Quiz 9 Flynn Effect, Encephalization

3. What is meant by the term "encephalization?" How is it different than the ratio of the brain to the body?

Encephalization is not just brain/body ratio which changes with size. It is a measure of the positive deviation with respect to the average brain/body size trend for mammals. Basically, it is a measure of brain proportion that tries to "correct" for allometric effects.

9. In what ways is the development of the brain analogous to the process of evolution by natural selection?

More nerve cells die within the first two years than during the rest of the brain's lifespan. This overproduction and selective elimination is due to competition as axons compete for a growth factor released by the muscle fiber when it contracts. Then the brain will "adapt" to the body it's in.

8. Neurons are the information carrying cells of the brain. Describe two ways in which neurons are special and are unlike most other cells in the body.

1. Once they are produced, neurons do not divide again, and stay as adult cells rather than regenerating. 2. Neurons' surfaces are highly reactive and polarized and are covered in ion pumps to regulate this.

5. What change of the pattern of brain/body growth causes most primates to be more encephalized than most non-primate mammals? What change of the pattern of brain/body growth causes humans to be more encephalized than other primates?

Primates start out at a smaller body size, but the brains of mammals all stay the same. Compared to brain size, humans are more encephalized. Humans' brains grow for a longer period of time after birth whereas primates' brains pretty much stop growing after birth.

7. What is the difference between a gyrus and a sulcus of the cerebral cortex?

Sulcus is the groove on the surface of the cerebrum while gyrus is the raised ridge.

1. What is the Flynn effect? Why is it a problem for the nature/nurture dichotomy?

The Flynn effect refers to the idea that average IQs around the world seem to get higher with time. The Flynn effect suggests that IQ isn't determined just by genes alone; environment matters.

4. Describe one way to make yourself more encephalized and one way to make yourself less encephalized over the course of a month.

To be more encephalized, one could lose weight/cut off their legs. To be less encephalized, one would gain body weight.

6. The tissues of the brain are traditionally divided into white and gray matter. What is the difference (i.e. what cellular structures distinguish white and gray matter)? Give the name of one white and one gray matter structure.

White matter is the tissue through which messages pass between different areas of gray matter within the nervous system. Gray matter consists of the densely packed neuronal soma where as white matter consists of densely packed myelinated connections. Gray matter sheets are called cortex. The corpus callosum is a white matter structure.