the somatic nervous system carries information to the

Several neuronal components of the PNS and CNS are involved in a reflex arc. Some reflexes are extremely important in the diagnosis and localization of neurologic problems. The effector response mediated by such a circuit is called a reflex response or simply a reflex. The simplest type of circuit is called a “reflex” or reflex arc and involves the interaction of sensory and motor neurons. Neurons do not function in isolation they are organized into specific neuronal circuits that process particular different kinds of information and control particular efferent organs. This system functions according to its own internal laws, largely unconsciously. The autonomic nervous system exerts control over the functions of many organs and brings the fine internal adjustments necessary for the maintenance of the optimal internal environment of the body. The term autonomic comes from auto (meaning self) and nomos (meaning law). The autonomic division innervates smooth muscles, cardiac muscle, and glands. The somatic division controls skeletal muscles and acts mainly under the direction of conscious voluntary control from the brain. The elements of the efferent component of the PNS can be further categorized into a somatic and an autonomic division. Reprinted by permission of John Wiley & Sons, Inc. Monosynaptic reflex arc, consisting of a primary sensory neuron activating a motoneuron by a single synapse. The motorneurons that innervate skeletal muscles are localized within the ventral horns of the spinal cord.įigure 1. The target organs, which respond to the stimuli carried by the efferents, are called effectors ( Fig.

The motor or efferent ( ex meaning from + ferre) component carries information from the CNS to the muscles. The sensory information from the face travels through the specialized cranial nerves. These ganglia are also known as sensory or spinal ganglia and convey information from the body. Sensory nerve fibers are the axons of a group of neurons situated within the dorsal root ganglia (DRG) at the distal end of dorsal roots ( Fig. These receptors are biological transducers, associated with the peripheral ends of afferent axons, which transform different stimuli into action potentials in these axons. We receive sensory information through the sensory endings (receptors) that are scattered throughout the body. The sensory component, also known as the afferent component ( ad meaning to + ferre meaning carry), is responsible for conveying information to the CNS from the body itself and from the environment ( Fig. The PNS has two components, a sensory (afferent) and a motor (efferent) component. The modern view of the organization of the PNS is based on the work of the English physiologist John Newport Langley (1852–1925).

The peripheral nervous system (PNS) connects the CNS to the different tissues and organs of the body. The brain (cerebrum, cerebellum, and brain stem) and spinal cord form the central nervous system (CNS).

Traditionally, the nervous system is divided into central and peripheral components.

The somatic nervous system carries information to the