Neuroscience UTD Exam 2: Hunger/Thirst (10)

Teenagers with Anorexia have larger parts of the brain

• larger insula - brain area active when you experience disgust • larger orbitofrontal cortex - brain area that tells you you shouldn't do that

What neurons detect pressure in heart and arteries? From here, what do they activate?

BARORECEPTORS detect the initial drop in blood pressure. These neurons fire to the vagus nerve which then goes to the brain to activate thirst and salt craving

What is bulimia? What are some symptoms?

BULIMIA is recurrent binge eating with recurrent inappropriate, compensatory behavior. It often goes on for at least 2x/wk for 3 months.

Of course there are external factors like emotions, food characteristics, and lifestyle behaviors that influences when to start and stop eating. What are some central signals to start eating?

Central Signals to start eating include NPY/AgRP NEURONS which produce neuropeptide Y and agouti-related peptide. This has two effects which leads to weight gain: a. STIMULATE appetite b. LOWER metabolism

diabetes insipidus

vasopressin is not produced - kidneys send more urine to the bladder, resulting in chronic thirst

High calorie diets causes

hypothalamic scarring and microglial activation, and 15% reduction of proopiomelanocortin (POMC) neurons, which are normally activated by leptin to block eating and increase energy expenditure

Izzy was obese and died of heart failure. How did he get up to 757 pounds?

Izzy might have had leptin deficiency or VMH lesion. a high set point from weight gain that made it hard to diet.

Lesions in what part of your brain would cause refusal to eat?

LATERAL HYPOTHALAMUS. a. LH lesioned animals stop eating, and stabilize their weight at a new lower level because of a new, lower set point. b. Perhaps anorexics have a lower set point

What is the prevalence of anorexia in women and in men?

0.5% in women, .05% in men

In hypertension, what hormone is inhibited?

ANGIOTENSIN II

What has the highest mortality rate of any psychiatric disorder?

Anorexia Nervosa

What is the main reason for why dieting is so hard?

Basal Metabolic Rate drops rapidly

What neurons respond to a rise in blood osmotic pressure? Where are they found?

OSMOSENSORY NEURONS, which are found in the anterior hypothalamus (OVLT)

What is minimum BMI for obesity?

30

Which of your organs helps resolve osmotic thirst?

OVLT

After going for a run through the neighborhood, you are getting thirsty. What biological cascade do you know is taking place in your body?

ANGIOTENSIN CASCADE. Because you have not been drinking water, you have a decrease in blood volume. This causes your kidneys to release RENIN, which triggers formation of ANGIOTENSIN II. Angiotensin II then causes 5 things: a. Blood vessels to constrict - more pressure tells your brain you are thirsty b. Circumventricular organs to trigger drinking c. Vasopressin to be released from the kidneys, blocking urine formation (you want to keep whatever what you have!) d. Aldosterone to be released from the kidneys, increasing salt retention. e. The SUBFORNICAL ORGAN (in the HYPOTHALAMUS) to send a signal to other brain sites to initiate drinking

What is anorexia nervosa? What are some symptoms?

ANOREXIA NERVOSA is the refusal to maintain body weight, coupled with fear of weight gain, body image disturbance, amenorrhea, thinning of bones, brittle hair and nails, dry/yellow-ish skin, anemia, muscle weakness and loss, lethargy, severe constipation, low blood pressure, slowed breathing and pulse, and drop in both temperature. It can be a restricting or a binge-eating/purging type.

After you've eaten, what central signals are in your body to stop eating?

Central signals: alpha-MSH, CRH/UCN, GLP-4, CART, NE, 5-HT. Most significantly, POMC/CART neurons produce pro-opiomelanocortin (opium) and CART, which do two things for weight loss: a. INHIBIT appetite b. RAISE metabolism c. PS: You've learned from the previous exam that cocaine and amphetamines suppress appetite

What are the only cells in the body that produce leptin?

FAT CELLS. Thus, you must have fat to get leptin's signal to make you less hungry.

If absolutely necessary, what other form of energy will your brain be willing to use?

FAT- but only if your brain is starving and there is no other glucose left. Lipids and fat tissue are generally for longer-term storage of energy.

