Chapter 10: Chapter 10: Internal RegulationInternal Regulation

HomeostasisHomeostasis1.1. This is Latin for ‘same state’This is Latin for ‘same state’

2.2. It is referring to a set of internal It is referring to a set of internal processes that keep the body processes that keep the body operating within a fixed range on a operating within a fixed range on a number of different variablesnumber of different variables

Body temperatureBody temperature Set point – this is a single value that Set point – this is a single value that

the body works to maintain under the body works to maintain under normal circumstancesnormal circumstances

Weight Weight

Body TemperatureBody Temperature1.1. What is meant when an animal is What is meant when an animal is

called ‘cold blooded’? called ‘cold blooded’? Poikilothermic – body temp matches Poikilothermic – body temp matches

the environmentthe environment Homeothermic – the body expends Homeothermic – the body expends

energy to maintain a constant tempenergy to maintain a constant temp

2.2. Why is being homeothermic better?Why is being homeothermic better? We can stay active no matter what the We can stay active no matter what the

ambient tempambient temp

How we maintain our How we maintain our TemperatureTemperature When cold we:When cold we:

1.1. Put on layers or fluff out our fur/hairPut on layers or fluff out our fur/hair

2.2. Huddle Huddle

3.3. Circulatory changesCirculatory changes

4.4. Shiver, activate musclesShiver, activate muscles

When hot we:When hot we:1.1. Take off layers, shed hairTake off layers, shed hair

2.2. Circulatory changesCirculatory changes

3.3. SweatSweat

More about Temp More about Temp ControlControl

1.1. Some of the things we just Some of the things we just discussed are behavioral, others are discussed are behavioral, others are physiologicalphysiological

2.2. How does the body know to change How does the body know to change circulation or turn on the faucets circulation or turn on the faucets (i.e. make you sweat)?(i.e. make you sweat)?

An area of your brain is constantly An area of your brain is constantly monitoring your temperature & monitoring your temperature & sending signals to the rest of the body sending signals to the rest of the body to make homeostatic adjustmentsto make homeostatic adjustments

The anterior hypothalamusThe anterior hypothalamus

Disorder of Disorder of Temperature: FeverTemperature: Fever

1.1. Fever occurs when the immune Fever occurs when the immune system is activated by a bacterial or system is activated by a bacterial or viral invaderviral invader

2.2. But the fever is not a direct result of But the fever is not a direct result of immune system activationimmune system activation

Immune cells release prostaglandins Immune cells release prostaglandins (hormone) into the blood, which (hormone) into the blood, which stimulate the anterior hypothalamus to stimulate the anterior hypothalamus to increase body tempincrease body temp

AnhidrosisAnhidrosis1.1. This is the inability to sweat in This is the inability to sweat in

response to increasing body response to increasing body temperature.temperature.

2.2. Can be caused by genetic or Can be caused by genetic or neurological disorders, or even just neurological disorders, or even just taking certain medications or taking certain medications or becoming dehydrated.becoming dehydrated.

3.3. Treatment/cure is simple for two of Treatment/cure is simple for two of the cases above the cases above

Otherwise, you just have to monitor and Otherwise, you just have to monitor and maintain your body temperature using maintain your body temperature using external methodsexternal methods

ThirstThirst There are two kinds of thirst (I bet There are two kinds of thirst (I bet

you didn’t know that!)you didn’t know that!)1.1. Osmotic thirst – this is your every day, eat Osmotic thirst – this is your every day, eat

a bag of chips get thirsty, kind of thirsta bag of chips get thirsty, kind of thirst

2.2. Hypovolemic thirst – this is thirst due to Hypovolemic thirst – this is thirst due to loss of blood volume from injury or illnessloss of blood volume from injury or illness

When you are thirsty, your body When you are thirsty, your body conserves water in several ways: no conserves water in several ways: no sweat, no urine, increase blood sweat, no urine, increase blood pressurepressure

Result from release of hormone Result from release of hormone vasopressinvasopressin

