Temperaturre and hunger Flashcards
Preoptic area ( POA)
The region of the hypothalamus involved in temperature regulation
Endotherms
Animals that can regulate body temperature through internal mechanisms
Ectotherms
Animals that have no internal mechanisms to regulate their body temperature.
Negative Feedback
A mechanism by which a stimulus input causes a system to react by causing an opposite output to maintain a desired set point
Cold defence
esponses decrease heat loss. They include the constriction of blood vessels of the skin (vasoconstriction). This results in increased blood circulation to the core of the body, preventing it from losing too much heat. Another response triggers skeletal muscles to shake in what is known as shivering. Shivering generates heat through the expenditure of energy.+
behavioural responses
Heat defence
responses increase heat loss. They include the dilation of blood vessels in the skin (vasodilation) and vasoconstriction of the blood vessels of internal organs, both resulting in a loss of heat from the core of the body. Another way in which the body loses heat is by evaporative cooling, which you may know as “sweating.” + behavioural responses
the spin-thalamus cortical pathway ( STC pathway )
the information about temperature is conveyed to the somatosensory cortex via the thalamus this conveys the temperature of the immediate surrounding detected by thermoreceptors at the surface of the skin
Lateral parabrachial nucleus ( LPB)
it is in the brainstem to the preoptic area ( POA) of the hypothalamus known as LPG-POA pathway .
it is dented by thrmoreceptors deep within the body
heat and cold seeking behaviours
Energy homeostasis
The process that maintain cellular metabolism
Prandial state
A state in which energy stores are replenished as nutrients are absorbed in the bloodstream and stored
( carbohydrates are stored as glycogen in the liver and fats as triglycerides in fat cells )
Postabsorptive state
a state in which nutrients are no longer entering the bloodstream and when the body relies on the release of stored energy from the liver as glucose and fat cells as fatty acids and ketones
Hunger
the drive generated when energy stores are not sufficient to sustain energy balance.
Satiety
the state of being fed or to the feeling of satisfaction that follows a meal.
Ghrelin / Hunger
Levels of ghrelin are high approximately 20–30 minutes before meals, only when there is no food in the upper gastrointestinal tract. Levels of ghrelin drop as soon as food is ingested.
1- the hormonal route to a region of the hypothalamus, called the arcuate nucleus, where it binds to receptors on neurons that contain two peptide neurotransmitters. One is called neuropeptide-Y (NPY) and the other agouti-gene-related peptide (AgRP)
NPY and AgRP to be released into another region of the hypothalamus called the paraventricular nucleus (PVN). There, NPY and AgRP bind to receptors on melanin-concentrating hormone (MCH) and corticotropin-releasing factor (CRF). this results in the generation of hunger signals, which promote energy homeostasis.
2- Ghrelin released in the stomach binds to receptors on the vagus nerve, which carries excitatory messages to the hypothalamus through the nucleus of the solitary tract (NST) of the brainstem.
Leptin / satiety
1- it does so by inhibiting the release of AgRP and NPY from those neurons
2- Leptin also suppresses hunger by having excitatory effects on neurons containing neuropeptides, which are molecules that can act as neurotransmitters or hormones. These neuropeptides are known as proopiomelanocortin (POMC) and cocaine-amphetamine-relatedtranscript (CART). In turn, the release of POMC and CART in the PVN produces anorexic effects and plays an important role in feelings of satiety.
3- Leptin is also produced and released by the stomach, where it binds to receptors on the vagus nerve, which sends inhibitory messages to the hypothalamus through the NST
it increases with high levels of insulin and glucose
