Consider the following statements about the circulatory system: 1. Arteries carry blood away from the heart. 2. Veins have valves to prevent backflow. 3. Capillaries are thick-walled vessels. Which of the above is/are correct? MCQ with Answer and Explanation

Explanation:
In the peripheral nervous system (PNS), Schwann cells wrap around axons to form the myelin sheath, which insulates axons and increases the speed of nerve impulse conduction (saltatory conduction). In the central nervous system (CNS), oligodendrocytes perform this function. Astrocytes support neurons, microglia act as immune cells. Nodes of Ranvier are gaps in the myelin sheath.

Explanation:
The hypothalamus is a small, highly complex region located at the base of the brain, near the pituitary gland. It is the primary link between the nervous and endocrine systems. It controls the pituitary gland (the 'master gland') both neurally (via the posterior pituitary, where it stores and releases ADH and oxytocin) and hormonally (via the anterior pituitary, by secreting releasing and inhibiting hormones that regulate the production of anterior pituitary hormones). Through the pituitary, the hypothalamus regulates a vast array of bodily functions.

Explanation:
The Calvin cycle fixes CO₂ into glucose, which is the primary organic product of photosynthesis. Oxygen is a byproduct of water splitting.