Hunger Flashcards
How is eating shut off?
Through a satiety system - we feel full.
What is metabolism?
How we extract energy
What is the Fasting phase of metabolism?
What is the main component the pancreas secretes during the fasting phase when we still need glucose in our bodies?
How is it converted into glucose?
Fasting Phase – how can we feed our cells when our gut is empty?
The pancreas secretes Glucogen, which transforms Glycogen into Glucose.
What is Absorptive Phase of metabolism?
Absorptive Phase – what happens to the food we eat?
Carbohydrates
Proteins
Fats
How do we keep ourselves going when we don’t have food in our gut? *Short-term reservoir
1) Short-term reservoir - Located in muscles and Liver - is stocked with Glycogen
> Glycogen, is the insoluble form of Glucose molecule that cannot diffuse through membranes.
> Glycogen is made from Glucose by Insulin.
> Insulin takes free-floating glucose and turns it into glycogen and stores into the reservoir.
What converts glycogen into glucose?
Which phase does this occur?
Why would we need to convert it?
Glucogen
During fasting phase
We convert it when we need to use it as energy
Glycogen is made from Glucose by __________.
Insulin
What phase is glucagon active in?
Where is glucagon secreted from?
When is it secreted?
Why is glucagon secreted?
Glucagon is active during the fasting phase.
Pancreas
> secreted when detectors signals low glucose levels in blood.
> It’s secreted to allow glycogen to be converted into glucose (usable form)
Why is pancreatic cancer usually deadly?
With the loss of pancreas, you cannot power yourself.
During fasting phase, what is our body cells powered by?
What is our brain powered by?
Triglycerides, in our long-term reservoir (Adipose tissue)
Glucose
What are triglycerides?
What happens as triglycerides are released?
3 fatty acid chains, connected through Glycerol.
When we release triglycerides from Adipose tissue, it gets pulled apart into the fatty acid chains, and glycerol is then converted into glucose. Then this glucose feeds our brain.
During fasting phase, where does glucose come from?
Both short-term and long-term reservoirs.
Why does the brain get all the glucose?
Why would there be a problem getting glucose into the body during the fasting phase?
1) Glucose is translated into ATP faster than fatty acid or carbohydrate chains.
2) During fasting phase, cells can’t utilize the glucose in blood because glucose only transports through glucose transporters.
The problem is that glucose transporters in the brain (astrocytes) don’t need a key to open them, but the glucose transporters in the body need the key, insulin, to enter the brain; this is why the brain can get glucose.
> During the fasting phase, insulin levels are low, relative to glucogon levels.
What’s the breakdown of how our brain and body gets “fed”?
Brain - During the fasting phase the pancreas secretes GLUCAGON which converts stored glycerol into glucose
Body - Also, triglycerides from adipose tissue can be broken down into glucose and fatty acids
When is short-term storage used?
When blood glucose levels get really low.
Explain the steps of digestion during absorptive.
We digest - starts with mouth with enzymes in saliva. Goes to stomach.
Partially digested food is released through the duodenum (connection between the stomach and the small intestine) into the small intestine.
Nutrients are absorbed from the small intestine.
Indigestible material is formed into feces in the large intestine.
Where is short term reservoir located?
What does the storage contain?
What is the synthesization and convertion process to and from glucose?
Located in liver and muscles
Contains glycogen (a complex, insoluble carbohydrate)
Glycogen is synthesized from glucose by insulin
Glycogen is converted back into glucose by glucagon
What are the function of small intestines?
Small intestines – part of the immune system ; bacteria is blocked from absorption, toxins eliminated;
Macronutrients and vitamin absorbed here in different parts, so taking surgery to take this part out = specific vitamin deficiency
Colon – pulls out water
Why is fiber important?
What’s the difference bw simple and complex carbohydrates?
Since it’s insoluble, it functions as a GI cleanser.
Increases peristalsis, which keeps food moving along.
Since complex carbohydrates have more fiber, there is more slow sustained release of macronutrients and blood sugar into bloodstream.
Simple carbs release blood sugar too quickly, resulting in spikes (makes sense when we talk about insulin and diabetes).
What is carbohydrates broken into?
What happens once it’s broken into _______.
*Insulin
Carbohydrates are broken down into glucose - once it hits blood stream, the increase in blood glucose levels trigger the pancreas to release insulin.
Insulin opens up the glucose transporter cells in our body cells so it can pull the glucose, also converts glucose into glycogen to be stored in liver and muscles.
Also transports glucose into adipose tissue where it’s converted into glycerol, then into triglycerides.
During absorptive phase levels of ___________ is much higher than levels of ___________.
Levels of insulin is much higher than levels of glucagon.
