Answer:
Neurotransmitters; neuromodulators; facilitation; an increased; an increased; inhibition; a decreased; a decreased.
Explanation:
In Biology, stimulus can be defined as an obvious change in either the chemical or physical structure of an organism' environment (either external or internal). Thus, all living organisms (both animals and plants) respond to changes in their environment and consequently, an appropriate response or reaction is made. Also, stimulus arising from within the organism is known as internal stimulus while those from its environment are known as the external stimulus.
In organisms, the specialized cells that detect stimulus are generally known as sensory receptors while a group of these receptors is referred to as sense organ.
Neuromodulation is the release of chemicals (other than neurotransmitters ) from cells that locally regulate or alter the response of neurons to neurotransmitters. The substances released are called neuromodulators. Neuromodulation generally results in either facilitation or inhibition. When there is greater response from a postsynaptic neuron because of the release of neuromodulators it is facilitation. This may result from either an increased amount of neurotransmitter in the synaptic cleft or an increased number of receptors on postsynaptic neurons. When there is less response from a postsynaptic neuron because of the release of neuromodulators, it is called inhibition. This results from either a decreased amount of neurotransmitter in the synaptic cleft or a decreased number of receptors on postsynaptic neurons.
