341770_ch_02_058 5/28/02 8:35 AM Page 58 mac117 mac117:1252_AS: 58 Chapter 2 Biological Foundations of Behavior when a gust of wind sent particles of debris hurtling toward your eyeballs. By saving the many milliseconds it would take to send a message to your brain, have it interpreted, and have a command sent back along the spinal highway to mo- tor neurons, spinal reflexes can spell the difference between a minor injury and a serious one. The Brain: Your Crowning Glory Concept 2.16 We begin our tour of the brain at the lowest level, the hindbrain—the part of the The brain is divided into three major brain where the spinal cord enters the skull and widens. We then work our way parts: the hindbrain, the midbrain, and upward, first to the midbrain, which lies above the hindbrain, and then to the the forebrain. forebrain, which lies in the highest part of the brain. Concept Chart 2.3 shows these major brain structures. The Hindbrain The lowest part of the brain, the hindbrain, is also the oldest part in evolutionary terms. The hindbrain includes the medulla, pons, and cere- bellum. These structures control such basic life-support functions as breathing and heart rate. The medulla and pons contain sensory neurons that transmit information from the spinal cord to the forebrain. The medulla is the section of the hindbrain that lies closest to the spinal cord. It forms the marrow, or core, of the brainstem, CONCEPT CHART 2.3 Major Structures of the Human Brain Forebrain Cerebral Cortex Higher mental functions including thinking, language, learning, memory, emotions, and control of voluntary movement Hindbrain Pons Corpus Callosum Conveying sensory Bundle of nerve fibers information from the that connect the two spinal cord to the cerebral hemispheres forebrain; regulation of states of wakefulness and sleep Thalamus Relay station for sorting and integrating sensory Cerebellum input; regulation Regulation of of sleep-wake cycles balance and coordination Limbic System Medulla Emotional processing, motivated Conveying sensory behavior, and learning and information from the memory functioning; consists spinal cord to the of amygdala, hippocampus, Midbrain forebrain; control of parts of the hypothalamus and basic bodily processes Reticular Formation thalamus, and nearby structures including heart rate Regulation of attentional and breathing and processes and states of Spinal certain reflexes Basal Ganglia alertness and arousal cord Regulation of movement and coordination.