chapter 6 motivation thirst & hunger

What are the four components of a homeostatic feedback system?

System variable, set point, detector, correctional mechanism

What is the system variable in homeostasis?

The variable being regulated (e.g., body temperature, blood glucose)

What is the set point in homeostasis?

The ideal level the body tries to maintain

What is the detector in homeostasis?

Monitors the current level of the system variable

What is the correctional mechanism in homeostasis?

The process that restores balance (e.g., eating, drinking, sweating)

What causes osmotic thirst?

Increased concentration of solutes in extracellular fluid, detected by osmoreceptors in the OVLT

What causes hypovolemic (volumetric) thirst?

Reduced blood volume/pressure due to fluid loss, detected by baroreceptors and angiotensin II

Which brain region integrates thirst signals and initiates drinking?

Median Preoptic Nucleus (MnPO)

What hormone converts glucose into glycogen for storage?

Insulin

What hormone converts glycogen back into glucose?

Glucagon

What happens when the lateral hypothalamus is destroyed?

Severely reduced appetite (aphagia)

What happens when the ventromedial hypothalamus is destroyed?

Overeating and obesity

Which hormone is secreted by fat cells and signals satiety?

Leptin

Which hormone is secreted by the stomach and stimulates hunger?

Ghrelin

Which neurotransmitter in the lateral hypothalamus stimulates eating?

Orexin

Which gut hormones promote satiety?

CCK and PYY

Which brain system reinforces food-seeking behavior?

Mesolimbic dopamine system (nucleus accumbens)