week 8

Question 1

What is Homeostasis?

Answer 1

An active process to maintain a variable within a fixed range, or to maintain a set point. Coined by Walter Cannon.

Question 2

What are the 4 features of the regulatory system?

Answer 2

System variable: variable to manipulate
Set point: optimal value of the variable
Detector: monitors the value of the variable
Correctional mechanism: restores the variable’s value to set point, if it deviates from set point

Question 3

Put the 4 features of regulatory system into context of a heating system. (and negative feedback)

Answer 3

So we can put this into context with respect to heating up a room
in this case the system variable is air temperature, hot or cold
the set point of interest is 21 degrees Celsius
the detector is the thermostat that tells us what is the air temperature and it will tell us whether air temperature is meeting the set point this optimal value or whether it deviates from this optimal value
it’s super cold outside and the room starts to get cooler. It drops below the 21 degrees Celsius set point
the thermostat indicates that the value of air temperature has decreased it’s gotten cooler and then the correctional mechanism is activated; electrical heaters is the correctional mechanism
in order to maintain homeostasis in order to maintain balance we don’t want that heater to keep heating the room
the negative feedback comes in such that, once the air temperature is brought back up to 21 C (set point) the correctional mechanism will be shut off

Question 4

What is the Negative Feedback in the regulatory process?

Answer 4

Negative Feedback: regulatory process that reduces discrepancies from the set point

Question 5

What is Basal Metabolism?

Answer 5

Energy used to maintain a constant body temperature while at rest
2/3 of total energy dedicated to maintaining basal metabolism

Question 6

What is Ectothermic? (hint: temperature)

Answer 6

Controlling temperature by relying on external sources of heat or cooling (e.g., reptiles) -> need to find sunny spot to be warm

Question 7

What is Endothermic?

Answer 7

Controlling temperature by the body’s physiological mechanisms (e.g., humans)

Question 8

In reference to Homeostatic mechanisms what part of the brain do we focus on?

Answer 8

When talking about homeostatic mechanisms, thermo fluid regulation and digestive behaviour. We are focusing on the hypothalamus

Question 9

What part of the brain are we focusing on in relation to hemostatic mechanisms, thermoregulation, fluid regulation and digestive behaviour?

Answer 9

hypothalamus

Question 10

What two parts of the hypothalamus receives input from thermoreceptors?

Answer 10

Anterior hypothalamus & preoptic area (POA)

Question 11

How does the body fight off an infection?

Answer 11

To fight off an infection the immune system has to activate and generate a fever which is important to fight off an infection
the hypothalamus receives input from the immune system which reacts to an infection by sending prostaglandins and histamines to the pre optic area and the hypothalamus and those chemicals cause shivering increase metabolism other processes that produce a fever.

If your body overheats then your body starts to destroy protein bonds and eventually lead to death

Question 12

What were the results in rats when lesions were performed on the POA ?

Answer 12

POA: Lesions in rats impair physiological response → shivering, sweating, metabolism in brown tissue
They can still compensate for the lesion, they can press a lever to turn on the heat or A/C

Question 13

What were the results in rats when lesions were performed on the Lateral Hypothalamus ?

Answer 13

Lateral Hypothalamus: Lesions in rats impair behavioural response → turning on the heater
Not able to turn on heater or A/C

Question 14

What does it mean for humans to be Homeothermic?

Answer 14

Despite changing environments we have physiological mechanisms in place to ensure that we maintain constant body temperature

Question 15

What is the reason humans are able to adjust to temperature changes in environments.

Answer 15

through the process of allostasis, which is similar to homeostasis
Homeostasis assumes a set point/range
Allostasis recognizes that sometimes this range may change, depending on the environment that we’re in

• Example, fluctuations in body weight, fatter in the winter vs. summer

Question 16

What happens in the body when the blood temperature is below optimal temperature?

Answer 16

The thermoreceptors detect that the blood is cooling
Therefore sends signal to preemptive area into you hypothalamus to start a physiological response i.e., shivering
Shivering; skeletal muscles activated to generate more heat
skin blood vessels constrict blood is diverted from the skin capillaries and withdrawn to deeper tissues so moving away from the surface of the skin moving deep into deeper tissues minimizing the overall heat loss from skin surface.
Negative feedback; Body temp increases and hypothalamus heat promoting center “shuts off”

Question 17

What happens in the body when the blood temperature is above optimal temperature?