Describe Type 1 and Type 2 Diabetes
Type 1 diabetes:
Cells that produce insulin in pancreas is degenerating.
Type 2 diabetes:
Fully functional cells stop producing insulin. Deuces (2) felicia.
Insulin dysregulation, but mechanism is different.
If you change your diet, which diabetes can you reverse?
Type 2 diabetes.
Why are diabetics always so thirsty?
Start with talking about Glucose transporters…
Diabetics obviously have insulin dyregulation.
Glucose must have a transporter (insulin) in the body to move around, because it is water soluble. Therefore, now there is increased tonicity in the blood.
Since diabetics cannot produce insulin, hormones signal to start pulling water from interstitial fluids, which makes you thirsty. The cells are saying, “you’re dying, we need more water”.
What’s insulin’s end goal?
What happens when we increase tonicity of the blood?
Insulin is not important for glucose, but really important for cardiac function, as it regulates the circulatory system.
Insulin’s end goal is to maintain TONICITY of blood. By pulling in water from the Interstitial fluid (2nd biggest compartment) to balance the tonicity of the blood, we stress the heart out.
-When we increase food, we increase tonicity of blood, and every time we increase tonicity in blood, we pull water in to balance the tonicity, thereby, increasing stress on heart and arteries
> Important for blood pressure and energy partitioning (regulates which reservoirs it goes to)
Long-term Reservoir
- Adipose tissue
- Contains triglycerides (a soluble carbohydrate combination of fatty acids and glycerol)
- Fatty acids are used by body cells
- Glycerol is converted to glucose by liver to feed brain
Is glycerol a short-term reservoir or long-term reservoir?
What is the conversion process?
LT reservoir
-Glycerol is converted to glucose by liver to feed brain
How come the brain gets all the glucose?
Because glucose transporters in the brain does not need insulin, or the key, to open.
In body cells, how do glucose transporters work?
In the body cells, glucose transporters only work when it is bound to insulin.
During the absorptive phase the pancreas secretes ________.
It opens glucose transporters in cells
It converts excess glucose into which of the following, for storage?:
a. Glucogon
b. Glycogen
c. Glycerol
d. Glue
During the absorptive phase, the pancreas secretes insulin.
It converts excess glucose into glycogen for storage.
Which diabetes cannot be reversed?
Type 1 - cells literally have degenerated.
Type 2 diabetes is usually diagnosed when?
What leads to insulin resistance?
Type 2 diabetes is usually diagnosed in middle aged adults.
Obesity leads to insulin resistance.
What percentage of type 1 diabetes is diagnosed in USA?
5-10%
Which diabetes is usually diagnosed in children or young adults?
Type 1. Destruction of insulin producing cells.
What is the def. of diabetes mellitus?
Failure to move glucose out of blood supply due to insulin dysfunction.
What are the internal cues of eating?
+Peristalsis - really the small intestines are empty, not stomach)
+Glucose availability
+Quantities of stored fats (low long-term reservoir)
What are the external cues of eating?
+Food availability: We eat more, when there’s food around us. The more food that is present, the more we eat (buffets).
+Smell - salivation preps our digestion system
+Conditioning -
Time of day: if I usually eat 11 am, looking at the clock at 11 am will make me hungry.
People: More people, more hunger… possibly competition?
Why does obesity problems continue? In other words, why is obesity so hard to fight?
Most treatments focus on internal cues rather than external cues. Calories in = Calories out… but it’s not always right.
How are internal hunger signals detected?
There are 2 internal detectors: Brain detectors and Liver detectors.
1) The brain hunger detectors are in the brain side of the BBB, monitors glucose availability only. The receptors are located in the nucleus of the solitary tract (NST), and info about glucose levels is communicated to the Hypothalamus.
2) The liver detectors are in the blood side of the BBB, monitors availability of both glucose AND fatty acids. It primarily regulates release of insulin when glucose levels in bloodstream drop.
Communicates the nutrient availability (glucose and fatty acids) to the Nucleus of the Solitary Tract and the brain via. Vagus nerve.
What drives craving?
Why is it so hard to not give into these cravings?
*bacteria
Bacteria in our small intestines. They crave certain macronutrients and produce neuropeptides and hormones.
Bacteria have receptors for Neurotransmitters like Serotonin and Dopamine.
They also induce production of Serotonin and Dopamine in brain. If they are NOT getting what they want, they start to release TOXINS and which signals the brain of a deficit of a food that the bratty bacteria wants.
We are just puppets to their self-serving ways.
What are the main brain structures involved in hunger?
Where are they all very close to?
- Lateral hypothalamus
- Ventromedial hypothalamus
- Arcuate nucleus
- Paraventricular nucleus
All close to the 3rd ventricle
A lab rat got legioned in the Lateral Hypothalamus, what happens to this rat?
