Hormones and the brain
In this section, we’ll look at several hormones (and related signals) that are produced in the body or brain and influence how the nervous system functions.
1) First, watch these videos:
2) Next, read this article to learn about pheromones—hormone-like chemical messengers that can carry information between members of the same species: Sex Smells - Pheromones in Humans
3) Finally, answer these questions to test your understanding:
1. This peptide hormone and neuropeptide has been called the "love hormone" because of its purported role in positive social interactions, but its best understood effects involve increasing uterine contractions during labor and the release of milk during lactation:
- A. melatonin
- B. vasopressin
- C. oxytocin
- D. cortisol
Show Answer
Correct answer: C
Oxytocin is involved with increasing uterine contractions during labor and with the milk let-down reflex, which causes milk to be released during breastfeeding. Some research suggests it is involved with positive social interactions and feelings of trust, empathy, and social bonding. In truth, however, the research in this area is very unclear, and there is no consensus on oxytocin's effects on behavior.
2. Beta-endorphin is a peptide neurotransmitter whose best-understood role involves:
- A. pain inhibition
- B. memory consolidation
- C. fight-or-flight responses
- D. regulating circadian rhythms
Show Answer
Correct answer: A
Beta-endorphin is a peptide neurotransmitter and hormone found in the central and peripheral nervous systems. It is best known for its role in pain inhibition. By binding to opioid receptors, beta-endorphin can elicit natural pain-relieving effects that have been found to be more potent than morphine.
3. The highest level of melatonin secretion from the pineal gland typically occurs at what time?
- A. mid-mornings
- B. in the afternoon
- C. early evening
- D. in the middle of the night
Show Answer
Correct answer: D
Melatonin secretion from the pineal gland occurs in the dark phase of the night. Melatonin secretion is inhibited by exposure to light, and the highest levels of secretion typically occur after midnight. Secretion from the pineal gland during the day is negligible.
4. If someone has high levels of ghrelin in their bloodstream, are they likely to be more hungry or less hungry?
- A. more
- B. less
- C. high levels of leptin are unlikely to have any effect on hunger
Show Answer
Correct answer: A
Ghrelin is produced mainly by the stomach and is released when energy availability is low, such as during a period of fasting. Ghrelin levels typically rise before meals and fall after eating, and thus may play an important role as a short-term driver of hunger and feeding. Ghrelin also exerts many of its effects through receptors in the hypothalamus, where it activates neurons that promote feeding behavior. Thus, higher levels of ghrelin would typically be associated with increased hunger.
5. In obesity, circulating leptin levels tend to be:
- A. higher than normal
- B. lower than normal
- C. the same as in someone who is of normal weight
Show Answer
Correct answer: A
Leptin is a hormone that is known to suppress hunger. Thus, one might expect leptin levels to be lower in obesity, but leptin levels are higher on average in obesity because adipose tissue produces leptin (and there is more adipose tissue in obesity). The brain, however, is often less responsive to leptin in obesity---a phenomenon known as leptin resistance.
