The central nervous system communicates with the rest of the body through the peripheral nervous system. We are conscious of some sensory information coming into the CNS, but we are not conscious of other afferent information used in physiological regulation. The brain develops from the anterior region of the embryonic neural tube. The forebrain gives rise to the cerebrum, which is divided into five lobes. Specific functions such as somatosensation, vision, hearing, motor control, smell, and speech are localized in specific cortical areas. At the center of the cerebrum is the limbic system which contributes to the processing of emotions, inborn responses, and some types of memory. Underneath the cerebrum is the hypothalamus, responsible for many autonomic functions, and the thalamus, which directs ascending information to the cortex. The midbrain and hindbrain constitute the brainstem, within which are located many nuclei that support autonomic functions, including sleep and wakefulness. Evolution of the human brain has resulted in a greatly increased cerebral cortex devoted to integration of information.
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learning outcomes
You should be able to:
Describe and classify the types of afferent information to and efferent information from the nervous system.
Describe the developmental relationships between the major brain regions, starting with the forebrain, midbrain, and hindbrain and ending with structures such as the amygdala, hypothalamus, primary motor cortex, reticular-
Sketch the five lobes of the cerebrum and identify the primary sensory and motor areas.
Characterize the human brain in comparison to other mammals.
Given your understanding of afferent and efferent systems operating in the nervous system, give examples of brain–
Voluntary behavior through a conscious sensory stimulus
Involuntary responses through a conscious sensory stimulus
Involuntary responses through an unconscious stimulus
The conscious sensory (afferent) stimulus of seeing a venomous snake prompts voluntary commands in the CNS to the muscles in the legs (efferent output) to run from the danger.The conscious sensory stimulus of the aroma of freshly baked bread can stimulate the autonomic responses of salivation and increased stomach activity.The unconscious stimulus of a fall in blood pressure can cause an involuntary command to increase heart rate.
In the developmental and lethal disorder anencephaly, the anterior-
Failure of the anterior region of the neural tube to close has the greatest effect on the telencephalon and results in lack of development of the cerebrum.
What is significant about the location of the reading and language areas of the cerebral cortex as shown in Figure 46.4B?
Areas of association cortex involved in reading and language are situated between the visual area in the occipital cortex and the auditory area in the temporal cortex. Reading integrates interpretation of visual images with the auditory patterns of spoken language.
Key Concept 45.3 described the two-
Areas of the body that are shown by the two-
The brain size of humans is significantly above the regression line for brain size as a function of body size in most other mammals. Why is this observation an understatement of the difference in cerebral cortical capacity in humans as compared with other mammals?
The comparison of cortical capacity of humans with that of other mammals cannot be based just on brain size, because the human cortex is highly convoluted, giving the cortex a larger area. A higher percentage of the human cortex is devoted to association functions (association cortex) that increase cortical capacity.
Having briefly described the structure and function of different regions of the nervous system, we will now explore some examples of how information is processed by the neural circuitry in some specific brain regions.