Chapter 6 – Motivation (BIOL 4490: Introduction to Neuroscience)

These flashcards review key concepts from Chapter 6 on homeostasis, hypothalamic control, motivation, feeding regulation, thirst, and reward pathways.

What is homeostasis?

The maintenance of relatively stable internal conditions despite continuous changes in the environment.

Which feedback mechanism maintains most homeostatic processes?

Negative feedback, where an output shuts off the original effect of the stimulus.

Give an example of negative-feedback–driven homeostatic regulation.

Sweating to cool the body when temperature rises.

How does positive feedback differ from negative feedback?

Positive feedback amplifies or exaggerates the original stimulus, driving the response in the same direction.

Name a physiological example of positive feedback.

Labor contractions during childbirth.

Which brain structure is central to homeostatic regulation?

The hypothalamus.

List the three components of a hypothalamic response to a stimulus.

Humoral response, visceromotor response, somatic motor response.

Humoral Response

Stimulates or inhibits pituitary hormones

What is motivation in a physiological context?

The drive to satisfy a need such as hunger, thirst, or temperature imbalance.

What are the two main time-scales of feeding regulation?

Short-term regulation and long-term regulation.

Which two signal types control short-term feeding behavior?

Orexigenic signals (stimulate eating) and satiety signals (inhibit eating).

List the three phases of digestion in order.

Cephalic, gastric, substrate phases.

What are the two major orexigenic signals?

Ghrelin and orexin (hypocretin).

Where is ghrelin released and what does it activate?

Released by the stomach; activates NPY/AgRP neurons in the arcuate nucleus of the hypothalamus.

Which hypothalamic area do NPY/AgRP neurons stimulate to trigger feeding?

The lateral hypothalamic area.

Where is orexin produced and what two main effects does it have?

Produced in the hypothalamus; promotes hunger/feeding and wakefulness.

Name three wider physiological systems influenced by orexin besides feeding.

Reticular activating system (wakefulness), sympathetic nervous system, pituitary hormone signaling.

Identify the three primary satiety signals.

Cholecystokinin (CCK), gastric distension, and gastric peptides such as GLP-1.

What nutrient triggers CCK release and from where?

Fats trigger CCK release from small-intestine cells.

How does gastric distension signal satiety?

Stretch receptors in the stomach wall send signals via the vagus nerve to the nucleus of the solitary tract, inhibiting feeding.

Name two main actions of GLP-1.

Increases insulin secretion, delays gastric emptying (enhancing satiety).

What is semaglutide (Ozempic) and how does it work?

A long-acting synthetic GLP-1 receptor agonist that mimics the 'too full' feeling, reducing appetite and increasing insulin release.

Which two factors govern long-term regulation of feeding?

Energy balance and adiposity signals.

Differentiate the prandial and postabsorptive states.

Prandial (absorptive) state stores nutrients (anabolism); postabsorptive state breaks down stored nutrients (catabolism).

What are adiposity signals and name the two primary ones.

Hormones produced in proportion to body fat; leptin and insulin.

Where is insulin produced and what are its two key roles?

Produced by the pancreas; enables cellular glucose uptake and promotes energy storage in adipose tissue.

What hormone is encoded by the ob gene and what is its main effect?

Leptin; it reduces appetite and increases energy expenditure.

Which hypothalamic peptides rise when leptin levels increase and what is their effect?

α-MSH and CART; they inhibit feeding behavior (anorectic peptides).

Which peptides are released when leptin falls and what do they do?

NPY and AgRP; they stimulate feeding behavior (orexigenic peptides).

What experimental technique led to the discovery of leptin?

Parabiosis—surgically joining the circulatory systems of two mice.

Define thirst and list its two main physiological triggers.

The drive to drink water, triggered by hypovolemia (low blood volume) and hypertonicity (high solute concentration).

Which brain areas detect hypovolemia and by what signals?

Subfornical organ (detects angiotensin II) and nucleus of the solitary tract (detects reduced blood flow).

How is hypertonicity sensed centrally?

By the vascular organ of the lamina terminalis (OVLT), which detects ion concentration changes.

What is reinforcement in behavioral neuroscience?

An event following a behavior that increases the likelihood of that behavior recurring (often a reward).

Which neurotransmitter is central to the brain’s reward pathway?

Dopamine.

Name the three major components of the mesocorticolimbic dopamine system.

Ventral tegmental area (VTA), nucleus accumbens/basal forebrain, and frontal cortex.

How do heroin and nicotine influence dopamine release?

They act on dopaminergic neurons in the VTA, increasing dopamine release.

How does cocaine affect dopamine signaling?

It blocks dopamine reuptake in the nucleus accumbens, prolonging dopamine’s action.

Why might people feel “hangry” during fasting?

Serotonin levels drop between meals, potentially lowering mood and increasing irritability.

What is the visceromotor response (in a hypothalamic context)?

Changes in the activity of the autonomic nervous system, such as altering gut motility or insulin release.

What is the somatic motor response (in a hypothalamic context)?

Behavioral responses like seeking food, water, or warmth, initiated by the somatic motor system.

What characterizes the cephalic phase of digestion?

The earliest phase of digestion, triggered by sensory input (sight, smell, thought of food), involving preparatory physiological responses like saliva and gastric juice secretion.

What happens during the gastric phase of digestion?

The digestive phase that begins when food enters the stomach, involving the release of gastric juices and stomach contractions to break down food.

Describe the substrate phase of digestion.

The final digestive phase where nutrients are absorbed in the intestines, causing the release of hormones like CCK and GLP-1 which often signal satiety.