anterior pit
Which hypothalamic nuclei is involved in blood pressure and volume control?
Paraventricular
Supraoptic
Which circumventricular organ senses changes to blood osmolarity?
OVLT
What exactly does the OVLT sense?
Extracellular NaCl and angiotensin II concentrations