Which hormone regulates the sleep-wake cycle?

Correct Answer: A

Rationale: Melatonin, produced by the pineal gland, is the hormone that regulates the sleep-wake cycle. Its secretion is influenced by light exposure, with levels typically rising in the evening to promote sleep and falling in the morning to encourage wakefulness. Insulin is involved in regulating blood sugar levels, not the sleep-wake cycle. Cortisol plays a role in the body's stress response and circadian rhythm but is not the primary hormone regulating sleep-wake cycles. Thyroxine is a hormone produced by the thyroid gland that regulates metabolism, not the sleep-wake cycle.

Correct Answer: C

Rationale: Veins are the blood vessels that carry deoxygenated blood back to the heart, except for the pulmonary veins which carry oxygenated blood from the lungs. Arteries carry oxygenated blood away from the heart. Capillaries facilitate the exchange of nutrients and gases between the blood and tissues but do not specifically carry blood back to the heart. Lymphatic vessels are part of the lymphatic system responsible for immune function and do not directly carry blood back to the heart. Therefore, the correct answer is veins.

Correct Answer: A

Rationale: The hippocampus is the correct answer. It plays a crucial role in memory formation, particularly in the creation of new memories and their association with learning and emotions. Damage to the hippocampus can result in memory impairments, highlighting its significance in cognitive functions. The amygdala (Choice B) is involved in the processing of emotions, while the cerebellum (Choice C) is primarily associated with motor control and coordination. The medulla oblongata (Choice D) is responsible for vital autonomic functions like breathing and heart rate regulation, not memory formation.

Correct Answer: A

Rationale: The parathyroid gland is not involved in the release of hormones during stress. It is responsible for regulating calcium levels in the blood by secreting parathyroid hormone. During stress, the adrenal cortex, posterior pituitary, and hypothalamus play crucial roles in releasing stress hormones like cortisol, adrenaline, and oxytocin. Therefore, the correct answer is the parathyroid gland, as it is not directly associated with the release of stress-related hormones.

Correct Answer: B

Rationale: The lens of the eye is responsible for focusing light onto the retina. It plays a crucial role in adjusting the focus to allow for clear vision. After the light passes through the lens, it reaches the retina where it is converted into neural signals for the brain to interpret. The cornea is the transparent outer layer of the eye that helps in focusing light, but its main function is to protect the eye. The pupil is the opening in the center of the iris that regulates the amount of light entering the eye. The iris is the colored part of the eye that controls the size of the pupil.

Correct Answer: A

Rationale: The correct answer is the Adrenal gland. The adrenal glands are located on top of the kidneys. They produce hormones such as adrenaline and cortisol, which play essential roles in regulating metabolism, immune response, and stress in the body. The Thyroid gland, Pineal gland, and Pancreas are not located on top of the kidneys. The Thyroid gland is located in the neck, the Pineal gland in the brain, and the Pancreas behind the stomach.

Correct Answer: C

Rationale: Veins are the blood vessels that carry deoxygenated blood from the body's tissues back to the heart. Deoxygenated blood is transported from the body to the heart through veins, while arteries carry oxygenated blood away from the heart. Capillaries facilitate the exchange of nutrients and gases between the blood and tissues. Lymphatic vessels are responsible for returning excess tissue fluid to the bloodstream and do not primarily carry deoxygenated blood.

Correct Answer: C

Rationale: The amygdala, located in the temporal lobe of the brain, is responsible for regulating emotions and memory, particularly those related to fear and pleasure. It plays a crucial role in processing emotional responses, forming emotional memories, and modulating emotional reactions. The cerebrum (Choice A) is responsible for higher brain functions such as thought and action. The cerebellum (Choice B) is mainly involved in coordination and balance. The brainstem (Choice D) controls basic life functions such as breathing and heart rate.

Correct Answer: B

Rationale: The pituitary gland, often referred to as the 'master gland,' is the correct answer. It is responsible for regulating the release of hormones from other endocrine glands in the body. The pituitary gland controls various bodily functions and plays a crucial role in maintaining hormonal balance, making it a central and vital component of the endocrine system. The other options, such as the thyroid gland (A), adrenal gland (C), and pineal gland (D), have important functions in the endocrine system but are not specifically known as the 'master gland.'