Lecture 18 of Physiological Psych (Metabolism & Energy Balance)

What is the primary function of homeostasis?

To maintain the body’s internal environment within a narrow physiological range.

Which brain structure is primarily responsible for controlling and regulating homeostasis?

The hypothalamus

Who first proposed the concept of ‘milieu interior,’ the stability of the internal environment?

Claude Bernard

Who coined the term, ‘homeostasis?’

Walter Cannon

What are the two primary purposes of metabolism?

To extract energy from nutrients and to use or store that energy.

The ________ ______ occurs after eating, when blood is filled with nutrients, and is associated with anabolic processes.

Prandial stage

The metabolic process of building macromolecules from smaller units is known as _________.

Anabolism

The _______ ______ occurs during fasting, when stored energy is broken down, and is associated with catabolic processes.

Postabsorptive stage

The metabolic process of breaking down macromolecules into smaller units to release energy is known as _________.

Catabolism

In what two forms is energy primarily stored in the body?

As glycogen (in the liver and skeletal muscle) and as triglycerides (in adipose tissue).

What is the amount of calories lost or energy expended even when not physically working, such as when you are sitting?

Basal Metabolic Rate (BMR)

Why does lean muscle mass have a higher oxygen consumption at rest compared to adipose tissue?

Because muscle tissue is more metabolically active than fat tissue.

A sustained calorie _________ leads to weight gain, while a sustained calorie ________ leads to weight loss.

Surplus; deficit

Which brain structure is known as the ‘master gland’ for its role in integrating somatic and visceral responses to maintain homeostasis?

Hypothalamus

What effect does an electrolytic lesion of the lateral hypothalamus (LH) have on feeding behavior in rats?

It causes anorexia, where the rats stop eating and lose weight.

What effect does an electrolytic lesion of the ventromedial hypothalamus (VMH) have on feeding behavior in rats?

It causes hyperphagia (overeating) and obesity.

The lateral hypothalamus (LH) is considered the ________ ________.

Hunger center.

The ventromedial hypothalamus (VMH) is considered the ____________ ________.

Satiety (fullness) center

What is the central idea of the lipostatic hypothesis proposed by Gordon Kennedy?

The brain monitors and defends the body’s energy stores (fat levels) against perturbations to maintain a stable body weight.

In parabiosis experiments, what happened when an obese ob/ob mouse was surgically joined to a normal wild-type mouse?

The ob/ob mouse's body weight returned to normal, indicating it was missing a blood-borne satiety signal.

The genetic mutation in ob/ob mice results in a deficiency of which hormone?

Leptin.

What is the effect of injecting leptin into an ob/ob mouse?

It reverses the obesity by reducing food intake and increasing energy expenditure.

The genetic mutation in db/db mice results in a deficiency of what?

The leptin receptor.

What term describes a substance or signal that stimulates feeding and increases appetite?

Orexigenic.

What term describes a substance or signal that suppresses feeding and reduces appetite?

Anorexic (or anorexigenic).

Name two key populations of neurons within the arcuate nucleus (ARC) that regulate feeding.

NPY/AgRP neurons and POMC/CART neurons.

Which peripheral hormone is released from the stomach when it is empty and acts as a powerful orexigenic signal?

Ghrelin.

Which peripheral hormone is released from adipocytes (fat cells) and acts as a long-term anorexic signal?

Leptin.

Which peripheral hormone, released from the small intestine in response to food, inhibits meal frequency and size?

Chlolecystokinin (CCK).

Pro-opiomelanocortin (POMC) is a precursor peptide that is cleaved into several active molecules, including _____.

ACTH, α-MSH, and β-endorphin.

Which neuropeptide, derived from POMC, inhibits food intake by activating melanocortin receptors?

α-MSH (alpha-melanocyte-stimulating hormone).

Which neuropeptide, synthesized in the arcuate nucleus, increases appetite and decreases metabolism?

Agouti-related peptide (AgRP).

AgRP and α-MSH have opposing effects by binding to which two key receptors involved in feeding?

MC3R and MC4R (melanocortin receptors 3 and 4).

AgRP acts as an _____ of the MC3R/MC4R receptors, promoting feeding.

Inhibitor (or antagonist).

α-MSH acts as an _____ of the MC4R receptor, suppressing feeding.

Activator (or agonist)

When you are full, the hormone _____ is released, which activates POMC neurons in the arcuate nucleus.

Leptin

The central action of leptin leads to the activation of MC3R/MC4R, which ________ feeding and _______ metabolism.

Inhibits; increases

When you are hungry, the hormone ________ is released, which stimulates NPY/AgRP neurons in the arcuate nucleus.

Ghrelin.

The central action of ghrelin leads to the inhibition of MC3R/MC4R, which _____ feeding and _____ metabolism.

Stimulates; decreases

Mutations in the _____ receptor account for 2-5% of early-onset obesity cases.

MC4R (melanocortin 4 receptor)

In addition to NPY and AgRP, which two neuropeptides found in the lateral hypothalamus are orexigenic?

Melanin-concentrating hormone (MCH) and Orexin.

What takes more energy to breaks down into glucose?

Complex carbs

What takes less energy to break down into glucose?

Simple carbs

What is a great source of amino acids?

Protein

What makes up triglycerides stored in adipose tissue?

Fat

_____ are 1 kcal/hr/kg of body weight.

Males

_________ are 0.9 kcal/hr/kg of body weight.

Females

True or false? Female have high er percentage of adipose tissue; males have more lean body mass.

True

Energy stored + energy intake - energy output = what?

Total Body Energy

Nutrients that we eat, digest, and absorb = what?

Energy Intake

Work + Heat (given off body) = what?

Energy Output

Who proposed the lipostatic hypothesis?

Gordon Kennedy