Hunger and thirst Flashcards
Homeostasis
Process of actively maintaining internal conditions, particularly with respect to food and water availability and body temperature.
When the body is too cold, basal metabolic rate _____increases/decreases ; calories are ____stored/burned to generate heat and raise body temperature
Increases and burned
When too cold, the body shivers, a way of burning _____ to generate heat
Calories
When too cold, peripheral blood vessels _____, moving blood to the interior of the body so less heat is lost through the skin.
Constrict
- We consciously experience thirst when there is either…
1) not enough water inside cells (osmometric thirst)
2) not enough blood (liquid) in our circulatory system (volumetric thirst)
First 2 steps of clenching thirst
- The body loses water
- Detectors are activated
What is the correctional mecanism activated by the detectors (step 3 of clenching thirst) ?
Drinking
Step 4 of clenching thirst : The ____ fills with water and sends a signal to the brain to tell it to stop drinking.
Stomach
Step 5 of clenching thirst : We immediately feel satiated as the ____ mechanism inhibits further drinking by inhibiting the correctional mechanism (Drinking).
Satiety
Step 6 of clenching thirst
Water is absorbed, body fluids are back to normal.
The dominant type of thirst is …
Osmometric
Tonicity of a solution
Relative concentration of dissolved molecules (solutes in solution or solvant) on either side of a membrane that is permeable only to the solution, not to the solutes dissolve in it.
Diffusion
Process by which molecules move from areas of high concentration to areas of low concentration.
Osmosis
Movement of a solution (solvent) from areas of high concentration (low tonicity) to areas of low concentration (high tonicity.
Isotonic solution
Similar concentrations of solute on either side of the membrane. The cell will neither gain nor lose water : no source of diffusion.
Hypotonic solution
Solute is less concentrated outside the cell than in, so water will enter the cell (water goes wherever there’s more solute). This happens until the cell inflates.
Inflation of the cell lowers the ______ tonicity.
Extracellular
Shrinking of the cell ____lowers/rises the extracellular tonicity
Rises
Extracellular solute concentrations vary according to what we…
Eat and drink
When we drink water, it ____ the tonicity of extracellular fluid , causing cells to expand in size as water moves into them from the extracellular fluid.
Lowers
When we consume salt, it increases the _____ of extracellular fluid, causing cells to shrink in size as water moves out of them.
Tonicity
Shrinkage of cell triggers _____ thirst (classical thirst).
Osmometric
Hypertonic (salty) solutions cause cellular _____ (cells lose water and shrink in size).
Dehydration
Osmoreceptors
Neurons whose membrane potential and neurotransmitter release are sensitive to the volume of the cell.
Volumetric thirst
When there is not enough blood circulating in the body. Losing blood causes this type of thirst.
The heart needs a certain amount of blood to keep beating, to trafic _____ across the body.
Nutrients
When you lose blood, the heart has a dangerously low blood _____ and is losing the ability to beat.
Pressure
Low blood pressure causes cells in the kidneys to release an enzyme called ____, which initiates a cascade of chemical reactions in the blood.
Renin
Renin converts ______ into ______I, which converts to ________II.
Angiotensin
Angiotensin II makes you retain all ___ and _____.
Salts and water
Angiotensin II pushes blood to the heart by increasing blood _____.
Pressure
Angiotensin II creates intense ____ and ____
Hunger and thirst
Feelings of thirst relate to neural activity in a few different brain regions, particularly a hypothalamic area known as…
Anteroventral tip of the third ventricle (the AV3V region).
Feelings of thirst activate neurons in the AV3V region as well as in the ____ ____ cortex
Anterior cingulate cortex.
AV3V is the trigger that says you’re thirsty. It does not create ____ feelings.
Satiety
AV3V neurons generally remain active until the water…
Reaches them (long after people have stopped drinking)
Cold ____ in the mouth and sensory fibers in the stomach are part of the rapid satiety feedback mechanism.
Sensors
Food mostly consists of:
- Lipids (triglycerides)
- Sugars (carbohydrates)
- Amino acids (proteins)
The body monitors 3 main things :
- What’s in the blood : nutrient related signal.
- Long term nutrients : adiposity-related signal
- short term nutrients : satiety signals
The pancreas monitors blood ____ levels.
Glucose
When blood glucose is ___, the pancreas releases insulin when we eat.
High
When blood glucose is low, the pancreas releases _____ between meals.
Glucagon
Insulin causes blood glucose to be stored as _____
Glycogen
Glycogen
Carbohydrate stored in liver and muscle cells for later use
After a couple hours, _____ causes glycogen to be broken down into glucose for the body to use.
Glucagon
Glycogen (sometimes referred to as animal starch) represents our ____-term storage of glucose.
Short (2000 calories)
We build up glycogen levels when we ___ (when insulin is released).
Eat
Cells in the brain can _____ take in glucose (using a glucose transporter).