They starve to death, even with appetizing food, because they do not initiate eating.
They can be force-fed and will eat.
Electrical stimulation of the LH produces what?
Overeating behavior - non-stop until food is gone
Hunger signals coming from the liver and brain project to what?
The arcuate nucleus
In response to the hunger signals, the Arcuate Nucleus releases what?
The arcuate nucleus neurons release NPY and AGRP.
NPY induces ravenous eating and increases Insulin release.
The AGRP also induces eating. A tiny amount infused into the 3rd ventricle made rats eat for 6 days!
What does the NPY/AGRP neurons stimulate?
LH MCH/orexin neurons.
Also increases eating behavior
AGrP is an _________ at receptors located in the Lateral Hypothalamus, called ______ receptors.
To decrease eating behavior, one idea would be to create a drug that is an ___________ at the MC4 receptors to block the effects of _____.
When stimulated, MC4 receptors produce what type of potential?
Stimulation of MC4 receptors decrease activity of _________________ neurons.
AGrP is an ANTAGONIST to receptors located in the Lateral Hypothalamus, also called MC4 receptors.
To decrease eating, create a drug that is an AGONIST to stimulate the MC4 receptors (αMSH), or just block the effects of AGrP.
When stimulated, MC4 receptors produce IPSPS- they decrease the activity of the NPY and AgRP neurons.
What type of cells secrete Leptin?
Once full, Leptin signals to the arcuate nucleus to _______ it.
What happens when there are low levels of Leptin?
Fat cells from the long-term storage, when full, secrete Leptin.
Leptin signals to the Arcuate nucleus to INHIBIT IT… no more food necessary.
When Leptin drops, the Arcuate Nucleus releases NPY and AgRP… and get increased eating.
Once Leptin drops and the Arcuate Nucleus releases NPY and AgRP, what does it communicate with?
What is being suppressed?
The NPY and AGrP communicates with LH and the paraventricular nucleus.
Pituitary hormones TSH and ACTH are suppressed.
What type of cells secrete Leptin?
Which cells are inhibited by Leptin?
What does it mean if Leptin levels drop?
Fat cells secrete Leptin.
Cells in the Arcuate Nucleus of the Hypothalamus is inhibited by Leptin.
This when fat stores are low, Leptin drops.
When Leptin drops, the Arcuate Nucleus releases NPY and AgRP.
The NPY and AGrP communicates with LH and the paraventricular nucleus. Then TSH and ACTH are suppressed.
What does the Nucleus of the solitary tract know?
How much glucose and fatty acids are available.
In response to knowing the glucose and fatty acid levels, the Nucleus of the Solitary Tract sends information to where?
What are the 2 things the Nucleus of the Solitary Tract regulates?
Arcuate nucleus
Lateral Hypothalamus
Paraventricular nucleus
1) To regulate how much we are going to eat and
2) whether or not we are in the Fasting or Absorptive phase.
>It influences the hormone release from the Pancreas, either Glucagon dominant or Insulin dominant.
How good are we estimating our blood glucose levels? What does this have to do with anything?
Terrible - our internal cues are not good at telling us how hungry we really are.
What are most of the protein amino acids used for?
Most of them are first converted into fats in LT storage and hang out in form of Triglycerides.
Insulin helps to convert free-floating glucose into ______________, to be stored in the liver and _______.
Insulin helps to convert free-floating glucose into glycogen, which is then stored into the liver and muscles.
Which macronutrient do we extract energy from?
Carbohydrates - Glucose!
Which levels are higher in the absorptive phase? Glucogon or Insulin?
Why?
Insulin - because once glucose hits the bloodstream, the pancreas signals the insulin. The insulin has many jobs. It’s the key to opening the door to the glucose-transporter cells in the body, so that it can now pull Glucose from the bloodstream.
Insulin also helps to convert free-floating Glucose into Glycogen, so that it can be stored in the liver and muscles.
Insulin also shunts glucose into the adipose tissues, which converts it into Glycerol, and converted into Triglycerides.
Glucogen is used when Glucose is gone ;), or during the fasting phase.
During the absorptive phase, what converts triglycerides?
Insulin takes Glucose and shunts it into the Adipose Tissue, which then converts it into Glycerol, which turns into Triglycerides in this long-term storage.
What happens with insulin-producing cells before type 2 diabetes?
The cells are fully functional, but they STOP producing insulin. It starts when they stop listening to the signal - so the insulin producing cells start to OVER-PRODUCE because they think the cells are deaf… but the cells keep ignoring the signals, so finally, they just shut down business and stop producing all together.
A change of diet can get those cells to produce insulin again.
What are macronutrients oxidized by?
Can be oxidized by AceythlCoA and prep cycle to be converted into ATP.
