A space between a synaptic knob and the receptive surface of another cell is called a synaptic .

The space between a synaptic knob and the receptive surface of another cell is called a "synaptic cleft." This gap is crucial in the process of neurotransmission, where chemical signals are transmitted from one neuron to another. When an electrical signal (action potential) reaches the synaptic knob, it triggers the release of neurotransmitters from vesicles into the synaptic cleft. These neurotransmitters then bind to specific receptors on the post-synaptic cell's membrane, leading to a response in that cell, which could be excitatory or inhibitory depending on the type of neurotransmitter and receptor involved. This process plays a vital role in communication between neurons and is fundamental to the functioning of the nervous system, influencing everything from reflexes to complex cognitive processes.