Mechanisms of ThirstMechanisms of Thirst In osmotic thirst, an area of the In osmotic thirst, an area of the

brain called the OVLT senses the brain called the OVLT senses the body’s osmotic balancebody’s osmotic balance

In hypovolemic thirst two things are In hypovolemic thirst two things are important:important:

1.1. Baroreceptors in the veins themselves Baroreceptors in the veins themselves detect pressuredetect pressure

2.2. An area of the brain called the An area of the brain called the subfornical organ (SFO)subfornical organ (SFO)

HungerHunger Did you know there are actual Did you know there are actual

biological constraints on what we biological constraints on what we eat? eat?

1.1. Dairy & lactose intoleranceDairy & lactose intolerance

2.2. Teeth!Teeth! HerbivoresHerbivores CarnivoresCarnivores OmnivoresOmnivores

3.3. Taste & experienceTaste & experience1.1. Sweet vs. bitterSweet vs. bitter

2.2. Conditioned aversionsConditioned aversions

What makes us feel What makes us feel full?full?

1.1. Would Willy Wonka’s gum actually Would Willy Wonka’s gum actually make us feel satisfied?make us feel satisfied?

2.2. Or could we just fill our stomachs Or could we just fill our stomachs with nutrients and be satisfied?with nutrients and be satisfied?

3.3. It turns out that both answers are It turns out that both answers are no.no.

We require both the early digestive We require both the early digestive processes (chewing and swallowing) processes (chewing and swallowing) and the filling of the stomach to feel and the filling of the stomach to feel satisfied satisfied

The StomachThe Stomach There are physical and chemical There are physical and chemical

messages from the stomach that messages from the stomach that tell our brains that we’ve had tell our brains that we’ve had enough to eatenough to eat

1.1. Stimulation of the vagus nerve tells the Stimulation of the vagus nerve tells the brain when the stomach is physically brain when the stomach is physically fullfull

2.2. Other nerves report to the brain about Other nerves report to the brain about the nutrient contentthe nutrient content

3.3. CCK is a hormone that is released from CCK is a hormone that is released from the small intestine to start reducing the small intestine to start reducing the amount you are bringing inthe amount you are bringing in

Energy Feedback Energy Feedback SystemSystem

1.1. What does the body use as fuel? What does the body use as fuel? GlucoseGlucose

2.2. When you eat, your body produces When you eat, your body produces insulin to help you get that glucose insulin to help you get that glucose into your cells, makes you less into your cells, makes you less hungryhungry

3.3. Glucagon later helps you get that Glucagon later helps you get that glucose back out of storageglucose back out of storage

4.4. What happens in diabetes?What happens in diabetes?

Brain Control of Brain Control of HungerHunger The hypothalamus is the hunger The hypothalamus is the hunger Wizard of Oz, there are two areas I Wizard of Oz, there are two areas I want you to know:want you to know:

1.1. Lateral hypothalamus seems to be Lateral hypothalamus seems to be involved in initiation of eating – if this involved in initiation of eating – if this area is damaged animals won’t eat and area is damaged animals won’t eat and lose weightlose weight

2.2. Ventromedial hypothalamus seems to be Ventromedial hypothalamus seems to be involved in satiety and reduction of involved in satiety and reduction of eating – damage to this area results in eating – damage to this area results in animals that will eat a lot more and have animals that will eat a lot more and have overactive insulinoveractive insulin

Chemical Control of Chemical Control of WeightWeight Leptin is a peptide chemical Leptin is a peptide chemical released by fat cells themselvesreleased by fat cells themselves

1.1. The body and brain are able to keep tabs The body and brain are able to keep tabs on the current fat stores on the current fat stores

2.2. Triggers puberty onsetTriggers puberty onset

3.3. Changes the way we eatChanges the way we eat

4.4. Changes functioning in other physiological Changes functioning in other physiological systems – i.e. immune systemsystems – i.e. immune system

