The first heart sound 'lub' is produced by the closure of: 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:
Bryophytes are non-vascular land plants that include mosses, liverworts, and hornworts. Funaria is a common moss and a classic example of a bryophyte. Spirogyra is a green alga, ferns are pteridophytes (vascular cryptogams), and Pinus is a gymnosperm.

Explanation:
Hemophilia A and B are X-linked recessive, affecting mostly males. Down syndrome is trisomy 21, Turner is XO, Klinefelter is XXY.