For example, if you touch a hot stove, the nerves in your skin shoot a message of pain to your brain. The brain then sends a message back telling the muscles in your hand to pull away. Luckily, this neurological relay race happens in an instant. The human brain is incredibly compact, weighing just 3 pounds. It has many folds and grooves, though.
These give it the added surface area needed for storing the body's important information. It extends from the lower part of the brain down through spine. Along the way, nerves branch out to the entire body.
Both the brain and the spinal cord are protected by bone: the brain by the bones of the skull, and the spinal cord by a set of ring-shaped bones called vertebrae. They're both cushioned by layers of membranes called meninges and a special fluid called cerebrospinal fluid. This fluid helps protect the nerve tissue, keep it healthy, and remove waste products. The forebrain is the largest and most complex part of the brain.
It consists of the cerebrum — the area with all the folds and grooves typically seen in pictures of the brain — as well as some other structures under it.
The cerebrum contains the information that essentially makes us who we are: our intelligence, memory, personality, emotion, speech, and ability to feel and move.
Specific areas of the cerebrum are in charge of processing these different types of information. These are called lobes, and there are four of them: the frontal, parietal, temporal, and occipital lobes.
The cerebrum has right and left halves, called hemispheres. They're connected in the middle by a band of nerve fibers the corpus callosum that lets them communicate.
These halves may look like mirror images of each other, but many scientists believe they have different functions:. So when you're balancing your checkbook, you're using the left side.
When you're listening to music, you're using the right side. It's believed that some people are more "right-brained" or "left-brained" while others are more "whole-brained," meaning they use both halves of their brain to the same degree. The outer layer of the cerebrum is called the cortex also known as "gray matter". Information collected by the five senses comes into the brain to the cortex. Afferent fibers, or nerves that receive information from external stimuli, carry sensory information through pathways that connect the skin and skeletal muscles to the CNS for processing.
The information is then sent back via efferent nerves, or nerves that carry instructions from the CNS, back through the somatic system. These instructions go to neuromuscular junctions—the interfaces between neurons and muscles—for motor output.
The somatic system also provides us with reflexes, which are automatic and do not require input or integration from the brain to perform.
Reflexes can be categorized as either monosynaptic or polysynaptic based on the reflex arc used to perform the function. Monosynaptic reflex arcs, such as the knee-jerk reflex, have only a single synapse between the sensory neuron that receives the information and the motor neuron that responds. Polysynaptic reflex arcs, by contrast, have at least one interneuron between the sensory neuron and the motor neuron. An example of a polysynaptic reflex arc is seen when a person steps on a tack—in response, their body must pull that foot up while simultaneously transferring balance to the other leg.
Privacy Policy. Skip to main content. Biological Foundations of Psychology. Search for:. The Nervous System. Introduction to the Nervous System The nervous system controls bodily function by gathering sensory input, integrating that information internally, and communicating proper motor output.
Learning Objectives Describe the hierarchical structure of the nervous system. The most basic unit of the nervous system is the neuron, which serves as both a sensor and communicator of internal and external stimuli. The nervous system can be broken down into two major parts—the central nervous system and the peripheral nervous system.
The central nervous system, the main data center of the body, includes the brain and spinal cord. The peripheral nervous system includes all of the neurons that sense and communicate data to the central nervous system.
The peripheral nervous system can be further divided into the autonomic system, which regulates involuntary actions, and the somatic system, which controls voluntary actions. Key Terms central nervous system : In vertebrates, the part of the nervous system comprising the brain, brainstem, and spinal cord. Neurons are connected by synapses. The Central Nervous System CNS The central nervous system is made up of the brain and spinal cord, which process sensory input and provide instructions to the body.
Learning Objectives Describe the structural elements of the central nervous system. All content. Course content.
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Histology, microscopy, anatomy and disease Start this free course now. Free course Histology, microscopy, anatomy and disease. As you read earlier in the course, the nervous system is divided into two main parts.
Both parts are illustrated in Figure View larger image. Long description. The roles and structures of neurons Around half of the cells that comprise the nervous system are called neurons. Figure 13 Different types of neuron. The researchers correlated the testosterone levels and the descriptions of each fraternity. They found that the fraternities with the highest average testosterone levels were also more wild and unruly, and one of these fraternities was known across campus for the crudeness of its behaviour.
On the other hand, the fraternities with the lowest average testosterone levels were more well behaved, friendly and pleasant, academically successful, and socially responsible. Banks and Dabbs found that juvenile delinquents and prisoners who had high levels of testosterone also acted more violently, and Tremblay and colleagues found that testosterone was related to toughness and leadership behaviours in adolescent boys.
Although testosterone levels are higher in men than in women, the relationship between testosterone and aggression is not limited to males. Studies have also shown a positive relationship between testosterone and aggression and related behaviours such as competitiveness in women Cashdan, Keep in mind that the observed relationships between testosterone levels and aggressive behaviour that have been found in these studies do not prove that testosterone causes aggression — the relationships are only correlational.
Recent research has also begun to document the role that female sex hormones may play in reactions to others. At this point you can begin to see the important role the hormones play in behaviour. But the hormones we have reviewed in this section represent only a subset of the many influences that hormones have on our behaviours.
In the chapters to come we will consider the important roles that hormones play in many other behaviours, including sleeping, sexual activity, and helping and harming others. Banks, T. Salivary testosterone and cortisol in delinquent and violent urban subculture. Journal of Social Psychology, 1 , 49— Cashdan, E. Hormones and competitive aggression in women. Aggressive Behavior, 29 2 , — Dabbs, J. Testosterone differences among college fraternities: Well-behaved vs. Personality and Individual Differences, 20 2 , — Gladue, B.
Hormonal response to competition in human males. Aggressive Behavior, 15 6 , — Macrae, C. Person perception across the menstrual cycle: Hormonal influences on social-cognitive functioning.
Psychological Science, 13 6 , — Mazur, A.
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