An Introduction to Brain and Behavior
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to talk about the to the outside,... outside the axon. financial potential of someone who has money in the bank—the person can spend the money at some future time. The resting potential, then, is a store Axon of energy that can be used at a later time. Most of your body’s cells have a resting potential, but it is not identical on every axon. A resting potential A– Cl– Na+ K+ Intracellular can vary from 240 to 290 millivolts on axons of different animal species. Extracellular The exact potential
belong to the Campbell lineage (family line), one Joan is not descended from the other. The two women live in different parts of North America, one in Texas and the other in Ontario, and both their families have been in those locations for many generations. Nevertheless, after comparing family histories, the two Joans discover that they have ancestors in common. The Texas Campbells are descended from Jeeves Campbell, brother of Matthew Campbell, from whom the Ontario Campbells are descended.
live in trees these days. Nevertheless, freeing the arms at the shoulder joint is handy for all sorts of human activities, from traversing monkey bars on the playground to competing in the Olympic hammer toss to raising one’s hand to ask a question in class. Apes are distinguished as well by their intelligence and large brains, traits that humans exemplify. Among the apes, we are most closely related to the chimpanzee, having had a common ancestor between 5 million and 10 million years ago. In
in brain size, which were accompanied by changes in behavior. Brain-size changes were probably driven by many influences. Among the wide array of hypotheses that seek to explain why the modern human brain enlarged so much and so rapidly, we will examine four ideas. The hypothesis detailed in Research Focus 1-3, “Climate and the Evolving Hominid Brain” on page 24 suggests that hominids were subjected to numerous, drastic climate changes that forced them to adapt and led to more complex behavior.
chimpanzee. Brain size is related to body size, and humans are bigger than chimps. But when we factor in the relative sizes of brain and body as measured by the encephalization quotient (EQ), the human brain is nearly three times the size of the brain of a primate of our body size and nearly four times as big as that of a monkey of our body size. This difference is huge. To put it in perspective, the gap in brain size between humans and chimpanzees is larger than the gap between chimpanzees and