Functional Organization of the Central Nervous System
The major function of the nervous system is the transmission, storage, and processing of information. It does this through electrical activity and by the synthesis and release of chemical agents called neurotransmitters. Information is conducted from one region to another through nerve impulses, generated by neuronal cell bodies and conducted by axons and dendrites. Information is transmitted between cells by neurochemical agents that convey the signals from one cell to the next. Information is integrated by the interaction of electrical activity in single cells and in groups of cells. The activity of the central and peripheral nervous systems never depends on the activity of a single neuron or axon but is always mediated by a group of cells or nerve fibers. Information is represented in the nervous system by a change in activity in a group of cells or fibers as they respond to some change in their input.
The nervous system is comprised of levels of hierarchy for sensory and motor processing. It is a computational system with serial (point-to-point information transfer) and parallel (segregated into separate channels for later, higher level analysis or convergence) processing capabilities with local circuits comprised of hundreds of thousands of neurons continuously performing rapid computations. Some functional elements are localized in one place (the hypothalamus) while others are broadly distributed (subdivisions of the cerebral cortex that control hypothalamic output).
The major and functional anatomic subdivisions create a picture of increasing level of complexity. The spinal cord has afferent (ascending) and efferent (descending) nerves and fiber tracts, the brain stem has nuclear groups, cranial nerves and the reticular formation, and the cerebrum has cerebral hemispheres separated into lobes of function and processing. The functional subdivisions of the afferent (sensory) nervous system receive input from the periphery and it's integration precedes higher level processing. The efferent (motor) system transmits output and coordination that translates central processing into decisions and action, the results of which feed forward onto the afferent system.
Neuronal organization is principally the patterns of connections between nerve cells which defines neural circuits and neural systems. Servomechanism (powered input) feedback plays an essential role in learning and motor behavior. Neuronal communication is chemical, electrical and hormonal. The synaptic function (junctional connection) has an excitatory synaptic mechanism, inhibitory synaptic mechanisms, a variety of synaptic organization (spatially and selectively on the neuron) and hormonal mechanisms that modulate neuronal excitability on a long-term basis. The vesicle hypothesis explains that chemical transmission is dependent on neural transmission on axoplasma, that electrical transmission involves gap junctions and are often transmitted bidirectionally. Receptors are the gateway for representing the external world in the brain substrate and control neuronal excitability.
The nervous system has varied receptors that are specialized transducers for vision, hearing, touch, taste and smell. Afferent sensory neurons which bring information from the periphery into the nervous system and ascend to the brain convey information to the brain and spinal cord. Projection neurons interconnect remote regions of the brain with one another. Internuncial cells or interneurons sample the interior milieu and make sensory-motor adjustments that are effected by smooth muscle.
The nervous system is comprised of levels of hierarchy for sensory and motor processing. It is a computational system with serial (point-to-point information transfer) and parallel (segregated into separate channels for later, higher level analysis or convergence) processing capabilities with local circuits comprised of hundreds of thousands of neurons continuously performing rapid computations. Some functional elements are localized in one place (the hypothalamus) while others are broadly distributed (subdivisions of the cerebral cortex that control hypothalamic output).
The major and functional anatomic subdivisions create a picture of increasing level of complexity. The spinal cord has afferent (ascending) and efferent (descending) nerves and fiber tracts, the brain stem has nuclear groups, cranial nerves and the reticular formation, and the cerebrum has cerebral hemispheres separated into lobes of function and processing. The functional subdivisions of the afferent (sensory) nervous system receive input from the periphery and it's integration precedes higher level processing. The efferent (motor) system transmits output and coordination that translates central processing into decisions and action, the results of which feed forward onto the afferent system.
Neuronal organization is principally the patterns of connections between nerve cells which defines neural circuits and neural systems. Servomechanism (powered input) feedback plays an essential role in learning and motor behavior. Neuronal communication is chemical, electrical and hormonal. The synaptic function (junctional connection) has an excitatory synaptic mechanism, inhibitory synaptic mechanisms, a variety of synaptic organization (spatially and selectively on the neuron) and hormonal mechanisms that modulate neuronal excitability on a long-term basis. The vesicle hypothesis explains that chemical transmission is dependent on neural transmission on axoplasma, that electrical transmission involves gap junctions and are often transmitted bidirectionally. Receptors are the gateway for representing the external world in the brain substrate and control neuronal excitability.
The nervous system has varied receptors that are specialized transducers for vision, hearing, touch, taste and smell. Afferent sensory neurons which bring information from the periphery into the nervous system and ascend to the brain convey information to the brain and spinal cord. Projection neurons interconnect remote regions of the brain with one another. Internuncial cells or interneurons sample the interior milieu and make sensory-motor adjustments that are effected by smooth muscle.