Peripheral effectors

At the end of this processing sequence, some of the interneurons connect with motor efferent neurons. These motor efferents leave the CNS and stimulate the peripheral effectors. Most of the effectors are muscles of various types smooth,... 

Binding of progesterone to the peripheral effector site has induced very little con-... 

Evidence has been presented for a correlation between the density of mature sympathetic innervation and the concentration of both NGF and mRNA ", although this has not been established for more than a few tissues and does not take into account the presence of sensory neurons (Korsching and Thoenene, 1983 Shelton and Reichardt, 1984 Harper and Davies, 1990). Nevertheless, this finding alone implies a close reciprocal regulation of NGF synthesis and neuronal metabolism by nerve and NGF, respectively. However, no clear evidence for an influence of nerve on NGF synthesis in peripheral effector tissues has been found (see Section 9). 

The effect of surgical interruption of the nerve supply has been examined in several peripheral effector tissues, and the results are summarized below. 

Do neurotransmitters regulate NGF synthesis in peripheral effector tissues ... 

Dopamine receptors Dopamine receptors are a subclass of adrenoceptors but with rather different distribution and function. Dopamine receptors are especially important in the renal and splanchnic vessels and in the brain. Although at least four subtypes exist, the Dj subtype appears to be the most important peripheral effector-cell dopamine receptor. D receptors are found on presynaptic nerve terminals. Dj, D and other types of dopamine receptors also occur in the CNS. 

M-2 In peripheral effector organs such as heart), there is considerable interest in the development of subtype-selective agents. 

Peripheral mAChRs are known to mediate the well-documented actions of ACh at parasympathetically innervated effector tissues (organs) including heart, endocrine and exocrine glands, and smooth muscle tissues [2, 4]. The most prominent peripheral actions mediated by activation of these receptors are reduced heart rate and cardiac contractility, contraction of... 

McColl SR, Hachicha M, Levasseur S, Neote K, Schall TJ. Uncoupling of early signal transduction events from effector function in human peripheral blood neutrophils in response to recombinant macrophage inflammatory proteins-1 alpha and -1 beta. J Immunol 1993 150 4550 1560. 

Fig. 3. DC network dictates peripheral tolerance and immunity. The type and activation of DCs recruited to effector lymph nodes determine the efficacy of immune responses, (a) Steady-state migration, (b) Skin infection model, (c) Liver inflammation model.

Figure 1.1 Functional components of the nervous system. The sensory division of the peripheral nervous system is sensitive to changes in the internal and external environment. The information gathered by this component is transmitted to the CNS where it is processed, integrated, and interpreted. The CNS then determines the appropriate response to this input. This response is carried out by the transmission of nerve impulses in the motor division of the peripheral nervous system to the effector tissues.

Afferent neurons lie predominantly in the PNS (see Figure 6.1). Each has a sensory receptor activated by a particular type of stimulus, a cell body located adjacent to the spinal cord, and an axon. The peripheral axon extends from the receptor to the cell body and the central axon continues from the cell body into the spinal cord. Efferent neurons also lie predominantly in the PNS. In this case, the cell bodies are found in the CNS in the spinal cord or brainstem and the axons extend out into the periphery of the body where they innervate the effector tissues. By way of convergence, the centrally located cell bodies may receive inputs from several different regions of the brain that will influence their activity. 

A reflex is initiated by stimulation of a sensory receptor located at the peripheral ending of an afferent or first-order sensory neuron. This afferent neuron transmits impulses to the spinal cord. Within the gray matter of the spinal cord, the afferent neuron synapses with other neurons. As such, the spinal cord serves as an integrating center for the sensory input. The afferent neuron must ultimately synapse with an efferent or motor neuron. When the afferent neuron synapses directly with the motor neuron, it forms a monosynaptic reflex. An example of this type of reflex is the stretch reflex. When the afferent neuron synapses with an intemeuron that then synapses with the motor neuron, it forms a polysynaptic reflex, e.g., the withdrawal reflex. Most reflexes are polysynaptic. The motor neuron then exits the spinal cord to innervate an effector tissue, which carries out the reflex response. 

---