Mrs P S Bhakare NEURON Neuron Structural It

Mrs P. S. Bhakare NEURON

� Neuron – � Structural � It and functional unit of nervous system. is specialized to carry messages from one part of brain to another by electrochemical process. � Electro part occurs in neuron itself. � Chemical part occurs at junction betn two neuron called synapse. � There are 100 billion neurons in human brain of many shapes and size.

Two parts - 1. cell body / soma/ perikaryon 2. processes – dendrites and axon

soma � � An aggregation of soma in CNS- nucleus Outside CNS- ganglion � Nissl bodies / granules - basophilic granules, Made of rough ER’ - -Synthesis of protein(repair), - Neurotransmitter & enzymes -present in dentrites, absent in axon hillock , axon.

Neurofibrillae network in cytoplasm (microfilament , microtubules) � Dendrites – (receptive � Processes of neuron) � receive signal from other neurons and do not produce action potential, but produces graded local potentials

� . � Axon – single long process, (length variable)begins at axon hillock. Ends by dividing into branches with terminal knob. -Myelin sheath produced by Schwann cell encircle axon below initial segment.

� Schwann cells wraps 100 times around axon, and myelin is compacted by protein zero (Po). � At every 1 mm distance there is a gap of 1µm in myelin sheath (nodes of Ranvier) which contain excess Na-K pump. � Myelination conduction) increases speed by 6 times (saltatory

Myelin sheath may be absent in some axons called unmyelinated axons

Types of neuron: 1. Depending of no. poles -

� Types � 1. of neuron: - Depending of no. poles – � Unipolar � Bipolar - present in embryonic stage –retina, cochlear, olfactory mucosa � Multipolar - CNS

2. Depending upon function – Sensory neuron – (afferent nerve cell) - carry sensory impulse from periphery to CNS. Motar neuron – (efferent nerve cell) - carry sensory impulse from CNS to periphery. 3. Depending upon length of axon – Golgi type I – long axon from CNS to periphery Golgi type II – short axon in cerebrum, cerebellum

� Neuroglia � They – (glial cells) are supporting cells present in brain and spinal cord. � They are 10 times more than neurons.

� Neuroglia Macroglia Astrocytes 1. Fibrous 2. protoplasmic Oligodendrocyctes Microglia

fibrous protoplasmic microglia Oligodendrocyctes

Astrocytes- star shaped with many processes. Two types – 1. fibrous – seen in white matter 2. protoplasmic - seen in gray matter Functions : ü Support ü Regulates synaptic activities ü Metabolism of neurotransmitters ü Maintenance of BBB

� Oligodendrocyctes – round or pear shaped ü They have scanty processes. ü Forms myelin sheath in CNS. � Microglia – small gial cells with flattened cell body and short processes. ü They are found more in grey matter. ü They act as phagoctes when nervous system is damaged by disease, trauma.

� SAQ � 1. Neuron � 2. Neuroglia � LAQ � 1. describe structure of neuron with functions and Classify neurons