Regulation Of Energy Metabolism By The Nervous System Flashcards by Elsa Lees

How have humans adapted to live with a lack of energy resources

Rhythm of fasting (sleep) and feeding (wake)
Conserve energy stores

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What regulates our energy balance by sensing plasma hormones and nutrients

The hypothalamus

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What are orexigenic signals

Hunger signals

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What is hypophagia

Reduced appetite, energy is sufficient

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What is hyperphagia

Increased appetite, energy is low

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What makes up the diencephalon in the brain

The hypothalamus and thalamus

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What is the function of the hypothalamus

Senses metabolic signals from the periphery via systematic circulation

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Which hormones increase hunger

Orexin, Ghrelin and insulin

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Which hormones decrease hunger

Leptin and PYY

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What are the 4 main hypothalamic nuclei/areas involved in eating behaviour

Paraventricular nucleus (PVN), ventromedial hypothalamus (VMH), Arcuate nucleus (Arc), Lateral Hypothalamic area (LHA)

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What is the main function of Arc

Appetite control

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What are the two main neuronal populations within Arc

POMC/CART neurons and NPY/AgRP neurons

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What are the POMC/CART neurons

Anorexigenic neurons that inhibit appetite and promote energy expenditure

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What are NPY/AgRP neurons

Orexigenic neurons that stimulate appetite, lower metabolism and promote weight gain

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What are the two key options/behaviour for the neuronal populations in Arc

1) stay in Arc and influence eachothers activity
2) projections leave Arc and move to other brain areas/ nuclei of the hypothalamus

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What can disruption between the balance of the signals between the two neuronal populations lead to

Imbalance in energy homeostasis

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What is ghrelin

Peptide hormones primarily secreted from P/D1 cells in stomach

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When is ghrelin highest

When are stomach is empty

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How does Ghrelin act on Arc

Inhibits the POMC/CART neurons and promotes the NPY/AgRP neurons to increase appetite

What other things can influence Ghrelin

Lifestyle factors and adiposity level

What is leptin

Peptide hormone secreted by adipocytes that acts as a saiety signal to reduce appetite and increase energy expenditure

What are the general functions of leptin

saiety signal that acts on Arc receptors
stimulates locomotor activity and FA oxidation (higher energy expenditure overall)

Describe leptin action

Leptin conveys information from periphery about energy stores (adipose) to brain to reduce (POMC/CART) or increase (AgRP/NPY) energy intake and expenditure.

What two key neurotransmitters regulate the POMC /CART and ArGP/NPY neurons to regulate food intake

GABAergic neurons
Glutamatergic neurons

What is the function of GABAergic neurons/GABA

Inhibits PIMC/CART neurons to promote feeding

What is the function of the PVN

Synthesise and secrete catabolic hormones to control sympathetic output to the peripheral metabolic organs to increase FA oxidation and lipolysis to play an inhibitor role in food intake and weight gain

What is the function of the glutamatergic neurons

Input into the AgRP neurons to promote an Anorexigenic effect

What is the function of the VMH

Projects axons onto other areas of the brain and is highly expressive of LRb which mediates the effect of leptin on energy homeostasis, which results in an Anorexigenic effect Also enhances glucose uptake in skeletal muscle

What is the function of the LHA

Feeding area that receives input from Arc and is regulated by leptin and ghrelin Adapts behaviour in response to energy state

What are the two distinct neuronal populations within the LHA

Orexin and MCH producing neurons

What is the function of MCH neurons

Neurons excited by glucose which promote sleep and energy conservation (weight gain) Communicate with NPY/AgRP neurons to promote feeding

What is the function of the orexin producing neurons

Activated by fasting and inhibits by glucose

What is the dorsomedial hypothalamus

Dorsomedial nucleus receives input from the Arc, expresses leptin and ghrelin receptors and is involved in glucocorticoid secretion, body temp, ariusal and circadian rhythms

What are the areas of the brain stem

Thalamus, midbrain, pons, medulla and spinal cord

What is the function of brain stem

Regulates nutrient supply by enabling locomotor activity (foraging) and termination of feeding due to aversive test or noxious stimuli Involved in autonomic control of eating (independent of hypothalamus)

Where are the NTS and AP located

Within the medulla, within the brain stem

What is the NTS and AP

Located in the medulla of the brain stem and function to stop feeding

What is amylin

Co secreted with insulin from beta cells, secretion of amylin is positively correlated with body adiposity

What is the midbrain-mesolimbic reward system

Intake of palatable foods elicits dopamine release from the midbrain ventral tegmental area (VTA). •Dopamine release acts downstream of the melanocortin system to promote feeding. •Leptin can act on dopaminergic neurons in VTA to suppress feeding.

What is the function of the sensory system

Sensory cues primes body for food intake

What is the role of POMC neurons in thermogenesis

ARC/POMC neurons increase BAT thermogenesis via α-MSH modulation of PVN and DMH neurons (GLP-1)

Where does thermogenesis primarily occur

Brown adipose tissue

What is the role of leptin receptors on DMH neurons in thermogenesis

Leptin receptors on DMH neurons stimulate BAT thermogenesis and energy expenditure

What is the role of AgRP/NPY neurons in thermogenesis

ARC AgRP/NPY neurons mitigate thermogenesis via NPY-mediated inhibition of PVN neurons

Describe neuronal regulation of the pancreas

Hypothalamus regulates insulin and glucagon secretion by pancreas

What is the effect of insulin on VMH

Inhibits glucagon secretions

What is the melanocortin system

Melanocortin system (Arc, VMH, DMH, PVN, LH) central to energy homeostasis.