Answer 17

The thermoreceptors detect that the blood is heating
Heat loss activation centre in hypothalamus
Therefore sends signal to preemptive area into you hypothalamus to start a physiological response i.e., sweat
perspiration we begin to sweat which vaporizes from the body heat and this helps pull down the body therefore bring body temperature back down

Question 18

What kinds of temperatures can Wim Hof withstand and how?

Answer 18

He is able to withstand very cold temperatures
shown scientifically that the autonomic nervous system, related to the innate immune response can be willfully consciously influenced
Wim Hof has shown we can control the autonomic nervous system
That control can be used to improve mood to enhance relaxation to boost immunity to disease and to infection and to also improve physical performance.

Question 19

What is the Satiety Mechanism?

Answer 19

A brain mechanism that causes cessation of hunger (or thirst), produced by adequate and available supplies of nutrients/energy (or water/fluid)

• monitors the correctional mechanism (ingestion)

Question 20

Where is most of the water in the water contained? Where is interstitial fluid and blood plasma contained?

Answer 20

Water constitutes 70% of our body
Most of body water is contained within our cells = Intracellular compartment
Extracellular compartment =interstitial fluid and blood plasma

Question 21

What is regulation of water important for in the body?

Answer 21

Rate of chemical reactions

Maintenance of blood pressure

Question 22

What are the two kinds of thirst?

Answer 22

Osmotic thirst: Too much sodium chloride (salt) in the extracellular fluid (e.g., From eating a big bag of salty chips)
Hypovolemic thirst: Loss of volume of extracellular fluid (e.g., from excessive sweating or bleeding)

Question 23

What is Osmotic pressure?

Answer 23

Tendency of water to move from areas of low solute concentration to areas of high solute concentration

• Semipermeable cell membrane allows for flow of water between intracellular and extracellular space
• Water moves from inside to outside the cell = osmosis
• Cellular dehydration occurs as water leaves intracellular space = osmotic thirst

Question 24

in more detail, explain what Hypovolemic Thirst is?

Answer 24

Loss of bodily fluids → loss in blood volume → lower blood pressure
Baroreceptors of heart(detect drop in blood pressure), blood vessels, and kidneys assess blood pressure →
Sympathetic NS stimulates muscles in arterial walls to constrict

Question 25

Briefly explain Physiological Regulatory mechanism.

Answer 25

1. body loses water 2. doctored signal loss of water 3. drink water 4. stomach fills with water, sends signal to brain 5. satiety mechanism inhibits further drinking 6. water is absorbed; body fluid back to normal

Question 26

What is digestion?

Answer 26

the process by which food is broken down to provide energy Energy is made from metabolism Begins in mouth (enzymes for carbs) Esophagus to stomach (hydrochloric acid and enzymes for proteins) Small intestine (enzymes for proteins, fats, and carbs) Absorbed into bloodstream Big intestine absorbs water and minerals (lubricated and expelled)

Question 27

What are some Energy substrates from food?

Answer 27

Carbohydrates → Glucose(primary energy source) Fats → Triglycerides & glycerol Protein → Amino acids we use oxygen to burn the substrate so after we burn them we give off water and carbon dioxide in the process of burning and we generate ATP(energy molecule)

Question 28

What are the 2 phases of digestion?

Answer 28

Absorptive/Digestive Phase and Fasting Phase

Question 29

Explain the Absorptive/Digestive phase.

Answer 29

Nutrients are being absorbed from the digestive system Insulin secreted from pancreas Glucose feeds cells Amino acids aid in protein synthesis Excess glucose stored in liver (glycogen) and adipose tissue (triglycerides) Fat stored in adipose tissue There is a rise in insulin from the pancreas and the rise in insulin is needed to ensure that glucose can be sent to cells in the peripheral nervous system, not the central nervous system

Question 30

Explain the Fasting Phase.

Answer 30

Nutrients not available from the digestive system Glucagon secreted from pancreas (short-term) Glucose derived from glycogen and triglycerides (fatty acids, glycerol) (long-term)

Question 31

What is Insulin?