What are some treatments for anorexia and bulimia?

For anorexia or bulimia, SEROTONIN is LOW. Treating this eating disorder as a mood disorder might be successful. Antidepressants and anti-schizophrenic drugs (like Olazapine) produces some benefit. Dopamine might be involved in some way as well.

What type of energy does your brain only want to use?

GLUCOSE. Your body even uses a process called glycogenesis to convert glucose to glycogen for storage

What is hypovolemic thirst?

Hypovolemic thirst is thirst stimulated by LOW OR LOSS OF EXTRACELLULAR/INTRAVASCULAR (WATER) VOLUME. Your outside cells have less water, and you get low blood pressure. Note: CONCENTRATION is not changed

Where in the brain would lesions cause overeating?

If you have lesions in the VENTROMEDIAL HYPOTHALAMUS, obesity may result. In an experiment, VMH lesioned rats OVEREAt until they become obese. Stability and a new SET POINT is made at this heavier weight. Thus, even if you are a scientist and force-feed VMH lesioned rats, the rats, when the force feeding stops, will drop back down to the new set point, as opposed to the original, healthy set-point. The lesion causes overeating and a new set point for "normal" in the rat. Perhaps Izzy has an abnormal set point. a. Even if you do not have a VMH-lesion, the concept of a set point is evident as you gain weight over the years. It's the holiday or exam cramming sessions in school that cause little weight gain, but if you accept the additional 5 pounds as normal, you'll find in a few years, a new extra 30 pound gain. Lose it before it gets hard to!

What kind of eating habits would you find in kids grades 5-8?

In kids grades 5-8, 30% are dieting, 5% are vomiting, and 2% use diet pills and diuretics.

What else is anorexia and bulimia correlated with in women?

In women, anorexia and bulimia is correlated 90% with depression, 30% attempted suicide, and 5% death from suicide. This is also correlation withTe childhood anxiety disorders, obsessive compulsive disorder, and abuse of alcohol or drugs

Overnutrition ____ the hypothalamus - obesity, diabetes, and heart disease

Inflames

What is the main homeostatic mechanism? If you deviate from ______, compensatory action begins.

NEGATIVE FEEDBACK SYTEMS. If you deviate from a SET POINT, your body tries to compensate and keep things balanced.

NPY/AgRP neurons produce

Neuropeptide Y and agouti-related peptide which STIMULATE appetite and LOWER metabolism.

What is osmotic thirst?

Osmotic thirst is thirst stimulated by HIGH EXTRACELLULAR SOLUTE CONCENTRATION. Water can pass, but salt cannot. When water leaves the cell, the cell shrinks

What disorder do some obese people have with a problem with peripheral signals?

PRADER-WILLI SYNDROME is when people have abnormally ELEVATED GHRELIN LEVELS. These people eat as if they were starving. Main question to ask over the phone to see if the caller's child has Prader-Willi- "Do you have a lock on the fridge?" People with Prader-Willi will eat as much as they can, even if it's rotten food. Imagine having this and trying to diet and maintain a healthy weight.

What are some peripheral signals to start eating?

Peripheral Signals: a. GHRELIN is released by STOMACH endocrine cells. This is an appetite stimulant that RISES DURING FASTING and DROPS AFTER EATING. b. CORTISOL stimulates appetite when you are stressed. A hungry body needs more energy. Then again, when you are stressed, you may not necessarily be hungrier. There are so many factors involved with hunger, but this is one correlation we see between ghrelin, cortisol, and appetite.

What peripheral signals help inhibit eating?

Peripheral Signals: Glucose, CCK, GLP-1, Apo A-IV Vagal Afferents, and most significantly, LEPTIN and INSULIN a. LEPTIN is a molecule in diet pills to make you less hungry. Fat cells actually produce this and secrete it into the blood stream, which eventually goes to your hypothalamus. b. Leptin inhibits the secretion of AgRP (see above!), neurons that stimulate appetite and lower metabolism. c. Defects in leptin production or sensitivity give a FALSELY LOW REPORT OF BODY FAT, causing animals to OVEREAT. d. A leptin deficient rat is obese. Perhaps Izzy had a leptin deficiency.

How can diet help epilepsy and Alzheimer's?

