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PSY324 > week 8 > Flashcards

week 8 Flashcards

1. Describe homeostasis and regulatory mechanisms 2. Describe homeostasis of temperature 3. Describe homeostasis of water regulation 4. Describe digestion and it’s reservoirs and phases 5. Describe the correlates of hunger and satiety 6. Describe the brain mechanisms involved in hunger and satiety 7. Describe digestive behavior disorders

1
Q

What is Homeostasis?

A

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

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2
Q

What are the 4 features of the regulatory system?

A

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

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3
Q

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

A

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

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4
Q

What is the Negative Feedback in the regulatory process?

A

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

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5
Q

What is Basal Metabolism?

A

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

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6
Q

What is Ectothermic? (hint: temperature)

A

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

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7
Q

What is Endothermic?

A

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

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8
Q

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

A

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

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9
Q

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

A

hypothalamus

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10
Q

What two parts of the hypothalamus receives input from thermoreceptors?

A

Anterior hypothalamus & preoptic area (POA)

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11
Q

How does the body fight off an infection?

A

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

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12
Q

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

A

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

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13
Q

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

A

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

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14
Q

What does it mean for humans to be Homeothermic?

A

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

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15
Q

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

A

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
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16
Q

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

A

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”

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17
Q

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

A

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

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18
Q

What kinds of temperatures can Wim Hof withstand and how?

A

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.

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19
Q

What is the Satiety Mechanism?

A

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)
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20
Q

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

A

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

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21
Q

What is regulation of water important for in the body?

A

Rate of chemical reactions

Maintenance of blood pressure

22
Q

What are the two kinds of thirst?

A

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)

23
Q

What is Osmotic pressure?

A

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
24
Q

in more detail, explain what Hypovolemic Thirst is?

A

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

25
Q

Briefly explain Physiological Regulatory mechanism.

A
  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
26
Q

What is digestion?

A

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)

27
Q

What are some Energy substrates from food?

A

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)

28
Q

What are the 2 phases of digestion?

A

Absorptive/Digestive Phase and Fasting Phase

29
Q

Explain the Absorptive/Digestive phase.

A

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

30
Q

Explain the Fasting Phase.

A

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

31
Q

What is Insulin?

A

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

32
Q

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

A

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

33
Q

What is Glucagon?

A

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

34
Q

What is Short-term Reservoir?

A

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.

35
Q

What is Long-term reservoir?

A

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

36
Q

What 3 signals inform your body that you are hungry?

A
  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
37
Q

What stops a meal?

A

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

38
Q

What are some short-term satiety signals?

A

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
39
Q

What are some Long-term Satiety Signals?

A

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

40
Q

How does the Medulla Oblongata play a part in Satiety?

A

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

41
Q

How does the Hypothalamus play a part in Satiety?

A

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

42
Q

What are important hunger-satiety pathways?

A

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

43
Q

What are some hunger chemicals inn the hypothalamus?

A

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)

44
Q

What are some satiety chemicals in the hypothalamus?

A

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

45
Q

Explain the Hunger System.

A 
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
46
Q

Explain the Satiety System.

A 
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
47
Q

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

A

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

48
Q

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

A 
Definition: BMI > 30
 60% adults and 30% children
Decreased life expectancy
Increased health problems:
CHD, diabetes, stroke, arthritis, cancer, cognitive impairment, early mortality
49
Q

What is the Etiology(cause) of Obesity?

A

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

50
Q

Describe the Syndromal Obesity: Prader-Willi Syndrome

A

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

51
Q

What is Bulimia and Anorexia? State health issues

A

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

PSY324 (11 decks)

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