Anatomy & Physiology

Anatomy & Physiology Study Guide In response, the vasomotor center decreases the blood supply to the skin, reducing the rate of heat loss. • The control of circadian rhythms: Daily cycles of activity are linked to the 24-hour day–night cycle and are coordinated by the suprachiasmatic nucleus. This nucleus accomplishes this control through input from the retina of the eye, and its output adjusts the activities of other hypothalamic nuclei, the pineal gland, and the reticular formation. 12.12 The Limbic System The limbic system is a group of tracts and nuclei with various functions. The limbic system includes nuclei and tracts along the border between the cerebrum and diencephalon. This system is a functional grouping rather than an anatomical one. Functions of the limbic system include linking the conscious, intellectual functions of the cerebral cortex with the autonomic functions of the brain stem; establishing emotional states; and facilitating memory storage and retrieval. The sensory cortex, motor cortex, and association areas of the cerebral cortex enable the performance of complex tasks. It is largely the limbic system that initiates the desire to perform these actions. As such, the limbic system is also known as the motivational system. There are several major components of the limbic system. The amygdaloid body , commonly referred to as the amygdala, appears to act as an interface between the limbic system, the cerebrum, and various sensory systems. It plays a role in the “fight or flight” response, the regulation of heart rate, and in linking emotions with specific memories. There are three gyri in the limbic lobe. The cingulate gyrus sits superior to the corpus callosum. The dentate gyrus and the parahippocampal gyrus form the posterior and inferior portions of the limbic lobe. These gyri conceal the hippocampus , a nucleus inferior to the floor of the lateral ventricle. The stimulation of specific regions of the hypothalamus can produce heightened alertness and a generalized excitement or generalized lethargy and sleep. These responses are caused by the stimulation or inhibition of the reticular formation. 12.13 The Electroencephalogram (EEG) The electrical activity of the brain is commonly monitored to assess brain activity. A printed report of the electrical activity of the brain is called an electroencephalogram (EEG). The electrical patterns observed are called brain waves . Alpha waves occur in the brains of healthy, awake adults who are resting with their eyes closed. While asleep, alpha waves disappear, but they also vanish when the individual begins to concentrate on some specific task. During attention to stimuli or tasks, alpha waves are replaced by higher- frequency beta waves.

©2018

Achieve Page 135

of 368