Brain Anatomy and Function

Brain Anatomy and Function

The brain is a complex and fascinating organ. It is responsible for senses, emotions and feelings, movement and control, language and communication, thinking and memory. Hence, the nervous system is like the body’s personal computer, constantly collecting, sorting and responding to all the information around it. It is responsible for controlling and communicating with all of the body parts; it is the center of mental activity, including thought and memory; and it monitors and responds to the environment, both inside and outside of the body.

For instance, imagine your phone rings. You take it out and see that it’s an unfamiliar number. You’re wary of telemarketers, but you’re also procrastinating doing homework, so you pick up the call anyway. You hear a voice say, ‘hello’; you perceive that the voice is your friend Aaron’s. He explains that he’s calling from a friend’s phone because his is dead, and you make plans to see a movie. Even though you didn’t recognize Aaron’s number, you heard his voice and recognized it as his. Hearing his voice was sensation; recognizing it was perception. Sensation is passively receiving information through sensory inputs, and perception is interpreting this information.

According to the diagram above, in order to receive information from the environment we are equipped with sense organs e.g. eye, ear, nose. Each sense organ is part of a sensory system which receives sensory inputs and transmits sensory information to the brain through a process called transduction, or transforming information from the eyes or ears, for example, into electrical impulses that the brain can understand.

Though each sense works a little differently to do this, psychologists have developed principles to describe overarching ways in which the body deals with sensation and perception. Gustav Fechner, psychologist in the nineteenth century, called the study of how external stimuli affect us psychophysics. He was interested in the point at which we become aware that we’re sensing something. There could be a low volume phone ringtone playing in the background at work, and you’d never notice it if you weren’t paying attention to it; if you were bored and the room were silent, you might hear the same volume of the ringtone playing as soon as it started.

Psychologists talk mainly about two different kinds of threshold for sensation and perception: the absolute threshold and the difference threshold. The absolute threshold, refers to the weakest possible stimulus that a person can still perceive. Since perception at these low levels can be a little unreliable, it’s defined as the lowest intensity at which people perceive the stimulus 50% of the time.

Hence, using millions of sensory receptors in the body, the nervous system constantly gathers sensory information by monitoring the changes in stimuli, that occur both inside and outside of the body. These receptors detect external variations, such as sound, as well as internal variations, like pH, concentrations of carbon dioxide, levels of salt and water, and the positions of your joints and muscles. All these various sensory stimuli are then translated into electrical impulses and sent to the brain for translation and interpretation.

The sensory signals all make their way to the brain and spinal cord. Here they are evaluated, and then either organized or discarded. Some might become physical sensations like pain, touch or hunger; some produce thoughts, and some are committed to memory. For example, if you sense that a car is going too fast behind you, this sensory information allows you to think ”maybe I should slow down and let them pass”. Or, say you view a really great sunset, integrative functions help you turn that visual stimuli into a memory. This continual process of evaluating and organizing the incoming sensory information is referred to as integration.

Using sensory stimuli and integration information, the nervous system reacts with a motor response. For example, if you need to hold your call so that you can pick a different call, the brain or spinal cord sends signals to muscles telling them to contract. The brain may also tell glands to produce hormones.

How much control you have over these actions depends on where these reactions originate (the brain or the spinal cord) and where they end up (such as the muscles in your arm or the muscles in your stomach). The operation of your organs and the release of hormones are never under your conscious control. But the muscles in your arms sometimes are and sometimes aren’t. When your brain suggests that you hold call conversation and pick a different one, your arms muscles are under voluntary and conscious control.

Sometimes, however, the situation is urgent, like when you want to make an emergency call. In that case, there is not enough time for the impulse to travel to the brain and back. Instead, the spinal cord intervenes, quickly sending out a signal that moves the muscles in your hand before you are consciously aware of it. This is known as a reflex.