Squids, octopus and cuttlefish (who all belong to the phylum of molluscs) are among the most intelligent animals in the sea, and definitely the most intelligent marine invertebrates. We should in fact ask ourselves if the human mind is capable of thinking as fast as these creatures do.
Contributed by
Neurons consist of a somatic cell body containing the nucleus with DNA, and several cell organelles in the cytoplasma surrounding the nucleus (see Figure 1). The somatic part has many dendritic ends who receive signals from many other neurons. A long axon runs from the somatic part of the neuron, where the electric nerve signal travels with an astonishing speed of about 360km per hour. This electrical signal finalizes its axonal journey into many synaptic ends, where it manages to trigger synaptic secretions of chemicals (neurotransmitters: e.g. certain hormones like oxytonin) which travel into the intercellular space and reaches specific receptors attached to the surface of adjacent neurons.
In squids, axons carry information to the muscles of a squid’s mantle when it is startled, causing them to contract and jet to safety. It is the axonal part of the neuron in squids which is rather large (considering that typical axons in humans are only a few micrometers in diameter)—up to 1mm in diameter. The squid giant axon is several hundred times larger than the typical human axon. Such neurons are obviously much easier to see in microscopes than the typical smaller neurons. This helps researchers to comprehend how the mind functions.
The mind
The mind is an intriguing part of the body. It is like an abstract work of art, which we have not come to fully comprehend yet. The nervous system is complex and consists of two departments: The CNS—which is the central nervous system—and the PNS, which is the peripheral nervous system. The CNS consists of the brain and spinal cord, while the PNS consists of two kinds of nervous cells: sensory nervous cells and motor nervous cells. The motor nervous cells carry electrical impulses sent from the CNS to organs, muscles and glands.
The motor nervous system is divided into the autonomic nervous system and the somatic nervous system. The autonomic nervous system controls involuntary muscles (smooth and cardiac muscles), which explains why our heart beats even though we are not conscious about it. The autonomic nervous system can be divided into two additional nervous systems, which illustrates the complexity of the nervous system.
The somatic nervous system controls skeletal muscles as well as external sensory organs such as the skin—this nervous system is unlike the autonomic nervous system “conscious” while we control it consciously (with the small exception of reflex reactions).
Cells of the sensory nervous system send information to the CNS from internal organs or from external stimuli. So basically, the CNS, which consists of loads of neurons, is the “masterkey” of the entire nervous system.
When looking closely at these neurons, it is inevitable that the most essential part of a neuron is the axons, because the axons carry the electrical impulses, which allow one part of the nervous system to communicate with another.
We have doctors and specialists examining these axons, and we are all very fascinated by our nervous system, but rarely is it acknowledged that squids actually have much bigger axons, which means that information runs far more rapidly through their nervous system, making their reactions much faster than those of human beings. So, the next time you are diving in the wondrous ocean—know that you will not be able to reach a squid! ■
