Exam 3 Flashcards
(240 cards)
Homeostasis
optimal, stable, and balanced internal environment
How does the body respond to deviations from homeostasis?
By initiating changes in motivation to restore balance
What are the four main processes of homeostasis?
Negative feedback, redundancy, behavioral compensation, and allostasis
Define negative feedback in homeostasis.
A process where restoring the set point turns off the response. Example: A thermostat regulating temperature
What is redundancy in homeostasis?
Multiple systems performing the same function to ensure fail-safety in vital processes
What is behavioral compensation in homeostasis?
Behavioral adjustments to maintain internal stability, such as seeking shade to cool down
Define allostasis.
Predictive regulation of bodily processes to maintain stability in response to stressors
What is allostatic load?
The wear and tear on the body from chronic stress, potentially causing system breakdown
What is thermoregulation?
The process of maintaining a stable internal body temperature
What are the main physiological effectors in thermoregulation?
Non-shivering thermogenesis, skin blood flow changes, water evaporation, and shivering thermogenesis
What are behavioral effectors in thermoregulation?
Actions like postural changes, temperature choice, and altering the microenvironment (e.g., using air conditioning)
How do endotherms and ectotherms differ in thermoregulation?
Endotherms generate heat internally through metabolism, while ectotherms rely on environmental heat sources
What percentage of food energy is used for basal metabolism?
About 80%
Why is losing weight difficult according to homeostasis?
Allostasis detects starvation and adjusts basal metabolism to conserve energy
What is the role of leptin in hunger regulation?
Leptin, produced by fat cells, signals long-term energy stores and decreases hunger
What is the function of ghrelin in hunger?
Ghrelin, released by the empty stomach, stimulates hunger by exciting NPY neurons
How do insulin and PYY regulate hunger and satiety?
Insulin suppresses hunger in response to high glucose; PYY signals to stop feeding
What is the role of the arcuate nucleus in hunger regulation?
It houses neurons that control hunger (NPY neurons) and satiety (POMC neurons)
What happens to leptin-deficient rodents?
They overeat, demonstrating leptin’s role in regulating energy storage
How does redundancy support homeostasis?
If one system fails, other systems compensate to maintain balance
Why is redundancy vital in thermoregulation?
It ensures survival-critical functions even if one neural region is damaged
What does lesioning the ventromedial hypothalamus (VMH) show?
VMH lesions lead to higher weight set points but still allow satiety
What does lesioning the lateral hypothalamus (LH) show?
LH lesions result in lower weight set points, but hunger is still experienced
How does the hypothalamus regulate hunger and satiety?
By integrating signals from gut hormones (e.g., leptin, ghrelin, PYY) to balance energy intake