Chapter 10 – Internal Regulation

Question 1

Tendency to maintain a variable, such as temperature, within a fixed range

Answer 1

Homeostasis

Question 2

A value that the body works to maintain

Answer 2

Set point

Question 3

Homeostatic process that reduce discrepancies from the setpoint

Answer 3

Negative feedback

Question 4

The adaptive way in which the body changes its set points depending on the situation

Answer 4

Allostasis

Question 5

How does the idea of allostasis differ from homeostasis?

Answer 5

Homeostasis is a set of processes that keep certain body variables within a fixed range. Allostasis is an adjustment of that range, increasing it or decreasing it as circumstances change

Question 6

Energy used to maintain a constant body temperature while at rest

Answer 6

Basal metabolism

Question 7

Maintaining the body at the same temperature as the environment

Answer 7

Poikilothermic

Amphibians, reptiles, and most fish are poikilothermic.
Poikilothermic animals like physiological mechanisms of temperature regulation, such as shivering and sweating. These animals remain warm most of the day by choosing an appropriate location.

Question 8

Using physiological mechanisms to maintain a nearly constant body temperature despite changes in the environment’s temperature

Answer 8

Homeothermic

Mammals and birds are homeothermic, except that certain species become poikilothermic during hibernation.
Homeothermy is costly, especially for small animals. And animal generates heat in proportion to its total mass, but it radiates heat in proportion to its surface area. A small mammal or bird such as a mouse or hummingbird, has a high surface to volume ratio and therefore radiates heat rapidly and need much fuel each day to maintain their body temperature.
The physiological mechanism to cool ourselves when the air is warmer is evaporation – humans sweat to expose water for evaporation. Other species that don’t sweat lick themselves and pant. If you do not drink enough water to replace the water you lose by sweating, you start becoming dehydrated and you then protect your body water by decreasing your sweat, despite the risk of overheating.
Several physiological mechanisms increase your body heat in a cold environment – one is shivering, any muscle contractions such as those of shivering, generate heat. Second, decreased blood flow to the skin prevents the blood from cooling too much. A third mechanism works well for most mammals, though not for humans – when cold, they fluff out their fur to increase insulation.

We also use behaviour mechanisms, just as poikilothermic animals do, and prefer to rely on behaviour when we can because it saves physiological energy. Example, moving to a warmer or cooler place, putting on or taking off clothes, becoming active or less active, huddling with others

Question 9

What is the primary advantage of maintaining a constant high body temperature?

Answer 9

A constant high body temperature keeps the animal ready for rapid, prolonged muscle activity even in cold weather.

Question 10

Why did mammals evolve a temperature of 37°C instead of some other temperature?

Answer 10

Animals gain an advantage in being as warm as possible and therefore as fast as possible. However, proteins lose stability at temperatures much above 37°C.

Our body temperature is a trade off between the advantages of high temperature for rapid movement and the disadvantages of high temperature for protein stability.

Question 11

Brain area important for temperature regulation, thirst, and sexual behaviour.
Physiological changes that defend body temperature – such as shivering, sweating, and changes in blood flow to the skin – depend on these areas

Answer 11

Preoptic area/anterior hypothalamus POA/AH

The POA/AH and a couple other hypothalamic areas send output to the hindbrain’s raphe nucleus, which controls the physiological mechanisms

Question 12

How does the preoptic/anterior hypothalamus or POA/AH monitor body temperature?

Answer 12

Partly by monitoring its own temperature. If an experimenter heats this area, an animal pants or sweats, even in a cool environment. If the brain area is cooled, the animal shivers, even in a warm room. Cells of the POA/AH also receive input from temperature receptors in the skin and spinal cord.

Question 13

What evidence do we have that the POA/AH controls body temperature?

Answer 13

Direct cooling or heating of the POA/AH leads to shivering or sweating. Also, damage there impairs physiological control of temperature

Question 14

How can an animal regulate body temperature after damage to the POA/AH?

Answer 14

It can regulate temperature through behavior, such as by finding a warmer or cooler place

Question 15

Small proteins that combat infections and communicate with the brain to elicit appropriate behaviours

Answer 15

Cytokines

Question 16

Bacterial and viral infections generally cause ______, an increase in body temperature. It is not part of the illness; it is part of the body’s defence against the illness.

