CHAPTER 11 Functional Organization of Nervous Tissue

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is an extensive network of axons and, in some cases, neuron cellbodies, located outside the CNS.The PNS has two subdivisions: The sensory division, or afferent (“toward”) division, transmits electrical signals, called action potentials, from sensory receptors in the body to theCNS (figure 11.2). The cell bodies of sensory neurons arelocated near the spinal cord in ganglia called dorsal root ganglia(figure 11.3 a ) or in ganglia near the origin of certain cranialnerves. The motor division, or efferent (“away”) division,

transmits action potentials from the CNS to effector organs,such as muscles and glands.The sensory division of the PNS detects stimuli and transmitsinformation in the form of action potentials to the CNS (seefigure 11.2). The CNS processes information, initiates responses,and integrates thoughts, emotions, and other mental processes. Itis much like a computer in its ability to receive input, process andstore information, and generate responses. The motor division of thePNS conducts action potentials from the CNS to muscles and glands.

Sensory input

Motor output

Effectors:Cardiac andsmooth muscle;glands

Effectors:Skeletal muscle

Sympatheticdivision

Parasympatheticdivision

Autonomicnervous system

Somaticnervous system

Sensory division

PNSReceptors, nerves,ganglia, plexuses

Sensory

Motor

Motor division

CNSBrain, spinal cord

FIGURE 11.2 Organization of the Nervous System

The sensory division of the peripheral nervous system (PNS) detects stimuli and conducts action potentials to the central nervous system (CNS). The CNS interpretsincoming action potentials and initiates action potentials that are conducted through the motor division to produce a response. The motor division is divided into thesomatic nervous system and the autonomic nervous system. The enteric nervous system is an independent branch of the PNS and is not illustrated in this figure.