Assertion (A): Plants take in carbon dioxide and release oxygen during the day. Reason (R): Photosynthesis produces oxygen as a byproduct. MCQ with Answer and Explanation

Explanation:
Thyroid Stimulating Hormone (TSH), also known as thyrotropin, is a glycoprotein hormone secreted by the thyrotroph cells of the anterior pituitary gland. Its primary and specific target is the thyroid gland. TSH binds to receptors on the thyroid follicular cells, stimulating all aspects of their function: the uptake of iodine, the synthesis of the thyroid hormones thyroxine (T4) and triiodothyronine (T3), and the release of these hormones into the bloodstream. TSH secretion is regulated by Thyrotropin-Releasing Hormone (TRH) from the hypothalamus and by negative feedback from T3 and T4.

Explanation:
The Blood-Brain Barrier (BBB) is formed by tight junctions between endothelial cells in brain capillaries, making it highly selective. It allows the free diffusion of small, lipid-soluble molecules and essential gases. Therefore, oxygen, carbon dioxide, and lipid-soluble substances (like alcohol, nicotine, and some anesthetics) easily cross. Glucose, a water-soluble molecule essential for brain energy, crosses via specific carrier-mediated transport (GLUT1 transporters). Large proteins, peptides, most water-soluble drugs, and pathogens like bacteria and viruses are generally blocked from entering the brain parenchyma.

Explanation:
Pertussis (whooping cough) is a respiratory infection characterized by severe coughing fits. Diphtheria is Corynebacterium, tetanus Clostridium, scarlet fever Streptococcus.