Differences Between Senses And Motor Behavior
The nervous system is equipped with special receptors to provide the brain with information about the environment. These receptors convert outside signals such as light, sound, and pressure into electrical impulses. Receptors are specialized for one particular type of signal. For example, receptors in the eye respond to light, but not to sounds. Electrical impulses generated by receptors are relayed to the central nervous system, where a perception of the signal is formed.
It is often said that humans have only five senses: touch, taste, sight, hearing, and smell. However, the inner ear has receptors that provide information related to balance, and joints and muscles have receptors that provide information about body position. Some animals have additional sensory systems or a greater sensitivity to particular information than humans do: fish can detect changes in water pressure; snakes can see infrared light; the platypus can detect electrical currents; bats can hear high-frequency sounds.
The nervous system also monitors sensory signals inside the body. Sometimes we are not aware of such internal sensory signals. For example, information related to body temperature and blood pressure is sent to the brain, but we are often not conscious of such signals. These signals are monitored by the brain and used to maintain a normal internal environment in the body.
A major function of the brain is to control movement, or motor behavior. Incoming sensory information sent to the brain can be processed by the brain and converted into outgoing signals to control muscles and glands. It is the pattern of outgoing signals that is ultimately responsible for an organism’s behavior.
Some movements do not require the brain. These automatic movements, called spinal reflexes, require processing only in the spinal cord. For example, when an area on your knee is lightly tapped, your leg will kick before the message is relayed to your brain. Although the information eventually does get to the brain, it is not required for the kick to occur.
More complex movements, such as talking, throwing a ball, or dancing, involve multiple areas of the brain. These brain areas include those involved with memory, perception, and planning. Neurons in an area of the cerebrum called the primary motor cortex send signals to neurons in the spinal cord to control muscles.
The basal ganglia and cerebellum are two other brain areas important for movement, particularly planned movements and those requiring smooth control.