Answer 16

Fever

When bacteria, viruses, fungi, or other intruders invade the body, they mobilize leukocytes to attack them. The leukocytes really small proteins called cytokines that attack the intruders. Cytokines also stimulate the vagus nerve, which sends signals to the hypothalamus, increasing the release of chemicals called prostaglandins. Stimulation of a particular kind of prostaglandin receptor in one nucleus of the hypothalamus is necessary for fever.

A fever represents an increased set point for body temperature, you shiver or sweat whenever your temperature deviates from that level.

Certain types of bacteria grow less vigourously at high temperatures than at normal mammalian body temperatures, and fever enhances activity of the immune system. However, a fever above 39°C in humans does more harm than good, and above 41°C is life-threatening.

Question 17

What evidence indicates that fever is an adaptation to fight illness?

Answer 17

The body will shiver or sweat to maintain its elevated temperature. Also, fish, reptiles, and immature mammals with infections use behavioural means to raise their temperature to a feverish level. Furthermore, a moderate fever inhibits bacterial growth and increases the probability of surviving a bacterial infection.

Question 18

Hormone released by posterior pituitary; raises blood pressure and enables kidneys to conserve water

Answer 18

Vasopressin or antidiuretic hormone

Question 19

Hormone that enables the kidneys to reabsorb water from urine; also known as vasopressin

Answer 19

Antidiuretic hormone ADH

Question 20

Different species have different strategies for maintaining water. Describe how beavers and gerbils maintain water

Answer 20

Beavers, which live in rivers or lakes, drink plenty of water, eat moist foods, and excrete dilute urine.

In contrast, gerbils, which are desert animals, don’t need to drink at all. They gain water from their food and they have many adaptations to avoid losing water, including the ability to excrete dry faeces and concentrated urine. Unable to sweat, they avoid the heat of the day by burrowing under ground and their highly convoluted nasal passages minimize water loss when they exhale

Question 21

Describe how humans conserve water

Answer 21

We conserve water by excreting more concentrated urine and decreasing our sweat. The posterior pituitary releases the hormone vasopressin that raises blood pressure by constricting blood vessels. The increased pressure helps compensate for the decreased blood volume. Vasopressin is also known as anti-diuretic hormone ADH because it enables the kidneys to reabsorb water from urine and therefore make the urine more concentrated.

Question 22

If you lacked vasopressin, would you drink like a beaver or like a gerbil? Why?

Answer 22

If you lacked vasopressin, you would have to drink more like a beaver. You would excrete much fluid, so you would need to drink an equal amount to replace it

Question 23

What are the two types of thirst?

Answer 23

Osmotic thirst and hypovolemic thirst

Question 24

Eating salty foods causes ______ thirst, and losing fluid by bleeding or sweating induces ______ thirst

Answer 24

Osmotic; hypovolemic

Question 25

Tendency of water to flow across a semipermeable membrane from the area of low solute concentration to the area of high solute concentration

Answer 25

Osmotic pressure

A semipermeable membrane is one through which water can pass but solutes cannot. The membrane surrounding a cell is almost a semipermeable membrane because water flows across it freely and various solutes flow either slowly or not at all between the intracellular fluid inside the cell and the extracellular fluid outside it. Osmotic pressure occurs when solutes are more concentrated on one side of the membrane then on the other.

Question 26

Thirst triggered by certain neurons that detect the loss of their own water

Answer 26

Osmotic thirst

Question 27

Describe what would happen regarding osmotic thirst if you eat something salty

Answer 27

If you eat something salty, sodium ions spread through the blood and the extracellular fluid but do not cross the membranes into cells. The result is a higher concentration of solute’s including sodium outside the cell then inside. The resulting osmotic pressure draws water from the cells into the extracellular fluid. Certain neurons detect their own loss of water and then trigger osmotic thirst, which helps restore the normal state. The kidneys also excrete more concentrated urine to rid the body of excess sodium and maintain as much water as possible

Question 28

Brain area that detects osmotic pressure and salt content of the blood

Answer 28

OVLT organum vasculosum laminae terminalis

Question 29

Brain structure adjoining the third ventricle of the brain, where it’s cells monitor blood volume and relay information to the preoptic area of the hypothalamus

