The Central Nervous System Consists of the Spinal Cord and the Brain
The Major Functional Systems Are Similarly Organized
Information Is Transformed at Each Synaptic Relay
Neurons at Each Synaptic Relay Are Organized into a Neural Map of the Body
Each Functional System Is Hierarchically Organized
Functional Systems on One Side of the Brain Control the Other Side of the Body
The Cerebral Cortex Is Concerned with Cognition
Subcortical Regions of the Brain Are Functionally Organized into Nuclei
Modulatory Systems in the Brain Influence Motivation, Emotion, and Memory
The Peripheral Nervous System Is Anatomically Distinct from the Central Nervous System
An Overall View
In the earlier chapters of this book we emphasized that modern neuroscience is based importantly on two tenets. First, the brain is organized into functionally specific areas, and second, neurons in different parts of the vertebrate nervous system, indeed in all nervous systems, are quite similar. What distinguishes one functionally distinct brain region from another, and one brain from the next, are the number and types of neurons in each and how they are interconnected through development. The specific patterns of interconnection and the resulting functional organization of neural circuits in distinct brain regions underlie the individuation of behavior.
All behavior, from simple reflex responses to complex mental acts, is the product of signaling between appropriately interconnected neurons. Consider the simple act of hitting a tennis ball (Figure 15–1). Visual information about the motion of the approaching ball is analyzed in the visual system. This information is combined with proprioceptive information about the position of the arms, legs, and trunk to calculate the movement necessary to intercept the ball. Once the swing is initiated, many minor adjustments of the motor program are made based on a steady stream of sensory information about the trajectory of the approaching ball. Finally, this entire act is accessible to consciousness, and thus may elicit memories and emotions. Of course, as the swing is being executed, the brain is also engaged in maintaining the player's heart rate, respiration, and other autonomic functions that are typically outside the awareness of the player.
A simple behavior is mediated by many parts of the brain.
A. A tennis player watching an approaching ball uses the visual cortex to judge the size, direction, and velocity of the ball. The premotor cortex develops a motor program to return the ball. The amygdala acts in conjunction with other brain regions to adjust the heart rate, respiration, and other homeostatic mechanisms and also activates the hypothalamus to motivate the player to hit well.
B. To execute the shot the player must use all of the structures illustrated in part A as well as others. The motor cortex sends signals to the spinal cord that activate and inhibit many muscles ...
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