Hypothalamus and appetite Flashcards
What is the limbic system? What does it coordinate?
Group of brain structure either side of thalamus, under cerebrum
Homeostasis, motivation and emotion
What is included in limbic system?
Hypothalamus Hippocampus Amygdala Olfactory cortex More NOT forebrain
What are the roles of the hypothalamus?
Hormone regulation
Arousal, sleep wake and circadian regulation
Regulation of blood volume and thirst
Regulation of temperature and appetite
What is Circadian rhythm?
Release of melatonin from pineal glands in 24 hr cycle
What controls Circadian rhythm?
Superchiasmatic nucleus of hypothalamus
What influences melatonin release?
Light - as light increases, melatonin decreases
Melatonin = slee hormone
Where is drinking controlled in the hypothalamus?
Superoptic nucleus of hypothalamus
What is hypocretin?
Hormone (neuropeptide) that regulates arousal, wakefulness and appetite
How does the effect of hypocretin (AKA orexin) differ in nocturnal/diurnal animals?
Nocturnal - negative effect from hypocretin
Diurnal - positive effect from hypocretin
What is narcolepsy? What causes it?
Lack of hypocretin
Destruction of the cells the produce it
Temperature increase should cause a negative feedback loop of thermogenesis to bring T back down. What happens if the body produces a positive feedback loop?
Hyperthermia
Hypothermia
What does the hypothalamus do if dehydrated?
Hypothalamus produces ADH
What is a neutral energy balance? What happens if this is a positive or negative balance?
Energy input = energy output
Positive - weight gain
Negative - weight loss
Give examples of when an energy imbalance might be adaptive
Hibernation
Reproduction
Lactation
What is the lipostat theory?
Hypothalamus detects signals from adipose tissue
Influences the hypothalamus to control eating behaviour and activity
What is leptin?
Cytokine produced by the obese gene in fat cells
Larger fat cells - more leptin
What does leptin act on? What does it do?
Neurones of hypothalamus
Decreases hunger to discourage eating (-ve feedback)
What happens if there is a mutation/defect in the ob (obese gene)?
Leptin not produced - doesn’t discourage hypothalamus from eating –> obesity
How does leptin decrease feeding behaviour?
Causes production of MSH in neurons (melanocyte stimulating hormone)
MSH binds to neuronal receptors and inhibits feeding behaviour
What is the glucose theory?
Hypothalamus has glucose sensing neurones - detect changes in blood glucose and alter food intake
Where is feeding regulated?
Hypothalamus (most parts, except superchiasmatica and super optic nuclei)
Brain stem
What are endocannabinoids?
Brains natural marijuana - blocking their receptors causes food cravings