Answer 29

Subfornical organ SFO

Question 30

Part of the hypothalamus that controls the release rate of vasopressin

Answer 30

Supraoptic nucleus

Question 31

Part of the hypothalamus in which activity tends to limit meal size and damage leads to excessively large meals

Answer 31

Paraventricular nucleus PVN

Question 32

Part of the hypothalamus that controls drinking

Answer 32

Lateral preoptic area

Question 33

Describe how the brain detects osmotic pressure

Answer 33

The brain gets part of the information regarding osmotic pressure from receptors around the third ventricle, which have the weakest blood-brain barrier and helps cells monitor the contents of the blood.
The areas important for detecting osmotic pressure and the salt content of the blood include the OVLT and the subfornical organ. The OVLT receives input from receptors in the brain itself and from receptors in the digestive tract, enabling the brain to anticipate an osmotic need before the rest of the body experiences it. Receptors in the OVLT, the subfornical organ, the stomach, and elsewhere relay their information to several parts of the hypothalamus, including the supraoptic nucleus and the paraventricular nucleus, which control the rate at which the posterior pituitary releases vasopressin. Receptors also relay information to the lateral preoptic area and surrounding parts of the hypothalamus, which control drinking

Question 34

After osmotic pressure triggers thirst, how do you know when to stop drinking?

Answer 34

The body monitors swallowing and detects the distension of the stomach and upper part of the small intestine. Those messages limit drinking to not much more than you need at a given time.

Question 35

Would adding salt to the body’s extracellular fluids increase or decrease osmotic thirst?

Answer 35

Adding salt to the extracellular fluid would increase osmotic thirst because it would draw water from the cells into the extracellular spaces

Question 36

Hormone that constricts the blood vessels, compensating for the drop in blood pressure; triggers thirst

Answer 36

Angiotensin II

Question 37

Thirst provoked by low blood volume

Answer 37

Hypovolemic thirst

Question 38

An automatic strong craving for salty tastes

Answer 38

Sodium-specific hunger

Depends partly on hormones. When the body sodium reserves are low, the adrenal glands produce the hormone aldosterone, which causes the kidneys, salivary gland’s, and sweat glands to retain salt. Aldosterone and angiotensin II together change the properties of taste receptors on the tongue, neurons in the nucleus of the track tractus solitarius (part of the taste system), and neurons elsewhere in the brain to increase salt intake

Question 39

Adrenal hormone that causes the body to retain salt.

Answer 39

Aldosterone

Question 40

Describe what happens when you lose a significant amount of body fluid by bleeding, diarrhea, or sweating

Answer 40

Although your body’s osmotic pressure stays the same, you need fluid. Your heart has trouble pumping blood to the head, and nutrients do not flow as easily as usual into your cells.
Your body will react with hormones that constrict blood vessels – vasopressin and angiotensin II. When blood volume drops, the kidneys release the enzyme renin, which splits a portion off angiotensinogen, a large protein in the blood, to form angiotensin I, which other enzymes convert to angiotensin II. Like vasopressin, angiotensin II constricts the blood vessels, compensating for the drop in blood pressure.
Angiotensin II also helps trigger thirst, in conjunction with receptors that detect blood pressure in the large veins. This thirst is different from osmotic thirst, because you need to restore lost salts and not just water. This kind of thirst is known as hypovolemic thirst, meaning thirst based on low-volume.
When angiotensin II reaches the brain, it stimulates neurons in areas adjoining the third ventricle. Those neurons send axons to the hypothalamus, where they release angiotensin II as their neurotransmitter. That is, the neurons surrounding the third ventricle both respond to angiotensin II and release it.

Whereas an animal with osmotic thirst needs water, one with hypovolemic thirst can’t drink much pure water because it would dilute its body fluids. It is therefore increases its preference for slightly salty water, this preference is known as sodium-specific hunger.

Question 41

Who drink more pure water – someone with osmotic thirst or someone with hypovolemic thirst?

Answer 41

Someone with osmotic thirst would drink more water. Someone with hypovolemic thirst would drink more of a solution containing salts.

