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Toxic Responses of the Nervous System
Published in Stephen K. Hall, Joana Chakraborty, Randall J. Ruch, Chemical Exposure and Toxic Responses, 2020
The nervous system is comprised of the brain, the spinal cord, and an extensive network of nerves and sensory organs. The two principal divisions of the nervous system are the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS serves as the control center for the entire system and consists of the brain and spinal cord. The PNS consists of countless nerve processes that connect the CNS with various receptors, muscles, and glands. The PNS may be divided into the afferent, or sensory system, and the efferent, or motor system. The afferent system conveys information from receptors to the CNS, while the efferent system conveys information from the CNS to muscles and glands. The efferent system may be further divided into the somatic nervous system, which conveys information from the CNS to skeletal muscles, and the autonomic nervous system, which conveys information from the CNS to smooth muscle, cardiac muscle, and glands. Finally, the viscera of the body receive nerve fibers from two divisions of the autonomic nervous system known as the sympathetic and parasympathetic nervous systems. In general, fibers of the sympathetic nervous system stimulate organ activity, while fibers from the parasympathetic system decrease or restrict organ activity.
Elements of Bioelectromagnetics
Published in Jitendra Behari, Radio Frequency and Microwave Effects on Biological Tissues, 2019
Natural bioelectric processes are responsible for nerve and muscle function. Externally applied electric currents can excite nerve and muscle cells. The nerve system is concerned with the rapid transfer of information through the body in the form of electrical signals. It is conveniently divided into the central nervous system (CNS) and the peripheral nervous system. The CNS consists of the brain and spinal cord. The peripheral nervous system consists of afferent neurons, which convey information inward to the CNS, and efferent neurons, which convey information from the CNS to the body. The efferent system is subdivided into a somatic nervous system and an autonomic nervous system. The autonomic nervous system consists of neurons that convey impulses to smooth muscle tissue, cardiac muscle tissue, and glands, which are usually considered involuntary, that is, not under conscious control.
Neurophotonics for Peripheral Nerves
Published in Yu Chen, Babak Kateb, Neurophotonics and Brain Mapping, 2017
Ashfaq Ahmed, Yuqiang Bai, Jessica C. Ramella-Roman, Ranu Jung
The sensory system consists of nerve cells with somata located outside the spinal cord in aggregates called dorsal root ganglia (Horch and Dhillon, 2004). These nerve processes are called afferent nerve fibers because they conduct action potentials and, therefore, information from the periphery to the central nervous system. Afferent sensory fibers can be myelinated or unmyelinated, the latter ranging from 2 to 20 μm in diameter, and convey various sensory inputs, mainly mechanical, thermal, and noxious stimuli (Navarro et al., 2005). Myelinated axons are used for tasks (such as control of skeletal muscle contraction or signaling of temporally rapid and brief events) where speed is required or where fine tactile or proprioceptive discriminations are to be made. Unmyelinated fibers are normally associated with control of smooth muscle or signaling diffuse, temporally sluggish events such as pain and temperature. The motor system consists of nerve cells with somata located in the ventral quadrant of the spinal cord (Horch and Dhillon, 2004). These nerve processes are called efferent nerve fibers because they conduct information in terms of action potentials from the central nervous system to the periphery. They can be divided into two types: alpha-motor fibers that innervate the skeletal extrafusal muscle fibers and gamma-motor fibers that innervate the spindle muscle fibers (Navarro et al., 2005).
Emerging memristive neurons for neuromorphic computing and sensing
Published in Science and Technology of Advanced Materials, 2023
Zhiyuan Li, Wei Tang, Beining Zhang, Rui Yang, Xiangshui Miao
Neurons, also known as nerve cells, are living electrochemical systems that are separated internally and externally by a neuronal membrane. In biological neural systems, there are a great variety of neurons with different structures and functions. For example, Figure 1(a) shows that a simple nerve circuity includes three different neurons: sensory neurons, relay neurons and motor neurons. Sensory neurons, also known as afferent neurons, are connected to a sensor (e.g. touch, vision, hearing, smell, etc.); motor neurons, also referred to as efferent neurons, are connected to muscle fibers (govern movement); while relay neurons, also referred to as interneuron, connect various neurons (e.g. sensory and motor neurons) within the brain and spinal cord, and are easy to recognize, due to their short axons. Information related to sensory-cognition-motor is transmitted between these different types of neurons that supervise the conveyance of information related to sensory-cognition-motor.
Baroreflex activation therapy systems: current status and future prospects
Published in Expert Review of Medical Devices, 2019
Gino Seravalle, Raffaella Dell’Oro, Guido Grassi
Arterial baroreceptors are mechano-receptors that are located closed to the bifurcation of the carotid sinus and in the aortic arch (Figure 1). These receptors contains several ion channels responsive to mechanical distortion [15] and an increase in wall strain elicits sodium and calcium ions inflow and an action potential that through afferent sympathetic fiber arrive into the nucleus tractus solitarius [16]. Stimulation or deactivation of arterial baroreceptors may be obtained both physiologically or induced by vasoactive drugs (phenylephrine or nitroprusside) or through the application of positive or negative pressures within a device positioned at the level of the neck [17]. In physiological conditions, the increase in blood pressure is accompanied by a marked deactivation of aortic and carotid baroreceptors. The result is a negative modulation of efferent sympathetic nervous system discharge and an increase in parasympathetic outflow. This induces a reduction in heart rate, an improvement in left ventricular geometry, a vasodilation and an increase in venous capacitance. Conversely, during blood pressure reduction, there is a stimulation of aortic and carotid baroreceptors inducing an increase in heart rate and an enhancement of sympathetic vasoconstriction with as net result an increase in blood pressure, cardiac output, and peripheral vascular resistance. In hypertensive patients, obese subjects, and patients with kidney diseases or heart failure, carotid and aortic baroreceptors fire at higher pressure and the compensatory mechanisms try to minimize the tachycardic and vasoconstriction response due to reflex saturation [18].
Bodies in mind: using peripheral psychophysiology to probe emotional and social processes
Published in Journal of the Royal Society of New Zealand, 2021
Gina M. Grimshaw, Michael C. Philipp
Effective communication between the brain and body is crucial for survival. The central nervous system (brain and spinal cord) extends its reach into the body via the peripheral nervous system. Communication flows in both directions: afferent signals project from the body to the brain, providing important information about its current state, while efferent signals project from the brain to the body, coordinating responses across multiple physiological systems to achieve goals.