Answer 31

Insulin is a pancreatic hormone that enables glucose to enter the cell Insulin levels rise as someone is getting ready for a meal and after a meal

Question 32

Describe the 3 phases of Cephalic , Digestive and Absorptive phase.

Answer 32

Cephalic phase; stomach response to the smell of food, arise or secretion of insulin arise essentially is preparing the body to receive glucose Digestive phase; significant rise in glucose levels to ensure it can send glucose to cells of the PNS Absorptive phase (glucodetectors of liver); ​​We have enough nutrients that have entered the body and and we have enough nutrients and substrates that will then feed the cells of the body, we stop eating

Question 33

What is Glucagon?

Answer 33

Glucagon is also a hormone released by the pancreas when glucose levels fall Glucagon stimulates the liver to convert some of its stored glycogen to glucose to replenish low supplies in the blood As insulin levels drop, glucose enters the cell more slowly and hunger increases

Question 34

What is Short-term Reservoir?

Answer 34

Located in cells of the liver Stores glycogen Reservoir reserved for CNS During short-term fasting your liver feeds the brain by converting glycogen into glucose (via glucagon) and releases it into the blood to nourish cells of the CNS.

Question 35

What is Long-term reservoir?

Answer 35

Located in adipose tissue Stores triglycerides Triglycerides contain glycerol and fatty acids Increase in triglycerides increases fat cells Important during fasting During log-term states of fasting, the adipose tissue supplies the brain with glucose and the rest of the body with fatty acids

Question 36

What 3 signals inform your body that you are hungry?

Answer 36

1. Signals from the environment 2. Signals from the stomach Stomach releases the hormone ghrelin to signal the brain Ghrelin is suppressed by duodenum - Ghrelin increases with fasting Injection of ghrelin increases food intake BUT - not the only factor involved .... 3. Metabolic signals Glucoprivation = decrease glucose available to cells that causes hunger (hypoglycemia) Lipoprivation = decrease fatty acids available to cells that causes hunger

Question 37

What stops a meal?

Answer 37

Satiety signals Oral factors? Is chewing and tasting enough? Liquid diet may still leave desire to taste or chew Sham-feeding experiments Food leaks out of tube Particpants do not become satiated

Question 38

What are some short-term satiety signals?

Answer 38

Stomach Distention (via vagus nerve) Gastric receptors that detect presence of nutrients in the stomach ( via splanchnic nerve to brain) Intestinal factors (duodenum): Chemoreceptors in the duodenum; send info to brain about amount and type of nutrient; CCK hormone in the duodenum when distended; controls rate of stomach emptying PYY increases in same proportion of calories that are ingested - Liver receives nutrients from intestines and sends satiety signal to brain - Insulin receptors in hypothalamus

Question 39

What are some Long-term Satiety Signals?

Answer 39

Leptin: hormone released by fat cells of adipose tissue determine long-term satiety cues When fat reserves decrease, leptin levels decline, and you react by eating more and becoming less active, to save energy. When leptin levels return to normal, you eat less and become more active Ob KO mouse: mutation of Ob gene that does not allow for the production of leptin

Question 40

How does the Medulla Oblongata play a part in Satiety?

Answer 40

Medulla Oblongata Contains neural circuits that detect hunger and satiety signals and controls some aspects of food intake Receive taste info from tongue; info from stomach, duodenum, & liver; detectors for glucose hunger increases activity of neurons in the medulla lesions abolish glucoprivic & lipoprivic feeding

Question 41

How does the Hypothalamus play a part in Satiety?

Answer 41

Ventromedial hypothalamus: Inhibits eating (Satiety center) Lesion leads to overeating (frequent eating of normal meals) and weight gain. Eating normal sized meals, but frequently (increased insulin and glucoprivation) Increase in insulin and storing glucose as fat Lateral hypothalamus: (a.k.a. Hunger/Eating center) controls eating/drinking behavior Lesion causes cessation of eating and drinking Lesions cause under-eating, weight loss. Communicates with taste pathway of solitary nucleus of medulla. Communicates with cortex to facilitate ingestion and swallowing and perception of food. Communicates with spinal cord for digestion of food. Communicates with pituitary to secrete hormones which further increase insulin

Question 42

What are important hunger-satiety pathways?