Question 42

Describe the process and different areas of digestion

Answer 42

Digestion begins in the mouth, where enzymes in the saliva break down carbohydrates. Swallowed food travels down the esophagus to the stomach, where it mixes with hydrochloric acid and enzymes that digest proteins. The stomach stores food for a time, and then a round sphincter muscle opens at the end of the stomach to release food to the small intestine.
The small intestine has enzymes that digest proteins, fats, and carbohydrates. It is also the site for absorbing digested materials into the bloodstream. The blood carries those chemicals to body cells that either use them or store them for later use. The large intestine absorbs water and minerals and lubricates the remaining materials to pass as feces.

Question 43

Sugar in milk

Answer 43

Lactose

Question 44

Intestinal enzyme that metabolizes lactose

Answer 44

Lactase

Most mammals at about the age of weaning lose the intestinal enzyme lactase, which is necessary for metabolizing lactose, the sugar in milk. From then on, milk consumption causes stomach cramps and gas.
Humans are a partial exception to this rule. Many adults have enough lactase levels to consume milk and other dairy products throughout life. However, nearly all the people in China and surrounding countries lack the gene that enables adults to metabolize lactose, as do varying numbers of people in other parts of the world.

Question 45

What genetic difference is most important for variance in the likelihood of drinking milk in adulthood?

Answer 45

The likelihood of drinking milk in adulthood depends largely on a gene that controls the ability to digest lactose (by the enzyme lactase), the main sugar in milk.

Question 46

Procedure in which everything that an animal swallows leaks out a tube connected to the oesophagus or stomach

Answer 46

Sham-feeding

Question 47

Describe oral factors in digestion. In particular, could you become satiated without tasting your food or if you tasted something without ingesting it?

Answer 47

Experiment: college students consumed lunch five days a week by swallowing a liquid diet that was pumped into the stomach. Most found the untasted meals unsatisfying, and reported a desire to taste or chew something.

Experiment: in sham-feeding experiments, everything an animal swallows leaks out of a tube connected to the esophagus or stomach. These animals eat and swallow almost continually without becoming satiated.

Taste and other mouth sensations contribute to satiety, but they are not sufficient

Question 48

What evidence indicates that taste is not sufficient for satiety?

Answer 48

It is not sufficient, because animals that sham-feed chew and taste their food but do not become satiated

Question 49

10th cranial nerve, which has branches to and from the stomach and several other organs

Answer 49

Vagus nerve

Question 50

Nerves that convey information about the nutrient contents of the stomach to the brain

Answer 50

Splanchnic nerves

Question 51

Hormone released from the duodenum that constricts the sphincter muscle between the stomach and duodenum, limiting the meal size

Answer 51

Cholecystokinin

Question 52

Part of the small intestine adjoining the stomach; first digestive site that absorbs nutrients

Answer 52

Duodenum

Question 53

Usually, what is the main signal to end a meal?

Answer 53

Distension of the stomach.

The stomach conveys satiety messages to the brain via the vagus nerve and the splanchnic nerves. The vagus nerve conveys information about the stretching of the stomach walls, providing a major basis for satiety. The splanchnic nerves convey information about the nutrient contents of the stomach.

Question 54

What is the evidence that stomach distension is sufficient for satiety?

Answer 54

If a cuff is attached to the junction between the stomach and duodenum so that food cannot leave the stomach, an animal becomes satiated when the stomach is full

Question 55

What are two mechanisms by which cholecystokinin or CCK increases satiety?

Answer 55

When the duodenum is distended, it releases CCK, which closes the sphincter muscle between the stomach and duodenum. CCK therefore increases the rate at which the stomach distended. Also, neural signals from the intestines cause certain cells in the hypothalamus to release CCK as a neurotransmitter, and at its receptors, it triggers decreased feeding

Question 56

Much digested food enters the bloodstream as ______, and important source of energy throughout the body and nearly the only fuel of the brain. When the blood glucose level is high, liver cells convert some of the excess into ______, and fat cells convert some of it into fat. When the blood glucose level starts to fall, the liver converts some of its glycogen back into glucose. In this way blood glucose level stay fairly steady for most people most of the time.

Answer 56

Glucose; glycogen

Question 57

Pancreatic hormone that enables glucose to enter the cells

Answer 57

Insulin

When insulin levels are high, glucose enters cells easily. When someone is getting ready for a meal, insulin levels rise, letting some of the blood glucose enter the cells in preparation for the rush of additional glucose about to enter the blood. Insulin continues to increase during and after a meal.
In general, high levels of insulin decreased appetite, because the insulin enables so much glucose to enter the cells. As time passes after a meal, the blood glucose levels fall. Therefore, insulin levels drop, glucose enters the cells more slowly, and hunger increases.

