I do believe that it is both naturally occurring and caused by human activity. Although science has proven that it is something that naturally progresses with time, humans have sped up the process. Hope this helps:)
Answer:
When a nerve impulse reaches the end of an axon, the axon releases chemicals called neurotransmitters. Neurotransmitters travel across the synapse between the axon and the dendrite of the next neuron.
Explanation:
The binding allows the nerve impulse to travel through the receiving neuron.
.......is secreted into the bloodstream, whereas _____ is secreted into mucus such as gastrointestinal fluid, colostrum, saliva, tears, and sweat:
a. Monomeric IgM; pentameris IgM
b. Monomeric IgA; dimeric IgA
c. Monomeric IgA; dimeric IgM
d. Dimeric IgA; monomeric IgA
Answer:
b. Monomeric IgA; dimeric IgA
Explanation:
IgA is a class of antibodies that are found mainly in body secretions. In sweat, tears, saliva, mucus, breast milk, and gastrointestinal secretions, IgA is secreted as a monomeric antibody. Smaller quantities of this class of antibodies are also present in blood and lymph. However, IgA is present in a dimeric form in the bloodstream. It makes up 10–15% of all antibodies in the blood. The main function of this class of antibodies is to give localized protection of mucous membranes against bacteria and viruses.