Test: Biological Basis of Behavior: Nervous System - 1 - MCAT MCQ

Ghrelin is produced mainly in the stomach and plays a role in regulating appetite and promoting hunger. It increases before meals and decreases after eating. Ghrelin stimulates the release of growth hormone and increases food intake, making it an important hormone in regulating appetite and energy balance.

The hormone that is not released by the anterior pituitary is option A: Estradiol. Estradiol is a form of estrogen, which is primarily produced by the ovaries in females and the testes in males. It is not directly released by the anterior pituitary gland. However, the anterior pituitary gland does secrete follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin, which are involved in various reproductive and physiological processes.

Peptide hormones are composed of amino acids and are typically hydrophilic or water-soluble. They cannot easily cross the cell membrane due to their hydrophilic nature. Therefore, they bind to receptors on the cell surface, triggering a series of intracellular signaling cascades.

On the other hand, steroid hormones are derived from cholesterol and are lipophilic or fat-soluble. Their lipophilic nature allows them to easily cross the cell membrane and enter the target cells. Once inside the cell, steroid hormones bind to intracellular receptors, forming hormone-receptor complexes that directly influence gene expression and protein synthesis.

So, the difference lies in their solubility and their ability to cross the cell membrane, with peptide hormones being lipophobic and unable to pass the membrane, while steroid hormones are lipophilic and can freely enter cells.

Insulin is a hormone released by the pancreas in response to increased blood glucose levels. Its primary function is to regulate glucose metabolism and maintain blood sugar levels within a normal range. However, insulin also plays a role in appetite regulation.

When insulin levels are high, such as after a meal, it signals to the body that there is an abundant supply of energy and nutrients available. This leads to a decrease in appetite or a feeling of satiety. Insulin acts on various regions of the brain, including the hypothalamus, to suppress hunger signals and reduce food intake.

Therefore, high levels of insulin are associated with decreased appetite, as the body perceives that its energy needs have been met and there is no immediate need for further food consumption.

Peptide YY (PYY) is a neurotransmitter that plays a role in regulating appetite and satiety. When PYY is released in the gastrointestinal tract, it signals to the brain that food intake has occurred and promotes feelings of fullness and satiety.

In this experiment, the researcher is injecting peptide YY directly into the paraventricular nucleus (PVN) of the hypothalamus, which is involved in regulating appetite and feeding behavior. By doing so, the researcher is artificially stimulating the satiety pathway in the brain.

Given that peptide YY functions similarly to neuropeptide Y (NPY), which is known to stimulate appetite and food intake, injecting peptide YY into the PVN would likely disrupt the normal satiety signals. As a result, the rat would be unable to stop eating because it would never feel satiated.

Therefore, option C is the correct answer: The rat will be unable to stop eating because it would never feel satiated.

Estrogen is a hormone that plays a crucial role in the menstrual cycle and has various effects on the body, including fluid balance regulation. During certain points in the menstrual cycle, particularly during the premenstrual phase, estrogen levels fluctuate.

High levels of estrogen can lead to fluid retention and bloating in some individuals. This occurs because estrogen promotes sodium and water retention in the body. The increased water retention can cause bloating and feelings of swelling or heaviness.

Therefore, in the case of the 23-year-old female experiencing severe bloating and water retention during her menstrual cycle, it is likely that the fluctuation and high levels of estrogen are causing her symptoms.

The natural variations in John's testosterone levels correspond with the times that he works out with Ariel, which could temporarily increase strength. Testosterone is a hormone that plays a role in muscle development and strength. It is known to fluctuate throughout the day, with higher levels typically observed in the morning.

In this scenario, John's increased strength when working out with Ariel could be attributed to the timing of his workouts coinciding with his natural testosterone peaks. When he works out with Ariel in the morning, his testosterone levels may be at their highest, leading to improved strength performance during those sessions compared to his evening workouts on his own.

It's important to note that this explanation assumes that John's increased strength is solely due to the timing of his workouts and the associated testosterone fluctuations. Other factors, such as motivation, guidance from a trainer, or increased effort during sessions with Ariel, may also contribute to the observed differences in strength.

The greatest ethical concern in this study is the use of a placebo control when effective treatments for diabetes already exist. Using a placebo control in a study when there are known effective treatments raises ethical concerns because it means that participants in the control group may not receive the standard care or treatment that could potentially benefit their health. This creates a situation where participants are exposed to unnecessary risks without the potential for receiving the benefits of existing treatments. Ethical guidelines prioritize the well-being and safety of research participants, and it is generally considered unethical to deny them access to established treatments when available.

It is important to note that ethical considerations may vary depending on the specific context and nature of the research. However, in the given scenario, the use of a placebo control in the presence of effective diabetes treatments raises significant ethical concerns.

Serotonin is not typically released after an orgasm. Endorphins, oxytocin, and prolactin are commonly released during sexual activity and orgasm.

Endorphins are neurotransmitters that act as natural painkillers and can induce feelings of pleasure and euphoria. Oxytocin is often referred to as the "love hormone" and is associated with bonding, trust, and social connection. Prolactin is involved in sexual satisfaction and plays a role in post-orgasmic relaxation.

While serotonin is involved in regulating mood and emotions, it is not specifically released after an orgasm. However, serotonin levels can fluctuate during sexual activity and may contribute to overall feelings of well-being and satisfaction.

Melatonin is the hormone that monitors circadian rhythm in diurnal animals. It is primarily produced by the pineal gland in the brain and is involved in regulating the sleep-wake cycle. Melatonin levels increase in the evening, signaling the body to prepare for sleep, and decrease in the morning, promoting wakefulness.

Dopamine is a neurotransmitter involved in various functions, including reward, motivation, and movement.

Cortisol is a stress hormone that plays a role in regulating metabolism, immune response, and stress responses, but it is not specifically responsible for monitoring circadian rhythm.

Growth hormone is involved in stimulating growth, cell reproduction, and regeneration, but it is not directly involved in regulating circadian rhythm.