Lecture-1 Neurophysiology Dr. Noor Jawad2021
The nervous system is the part of an animal's body that coordinates its actions and transmits signals to and from different parts of its body. In vertebrate species it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS).
Nervous system
The CNS contains the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body.
Nerves that transmit signals from the brain are called motor or efferent nerves, while those nerves that transmit information from the body to the CNS are called sensory or afferent. Most nerves serve both functions and are called mixed nerves
The PNS is divided into a) somatic and b) autonomic nervous system, and c) the enteric nervous system. Somatic nerves mediate voluntary movement..
The autonomic nervous system is further subdivided into the sympathetic and the parasympathetic nervous systems. Both autonomic and enteric nervous systems function involuntarily. Nerves that exit from the cranium are called cranial nerves while those exiting from the spinal cord are called spinal nerves
Physiological anatomy of cerebral cortex
The functional part of the cerebral cortex is a thin layer of neurons covering the surface of all the convolutions of the cerebrum. This layer is only 2 to 5 millimeters thick, with a total area of about one quarter of a square meter. Most of the neurons are of three types: (1) granular (also called stellate), (2) fusiform, and (3) pyramidal, the last named for their characteristic pyramidal shape.
The granular neurons generally have short axons and, therefore, function mainly as interneurons that transmit neural signals only short distances within the cortex. Some are excitatory, releasing mainly the excitatory neurotransmitter glutamate, whereas others are inhibitory and release mainly the inhibitory neurotransmitter gamma-aminobutyric acid (GABA).
The pyramidal and fusiform cells give rise to almost all the output fibers from the cortex. The pyramidal cells, which are larger and more numerous than the fusiform cells, are the source of the long, large nerve fibers that go all the way to the spinal cord.
