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..
There are two mechanisms by which fertilization can take place. 1  The first is external fertilization (the eggs are fertilized outside of the body), and the second is internal fertilization (the eggs are fertilized within the female reproductive tract). While fertilization is necessary for organisms that reproduce sexually, individuals that reproduce asexually do so without the need for fertilization.