5.5. We have discovered a gene (in mice) that We have discovered a gene (in mice) that prevents leptin production = obese miceprevents leptin production = obese mice

More Chemical Control of More Chemical Control of WeightWeight Neuropeptide Y (NPY) is a chemical Neuropeptide Y (NPY) is a chemical

that acts on the hypothalamusthat acts on the hypothalamus1.1. Specifically it acts on the PVN of the Specifically it acts on the PVN of the

hypothalamus and results in increased hypothalamus and results in increased meal sizemeal size

There are approximately 21 other There are approximately 21 other hormones/neurotranmitters that hormones/neurotranmitters that influence when, how frequently and influence when, how frequently and how much we eat – very complex how much we eat – very complex systemsystem

External Effects on External Effects on Meal SizeMeal Size

1.1. Time of weekTime of week

2.2. Alone or with othersAlone or with others

3.3. Time of day and cultureTime of day and culture

4.4. ““Low-fat”Low-fat”

Prader-Willi SyndromePrader-Willi Syndrome1.1. Genetic condition due to a random Genetic condition due to a random

mutation on chomosome 15.mutation on chomosome 15.

2.2. Symptoms include: Symptoms include: Mild mental retardation/developmental Mild mental retardation/developmental

delaydelay Incomplete sexual development Incomplete sexual development

(puberty)(puberty) Insatiable appetite –Insatiable appetite – health probs health probs

related to obesityrelated to obesity

3.3. Treatment – food restriction (& I Treatment – food restriction (& I mean RESTRICTION!)mean RESTRICTION!)

ObesityObesity1.1. Obesity is defined as being 20% Obesity is defined as being 20%

over your ideal weightover your ideal weight ‘‘Ideals’ are based on height, age, sex and Ideals’ are based on height, age, sex and

mass indexmass index

2.2. About 25% of adults in the U.S. are About 25% of adults in the U.S. are obeseobese

3.3. Major health problems – Type II Major health problems – Type II diabetes, heart diseasediabetes, heart disease

4.4. Genetics, life style & stress are all Genetics, life style & stress are all contributorscontributors

AnorexiaAnorexia1.1. This is basically controlled This is basically controlled

starvation of yourselfstarvation of yourself

Fewer than 800 calories per day, Fewer than 800 calories per day, usually from a restricted number of usually from a restricted number of foodsfoods

Much more common in women than in Much more common in women than in menmen

More common in upper socio-economic More common in upper socio-economic & Caucasian women& Caucasian women

AnorexiaAnorexia Characteristics of girls who develop Characteristics of girls who develop

anorexia:anorexia:1.1. Come from overbearing/controlling Come from overbearing/controlling

parentsparents

2.2. Anxious personality traits – shyness, Anxious personality traits – shyness, perfectionism, social anxietyperfectionism, social anxiety

3.3. Loss of a family member early in lifeLoss of a family member early in life

4.4. DepressionDepression

Anorexia is not just about wanting Anorexia is not just about wanting to be thin, it is about feeling out of to be thin, it is about feeling out of control –it is an anxiety disordercontrol –it is an anxiety disorder

BulimiaBulimia1.1. This disorder is typified by intense binge This disorder is typified by intense binge

eating, followed by purgingeating, followed by purging

2.2. Purging is usually through vomiting, but Purging is usually through vomiting, but can also be achieved through improper can also be achieved through improper use of laxativesuse of laxatives

3.3. Psychological aspects of the disease are Psychological aspects of the disease are similar to those of anorexiasimilar to those of anorexia

4.4. Often more difficult to diagnose – Often more difficult to diagnose – secretive behavior and less obvious secretive behavior and less obvious resultsresults

Consequences of Eating Consequences of Eating DisordersDisorders1.1. DeathDeath

2.2. OsteoporosisOsteoporosis

3.3. Heart and other cardiovascular Heart and other cardiovascular problems, including strokeproblems, including stroke

4.4. Damage to the esophagus, Damage to the esophagus, stomach, teeth, mouthstomach, teeth, mouth