Question 58

Pancreatic hormone that stimulates the liver to convert stored glycogen to glucose

Answer 58

Glucagon

Question 59

What are the two pancreatic hormones that regulate the flow of glucose?

Answer 59

Insulin and glucagon

Question 60

What happens if the insulin level stays constantly high?

Answer 60

If the insulin level stays constantly high, the body continues moving blood glucose into the cells, including the liver cells and fat cells, long after a meal. Before too long, blood to close drops, because glucose is leaving the blood without any new glucose entering. In this case, despite the high insulin level, hunger increases. In autumn, animals that are preparing for hibernation have constantly high insulin levels. They rapidly deposit much of each meal is fat and glycogen, grow hungry again, and continue gaining weight.

Question 61

What happens if the insulin level remains constantly low, as in people with diabetes?

Answer 61

In people with diabetes, blood glucose levels may be three or more times the normal level, but a little love it enters the cells. People and animals with diabetes eat more food than normal because their cells are starving, but the excrete most of their glucose, and they lose weight. Note that either prolonged high or prolonged low insulin levels increase eating, but for different reasons and with different effects on body weight.

Question 62

Why do people with very low insulin levels eat so much? Why do people with constantly high levels eat so much?

Answer 62

Those with very low levels, as in diabetes, cannot get glucose to enter their cells, and therefore, they are constantly hungry. They pass much of their nutrition in the urine and feces.

Those with constantly high levels deposit much of their glucose into fat and glycogen, so within a short time after a meal, the supply of blood glucose drops

Question 63

What would happen to someone’s appetite if insulin levels and glucagon levels were both high?

Answer 63

When glucagon levels rise, stored glycogen is converted to glucose, which enters the blood. If insulin levels are high also, the glucose entering the blood is free to enter all the cells. So the result would be decreased appetite.

Question 64

Peptide produced by the body’s fat cells.
Signals your brain about your fat reserves, providing a long-term indicator of whether you have been over eating or under eating. Also released with each meal, so the amount circulating indicate something about short-term nutrition as well

Answer 64

Leptin

Question 65

What do animal studies show when leptin levels are high?

Answer 65

You act as if you have plenty of nutrition; you eat less, become more active, and increase the activity of your immune system.

In adolescence, a certain level of leptin triggers the onset of puberty.

Question 66

Why are leptin injections less helpful for most overweight people than for mice with the obese gene?

Answer 66

Nearly all overweight people produce leptin in proportion to body fat. However, they have low sensitivity to it

Question 67

Hypothalamic area with sets of neurons for hunger and satiety

Answer 67

Arcuate nucleus

Question 68

Chemical released by the stomach during a period of food deprivation, where it triggers stomach contractions; also released as a neurotransmitter in the brain, where it stimulates eating.

Answer 68

Ghrelin

Question 69

Type of chemical that promotes satiety

Answer 69

Melanocortin

Question 70

Peptide of that blocks the satiety actions of the paraventricular nucleus

Answer 70

Neuropeptide Y, NPY

Question 71

Inhibitory transmitter that blocks the satiety actions of the paraventricular nucleus

Answer 71

Agouti-related peptide AgRP

Question 72

Much of the output from the arcuate nucleus goes to the ________ nucleus of the hypothalamus, which inhibits the lateral hypothalamus, an area important for eating. So this area is important for satiety.

Answer 72

Paraventricular nucleus

Question 73

Describe what happens when axons from the satiety-sensitive cells of the arcuate nucleus deliver a message to the paraventricular nucleus

Answer 73

Axons from the satiety-sensitive cells of the arcuate nucleus deliver an excitatory message to the paraventricular nucleus, releasing the neuropeptide melanocyte stimulating hormone, which is a type of chemical called a melanocortin. Receptors here are important for limiting food intake, and deficiencies of this receptor lead to overeating

Question 74

Describe what happens with input from the hunger-sensitive neurons of the arcuate nucleus.

