Chapter 16

What is Homeostasis?

Process that maintains the bod within a narrow and stable physiological range. Like temp, volume, pressure, Blood O2 and Glucose concentrations

What part of the brain maintains Homeostasis?

The hypothalamus helps maintains homeostasis

Where do the neurons that detect changes in homeostasis lie?

They lie in the Periventricular zone of the hypothalamus

What are the 3 components of the hypothalamic response?

1. Humoral

2. Visceromotor

3. Somatic motor

What is the Humoral component of the hypothalamic response responsible for?

It is responsible for the stimulation and inhibition of the release of pituitary hormones into the bloodstream

What is the Visceromotor component of the hypothalamic response responsible for?

The Visceromotor response adjusts the balance of sympathetic and parasympathetic outputs of the autonomic nervous system. This is a unconscious or reflexive movement

What is the Somatic motor component of the hypothalamic response responsible for?

A somatic motor response, as initiated by the lateral Hypothalamus is a conscious and willful movement.

What is the Prandial state?

The state during eating and right after eating when the blood is full of nutrients

What is the Postabsorptive state?

The fasting states in between meals

What is Anabolism?

Making macromolecules from simple precursors during the prandial state.

What is Catabolism?

Breaking down complex macromolecules during the post-absorptive state

What kinds of molecules are involved in anabolism and catbolism relating to energy stores?

Carbohydrates, Lipids, Glycogen, protein and nucleic acids

During the Prandial State, what is energy stored as?

Glycogen and Triglycerides

What is glycogen?

It is a finite reserve that is found in the liver and skeletal muscle

What are triglycerides?

Unlimited reserve that is found in adipose/fat tissue

What is the post absorptive state?

Here glycogen and triglycerides are broken down to supply the body with a constant source of energy

If intake is equal to expenditure,

The body fat remains the same

What is Lipostatic hypothesis?

This is an innate mechanism to maintain energy hypothesis where the body fat is maintained hemostatically at a specific level

What happens in the doctrine of Lipostatic Hypothesis?

After Periods of starvation or forced feeding the body would return to its homeostatic level of body fat, and this suggests that fat or adipose tissue and the brain communicate

Who discovered Leptin?

Jeff Friedman in 1994

What is Leptin?

It’s a hormone that is released by adipocytes. It It’s responsible for decreasing appetite and increasing metabolism

If the hypothalamus is severed, and leptin signaling is disrupted, what two instances could happen?

1. Lateral Hypothalamic Syndrome - Anorexia

2. Ventromedial Hypothalamic syndrome - obesity

Which part of the hypothalamus detects changes in leptin?

The arcuate nucleus of the perventricular zone

Which population can only benefit from Leptin supplementation?

Those with leptin deficiency, see reversal of obesity, If supplemented with Leptin.

What is the neural response when Leptin is elevated?

Neurons in the arcuate nucleus are stimulated to release ALPHA-MSH and CART, which activate catabolic pathways!

What is the Humoral response when Leptin is elevated?

The stimulation and release of ACTH and TSH - Thyrotropin from anterior pitiutary

Which peptide stimulates appetite? Give egs

Orexigenic Peptides like NPY and AgRP

Which peptides diminishes appetite? Give egs

Anorectic Peptides like Alpha-MSH and CART mimics high levels of leptin

What drives the somatic motor response?

Lateral hypothalamic neurons have widespread connections across the brain, and they secrete peptides that drives the somatic model response.

What peptides are released by hypothalamic neurons to drives somatic motor ?

MCH and Orexin

What does the peptide MCH as released by the hypothalamic neurons to drive somatic motor response, do?

MCH prolongs consumption and stimulates feeding

What does the peptide Orexin as released by the hypothalamic neurons to drive somatic motor response, do?

Promotes meal initiation and arousal or alertness

What regulates feeding in the short term?

The time since last meal and how much was eaten

What does balance between satiety and Orexigenic signals?

Sateity signals decrese in hunger and stops feeding. Orexigenic signals increase hunger and initiate feeding

What are the phases of digestion?

1. Cephalic or appetite

2. Gastric or eating

3. Substrate or satiety

What is the cephalic phase of digestion?

This phase of digestion is when sight and smell of food physiological response responses in anticipation of food.

What happens in the gastric or eating phase of digestion?

You start to eat chew swallow and fill your stomach with food

What happens in the substrate or satiety phase of digestion?

Stomach fills up with food and partially digested food, move to the small intestines where nutrients are absorbed into the bloodstream

What hormone is released when the stomach is empty during the cephalic phase?

Ghrelin

What does Grehlin activate In the arcuate nucleus to stimulate feeding?

Ghrelin activates NPY/AgRP- containing neurons in the arcuate nucleus to stimulate feeding

What hormone is released during the Cephalic phase of digestion when food is anticipated?

Anticipating food causes vagus nerve stimulation that stimulates the pancreas to release insulin And this causes blood sugar to drop, and this drop is detected by the NYP / AgRP neurons which increases the drive to eat.

IV administration of Ghrelin does what?

It stimulates feeding