The Ketogenic Diet can actually help epilepsy and Alzheimner's, as seen in prisoners, in which starvation of glucose stopped seizures, because that is what the brain uses for fuel

Reduces ghrelin and increases PYY and GLP-1 does what?

Reduces hunger

Which of your organs helps resolve hypovolemic thirst?

SUBFORNICAL ORGAN Circulating angiotensin II acts in the subfornical organ to signal other brain sites to initiate drinking

When you ingest water, what are short term and long term mechanisms that inhibit thirst?

Short term- your stomach and intestines distend. Water cools and moistens your mouth, as well. Long term- your blood is rehydrated. Yay!

You are still trying to lose weight (summer is coming soon). Why do diets fail for most people?

The first week of the diet is probably decently successful. People reduce caloric intake drastically, and see they've lost a lot of weight, 6 pounds. Eating this same amount of food the second week, people see a much less drop in weight, maybe 2 pounds. This happens because your BASAL METABOLIC RATE falls to PREVENT losing weight. Your body is working against your diet because it is scared you will die! Essentially, your body gets used to however little food you give it. The better strategy, instead of cutting 1000 calories the first week, may be to cut 100 calories the first two weeks, and another 100 the next, and so on, so your body doesn't get used to it. Exercise is helpful, too (but not as essential as reduced intake)!

As a result of HYPO thirst, what do arteries do to raise blood pressure?

They CONSTRICT. This is the easiest and shortest change your body does when you are thirsty.

NPY/AgRP neurons produce neuropeptide Y and agouti-related peptide. What do these do?

They STIMULATE appetite and LOWER metabolism.

What are some treatments for obesity?

Treatments: a. EATING LESS (perhaps daily deficit of 500-1000 calories). 200 on slide. Modifying behavior and exercising will help, but it must be intense to really show results. b. Giving a cannabinoid receptor antagonist. However, if you block cannabinoids, you get suicidal thoughts. Not a viable option. c. If you treat obesity as an addiction, for instance, REDUCING D2 receptors and DECREASING IN PREFRONTAL METABOLISM, the treatment may be somewhat effective. d. GASTRIC BYPASS SURGERY is the best, in which GHRELIN IS REDUCED and PYY AND GLP-1 IS INCREASED, reducing hunger. 25% average weight loss in patients is long lasting, reduces mortality, and has many health benefits. Yay!

What hormone is released to help reduce blood flow to the bladder?

VASOPRESSIN aka ANTIDIURETIC HORMONE. This induces blood vessel constriction and tries to prevent peeing (to conserve water) while you are thirsty

What happens to rats who fast?

When rats fast, they live up to 40% longer! Crazy. There isn't anything like this for humans that we know of

You're trying to lose weight after your run, and though you crave eating potato chips, you choose not to. Why could this be a bad thing?

When you are rehydrating yourself, you need both water and salt replacement. Without the salt, you won't retain the water, which could lead to dehydration. Perhaps you can choose to not have potato chips, but have saltine crackers instead!

Why would a tumor in the pituitary be bad?

With a PITUITARY ADENOMA, you may not be able to store pee. Remember, your posterior pituitary makes vasopressin!

How would you increase the life span of lab animals? How is the basal metabolism affected?

You would INDUCE food deprivation, which causes the basal metabolism to DECREASE.

Your friend is over for Spring Break and he seems to be peeing a lot and drinking gallons of water at a time. What hormone is he possibly not making? What are some implications? What is this condition called?

Your friend may not be making vasopressin, and thus pees so much. This may cause dehydration and chronic thirst, because the water is not being retained. This condition in which vasopressin is not produced and kidneys send more urine to the bladder is called DIABETES INSIPIDUS. Your friend may have it

You have high blood osmotic pressure, and you're really thirsty. How is your body trying to respond/compensate?

Your rise in blood osmotic pressure causes OSMOSENSORY NEURONS' cell membranes to shrink. Because of this, mechanical-gated Na+ channels open, which causes the PITUIRARY TO RELEASE ANTI-DIURETIC HORMONE (once again. ADH is part of both thirst systems!)

If blood volume decreases, kidneys release renin, which triggers formation of ____

angiotensin II