Chapter 15 - The Autonomic Nervous System and Visceral Reflexes - Study Guide - Testing Your Comprehension - Page 577: 1

When you're dicing raw onions and the vapor makes your eyes water, it's due to a natural protective response of your body. This response involves both afferent (sensory) and efferent (motor) pathways: 1. Afferent Pathway: - The process begins when you cut the raw onion, releasing certain compounds, including sulfur compounds, into the air. - These compounds can stimulate sensory receptors in the nasal and ocular regions, particularly in the eyes and nose. - Specialized nerve endings, called nociceptors, which are sensitive to irritants, are activated in response to these compounds. 2. Sensory Neurons: - The activated nociceptors send signals as action potentials to the central nervous system (CNS). These signals travel along sensory neurons. - The sensory neurons involved are part of the trigeminal nerve (cranial nerve V), which carries sensory information from the face, including the eyes and nose. 3. Integration in the Central Nervous System: - The sensory signals generated by the activated nociceptors are transmitted to the brain, specifically the brainstem and higher centers in the brain. - In the brain, the sensory information is processed and interpreted. The brain recognizes the irritant nature of the onion vapors and initiates a response to protect the eyes. 4. Efferent Pathway: - Once the brain has processed the sensory information and determined the need for a protective response, it sends signals back down through efferent pathways to the appropriate effectors. - The primary effector in this case is the lacrimal gland, which produces tears. 5. Motor Neurons: - The efferent signals travel along motor neurons that innervate the lacrimal gland. - These motor neurons carry the message to stimulate the gland to secrete tears. 6. Tear Production: - The lacrimal gland responds to the signals by producing a flow of tears. - These tears serve to dilute and wash away the irritant compounds released by the onions, thus protecting the sensitive surface of the eye. In summary, when dicing raw onions, the afferent pathway involves sensory neurons detecting the irritant compounds, which then send signals to the brain. The brain processes this information and sends efferent signals to the lacrimal gland, leading to tear production as a protective response to flush out the irritants and minimize eye discomfort.

When you're dicing raw onions and the vapor makes your eyes water, it's due to a natural protective response of your body. This response involves both afferent (sensory) and efferent (motor) pathways: 1. Afferent Pathway: - The process begins when you cut the raw onion, releasing certain compounds, including sulfur compounds, into the air. - These compounds can stimulate sensory receptors in the nasal and ocular regions, particularly in the eyes and nose. - Specialized nerve endings, called nociceptors, which are sensitive to irritants, are activated in response to these compounds. 2. Sensory Neurons: - The activated nociceptors send signals as action potentials to the central nervous system (CNS). These signals travel along sensory neurons. - The sensory neurons involved are part of the trigeminal nerve (cranial nerve V), which carries sensory information from the face, including the eyes and nose. 3. Integration in the Central Nervous System: - The sensory signals generated by the activated nociceptors are transmitted to the brain, specifically the brainstem and higher centers in the brain. - In the brain, the sensory information is processed and interpreted. The brain recognizes the irritant nature of the onion vapors and initiates a response to protect the eyes. 4. Efferent Pathway: - Once the brain has processed the sensory information and determined the need for a protective response, it sends signals back down through efferent pathways to the appropriate effectors. - The primary effector in this case is the lacrimal gland, which produces tears. 5. Motor Neurons: - The efferent signals travel along motor neurons that innervate the lacrimal gland. - These motor neurons carry the message to stimulate the gland to secrete tears. 6. Tear Production: - The lacrimal gland responds to the signals by producing a flow of tears. - These tears serve to dilute and wash away the irritant compounds released by the onions, thus protecting the sensitive surface of the eye. In summary, when dicing raw onions, the afferent pathway involves sensory neurons detecting the irritant compounds, which then send signals to the brain. The brain processes this information and sends efferent signals to the lacrimal gland, leading to tear production as a protective response to flush out the irritants and minimize eye discomfort.