Neurotransmitters

Explanation:

Neurotransmitters are the chemicals which are involved in the transmission of nerve impulses at the synaptic junction.

Hormones chemicals which act as intercellular messengers and are produced in trace amounts.

Cerebrospinal fluid is a clear, colourless fluid which is found in brain and spinal cord and provides shock resistance to the brain.

Lymph is a clear-to-white fluid made of white blood cells, especially lymphocytes, the cells that attack bacteria in the blood.