Answer 74

Input from the hunger sensitive neurons of the arcuate nucleus is inhibitory to both the paraventricular nucleus and the satiety-sensitive cells of the arcuate nucleus itself. The inhibitory transmitter’s here are a combination of GABA, neuropeptide Y, and agouti-related peptide. These transmitters block the satiety actions of the paraventricular nucleus, in some cases provoking extreme overeating. Conversely, a lot of neuropeptide Y, and PY, leads to decreased eating.

Question 75

Describe the role of Orexin/hypocretin in hunger

Answer 75

Has two roles in feeding: first, it increases animals persistence in seeking food. Second, responds to incentives or reinforcement in general. If Orexin receptors are blocked, and animal becomes less active and less likely to work for reinforcement of any kind.

Question 76

Name three hormones that increase satiety and one that increases hunger

Answer 76

Insulin, CCK, and leptin increase satiety. Ghrelin increases hunger

Question 77

Which neuropeptide from the arcuate nucleus to the paraventricular nucleus is most important for satiety?

Answer 77

Melanocortin

Question 78

Area of the hypothalamus that controls insulin secretion, alters taste responsiveness, and facilitates feeding in other ways

Answer 78

Lateral hypothalamus

Question 79

What happens when the lateral hypothalamus in animals is damaged?

Answer 79

An animal with damage in this area refuses food and water, averting its head as if the food were distasteful. The animal may starve to death unless it is force-fed, but if kept alive, it gradually recovers much of its ability to eat. In contrast, stimulation of the lateral hypothalamus increases the drive to eat

Question 80

Name four ways the lateral hypothalamus contributes to feeding

Answer 80

1. Improves taste
2. Enhances cortical responses to food – facilitating ingestion and swallowing and causing cortical cells to increase their response to the taste, smell, or sight of food
3. Increases the pituitary gland’s secretion of hormones that increase insulin secretion
4. Increases digestive juices

Question 81

Region of the hypothalamus in which damage leads to faster stomach emptying and increased secretion of insulin.

Output from this area inhibits feeding. Damage to this area leads to overeating and weight gain.

Answer 81

Ventromedial hypothalamus VMH

Those with damage in the ventromedial area eat normal size meals, but eat more frequently. One reason is that they have increased stomach motility and secretions, and their stomachs empty faster than normal. The faster the stomach empties, the sooner the animal is ready for his next meal. Another reason is that the damage increases insulin production, and therefore much of each meal is stored as fat. The high insulin levels keep moving blood glucose into storage, even when the blood glucose level is low.

Question 82

In what way does eating increase after damage in and around the ventromedial hypothalamus? After damage to the paraventricular nucleus?

Answer 82

Animals with damage to the ventromedial hypothalamus eat more frequent meals. Animals with damage to the paraventricular nucleus of the hypothalamus eat larger meals.

Question 83

Why did the Pima begin gaining weight in the mid-1900s?

Answer 83

They shifted from a diet of local plants that were seasonally available to a calorie-rich diet that is available throughout the year.
Their former strategy of over eating and inactivity to conserve energy became maladaptive.

Question 84

Obesity that results from a medical condition

Answer 84

Syndromal obesity

Some people with severe, early onset obesity have deletions of part of a chromosome. If the deletion includes genes for leptin receptors, insulin receptors, or other key elements in regulation of eating, the outcome includes obesity as well as other problems

Question 85

In one study, rats eating the less-caloric yoghurt gained more weight than those eating the more-caloric type. What explanation was proposed?

Answer 85

The rats unlearned their usual calibration that more sweet means more energy and therefore stopped compensating after eating other sweets.

(The less-caloric yoghurt with sweetened with a non-caloric sweetener)

Question 86

A condition in which people alternate between binges of overeating and periods of strict dieting

Answer 86

Bulimia nervosa

Question 87

Researchers have found that people with bulimia nervosa have elevated ghrelin levels. Why are those levels probably not the cause of bulimia?

Answer 87

As people recover from bulimia, the ghrelin returns toward normal levels. If their genetics or other factors produce constantly high ghrelin, it should remain high regardless of current diet

Question 88

What evidence from rats suggests that bulimia at resembles an addiction?

Answer 88

Rats that alternate between food deprivation and a very sweet diet gradually eat more and more, and they react to deprivation of the sweet diet with head shaking and teeth chattering, like the symptoms of morphine withdrawal