Brain-body systems for energy balance and response to stress Flashcards
What hormone maintains body weight?
Leptin
Level of leptin in the blood is directly linked to the amount of body fat you have
What is the function of ghrelin?
Ghrelin is a hormone produced by enteroendocrine cells of the gastrointestinal tract, especially the stomach, and is often called a “hunger hormone” because it increases the drive to eat
What signalling inhibits feeding behaviour?
Low energy reserves establish a motivational state that leads to feeding behaviour - this can either be promoted or inhibited via the hypothalamus
Signalling from fat cells (leptin) and via insulin levels inhibit feeding behaviour
What signalling promotes feeding behaviour?
Signalling by cells of the stomach/GI system (ghrelin) when empty promotes feeding behaviour
Mechanoreceptors in GI tract also sense fullness and signal to brain via vagus nerve
What is a complication with brain-body system for energy balance?
Not just as simple as signalling for appetite control to maintain energy balance
Need to remember the objective is energy balance so responses will also impact on metabolism of fat and autonomic nervous system actions to prepare for physical activity
What is the ARC?
The arcuate nucleus of the hypothalamus
Integrates circulating signals of hunger and satiety reflecting energy stores and nutrient availability
Is a key integrator for hormone signalling input
Projects to other hypothalamic structures and onwards into cortical and limbic circuits
What is hedonic hunger?
Hedonic = refers to one’s preoccupation with and the desire to eat foods for the sole purpose of pleasure and in the absence of physical hunger
What is the reasoning behind the hedonic regulation of feeding behaviour?
Food as a primary reinforcer activates brain reward circuitry to establish a ‘liking’ for food alongside a ‘wanting’ as behavioural motivators
Dopaminergic signalling from the ventral tegmental area (VTA) to the nucleus accumbens underlies food reward and this ‘hedonic drive’
What is the evolutionary reasoning behind hedonic regulation of feeding behaviour?
Powerful motivational mechanisms for seeking and consumption of food arise from evolutionary pressures in the context of general scarcity of this key resource
As a result, overeating in the face of present abundance could be an understandable overshoot inherited from our evolutionary past.
What controls hedonic regulation of feeding behaviour?
Mesolimbic system - dopaminergic pathway (reward pathway)
Ventral tegmental area in the midbrain projects to the nucleus accumbens (ventral striatum) causing dopamine levels to rise
The ventral striatum includes the nucleus accumbens and the olfactory tubercle
How are the hedonic and homeostatic circuits for regulating feeding and energy balance integrated?
HEDONIC
- Prefrontal cortex
- Nucleus accumbens
- Ventral tegmental area
HOMEOSTATIC
- Lateral hypothalamus
- Arcuate nucleus of hypothalamus
What is the role of the PFC in hedonic hunger?
Executive functions
Goal directed behaviour
Information processing
Working memory
Emotional regulation
Retrieval of memory
“Learning” component
What is the role of the NAc in hedonic hunger?
Cognitive processing of reward
Motivational salience
Positive reinforcement
Hedonic hotspot or pleasure centre
“Liking” component
What is the role of the VTA in hedonic hunger?
Main dopaminergic centre
Reward seeking
Reward prediction
“Wanting” component
Binge/intoxication (addiction)
What is the role of the LH in homeostatic hunger?
Integration of information from cortical, extended amygdala and basal forebrain networks
Generation of a highly specified and invigorated behavioural state
Primary orexinergic nucleus
LH also plays a role in hedonic hunger