Neurons and Synaptic Transmission

Neurons are the fundamental units of the nervous system. They are specialised cells that transmit electrical impulses and communicate with one another via chemical signals at junctions called synapses. Understanding neuronal structure, electrical transmission, and synaptic transmission is essential for explaining how information flows through the nervous system and how drugs, neurotransmitters, and mental disorders affect behaviour.

Key Definition: A neuron is a specialised nerve cell that receives, processes, and transmits information through electrical and chemical signals.

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Types of Neurons

There are three main types of neurons in the human nervous system, each with a distinct function:

Neuron Type	Function	Direction of Impulse	Location
Sensory neuron	Carries nerve impulses from sensory receptors to the CNS	From receptors → CNS	PNS (connecting receptors to spinal cord/brain)
Relay neuron (interneuron)	Connects sensory and motor neurons within the CNS	Within the CNS	Brain and spinal cord
Motor neuron	Carries nerve impulses from the CNS to effectors (muscles or glands)	From CNS → effectors	CNS to PNS