Motivation Flashcards
What are the phases of motivated behaviours?
- Consummatory: The actual (often involuntary) process of interacting with the source of motivation (e.g. eating, drinking, copulation).
- Appetitive: The voluntary process of seeking out source of motivation (e.g. searching for food, attracting mate).
What are the sources of inputs into the hypothalamus?
- Inputs from brainstem:
1. Somatosensory: Does not have any role in general sensation. Instead, mediates basic reflexes that require sensory input (e.g. lactation, copulation).
2. Visceral afferents: From nucleus tractus solitarius (NST) and reticular formation convey information from the viscera to the hypothalamus regarding internal states. - Forebrain: Afferent fibres from amygdala and orbitofrontal cortex carry information about external stimuli and how they contribute to motivation (e.g. sight, smell of food).
- Hormones: Many areas of the hypothalamus have receptors that detect and respond to hormones.
- Blood: Receptors in the hypothalamus can directly detect characteristics of the blood (e.g. osmoreceptors in OVLT respond to changes in blood osmolality and regulate release of ADH, thermoreceptors in the preoptic area).
What types of actions are mediated by the outputs of the hypothalamus?
- Endocrine responses: Hypothalamic neurones can directly project into the pituitary gland (posterior pituitary) and control the secretion of the hormones ADH and oxytocin. It can also indirectly control hormone secretion (anterior pituitary) via the release of specific “releasing hormones”.
- Behavioural responses: The hypothalamus is able to trigger a small number of reflex movements (e.g. shivering, biting…) via its projections into the brainstem.
- Autonomic responses: The hypothalamus can be considered the ‘top ganglion’ in the control of autonomic responses. It can achieve this control both directly (via neural projections) or indirectly (via hormones), but also projects into the NTS, which together, it can coordinate autonomic activity with.
What are the hormones involved in controlling satiety?
- Ghrelin: Secreted by stomach under conditions of starvation.
- Leptin: Secreted by adipose tissue under conditions of satiety and inhibits NPY production.
- Melanin concentrating hormone (MCH): Produced in the LH and stimulates feeding behaviours.
- Orexin: Produced in the LH and stimulates feeding behaviours.
- Neuropeptide Y (NPY): Produced in the arcuate nucleus and promotes MCH and orexin secretion.
What type of motivated behaviour is directly controlled by the hypothalamus in general?
Consummatory behaviour: It mediates the reflexes and involuntary behaviours required to interact with targets in external environment.
Which hypothalamic nuclei are involved in control of feeding?
- Arcuate nucleus
- Lateral hypothalamus
What is the sequence of hypothalamic events that occur during starvation?
- During starvation, ghrelin is released from the stomach.
- There is also a decrease in production of leptin, thus relieving inhibition of NPY production.
- There is an increased production of NPY from arcuate nucleus.
- NPY stimulates production of MCH and orexin from LH that act on higher centres to promote feeding behaviours.
- NPY also inhibts the paraventricular nucleus which in turn, causes reductions metabolic rate and insulin secretion.
What is the sequence of hypothalamic events that occur during satiety?
- During satiety, increased release of leptin from adipose tissue inhibits NPY production.
- This causes decreased production of MCH and orexin, decreasing feeding drive.
- The metabolic rate and insulin secretion increases as a result of relief of inhibition on the PVN.
What are the factors that initiate feeding?
- Internal:
1. ↓ Blood [glucose]
2. Empty stomach → Ghrelin release - External:
1. Sight/smell of food
2. Other signs associated with food (conditioning)
What are the factors that stop feeding?
- Short-term:
1. Food in mouth (tasting, swallowing…)
2. Distension of stomach and other parts of GI tract
3. Satiety hormones released as result of digestion (e.g. CCK) - Long-term:
1. Leptin from adipose tissue
2. ↑ Metabolic rate
3. ↑ Sensitivity to satiety hormones
What type of sexual behaviour is directly controlled by the hypothalamus?
Consummatory behaviour
Which areas of the hypothalamus control sexual behaviour in male/females respectively?
- Male: Medial pre-optic area (mPOA) under permissive influence of androgens
- Female: Ventromedial hypothalamus (VMH) under permissive influence of oestrogens
What are the divisions of the amygdala?
- Cortico-medial division (olfaction/pheromones)
- Central nucleus (autonomic/endocrine)
- Baso-lateral amygdala (sensation/motivation/emotion)
What are the functions of the cortico-medial division of the amygdala?
Receives olfactory information and may be important in mediating the behavioural responses to pheromones in animals (not humans).
What are the functions of the central nucleus of the amygdala?
Controls simple motor and endocrine autonomic reflexes. It receives afferents from the NTS, and projects to the hypothalamus/brainstem.
