Answer:
1. Based on their physical features and conduction properties
2. 80m/s to 120m/s
3. Has both sensory fibers and motor fibers
4. Group B conduct at 3m/s to 15m/s
5. Group C conduct at 0.5m/s to 15m/s
6. They generally have low conduction velocity and are polymodal
Explanation:
Axons were know to have different thickness and this differences were thought to relate to the speed at which the action potential could travel. This hypothesis was proved by Erlanger and Gasser.
D. Man-Made is the answer
Lead.
"Due to insufficient water treatment, lead leached from water pipes into the drinking water, exposing over 100,000 residents to elevated lead levels."
Answer:
Blood Brain Barrier(BBB)
Explanation:
This is a biological interface of special endothelial cells of astrocytes, pericytes , capillaries, neurons and other structures, acting as a physical barrier or gate separating the Central Nervous system from the peripheral blood circulations. Thus it formed a tight junction serving as a physical barrier to selectively regulate the entrance of substances from the cerebral blood flow into the brain, therefore maintaining homeostasis of the brain.
From above any substances absorbed into the blood stream irrespective of the mode of entry are transported through the BBB, and are selectively regulated to enter the brain cells by the BBB's interactions with the blood vessels, hormones etc.
Basically it allows the passage of nutrients, a few drug, hormones and resists certain toxins and pathogens for the brain homeostasis.
