What are the three types of neurons found in the body? Describe their structure and function. Which components make up the central nervous system; which make up the peripheral nervous system?
There are three types of neurons or nerve cells in vertebrates: sensor neurons, effector neurons, and inter neurons. Sensor neurons conduct impulses from peripheral sensory organs to the central nervous system (CNS) which is composed of the brain and spinal chord. Sensor neurons often lack dendrites and, instead, have only one fiber which branches just after leaving the cell body. One branch of the sensor neuron fiber runs to the receptor site while the other branch enters the spinal chord or brain. Structurally and functionally, both branches of the fiber are of the axonal type as they both run for long distances and are sheathed along their lengths by glial cells. Effector neurons or motor neurons conduct impulses from the CNS back to the peripheral nervous system (PNS). The PNS includes the 31 spinal and 10 of the 12 cranial nerve pairs which enervate the whole body. Effector neurons have short dendrites that synapse in the spinal chord or in the brain with the axons of sensor neurons or inter neurons. Effector neurons have long axons which are often myelinated that connect the CNS to effector organs. Inter neurons link sensor neurons to effector neurons within the spinal chord or the brain. Inter neurons most often have short
