16.2
Functional Divisions of the Nervous System
The nervous system, responsible for sensing, integrating, and responding to various stimuli, is divided into the central nervous system (CNS) and the…
The nervous system senses, integrates, and responds to various stimuli. Based on bodily control, the central nervous system cannot be divided functionally, but the peripheral nervous system, or PNS, has two functional divisions.
The sensory or afferent division consists of nerves that carry external information from sensory receptors to the CNS.
In contrast, the motor or efferent division comprises nerves that relay impulses from the CNS to effectors like muscles and glands.
The motor division is subdivided into the somatic and autonomic systems. The somatic branch controls skeletal muscle movement— both voluntary and specialized involuntary movements called reflexes.
The autonomic branch controls smooth and cardiac muscle and glands, subconsciously regulating physiological processes.
The autonomic branch consists of the sympathetic and parasympathetic divisions, which regulate opposing functions. For instance, the sympathetic division can increase the heart rate while the parasympathetic division slows it down.
The enteric nervous system, a third division of the autonomic branch, consists of a network of neurons that regulates movement and secretions of the gastrointestinal tract.
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Q1: What are the two main functional divisions of the peripheral nervous system?
The peripheral nervous system divides into the sensory (afferent) division and the motor (efferent) division. The sensory division carries external information from sensory receptors to the central nervous system, providing knowledge about somatic and special senses. The motor division relays impulses from the CNS to effectors like muscles and glands, enabling bodily responses.
Q2: How do the somatic and autonomic nervous systems differ in function?
The somatic nervous system controls skeletal muscle movement, including both voluntary actions and specialized involuntary movements called reflexes. The autonomic nervous system controls smooth muscle, cardiac muscle, and glands, subconsciously regulating physiological processes like heart rate and digestion without conscious effort.
Q3: What opposing functions do the sympathetic and parasympathetic divisions perform?
The sympathetic division supports fight-or-flight responses, increasing heart rate and preparing the body for emergency actions. The parasympathetic division manages rest-and-digest activities, slowing heart rate and promoting recovery. These divisions typically have opposing effects, allowing the body to balance activity and relaxation.
Q4: What is the enteric nervous system and what does it control?
The enteric nervous system is a network of over 100 million neurons confined to the gastrointestinal tract wall. It regulates movement and secretions of the GI tract, controlling smooth muscle and gland activity. The enteric nervous system communicates with and is regulated by other autonomic nervous system branches.
Q5: How does the sensory division transmit information to the central nervous system?
The sensory or afferent division consists of nerves that carry external information from sensory receptors throughout the body to the CNS. It transmits somatic senses such as tactile, thermal, pain, and proprioceptive sensations, as well as special senses including smell, taste, vision, hearing, and equilibrium.
Q6: Why is the motor division subdivided into somatic and autonomic branches?
The motor division subdivides because it controls different types of effectors and operates under different levels of conscious control. The somatic branch directs voluntary and reflex movements of skeletal muscles, while the autonomic branch manages involuntary control of smooth muscle, cardiac muscle, and glands through subconscious regulation.
Q7: What are the three subdivisions of the autonomic nervous system?
The autonomic nervous system comprises three subdivisions: the sympathetic division, which supports emergency responses; the parasympathetic division, which promotes rest and recovery; and the enteric nervous system, which specifically regulates gastrointestinal tract function. Together, these divisions maintain homeostasis through coordinated control of internal organs.