Nervous System - Nerve Cells

Features of nerve cell

Dendrites - short extensions of cytoplasm, receive nerve impulses

Axon - carries impulses away from cell body

Cell body - collects impulses, contains nucleus

Myelin sheath - layer of fatty tissue, insulates axon

Nodes of Ranvier - gaps inbetween axon in myelinated nurons, where action potential travels

Neurons

Basic structural and functional unit of nervous system

Myelin sheath

Grey matter - nerve cell bodies, unmyelinated

White matter - myelinated fibres

Myelin sheath functions

Protects axon from damage, speeds up movement of nerve impulses, acts as an insulator

Myelin sheath formation

In PNS - Schwann cells

In CNS - oligodendrocytes

Wrap plasma membrane around axons to create sheath

Neurilemma

Outermost coil formed from Shwann cells, helps repair injured fibres

Support cells of nervous system

Two main types of cells in nervous tissue:

Nerve cells - transmit electrical signals

Neuroglia - provide support for nerve cells, myelinates axons, removes cell waste and pathogens, produces CSF, regulates nutrient concentration

Types of neurons

Sensory (receptor) neurons - carry messages from receptors in the sense organs/skin to CNS

Motor (effector) neurons - carry messages from CNS to muscles/glands

Interneurons - link sensory and motor neurons, located in CNS

Structural types of neurons

Multipolar neurons - one axon, multiple dendrites (most common)

Bipolar neurons - one axon, one dendrite (occur in eyes, ears and nose)

Psuedounipolar neurons - one axon, separates into two extensions, one connects to dendrites and other ends in axon terminals. Cell body lies to side of main axon