Hierarchical neuronal systems

Catecholamines (dopamine, norepinephrine), opioid peptides, and serotonin act as neurotransmitters in nonspecific or diffuse neuronal systems. Glutamate is the primary excitatory transmitter in hierarchical neuronal systems. The answer is (B). 

Most of the neuronal systems in the CNS can be divided into two broad categories hierarchical systems and nonspecific or diffuse neuronal systems. 

Neuronal systems that contain one of the monoamines—norepinephrine, dopamine, or 5-hydroxytryptamine (serotonin)— provide examples in this category. Certain other pathways emanating from the reticular formation and possibly some peptide-containing pathways also fall into this category. These systems differ in fundamental ways from the hierarchical systems, and the noradrenergic systems serve to illustrate the differences. 

C. Role of CNS Organization The CNS contains two types of neuronal systems hierarchical and diffuse. 

Although there is a great variety of synaptic connections in these hierarchical systems, the fact that a limited number of transmitters are used by these neurons indicates that any major pharmacologic manipulation of this system will have a profound effect on the overall excitability of the CNS. For instance, selectively blocking GABAa receptors with a drug such as... 

Whatever the answer to this question, it seems to me reckless to propose that any part of the brain operates independently of any other. This is especially true of a hierarchical system like the reticular thalamic one that controls forebrain activation so prominently. Of course, the several neuronal participants in this hierarchical system will occasionally become dissociated so that now the cortex, now the thalamus, now the brain stem takes the lead in state component generation, but in order for state control to have any reliability, the flow of control has to be from the bottom up. 

Hierarchical systems Neuronal pathways involved in sensory perception and motor control relay or projection neurons and local circuit neurons glutamate commonly the excitatory transmitter GABA and glycine usually inhibitory transmitters... 

The way that information flows in a feed-forward network classifies them as hierarchical systems. In such systems, members are categorized by levels, from lowest to highest and they can only communicate from low level to higher but not in the opposite direction. It is worth noting that in a MLP network, input layer neurons do not act as real neurons in the sense that they do not apply an activation function, they act as buffers instead and only distribute the signals coming from outside world to the first hidden layer neurons. 

A biomedical control system that utilizes a neurophysiologically-based approach has been developed for use in Functional Neuromuscular Stimulation (FNS) systems [Abbas, 1995 Abbas and Chizeck, 1995). FNS is a rehabilitation engineering technique that uses computer-controlled electrical stimuli to activate paralyzed muscle. The task of a control system is to determine appropriate stimulation levels to generate a given movement or posture. The neural network control system utilizes a block diagram structure that is based on hierarchical models of the locomotor control system. It also utilizes a heterogenous network of neurons, some of which are capable of endogenous oscillation. This network has been shown to provide rapid adaptation of the control system parameters [Abbas and Chizeck, 1995 Abbas and Triolo, 1997] and has been shown to exhibit modulation of reflex responses [Abbas, 1995]. 

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