1 Transmission: neurons transmit these signals to pain-processing structures of the spinal cord and brain. 2  Modulation: the signals can be amplified or dampened at various points in the pathway to facilitate or inhibit transmission, thereby enhancing or reducing the sensation of pain.
The sperm usually fertilizes the egg in the Fallopian tubes. Then, the fertilized egg moves down to the uterus where it implants, causing pregnancy. The segment of the Fallopian Tube where fertilization commonly occurs is the ampulla..
External and Internal Fertilization. External fertilization usually occurs in aquatic environments where both eggs and sperm are released into the water. After the sperm reaches the egg, fertilization can then take place. Most external fertilization happens during the process of spawning where one or several females release their eggs and the male(s) release sperm in the same area, at the same time.