everything uh psychological so every idea every mood every urge is biological uh psychologists working from a biological perspective study the links between biology and behavior so it's important to note that humans are biopsychosocial systems in which biological psychological and social cultural factors interact to influence behavior so remember we talked about this a little bit in chapter one when we talked about the different influences that are present in modern approaches to psychology so back in the 1800s Franz Gaul invented phrenology so phrenology was a popular theory that claimed that bumps on the skull reveal our mental abilities and our character traits so phrenologists would feel a person's skull to identify the shape and the bumps and the size of the bumps on a person's skull and they claimed that this would tell them a lot about the person including things about their personality and their character these were called skull readings so we know now that the bumps on the skull reveal nothing about the brain's underlying functions but Gaul was accurate in supposing that the various brain regions have particular functions and we're going to learn more about this as we progress through the chapter so during the past Century researchers have discovered a lot about biology behavior and mind so what we know is that nerve cells conduct electricity and communicate through chemical messages across tiny gaps that separate neurons we know that specific brain systems serve specific functions and information is integrated to construct a wide range of experiences and that the Adaptive brain is wired by experience meaning that through our experiences the brain can can change foreign the two primary systems that we're going to talk about in chapter three and that direct the activities of the body are the nervous system and the endocrine system we're going to start by talking about the nervous system which is a vast network of nerve cells that work together um so what does the nervous system do so the nervous system receives input from our senses and then it takes the information that it receives it integrates it with past experiences and knowledge that we have and then it guides our actions in response to that input that it receives um and we're going to learn more about the cells of the nervous system the brain and the endocrine system throughout the rest of chapter three