Metabolism Flashcards
Where are tanycytes located?
in the hypothalamys, extending processes to the fenestrated capillary network
3 roles of tanycytes
1) regulate exchange of molecules between BBB
2) sensory & signalling functions
3) express GABA receptors
There are 4 main types of tanycytes. Where are the a-1 and a-2 tanycytes found & what do they express?
found along the ependymal surface of the VM & ARC, contact blood vessels & neurons, express GFAP
There are 4 main types of tanycytes. Where are the B1 & B2 tanycytes found?
B1 - found in lateral extensions of infundibular recess
B2 - found in floor of ventricles, contact capillaries of median eminence
Both contact the median eminence
How do tanycytes increase the permeability of the BBB during fasting?
They secrete VEGF during fasting, which increases permeability & facilitates molecular exchange
induces fenestration of microvessels contacted by them
helps to promote hunger signals and food intake
What happens to WAT browning during the fasted state?
MC4R is heavily expressed on cell bodies of PVH & LH
reduced activation of MCR4 (since ghrelin is its antagonist)
via PVH, therefore there is a DROP in WAT browning
besides reducing AgRP firing, what does the insulin released from B cells of pancreas do during the fed state?
signals muscles and fat to uptake glucose
induces liver to STOP GNG (via vagal innervation to receptor on hepatocytes)
insulin signals to ARC to coordinate “FEEDING INDUCED THERMOGENESIS”
During the fed state, AgRP firing drops. This cases which protein to increase?
UCP-1
Increased activity of PVH in fed state causes. . .
increased WAT browning via neurons of PVH, which results in HIGHER beige adipocyte formation
How do tanycytes respond in the FED state?
tanycytes sense changes in GLUCOSE levels & close BBB or brain windo
the level of hormonal input into ARC is coordinated by nutritional status
What are 3 structural properties of tanycytes?
1) contain microvilli that ptoject into 3rd & 4th ventricles (increase SA for abs / communication)
2) are monociliated & bipolar
3) have tight junctions to prevent diffusion of blood-borne molecules into adjacent CSF
Tanycytes share some properties with glia / astrocytes
What role do SAN neurons from PVH play in WAT browning?
SAN neurons from PVH –> release norepinephrine (a catecholamine) –> innervates beige / brown adipocytes –> promotes their activation
The SAN neurons contain tyrosine hydroxylase (TH)
How does norepinephrine influence beige / brown adipocytes?
NE activates B-adrenoreceptors on beige / brown adipocytes –> promotes UCP-1 expression in mitochondria –> uncouples oxidative phosphorylation to generate heat
What is the significance of UCP-1 expression in adipocytes?
leads to generation of heat instead of ATP, contributing to energy expenditure
What encodes the Leptin hormone and its receptor?
Leptin is encoded by “ob” gene and its receptor is encoded by “db” gene
