3. The Neuron

• Made up of a cell body (soma, with nucleus and Nissl’s granules), dendrites/dendrons (receive and carry impulses towards the cell body), and an axon (carries impulses away from the cell body).
• The axon is wrapped in a myelin sheath (produced by Schwann cells) that insulates it and speeds up conduction; gaps in the sheath are Nodes of Ranvier.
• Grey matter = cell bodies and dendrites; White matter = myelinated axons (appear white due to fat).

Types of Neurons

• Sensory (afferent) neuron: carries impulses from receptors to the CNS; cell body outside the CNS; long dendron.
• Relay/interneuron: found entirely within the CNS; connects sensory and motor neurons.
• Motor (efferent) neuron: carries impulses from the CNS to effectors; cell body in the CNS.

Structure of a motor neuron