Unit 7 Parts 3 and 4 - Screencasts

Question 1

What condition do some obese individuals experience regarding leptin signaling?
a) Leptin overproduction
b) Leptin receptor deficiency
c) Leptin resistance
d) Hypoleptinemia

Answer 1

c) Leptin resistance

Explanation: In leptin resistance, leptin is produced normally by adipose tissue, but the brain does not respond appropriately to reduce appetite.

Question 2

What pancreatic cells produce insulin?
a) Alpha cells
b) Beta cells
c) Delta cells
d) Acinar cells

Answer 2

b) Beta cells

Explanation: Insulin is produced by beta cells in the islets of Langerhans in the pancreas.

Question 3

What is a ‘cafeteria diet’ in nutritional research?
a) A high-fiber animal diet
b) A nutritionally balanced rodent diet
c) A calorie-controlled human diet
d) A high-palatability diet mimicking human junk food

Answer 3

d) A high-palatability diet mimicking human junk food

Explanation: It includes highly processed, palatable items like cookies and chips to induce obesity in lab animals.

Question 4

What type of stimulus primarily triggers insulin secretion after a meal?
a) Rising plasma glucose and amino acids
b) High cortisol levels
c) Low potassium levels
d) Fasting glucagon release

Answer 4

a) Rising plasma glucose and amino acids

Explanation: Beta cells in the pancreas sense increases in glucose and amino acids, triggering insulin release in the fed state.

Question 5

What evolutionary explanation is offered for why humans are more vulnerable to obesity?
a) Stronger mechanisms to prevent weight gain than weight loss
b) Better mechanisms to survive starvation than to limit excess fat
c) Evolution prioritized leanness for reproduction
d) Leptin deficiency is common

Answer 5

b) Better mechanisms to survive starvation than to limit excess fat

Explanation: Evolution favored mechanisms that ensure survival during food scarcity (e.g., strong hunger drives), but not those that prevent excess fat accumulation.

Question 6

What are incretins, and what do they do?
a) Gut peptides that inhibit digestion
b) Neural signals that stimulate glucagon
c) Hormones like GLP-1 and GIP that enhance insulin secretion
d) Bile acids that trigger pancreatic enzyme release

Answer 6

c) Hormones like GLP-1 and GIP that enhance insulin secretion

Explanation: Incretins are gut-derived hormones released during meals that act on beta cells to promote insulin secretion.

Question 7

What glucose transporter is used by beta cells to sense plasma glucose?
a) GLUT1
b) GLUT2
c) SGLT1
d) SGLT2

Answer 7

b) GLUT2

Explanation: GLUT2 facilitates glucose entry into beta cells, allowing intracellular metabolism to increase ATP and trigger insulin release.

Question 8

What genetic condition was corrected with recombinant leptin in early human trials?
a) Type 1 diabetes
b) Leptin receptor deficiency
c) Ghrelin overproduction
d) Homozygous mutation in the LEP gene

Answer 8

d) Homozygous mutation in the LEP gene Explanation: Children with mutations in the LEP gene (analogous to ob/ob mice) had obesity that was reversed with recombinant leptin therapy.

Question 9

How does ATP influence insulin secretion in pancreatic beta cells?
a) Inhibits GLUT2
b) Opens voltage-gated calcium channels directly
c) Stimulates glucagon release
d) Closes potassium channels, causing depolarization

Answer 9

d) Closes potassium channels, causing depolarization

Explanation: Increased ATP from glucose metabolism closes ATP-sensitive K+ channels, leading to depolarization and insulin release via Ca2+ influx.

Question 10

What effect does parasympathetic activity have on insulin secretion?
a) Stimulates insulin via vagus nerve input
b) Inhibits insulin via norepinephrine
c) Has no effect on pancreatic function
d) Triggers glucagon from alpha cells

Answer 10

a) Stimulates insulin via vagus nerve input

Explanation: Parasympathetic (rest-and-digest) signals stimulate insulin release through vagal innervation of beta cells.