Answer 42

Arcuate nucleus - PVN - Lateral hypothalamus - Arcuate Nucleus - “Master Area” for appetite control, has neurons sensitive for hunger (ghrelin) and satiety (cck, insulin) Paraventricular nucleus (PVN) - Inhibits the lateral hypothalamus - Receives input from arcuate nucleus (excited or inhibited) - Important for satiety - Lesions cause increased meal size, especially increased intake of carbohydrates

Question 43

What are some hunger chemicals inn the hypothalamus?

Answer 43

Production of orexigens (appetite inducing chemicals) In AN: neuropeptide Y (NPY) and agouti-related peptide (AgRP) Project to Lateral hypothalamus (+) and PVN (-) Inhibit satiety cells of the AN In LH: melanin-concentrating hormone (MCH) & orexin- Project to brain areas important for feedings (motivation, motor) and to the ANS (metabolism)

Question 44

What are some satiety chemicals in the hypothalamus?

Answer 44

Production of melanocortins (appetite suppressing chemicals) In AN: Alpha-melanocyte-stimulating hormone (α-MSH) Stimulates PVN which inhibits LH Inhibit hunger cells of the AN Leptin receptors inhibit NPY/AgRP neurons Excitatory effect on melanocortin PYY in gastrointestinal tract inhibit NPY/AgRP of AN

Question 45

Explain the Hunger System.

Answer 45

``` Hunger-sensitive neurons (NPY/AgRP) of the AN are stimulated by Ghrelin from stomach and/or from glucose-sensitive cells of the medulla. Hunger-sensitive neurons of AN inhibit satiety cells of AN (α-MSH) and inhibit project to PVN. AN stimulate orexigens (MCH and Orexin) of the Lateral hypothalamus Projections from LH innervate other brain regions to facilitate motivation and eating behaviors ```

Question 46

Explain the Satiety System.

Answer 46

``` Hunger-sensitive neurons in AN (NPY/ArGP) are inhibited by PYY and Leptin. Satiety-sensitive neurons in AN (α-MSH) are stimulated by Leptin and insulin. Satiety-sensitive neurons of AN project to PVN and excite satiety action of PVN ```

Question 47

Describe what happens to certain parts of the hypothalamus when a lesion is performed. hint; POA, LPOA, L hypothalamus, vM hypothalamus, pV nucleus

Answer 47

pre optic area - defect in physiciloigcal mechanisms of temp regulation lateral pre optic area - defect in osmotic thirst due partly to damage to cells and partly to interruption of passing axons lateral hypothalamus - undereating, low insulin underresponsiveness ventromedial hypothalamus- increase meal frequency, weight gain, high insulin paraventuxcular nucleus - increased meal size, increase carb intake during first meal

Question 48

What are some facts about eating disorders that lead to obesity.

Answer 48

``` Definition: BMI > 30 60% adults and 30% children Decreased life expectancy Increased health problems: CHD, diabetes, stroke, arthritis, cancer, cognitive impairment, early mortality ```

Question 49

What is the Etiology(cause) of Obesity?

Answer 49

Epigenetic changes in DNA expression (Dutch famine and Obese parents) Epigenetic effects following bariatric surgery Genetic mutations Congenital Leptin Deficiency Intrauterine environment Lifestyle behaviors

Question 50

Describe the Syndromal Obesity: Prader-Willi Syndrome

Answer 50

Genetic disruption on chromosome 15 which affects function of hypothalamus No satiety signals High ghrelin levels, normal NPY/AgRP, normal leptin receptors Video: http://www.youtube.com/watch?v=OB7tbp3rzv4&feature=related

Question 51

What is Bulimia and Anorexia? State health issues

Answer 51

Bulimia Nervosa: binging followed by purging Anorexia Nervosa: Excessive dieting and compulsive exercise due to exaggerated concern with overweight Health problems: dental erosion, osteoporosis, mood disorder, cognitive impairment, cardiovascular problems Elevated ghrelin in BN and elevated NPY levels in AN