Lecture 21: Motivation of Basic Drives

Question 1

Motivation Definitions

Answer 1

• The reason one has for behaving in a particular way
• The desire to act in service of a goal

Question 2

High-level Motivation

Answer 2

• Strategic; long term
• “I want to be a ________”

Question 3

Low-Level Motivation

Answer 3

• Immediate; innate
• “I am hungry”
• “I am tired”

Question 4

Motivation as Homeostasis

Answer 4

• Ex. blood sugar levels leading to wanting to eat certain foods
• Body fluid levels
• Body waste levels
• Body temperature
• Hypothalamus is a key player in these regulations

Question 5

Lateral Hypothalamus Nucleus (LH)

Answer 5

• Early studies lesioned the LH in cats
• Results in aphasia (no eating)
• Also involved in arousal (sleep vs. wake)

Question 6

Ventromedial Hypothalamus (VMH)

Answer 6

• Lesions cause hyperplasia: abnormally increased eating
• Satiety center

Question 7

POMC/CART Neurons

Answer 7

• In the AN
• Stimulated by leptin
• Increases satiety
• Leptin –> POMC neuron –> satiety neuron –> …

Question 7

Leptin

Answer 7

• Satiety hormone
• Produced by fat-storing cells
• Long-term signal of stored energy
• Its level in the blood is correlated with amounts of fat
• Can cross the blood brain barrier
• People who lack leptin due to a mutation are morbidly obese and hypothermic

Question 8

Ghrelin

Answer 8

• Hunger hormone
• Stomach hormone secreted before meal
• Promotes eating

Question 9

Arcuate Nucleus of Hypothalamus (AN)

Answer 9

• Involved in control of hunger and feeding
• projects to LHA, VMN, and the paraventricular nucleus (PVN)
• Includes diverse types of cells

Question 10

NPY/AGRP Neurons

Answer 10

• In the AN
• Inhibited by leptin, stimulated by ghrelin
• Increases feeding
• No leptin/much ghrelin –> AGRP neuron –> satiety neuron –> …
• Inhibits POMC

Question 11

Hypovolemic Thirst

Answer 11

• Too little volume of fluid in the body (dehydration, blood loss, vomiting, diarrhea)
• Triggered by blood pressure drop detected by baroreceptors in heart and veins
• Sends info to the brain via a neural and endocrine pathway

Question 12

Osmotic Thirst

Answer 12

• Increase in extracellular salt (high intake of sodium in diet)
• Hypertonic extracellular fluid pulls water from neurons into extracellular space
• Detected by osmoreceptor neurons in the hypothalamus
• Sends signal to decrease urinary output and increase thirst

Question 13

Neural Pathway of Hypovolemic Thirst

Answer 13

baroreceptors send info to the nucleus of the solitary tract in the brainstem which increases HR and constricts blood vessels. Also send info to hypothalamus which sends signals to increase reabsorption of water in kidney and triggering thirst.

Question 14

Endocrine Pathway of Hypovolemic Thirst

Answer 14

• Low BP causes kidneys to release renin
• Angiotensin II produced in blood
• ANG II enters brain and causes thirst