_______ are swellings containing sensory cell bodies.
Here is a schematic drawing of a typical nerve cell. All neurons have a cell body (or SOMA) which contains cellular organelles which are typical of most of the cells in the body, including a nucleus, a nucleolus, lots of rough endoplasmic reticulum, and so on. The peripheral nervous system refers to parts of the nervous system outside the brain and spinal cord. It includes the cranial nerves, spinal nerves and their roots and branches, peripheral nerves, and neuromuscular junctions. The anterior horn cells, although technically part of the central nervous system (CNS), are sometimes discussed with the peripheral nervous system because they are part of the motor unit. The spinal cord is continuous with the caudal portion of the medulla, running from the base of the skull to the body of the first lumbar vertebra. It does not run the full length of the vertebral column in adults. It is made of 31 segments that each contain sensory nerve root and motor nerve root. In contrast to the motor system, the cell bodies of the afferent sensory fibers lie outside the spinal cord, in posterior root ganglia. Nerve fibers outside the spinal cord join to form anterior (ventral) motor roots and posterior (dorsal) sensory root nerve roots. Through the dorsal root, pseudounipolar sensory axons continue, exclusively, from the nerve, to the spinal cord, entering the spinal cord along the cord's dorsolateral surface. The dorsal root ganglion contains the cell bodies of these pseudounipolar sensory neurons. The other nerve root, the ventral root, contains the axons of the large multipolar motor neurons. The cell body is mainly responsible for meeting the metabolic needs of the cell and its position with respect to the axon and dendrites is somewhat variable. The drawing below shows you a type of neuron you will encounter in your study of the peripheral nervous system. It is a dorsal root ganglion cell, or primary sensory neuron. Note that the arrangement of dendrites, cell body and axon is somewhat different than for the neuron drawn above. Note that over part of its length, the sensory axon is actually conducting nerve impulses TOWARD the cell body; over the rest of its length the axon is conducting nerve impulses AWAY from the cell body. Histology of the Dorsal Root Ganglion. Many of the cell bodies of the sensory and motor neurons of the peripheral neves are grouped into nodules or swellings called ganglia. There are two major types of ganglia in the peripheral nervous system: the craniospinal ganglia contain the cell bodies of sensory neurons of cranial and spinal nerves. The autnomic ganglia of the autonomic nervous system contain the cell bodies of the motor neurons of autonomic nerves. Major divisions of the peripheral nervous system. Nerve cells are called neurones. A neurone consists of a cell body (with a nucleus and cytoplasm), dendrites that carry electrical impulses to the cell, and a long axon that carries the impulses away from the cell. Nerve fibers of the PNS are classified according to their involvement in motor or sensory, somatic or visceral pathways. Mixed nerves contain both motor and sensory fibers. Sensory nerves contain mostly sensory fibers; they are less common and include the optic and olfactory nerves. Motor nerves contain motor fibers. The CNS is made of the brain and spinal cord. The cranial nerves, spinal nerves and ganglia make up the PNS. The cranial nerves connect to the brain. The cranial and spinal nerves contain the axons (fibres) of sensory and motor nerve cells. Nerve cells areas are also known as neurons. Neurons are the basic unit of the nervous system. They carry information or impulses as electrical signals from one place to another in the body.
Ganglia