Nervous Tissues Generally nervous tissues represent the structural

Nervous Tissues

Ø Generally, nervous tissues represent the structural basis of the nervous system. Ø Nervous tissues are responsible for receiving internal and external stimuli and sending appropriate responses.

Nerve Cell (Neuron)

Ø A neuron is the basic anatomical and functional unit of the nervous system that varies in size and shape. Ø A ratio of 90% of it is found in the brain and the remained ratio in the rest of the central and peripheral nervous system. Ø Neurons do not divide or regenerate, and what is destroyed from them is not replaced, just as a person loses them gradually as he ages.

Structure of nervous tissues

Ø Nervous tissues are distinguished into two types of cells: ü Neurons: that receive, transmit and send nerve stimuli. ü Glial cells: that connect neurons to each other, and work to protect, support and provide them with necessary food so as neurons can perform their functions. Glial cells surround neuron and are located either between neurons and each other, between neurons and blood vessels, or between neurons and brain surface.

Types of neurons

Ø 1 - Unipolar: they are cells with a single axon that is branched into two axons, and usually found in the spinal nerve ganglia in the spinal cord. Ø 2 - Bipolar: each have one cell body from which two appendages emerge, one of which is dendrite and the other is the axon. This type is found in retina. Ø 3 - Multipolar: where cell body is polygonal and many dendritic appendages emerge from it, as well as the cell axon. They are the most widespread type, especially in the brain and spinal cord.

Types of neurons

End of Lecture