At the neuromuscular junction,

After the transmission of one impulse from the synapse,it cannot transmit another impulse immediately because one of the following chemicals is active there:

Identify the location and function of the following structures:
$(1)$ Synaptic Knob
$(2)$ Bipolar nerve cell

$GABA$ (Gamma-aminobutyric acid) is a:

Given below are two statements.
Statement $I$ - In chemical synapse,the rate of transmission of impulse is higher in homeotherms than poikilotherms.
Statement $II$ - In chemical synapse,the synaptic cleft has a width of about $3.8 \ nm$.
In the light of the above statements,select the correct option given below:

Synaptic fatigue is due to