Hunger, Thirst, Homeostasis

Question 1

Homeostatic systems

Answer 1

use our behavior to keep things balanced

Question 2

Negative feedback

Answer 2

systems are the main homeostatic mechanisms

If a desired set point is deviated from, compensatory action begins

Question 3

Hypovolemic thirst

Answer 3

stimulated by low extracellular/intravascular volume
Triggered by loss of water volume – concentration is not changed
Baroreceptors in blood vessels and heart detect the initial drop
Brain activates thirst and salt craving
Arteries constrict to raise BP

Question 4

Osmotic thirst

Answer 4

stimulated by high extracellular solute concentration

Question 5

Hypovolemia

Answer 5

causes release of vasopressin (antidiuretic hormone) – induces blood vessel constriction and reduces flow to the bladder

Question 6

diabetes insipidus

Answer 6

vasopressin is not produced – kidneys send more urine to the bladder, resulting in chronic thirst

Question 7

Angiotensin (II) Cascade

Answer 7

With decreased blood volume, kidneys release renin, which triggers formation of angiotensin II
angiotensin II:
1)blood vessels constrict
2)circumventricular organs trigger drinking
3)vasopressin is realeased
4)aldosterone is realeased
Circulating angiotensin II acts in the subfornical organ to send a signal to other brain sites to initiate drinking

Question 8

Osmosensory neurons

Answer 8

reside in anterior hypothalamus (OVLT)
respond to rise in blood osmotic pressure
cell membranes shrink, opening mechanical-gated Na+ channels
in hypothalamus, respond to increased osmotic pressure causing the pituitary to release antidiuretic hormone

Question 9

Diet

Answer 9

At the start of a diet, the basal metabolic rate will fall – to prevent losing weight

Question 10

Glucose

Answer 10

the principal sugar used for energy

Question 11

Glycogen

Answer 11

glucose stored for short term in the liver

Question 12

Glycogenesis

Answer 12

converting glucose to glycogen, using pancreas hormone insulin

Question 13

Lipids

Answer 13

fat tissue for longer-term storage

Question 14

leptin

Answer 14

produced by fat cells and secreted it into the bloodstream
Defects in leptin production or sensitivity give a falsely low report of body fat, causing animals to overeat
Leptin inhibits secretion of AgRP

Question 15

Ghrelin

Answer 15

Released by stomach endocrine cells (Appetite stimulant)
Rises during fasting; drops after eating
Some obese people have elevated ghrelin levels

Question 16

Prader-Willi syndrome

Answer 16

genetic disease that causes a sense of never being full or satisfied
Ghrelin levels are elevated in Prader-Willi

Question 17

Lateral hypothalamus (LH) lesions

Answer 17

refusal to eat

LH-lesioned animals stop eating, but will resume and stabilize their weight at a new, lower level

Question 18

Ventromedial hypothalamus lesions

Answer 18

cause obesity
VMH-lesioned animals exhibit overeat until they become obese
Increased weight stabilizes - this weight is maintained even after food manipulations

Question 19

NPY/AgRP neurons

Answer 19

produce neuropeptide Y and agouti-related peptide

stimulate appetite and lower metabolism -> weight gain

Question 20

POMC/CART neurons

Answer 20

produce pro-opiomelanocortin and cocaine- and amphetamine-related transcript (CART)
inhibit appetite and raise metabolism -> weight loss

Question 21

Anorexia Nervosa

Answer 21

Refusal to maintain body weight
Fear of weight gain
Body image disturbance
Amenorrhea
Restricting or Binge-Eating/Purging type
0.5% lifetime prevalence in women (.05% in men)
Other symptoms of anorexia
thinning of the bones
brittle hair and nails, dry and yellowish skin
mild anemia, muscle weakness and loss, lethargy
severe constipation
low blood pressure, slowed breathing and pulse
drop in body temperature

Question 22

Bulimia

Answer 22

Recurrent binge eating
Recurrent inappropriate compensatory behavior
At least 2x/wk for 3 months

Question 23

Eating Disorders Occur with Other Psychiatric Conditions

Answer 23

Women with Anorexia or Bulimia
40% Childhood anxiety disorders 
20% Obsessive compulsive disorder 
30% Abuse alcohol or drugs 
90% Depression
246 Women with an Eating Disorder:
30% Attempted suicide 
  5% Died

Question 24

Treatment of Obesity

Answer 24

Eat less: A daily deficit of 500 to 1000 calories is reasonable. This is the most important part of therapy and most difficult to do.

Modify behavior to avoid temptation to pig out. This means lifestyle change. Self-monitoring and social support are essential.

Exercise. A lot: Strenuous aerobic activity for over 200 minutes per week maintained for a long time with calorie restriction works.

Question 25

treating obesity as an addiction

Answer 25

Obese people share several characteristics with addicts:
They have reduced numbers of dopamine D2 receptors and associated decrease in prefrontal metabolism
Peptides that induce eating target dopamine neurons
Anti-addiction drugs are somewhat effective in weight loss

Question 26

Obesity and Reduced Metabolism

Answer 26

Basal metabolic rate (BMR):
energy required to fuel the brain/body and maintain temperature
75% of energy expenditure in average sedentary student

Of women on a diet, the 1/3 who failed to lose weight had low BMRs
Heredity accounts for 40% of a person’s BMR. But, spontaneous activity can increase it

Question 27

Gastric bypass surgery

Answer 27

Weight loss averages 25% and is long-lasting (compared to 5%-10% with dieting and relapse within a year)
Reduces ghrelin and increases PYY and GLP-1, reducing hunger
Reduces mortality and has many health benefits

Question 28

In a survey of students in grades 5-8, _____% were dieting and _____% were fasting.

Answer 28

30, 10

Question 29

The anterior pituitary produces _____.

Answer 29

growth hormones

Question 30

The posterior pituitary produces _____ and _____.

Answer 30

ADH, oxytocin