Internal regulation

Question 1

Homeostasis:

Answer 1

Temperature regulation and other biological processes that keep certain body variables within a fixed range.

Question 2

Set point:

Answer 2

Level at which a homeostatic process maintains a variable.

Question 3

Negative feedback:

Answer 3

Processes that reduce discrepancies from the set point.

Question 4

Allostasis:

Answer 4

Dynamic, adaptive and anticipatory changes in the body’s set points in response to changes in its life or changes in the environment (much of this control depends on cells in the hypothalamus)

Question 5

Basal Metabolism:

Answer 5

Energy used to maintain a constant body temperature at rest. Twice as much energy is used for temperature regulation as all other activities combined (2/3 of energy is spent on basal metabolism)

Question 6

Poikilothermic:

Answer 6

Animals with body temperatures the same as their environment (i.e., fish and lizards).

Question 7

Homeothermic:

Answer 7

Animals with physiological mechanisms that maintain an almost constant body temperature despite variations in environmental temperature. These types of animals generate heat in proportion to their total mass but radiate heat in proportion to their surface area. For these animals, sweating, licking themselves, and panting are used as cooling mechanisms. Shivering and fluffing are used as heating mechanisms

Question 8

preoptic area/anterior hypothalamus (POA/AH).

Answer 8

The brain regions most critical for temperature control are the anterior hypothalamus and the preoptic area of the hypothalamus (preoptic because it is near the optic chiasm). Because of the close relationship between these areas, they are often treated as one area, the preoptic area/anterior hypothalamus (POA/AH).
b. The POA/AH controls the physiological mechanisms such as shivering, sweating, changes in heart rate and metabolism and changes in blood flow to the skin

Question 9

Fever

Answer 9

Fever is part of the body’s defences for illness (not the illness itself).
d. Fever works because certain types of bacteria grow less vigorously at high temperatures, and it enhances the activity of the immune system. However, a fever above 39C does more harm than good, and a fever above 41C is life threatening.

Question 10

Water

Answer 10

• Mammalian body is about 70% water

- Water determines the rate of all chemical reactions in the body, the water must be regulated within narrow limits

Question 11

vasopressin, also known as antidiuretic hormone (ADH)

Answer 11

For humans, when your body needs water, the posterior pituitary gland releases vasopressin, also known as antidiuretic hormone (ADH), which enables the kidneys to reabsorb water and secrete highly concentrated urine.

Question 12

Thirst can be divided into two types:

Answer 12

thirst due to eating salty foods (osmotic thirst) and thirst due to a loss of fluids (hypovolemic thirst).

Question 13

Osmotic pressure:

Answer 13

The tendency of water to flow across a semipermeable membrane from an area of low concentration to areas of high concentration. In cells, the membrane works as a semipermeable membrane and water, but not all solutes, flows freely between the extracellular fluid (fluid outside the cell) and intracellular fluid (fluid inside the cell).

Question 14

Osmotic thirst: Occurs when certain neurons detect their own loss of water. This loss of water happens when solute concentrations in the extracellular fluid are higher than the concentration of solutes in the intracellular fluid, causing water to be drawn from the intracellular compartment to dilute the solutes in the extracellular fluid.

Answer 14

Occurs when certain neurons detect their own loss of water. This loss of water happens when solute concentrations in the extracellular fluid are higher than the concentration of solutes in the intracellular fluid, causing water to be drawn from the intracellular compartment to dilute the solutes in the extracellular fluid.

Question 15

Organum Vasculosum Laminae Terminalis (OVLT) and subfornical organ:

Answer 15

Areas located around the third ventricle that are responsible for detecting osmotic pressure.
5. The brain also receives information from receptors in the periphery, including the stomach, that detect high levels of sodium.

Question 16

The supraoptic nucleus and paraventricular nucleus:

Answer 16

are brain areas located in the hypothalamus that control the rate at which the posterior pituitary gland releases vasopressin.
- Both of these brain areas and the lateral preoptic area (which controls drinking) receive information from the OVLT, the subfornical organ, the stomach, and elsewhere.

Question 17

angiotensin II

Answer 17

this hormone constricts blood vessels in order to reverse the loss of blood volume and triggers hypovolemic thirst
1. When you lose a significant amount of body fluid by bleeding, diarrhea, or sweating, the body will release hormones, including vasopressin and angiotensin II, that constrict blood vessels. When blood volume decreases, kidneys release the hormone rennin, which splits a portion off angiotensinogen (a large protein in the blood) to form angiotensin I, which is then converted into angiotensin II

Question 18

hypovolemic thirst

Answer 18

(thirst based on low volume).