Always
Most cells outside the brain use a glucose transporter that requires _____to be functional
Insulin
Cells outside the brain can only take in glucose when _____ is present
Insulin
About 2 hours after a meal, cells outside the brain can only use ______ (made from fatty acids) for energy.
Ketones
Insulin causes fatty acids to be stored as ______ in adipose tissue (fat cells) for long term usage.
Triglycerides
_____ causes triglycerides to be broken down into fatty acids and glycerol to be used.
Glucagon
The liver converts _____ into sugar and fatty acids into _____.
Glycerol and kerones
Cells in the liver monitor glucose levels, and this information is brought to the brain by the 10th _____ nerve (the vagus).
Cranial
One controller of hunger is blood _____ levels.
Glucose
An empty stomach is communicated to the brain by the stomach’s release of a peptide called ____.
Ghrelin
Levels of circulating ghrelin increase with ____ and fall with _____.
Increase with hunger, fall with satiation
Exogenous administration of ghrelin increases ____ and food intake, which increases body weight.
Hunger
The hormones ___ and ____regulate the release of digestive enzymes and insulin.
CCK and GLP-1
Repeated administration of ___ to healthy people does not reliably cause sustained weight loss. It sometimes decreases meal size, but people typically respond by eating small meals more frequently.
CCK
____ agonists have recently proven to be highly effective in reducing hunger and weight in most people.
GLP-1
____ is a circulating hormone that is secreted by adipocytes (fat cells).
Leptin
Leptin levels correlate with the amount of ___ in the body.
Fat
As fat cells grow and proliferate, leptin levels _____increase/decrease
Increase
If leptin levels fall below some threshold, animals feel intense ____
Hunger
To some extent, leptin levels regulate the sensitivity of _____ neurons to short-term satiety signals (e.g., CCK and GLP-1).
Hypothalamic
____ administration of leptin can slightly decrease meal size in healthy people, but this effect is short-lived.
Exogenous
Ob mouse
Strain of mice whose obesity and low metabolic rate are caused by mutation that prevents production of leptin. In humans, this is called congenital leptin deficiency
Emergency hunger circuits are activated when…
A specific critical need to eat or not eat overrides energy homeostasis circuitry.
Glucoprivation
Dangerously low blood-glucose levels (i.e., not enough immediately available sugar in the blood) can cause intense hunger
Glucoprivation can result from ____ insulin signaling and from drugs that inhibit glucose metabolism
Excessive
Lipoprivation
Dangerously low levels of fat (i.e., not enough fat on the body or free fatty acids in the blood)
Lipoprivation can be caused by…
drugs that inhibit fatty acid metabolism
When the brain senses that energy stores are dangerously low (glucoprivation or lipoprivation), it launches an ______ cascade of effects
Emergency
In emergencies, insulin release is ____, and glucagon release is triggered.
Suppressed
In emergencies, short-term satiety signals are _____.
Ignored
In emergencies, energy expenditure ___ (basal metabolic rate), halting growth and reproductive systems
Slows
In emergencies, a potent and sustained feeling of ____ takes hold
Hunger
In emergencies, Adrenalin is released as part of the fight or flight response increasing blood ___
Rate
Diabetes
Condition where people are either insensitive to insulin signaling or they do not release enough insulin.
Diabetes results in ____ blood glucose levels and an inability to store glucose as ___ (it just stays in the blood streams).
Higher, fat
If diabetes is left untreated, it leads to …
intense thirst and progressive weight loss
As fat cells become depleted, leptin levels fall, and a lipoprivation-related feeding emergency takes hold, resulting in intense ____, even if there is tons of glucose in the blood.
Hunger
Two cell populations in the ___ nucleus of the hypothalamus have opposing influences on hunger.
Arcuate
The neurons that co-release the peptides AGRP and NPY – causes dramatic____undereating/overeating. They are inhibited by leptin and activated by ghrelin.
Overeating
Neighboring (POMC) neurons ___elicit/inhibit hunger. They are activated by leptin and inhibited by ghrelin.
Inhibit
These two cell populations project to the paraventricular nucleus (PVN) of the _____.
Hypothalamus
Artificially increasing PVN neuron activity does not substantially/reliably change ____
Hunger
Cells in the PVN tend to cause a ___ response
Lypoprivation
Prader-Willi syndrome
Rare chromosomal abnormality in which up to 7 genes are deleted from chromosome 15. One of these genes is critical for the development/survival of a population of PVN neurons.
People with Prader-Willi syndrome are born with very low muscle mass and have little interest in eating. But between 2 and 8 years of age, they develop a heightened, permanent and painful sensation of ____
Hunger
About __% of the variability in people’s body fat is due to genetic differences.
50
Bariatric surgery
Modifies the stomach, small intestine, or both.
Roux-en-Y gastric bypass (RYGB).
Bariartric surgery. The second part of small intestine (the jejunum) is cut and attached to the top of the stomach. The stomach is also stapled to make it much smaller.
Changes in hunger do not seem to correlate with any observed changes in hormone signaling from the ____.
Stomach
