Chapter 15 - Section 15.3 - Study Guide - Assess Your Learning Outcomes - Page 575: 8

The autonomic nervous system (ANS) regulates various organs and tissues throughout the body, but not all of them receive dual innervation. In some cases, an organ may be predominantly innervated by either the sympathetic or parasympathetic division of the ANS. However, even in cases where dual innervation is not present, the ANS can still regulate these organs through a variety of mechanisms. Here's how the ANS can regulate organs that do not have dual innervation: 1. **Predominant Sympathetic Innervation**: - Some organs and tissues are primarily innervated by the sympathetic division. For example, most blood vessels, sweat glands, and the adrenal medulla receive sympathetic innervation. - In these cases, the sympathetic division plays a more dominant role in regulating organ function. - The sympathetic division can exert its effects by releasing norepinephrine or epinephrine (from the adrenal medulla) to activate adrenergic receptors on target cells. - Regulation typically involves the "fight or flight" response, such as vasoconstriction to increase blood pressure, sweating to cool the body, and the release of adrenaline for a rapid stress response. 2. **Predominant Parasympathetic Innervation**: - Conversely, some organs, like the salivary glands, receive predominantly parasympathetic innervation. - In these cases, the parasympathetic division plays a more dominant role in regulating organ function. - Parasympathetic stimulation typically occurs during rest and digestion, promoting activities like salivation and digestion. - Parasympathetic fibers release acetylcholine (ACh) to activate muscarinic receptors on target cells. 3. **Monosynaptic Reflexes**: - Some organs and tissues can be regulated through monosynaptic reflexes involving a single synapse between a sensory neuron and a motor neuron. - These reflexes allow for rapid, localized responses. For example, the pupillary reflex involves the autonomic regulation of pupil size in response to changes in light intensity, and it is predominantly mediated by the parasympathetic division. 4. **Peripheral Ganglia**: - In certain cases, peripheral ganglia (collections of nerve cell bodies outside the central nervous system) may be involved in regulating specific organs. - For example, the enteric nervous system, a complex network of neurons in the gastrointestinal tract, can regulate digestive functions without direct input from the central nervous system. 5. **Hormonal Regulation**: - The ANS can also indirectly influence organ function through the release of hormones. - For instance, the sympathetic division can stimulate the adrenal medulla to release epinephrine and norepinephrine into the bloodstream, affecting various organs and tissues throughout the body. In summary, while some organs may not have dual innervation, the ANS can still regulate them through predominant sympathetic or parasympathetic innervation, monosynaptic reflexes, peripheral ganglia, and hormonal regulation. These mechanisms allow the ANS to exert control over a wide range of physiological processes and adapt to various situations, whether they involve stress responses, rest and digestion, or localized reflexes.

The autonomic nervous system (ANS) regulates various organs and tissues throughout the body, but not all of them receive dual innervation. In some cases, an organ may be predominantly innervated by either the sympathetic or parasympathetic division of the ANS. However, even in cases where dual innervation is not present, the ANS can still regulate these organs through a variety of mechanisms. Here's how the ANS can regulate organs that do not have dual innervation: 1. **Predominant Sympathetic Innervation**: - Some organs and tissues are primarily innervated by the sympathetic division. For example, most blood vessels, sweat glands, and the adrenal medulla receive sympathetic innervation. - In these cases, the sympathetic division plays a more dominant role in regulating organ function. - The sympathetic division can exert its effects by releasing norepinephrine or epinephrine (from the adrenal medulla) to activate adrenergic receptors on target cells. - Regulation typically involves the "fight or flight" response, such as vasoconstriction to increase blood pressure, sweating to cool the body, and the release of adrenaline for a rapid stress response. 2. **Predominant Parasympathetic Innervation**: - Conversely, some organs, like the salivary glands, receive predominantly parasympathetic innervation. - In these cases, the parasympathetic division plays a more dominant role in regulating organ function. - Parasympathetic stimulation typically occurs during rest and digestion, promoting activities like salivation and digestion. - Parasympathetic fibers release acetylcholine (ACh) to activate muscarinic receptors on target cells. 3. **Monosynaptic Reflexes**: - Some organs and tissues can be regulated through monosynaptic reflexes involving a single synapse between a sensory neuron and a motor neuron. - These reflexes allow for rapid, localized responses. For example, the pupillary reflex involves the autonomic regulation of pupil size in response to changes in light intensity, and it is predominantly mediated by the parasympathetic division. 4. **Peripheral Ganglia**: - In certain cases, peripheral ganglia (collections of nerve cell bodies outside the central nervous system) may be involved in regulating specific organs. - For example, the enteric nervous system, a complex network of neurons in the gastrointestinal tract, can regulate digestive functions without direct input from the central nervous system. 5. **Hormonal Regulation**: - The ANS can also indirectly influence organ function through the release of hormones. - For instance, the sympathetic division can stimulate the adrenal medulla to release epinephrine and norepinephrine into the bloodstream, affecting various organs and tissues throughout the body. In summary, while some organs may not have dual innervation, the ANS can still regulate them through predominant sympathetic or parasympathetic innervation, monosynaptic reflexes, peripheral ganglia, and hormonal regulation. These mechanisms allow the ANS to exert control over a wide range of physiological processes and adapt to various situations, whether they involve stress responses, rest and digestion, or localized reflexes.