- During hypovolemic thirst the body needs to replenish both water and lost solutes such as salt.

Question 19

aldosterone:

Answer 19

Specific sodium cravings (due to bleeding or excessive sweating) are caused by the release of aldosterone, a hormone which causes the kidneys, salivary glands, and sweat glands to conserve sodium and excrete more watery fluids than usual.

Question 20

lactase

Answer 20

Many mammals lose the intestinal enzyme lactase, which allows them to metabolize lactose (sugar found in milk). Losing the enzyme lactase may be an evolved mechanism to encourage weaning.

d. The ability to consume large amounts of milk products varies geographically. In China and surrounding countries, nearly everyone lacks the ability to metabolize lactose.
e. The ability to digest lactose depends on the origins of our ancestors (more likely in places that domesticated cattle).

Question 21

In sham-feeding experiments

Answer 21

everything an animal eats leaks out a tube connected to the esophagus or stomach (under these conditions, animals consume several times as much as untreated animals during each meal).
c. These studies demonstrate that although taste and mouth are important cues, they are not sufficient alone to produce satiety.

Question 22

The vagus nerve (cranial nerve X)

Answer 22

carries information to the brain regarding the stretching of stomach walls, providing a major basis for satiety.

Question 23

The splanchnic nerves

Answer 23

convey information about the nutrient contents of the stomach, carrying impulses back and forth from the spinal cord to the digestive organs.

Question 24

The duodenum

Answer 24

is part of the small intestine adjoining the stomach. The duodenum also releases a hormone called oleoylethanolamide (OEA) to cause satiety.

Question 25

Cholecystokinin (CCK):

Answer 25

A hormone released by the duodenum to inhibit appetite.

Question 26

Insulin:

Answer 26

Facilitates entry of glucose from the bloodstream into the body’s cells. (Brain cells do not need insulin for glucose to enter).

Question 27

Glucagon:

Answer 27

Stimulates the liver to convert stored glycogen to glucose.

Question 28

Leptin

Answer 28

a. A recently discovered hormone that monitors the body’s fat reserves to account for day-to-day mistakes in consumption.
b. Leptin is normally made by fat cells so that the more fat cells, the higher the levels of leptin. When fat cell reserves are low, there are low levels of leptin and hunger increases.

Question 29

Improving production of leptin:

Answer 29

d. Some mice genetically predisposed to obesity fail to produce leptin. The brain then acts as if the body has no fat stores and signals the mouse to eat more and be less active (to conserve energy). Leptin injections have reversed these symptoms in mice.
e. Humans become less sensitive to leptin during pregnancy. Obesity also lowers leptin sensitivity by damaging the endoplasmic reticulum in neurons of the hypothalamus. This can only be reversed through physical exercise.

Question 30

The arcuate nucleus of the hypothalamus

Answer 30

has a set of neurons sensitive to hunger signals and another set of cells sensitive to satiety signals. The hunger- sensitive cells receive input from the taste pathway and from ghrelin (a neurotransmitter released from the stomach during periods of food deprivation), released by axons.

Question 31

paraventricular nucleus (PVN)

Answer 31

Much of the input from the arcuate nucleus goes to the paraventricular nucleus (PVN). The PVN inhibits the lateral hypothalamus (an area important for eating) and is involved in satiety. If the PVN is damaged, rats eat larger than normal meals.

Question 32

Deficiencies in melanocortin receptors cause people to:

Answer 32

overeat as they do not respond to satiety signals.

Question 33

The Lateral Hypothalamus

Answer 33

a. The lateral hypothalamus controls insulin secretion, alters taste responsiveness, and facilitates feeding in other ways. Damage to the lateral hypothalamus causes an animal to refuse food and water.
b. Contributions of the lateral hypothalamus include: altering the taste of food (when one is hungry, food tastes better), causing cortical cells to increase their response to taste, smell, or sight of food, controlling insulin secretion, controlling digestive secretions.

Question 34

Ventromedial hypothalamus (VHM):

Answer 34

Damage centered around this area leads to overeating and weight gain (after gaining weight, these animals become picky eaters, as they consume bitter foods far less than normal but eat more than normal of a sweetened or normal diet).

Question 35

Syndromal obesity:

Answer 35

obesity that results from a medical condition. The genetic disorder Prader-Willi syndrome leads to obesity, possibly by inducing high levels of the peptide ghrelin.

Question 36

ghrelin

Answer 36

(a neurotransmitter released from the stomach during periods of food deprivation), released by axons.