Ingestive behavior

Malnourished animals after returning to calories

Set-Point Theory:

• Each living organism has a baseline weight

• After being deprived of calories, if we give an animal free reign to eat, they eat till they get to the same baseline weight

Set-Zone Theory:

• We have a weight range (Max and Min weight)

• Body works to maintain the range (Getting hungry and not hungry)

Homeostasis

• “Narrow Range”

Hypothalamus role in ingestive behavior

• Release homeostasis

• Controls release of hormones that causes hunger

• Regulates the 3 components of neuronal response in this order:

  • Humoral

    • Stimulating release hormones into blood stream

    • Vasopressin

  • Visceromotor (internal)

    • How sympathetic + parasympathetic of ANS respond

    • Urine

    • Blood is shunted from the surface of body

    • Shiver/Goosebumps

  • Somatic (external)

    • How our body physically respond

    • Find water to drink

    • Find warmth

Long-term feeding Mechanisms

• Maintains fat reserves

Short-term feeding Mechanisms

• Meal size

• Frequency of meals

Anabolism — creation of fat reserves after eating

Catabolism — Breakdown of fat reserves

• Provides us with energy

Proper balance of feeding

• Intake = Outtake

Feeding is stimulated when we stop releasing hormones

Lesions in in VMH $\Rightarrow$ Mr. Fat Rat

LH $\Rightarrow$ Y/N

ob. gene $\rightarrow$ leptin

no ob. gene $\rightarrow$ no leptin $\rightarrow$ low fat $\rightarrow$ Mr. Fat Rat

$\uparrow$ leptin $\rightarrow$ full $\rightarrow$ Y/N

High leptin Response

• $1)$ Sensory Transduction aMSH + Cart Neurons inhibition of NPY/AgRP neurons

• $2)$ Humoral: $\uparrow$ TSH + ACTH $\rightarrow$ thyroid + adrenal glands $\rightarrow$ metabolic rate

• $3)$ Visceromotor response: Sympathetic $\uparrow$ $\rightarrow$ $\uparrow$ Metabolic rate + temp

• $4)$ Somatic response: $\downarrow$ Feeding

$1)$ NPY/AgRP: Neurons Activate, aMSH + Cart are now inhibited

$2)$ TSH + ACTH are now inhibited $\rightarrow \downarrow$ metabolic rate + temp

$3)$ Parasympathetic to activate

Anorectic 

• Decrease in hunger

• Astonish aMSH + Cart

Orexigenic

• Increases hunger

• NPY + AGRP

LH

• Simulation $\uparrow$ feeding

• MCH prolong, short

• Orexin cells promote meal initiation, short

  • Weight loss

$\uparrow$ Leptin aMSH + CART $\rightarrow$ inhibit LH

$\downarrow$ NPY/AgRP $\rightarrow$ stimulate LH