Who was the first scientist to view live sperm cells and bacteria under a microscope?
A. Louis Pasteur
B. Robert Hooke
C. Antonie van Leeuwenhoek
D. Robert Koch
Answer: Option C
Solution (By JKExamLibrary)
Antonie van Leeuwenhoek, using his hand-crafted single-lens microscopes, was the first to observe and describe living sperm cells, bacteria, protozoa, and red blood cells in the 1670s. Hooke saw dead cork cells, Pasteur and Koch later advanced microbiology with germ theory and pure culture techniques.
Explanation:
The hypothalamus contains numerous nuclei, each with specific functions. The supraoptic nucleus (SON) and the paraventricular nucleus (PVN) are large neurosecretory nuclei located in the anterior hypothalamus. The supraoptic nucleus primarily synthesizes Antidiuretic Hormone (ADH, or vasopressin), while the paraventricular nucleus primarily synthesizes Oxytocin (though both nuclei produce both hormones in smaller amounts). These hormones are transported down the axons of these neurons and stored in the posterior pituitary for release into the bloodstream.
Explanation:
Adenylyl cyclase converts ATP to cyclic AMP, a second messenger. Guanylyl cyclase makes cGMP, phospholipase C produces IP₃/DAG, PKA is activated by cAMP.
Explanation:
Neurotensin is a 13-amino acid peptide that functions as both a neuromodulator in the central nervous system and a hormone in the gastrointestinal tract. In the gut, it is secreted by the N cells in the ileum in response to fat ingestion. Its primary gastrointestinal functions are to inhibit gastric motility and gastric acid secretion (contributing to the 'ileal brake'), and to stimulate the release of histamine from mast cells and glucagon from the pancreas. It also causes vasodilation in the intestinal mucosa.
No comments yet. Be the first to start the discussion!