NEURO

• PNS AND CNS - main parts of nervous system
• In the central nervous system, the brain and spinal cord are the main centers
• Both the brain and spinal cord are covered with a system of membranes,called meninges, and are suspended in the cerebrospinal fluid
• The central nervous system is composed of large numbers of excitable nerve cells and their processes,called neurons, which are supported by specialized tissue called neuroglia
• The spinal cord is situated within the vertebral canal of the vertebral column
• The spinal cordis surrounded by three meninges the dura mater, the arachnoid mater, and the pia mater
• The spinal cord is roughly cylindrical and begins superiorly at the foramen magnum in the skull
• The spinal cord terminates inferiorly in the lumbar region. Below, the spinal cord tapers off into the conus medullaris,
• The brain is conventionally divided into three major divisions. These are, in ascending order from the spinal cord, the hindbrain, the midbrain, and the forebrain.
• The hindbrain may be subdivided into the medulla oblongata, the pons, and the cerebellum
• The medulla oblongata is conical in shape and connects the pons superiorly to the spinal cord inferiorly
• The pons,or bridge,derives its name from the large number of transverse fibers on its anterior aspect connecting the two cerebellar hemispheres
• The pons is situated on the anterior surface of the cerebellum, inferior to the midbrain and superior to the medulla oblongata
• The cerebellum lies within the posterior cranial fossa of the skull posterior to the pons and the medulla oblongata.
• . The cerebellar cortex is thrown into folds, or folia, separated by closely set transverse fissures
• The surface layer of each cerebellar hemisphere is called the cortex
• Forebrain or known as Prosencphalon
• Hindbrain or Rhombencephalon
• Corpus Callosum - connects left and right cerebral hemispheres
• Diencephalon - located between midbrain and forebrain; includes thalamus, hypothalamus, epithalamus, subthalamic area, pineal gland, and pituitary gland
• The longtidual space between the two heimisphere is called longtidual fissure and protected by falx celebri
• A fan-shaped collection of nerve fibers, termed the corona radiata passes in the white matter to and from the cerebral cortex to the brainstem.
• There are 12 pairs of cranial nerves
• There are 31 pairs of spinal nerves
• The spinal nerves are named according to the regions of the vertebral column with which they are associated: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
• Each spinal nerve is connected to the spinal cord by two roots:the anterior root and the posterior root
• The anterior root consists of bundles of nerve fibers carrying nerve impulses away from the central nervous system. Such nerve fibers are called efferent fibers or motor fibers
• The posterior root consists of bundles of nerve fibers, called afferent fibers, that carry nervous impulses to the central nervous system.
• Because these fibers are concerned with conveying information about sensations of touch,pain, temperature, and vibration, they are called sensory fibers.
• Sensory ganglia are fusiform swellings (Fig. 1-6) situated on the posterior root of each spinal nerve just proximal to the root’s junction with a corresponding anterior root They are referred to as posterior root ganglia
• Neuron is the name given to the nerve cell and all its processes
• Unipolar neurons are those in which the cell body has a single neurite that divides a short distance from the cell body into two branches,
• Bipolar neurons possess an elongated cell body, from each end of which a single neurite emerges
• Multipolar neurons have a number of neurites arising from the cell body
• The plasma membrane forms the continuous external boundary of the cell body and its processes,and in the neuron
• The sudden influx of Na ions followed by the altered polarity produces the so-called action potential, which is approximately 40 mV
• a refractory period is a period of time during which an organ or cell is incapable of repeating a particular action
• The plasma membrane bounding the axon is called the axolemma
• The cytoplasm of the axon is termed the axoplasm.
• It should be noted that all skeletal neuromuscular junctions use only acetylcholine as the transmitter