The limbic system, autonomic nervous system, and reticular activating system interact in the processing of emotion.
Emotions can be explained in biological and neurological terms. The limbic system, autonomic nervous system, and reticular activating system all interact to assist the body in experiencing and processing emotions.
The limbic system is the area of the brain most heavily implicated in emotion and memory. Its structures include the hypothalamus, thalamus, amygdala, and hippocampus. The hypothalamus plays a role in the activation of the sympathetic nervous system, which is a part of any emotional reaction. The thalamus serves as a sensory relay center; its neurons project signals to both the amygdala and the higher cortical regions for further processing. The amygdala plays a role in processing emotional information and sending that information on to cortical structures. The hippocampus integrates emotional experience with cognition.
The processes of the limbic system control our physical and emotional responses to environmental stimuli. This system categorizes the experience of emotion as a pleasant or unpleasant mental state. Based on this categorization, neurochemicals such as dopamine, noradrenaline, and serotonin increase or decrease, causing the brain’s activity level to fluctuate and resulting in changes in body movement, gestures, and poses.
The amygdala, located in the left and right temporal lobes of the brain. The amygdala is an important brain region in responding to fear. Research suggests that the amygdala is involved in mood and anxiety disorders. Changes in amygdala structure and function have been found in adolescents who either are at risk for or have been diagnosed with a mood or anxiety disorder.
The hippocampus is also involved in emotional processing. As with the amygdala, research has demonstrated that hippocampal structure and function are linked to a variety of mood and anxiety disorders. Individuals suffering from posttraumatic stress disorder ( PTSD ) show marked reductions in volume in several parts of the hippocampus.
The autonomic nervous system (ANS) is part of the peripheral nervous system in humans. It is regulated by the hypothalamus and controls our internal organs and glands, including such processes as pulse, blood pressure, breathing, and arousal in response to emotional circumstances. The ANS is generally thought to be outside of voluntary control.
The ANS can be further subdivided into the sympathetic and parasympathetic nervous systems. When activated, the sympathetic nervous system (SNS) controls the endocrine glands to prepare the body for emergency action. SNS activation causes the adrenal glands to produce epinephrine (also known as adrenaline), which results in the “fight-or-flight” response. The fight-or-flight response involves increased blood flow to the muscles, increased heart rate, and other physiological responses that enable the body to move more quickly and feel less pain in situations perceived to be dangerous.
Conversely, the parasympathetic nervous system (PN) functions when the body is relaxed or at rest; it helps the body store energy for future use. Effects of PN activation include increased stomach activity and decreased blood flow to the muscles.
The parasympathetic and sympathetic divisions of the ANS have complementary functions, and they operate in tandem to maintain the body’s equilibrium. Equilibrium of the body, in which biological conditions (such as body temperature) are maintained at optimal levels, is known as homeostasis.
As well as studying the nervous system and the brain to investigate emotions, we can use physiological markers. For example, when a person is emotional, often there is increased sweating, more respiration and increased blood pressure. Another good example is when a person is upset, they cry, and the body produces tears.
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Key Points
• The limbic system, autonomic nervous system, and reticular activating system all interact in the physiological processing of emotion.
• The limbic system categorizes human emotional experiences as either pleasant or unpleasant mental states. Neurochemicals such as dopamine, noradrenaline, and serotonin are important components of the limbic system.
• The autonomic nervous system, together with the hypothalamus, regulates pulse, blood pressure, breathing, and arousal in response to emotional cues.
• When activated, the sympathetic nervous system prepares the body for emergency actions by controlling the glands of the endocrine system. Conversely, the parasympathetic nervous system functions when the body is relaxed or at rest and helps the body store energy for future use.
• The reticular activating system is believed to first arouse the cortex and then maintain its wakefulness so that sensory information and emotion can be interpreted more effectively.
Key Terms
homeostasis: equilibrium of the body, in which biological conditions (such as body temperature) are maintained at optimal levels
amygdala: a part of the brain located in the medial temporal lobe. It is believed to play a key role in emotion in both animals and humans, particularly in the formation of fear-based memories
hippocampus: a part of the limbic system, located in the temporal lobe of the brain and consisting mainly of grey matter. It plays a role in memory and emotion
emotion: the complex psychophysiological experience of an individual’s state of mind as it is interacting with biochemical (internal) and environmental (external) influences
limbic system: a set of structures in the brain that deal with emotions and memory
thalamus: functions to relay motor and sensory signals to the cerebral cortex
autonomic nervous system: a control system that acts largely unconsciously and regulates bodily functions