Lecture 13 - Hunger and Thirst Flashcards
What is homeostasis?
Homeostasis is the body’s process for maintaining internal conditions, such as temperature and water levels, within a range that supports survival.
Why do cells need a stable temperature and steady supply of food and water?
Cells need a stable temperature and a consistent supply of food and water to function properly; without these, they cannot survive.
How do animals survive in diverse environments?
Animals have systems that help them maintain stable internal conditions, allowing them to survive in various environments, from hot and dry to cold and wet.
What is unconscious temperature regulation in warm-blooded animals?
Unconscious temperature regulation in warm-blooded animals involves automatic processes that maintain a stable internal temperature, such as shivering, blood vessel constriction, sweating, and blood vessel expansion.
How does the body respond when it gets too cold?
When it’s too cold, the body increases metabolic rate, causes shivering, and constricts blood vessels near the skin to retain heat.
How does the body cool down when it gets too hot?
The body cools down by sweating or panting, which helps heat escape through evaporation, and by expanding blood vessels near the skin to release heat.
How do cold-blooded animals regulate their temperature?
Cold-blooded animals rely mostly on their environment to regulate their temperature, as they cannot adjust their internal temperature as effectively as warm-blooded animals.
What motivates conscious temperature regulation?
Conscious temperature regulation is motivated by discomfort, which creates a “need state” that encourages actions like seeking warmth or cooling down.
Why do we sometimes anticipate relief or pleasure when adjusting the temperature?
Anticipation of relief or pleasure can motivate us to act, such as putting on a sweater before going outside, even if we don’t feel cold yet.
Imagine you’re outside on a cold day without a jacket and begin to shiver. Which processes are involved in helping you stay warm?
The body would increase metabolic rate, trigger shivering, and constrict blood vessels near the skin to reduce heat loss and protect core temperature.
How does homeostasis help regulate thirst?
Homeostasis regulates thirst by monitoring water levels in the body; when levels are low, it prompts us to drink water to restore balance.
What are the steps in the body’s response to water loss?
When water is lost, the body detects low water levels, triggers thirst, signals the brain when drinking starts, and eventually provides a “stop” signal when enough water is consumed.
What role do stomach signals play in thirst regulation?
Stomach signals help regulate thirst by informing the brain as the stomach fills with fluid, providing early feedback to reduce the drive to drink and prevent overhydration before blood hydration levels actually rise.
What is osmometric thirst?
Osmometric thirst is the sensation of thirst that arises when there is not enough water inside the body’s cells.
What is volumetric thirst?
Volumetric thirst occurs when there isn’t enough blood or liquid in the circulatory system.
How does the body signal us to stop drinking once we’ve had enough?
When the body has absorbed enough water and the fluid balance is restored, the brain receives signals indicating satiety (fullness). These signals come from stretch receptors in the stomach and changes in blood osmolarity, which tell us that we’ve had enough to drink, prompting us to stop.
What is the definition of osmometric thirst?
Osmometric thirst is thirst that arises when there is an insufficient amount of water inside the body’s cells.
What is the definition of volumetric thirst?
Volumetric thirst is thirst that occurs when there is a low volume of blood or liquid in the circulatory system.
If you’ve been sweating after exercise, which type of thirst is most likely to be triggered?
Volumetric thirst would likely be triggered, as sweating can lead to a reduction in blood volume, prompting the need to drink.
How might you experience osmometric thirst on a very hot day?
On a hot day, you might experience osmometric thirst due to dehydration, as water inside your cells decreases from excess sweating or lack of fluid intake.
What is tonicity?
Tonicity refers to the balance of solutes inside and outside cells, which affects the movement of water.
What is diffusion?
Diffusion is the movement of solutes from areas of higher concentration to areas of lower concentration.
What is osmosis?
Osmosis is the movement of water toward areas where solutes are more concentrated.
What is an isotonic solution, and how does it affect cells?
An isotonic solution has the same concentration of solutes inside and outside the cell, resulting in balanced water movement.
What is a hypotonic solution, and how does it affect cells?
In a hypotonic solution, there are fewer solutes outside the cell, causing water to move into the cell, making it swell.
What is a hypertonic solution, and how does it affect cells?
In a hypertonic solution, there are more solutes outside the cell, causing water to move out of the cell, making it shrink.
How does osmometric thirst develop?
Osmometric thirst occurs when hypertonic (salty) conditions outside cells cause them to lose water and shrink, leading to dehydration.
What are the main body fluid compartments, and how are they distributed?
The main fluid compartments are intracellular fluid (67% inside cells) and extracellular fluid, which includes cerebrospinal fluid (less than 1%), intravascular fluid (7% in blood plasma), and interstitial fluid (26% between cells).
How does the body maintain fluid balance after drinking water?
Drinking water makes extracellular fluid less concentrated, causing water to flow into cells and expand them. Any extra water is eliminated through urine.
How does the body respond when you eat salty food?
Eating salty food makes extracellular fluid more concentrated, causing water to leave cells and shrink them, which triggers thirst to help dilute the saltiness.
What role do osmoreceptors play in thirst?
Osmoreceptors are neurons that detect changes in cell size. When they shrink due to hypertonic conditions, they signal the brain to trigger thirst.
What triggers volumetric thirst?
Volumetric thirst is triggered by a loss of blood or other fluids that reduces blood volume, signaling the body to increase fluid intake to restore blood levels.
Why does blood loss lead to feelings of extreme thirst?
Blood loss lowers blood volume, prompting the body to signal for fluids to restore proper volume for heart function.
How does low blood pressure lead to the release of renin?
When blood pressure drops, especially due to a decrease in blood volume (like from dehydration or blood loss), the kidneys detect this through sensors in the blood vessels. In response, the kidneys release renin. Renin starts a process that helps raise blood pressure by constricting blood vessels and prompting the kidneys to retain sodium and water, which increases blood volume. This chain of events helps restore normal blood pressure.
What does renin do in the body?
Renin triggers the formation of angiotensin II, which helps the body retain sodium and water, raises blood pressure, and increases salt and water cravings.
What happens when the body detects hypovolemia (low blood volume)?
Blood flow to the kidneys decreases, leading to the release of renin, which combines with angiotensinogen to form angiotensin II, triggering responses to restore blood volume.
What is the role of angiotensin II in the body?
Angiotensin II helps the body retain sodium and water, raises blood pressure, and stimulates salt cravings and the urge to drink fluids.
What brain region is primarily involved in the sensation of thirst?
The anteroventral tip of the third ventricle (AV3V region) in the hypothalamus is primarily involved in controlling thirst sensations.
Which two brain regions show increased activity when a person feels thirsty?
The AV3V region of the hypothalamus and the anterior cingulate cortex show increased activity when a person feels thirsty.
