Abnormal peripheral nervous system morphology Decreased size of nerve terminals Nerve terminals are the output region of nerves located presynaptically and (in the case of chemical synapses) containing vesicles of chemical neurotransmitters. Presynaptic nerve terminals normally are larger in diameter than the axon and have the appearance of a bud. This feature can be demonstrated by muscle biopsy. A reduction in the size of nerve terminals. HP:0003443 UMLS:C4025615