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Histology of t he Nervous System. Nervous system.

Neurons communicate within the body by transmitting electrochemical signals..

Long transmitting processes called axons (sometimes called a nerve fiber) extend from the cell body to send electrical signals onward to other neurons or effector cells in the body..

(a) A Structure of a motor neuron B Axon.

In the CNS and PNS, specific neuron components group together….

Presynaptic cell synapse with the postsynaptic cell including neuron, muscle, or gland cell..

Neurons can be classified according to both their function and their structure..

apsntu. Cross-sectional schematic of the spinal cord depicting on the right side the origin of interneuron and motor neuron populations defi ned in developmental studies using molecular markers for cell identifi cation. The ventral interneurons (V) are marked as V0–V3 based on the distinct position along the dorso -ventral axis (0 most dorsal, 3 most ventral) of the ventral horn. The left side of the spinal cord depicts the general location of commissural interneurons (CINs) and the Rexed’s laminae..

Structurally , Neurons vary widely in shape, with the greatest structural variation seen in the number and form of the processes extending from the cell body. On this basis, neurons are classed structurally into three groups:.

MULTIPOLAR NEURON TYPE BIPOLAR Structural Class: Neuron Type According to the Number of Processes Extending from the Cell Body Many processes extend from the cell body; all are dendrites except for a Single axon. Two processes extend from the cell body: One iS a fused dendrite, the other iS an axon. Cell body Dendrite UNIPOLAR (PSEUDOUNIPOLAR) One process extends from the cell body and forms central and peripheral processes, which together comprise an axon. Peripheral Cell body Central Cell body Dendrites Axon Axon process Receptive endings process Axon.

Most abundant in body. Major neuron type in the CNS. Structural Variations Dendrites Rare. Found in some special sensory organs (olfactory mucosa, eye, ear). Bipolar Dendrite Cell Cell Axon Axon Cell bcdy Purkinje cell of cerebellum Cell Axon Pyramidal cell Olfactory cell Retinal cell Found mainly in the PNS. Common only in dorsal root ganglia of the spinal cord and sensory ganglia of cranial nerves. Unipolar endings peripheral process (axon) cell Central process (axon) Dorsal ganglion cell.

MULTIPOLAR NEURON TYPE BIPOLAR Functional Class: Neuron Type According to Direction of Impulse Conduction 1. Most multipolar neurons are interneu- rons (association neurons) that conduct impulses within the CNS, integrating sen- sory input or motor output; may be one of a åain of CNS neurons, or a single neu- ron conne:ting sermry and motor neurons. 2. Some multipolar neurons are motor neurons that conduct impulses along the efferent pathways from the CNS to Essentially all bipolar neurons are sensory neurons that are located in some special sense organs. For example, bipolar cells of the retina are involved with the transmission of visual inputs from the eye to the brain (via an intermediate chain of neurons). UNIPOLAR (PSEUDOUNIPOLAR) Most unipolar neurons are sensory neurons that conduct impulses along afferent path- ways to the CNS for interpretation. (These sensory neurons are called primary or first- order sensory neurons.) an effector (muscle/gland). Intemeuron (association neuron) Muscle Eye Bipolar neuron of retina of eye Brain Motor neuron Impulse Sensory neuron Impulse Skin.

Also known as glial cells “Nerve glue”, act as the “helper” cells of the nervous system..