Every single life form can detect the presence of the gravity vector. Gravity has asserted itself into this constancy by its presence since life evolved on our Planet Earth. If you want to understand how a gravity accident, like a brain concussion happens, you have to begin to comprehend how Nature first started sensing gravity direction in one the oldest of its creatures, the ciliates, over one billion years old. Our brain sits on the hierarchy of such ancient creatures.
As we gaze skywards into an imaginary city of skyscrapers we see in the scale of our perception the rising definition of buildings anchored against gravity. The soaring spectacle spins overhead into dizzying heights we marvel at the reach of height. Yet if we were to look into life’s smaller cells even into the murky bottom of a puddle at the base of such imaginary skyscrapers we would see the relevance of gravity applying its vector of direction down even at the lowly scale of such minute life forms. The first sensing apparatus evolved around the vector of gravity, all subsequent brain power focused into that sense of where the real down is toward interpreting this direction.
This years Nobel Prize in Medicine concerns the work of discovering the importance of vesicles inside cells. The joint 2013 winners are: James E. Rothman, Randy W. Schekman and Thomas C. Südhof. The citation form the Nobel web site reads as follows, “for their discoveries of machinery regulating vesicle traffic,
a major transport system in our cells.”
” Each cell is a factory that produces and exports molecules. For instance, insulin is manufactured and released into the blood and chemical signals called neurotransmitters are sent from one nerve cell to another. These molecules are transported around the cell in small packages called vesicles. The three Nobel Laureates have discovered the molecular principles that govern how this cargo is delivered to the right place at the right time in the cell.”
“Randy Schekman discovered a set of genes that were required for vesicle traffic. James Rothman unravelled protein machinery that allows vesicles to fuse with their targets to permit transfer of cargo. Thomas Südhof revealed how signals instruct vesicles to release their cargo with precision.”
“Through their discoveries, Rothman, Schekman and Südhof have revealed the exquisitely precise control system for the transport and delivery of cellular cargo. Disturbances in this system have deleterious effects and contribute to conditions such as neurological diseases, diabetes, and immunological disorders.”
Within each cell is a GPS of orientation that permits all this exquisite trafficking to become functional at delivery at the right time at the right place in a gravity coordinated apparatus. But to see all of gravity’s influence it is best to appreciate its detection at the simplest, tiniest aspect, where else but in a shimmering slime puddle at the base of a sky piercing tower. Micro creatures lurk beneath the surface each with vesicles, acting as micro bubbles within cells tempers their delivery motions with the buoyancy path of their progress acting within a gravity field of one, which is our Earth field.
But how does a cell sense gravity? Does it just happen that in seeking to get away from bright light into the tension gradient of oxygen at the bottom of such a puddle what happens to the motion of the cell to discriminate the descent into the favoured oxygen tension level by swimming downward?
A Abundant varieties of shapes on unicellular life are like children’s scribbles, yet they all behave to the hidden vector of a constant gravity presence, every single one of the thousands of protozoa found in our little puddle on the ground.
To better understand gravity effects on puddle dwelling ciliates I will be referring to a paper entitled: The Structure and Function of Muller Vesicles in Loxodid Ciliates by Tom Fenchel and Bland J. Finlay from the Journal of Protozoology, Vol. 33, No. 1, February 1986, 69-76.
The authors employ the term, geotaxis, to describe the sensing of gravity.
“Recently, we have shown experimentally that the ability of these ciliates to orient
themselves in oxygen gradients depends on a true geotaxis. Under anaerobic conditions the ciliates tend to swim upwards, but if the oxygen, tension exceeds about 10% atmospheric saturation, they will swim downwards. Around 5% atmospheric saturation,
vertical drift (and random motility) takes minimum values and the cells therefore congregate in this region. Cells in anoxic water swimming upwards will, if turned 180 degrees, immediately start to tumble and manage to bring their anterior end to point upwards again after about 40 seconds. Conversely, if a cell swimming downwards is turned 180 degrees, it will be able to turn and resume downwards swimming within 20-30 sec.”
“Loxodid ciliates must therefore possess a mechanoreceptor which tells them what is up and what is down. A likely candidate is the Müller vesicle, a peculiar organelle characteristic of loxodid ciliates. Superficial observations with the light microscope
reveal these organelles (numbering one to about 30 according to species) as vacuoles containing a mineral concretion (the Müller body).”
“They are situated on the left side of the cells, close to the dorsal rim. Penard noted that the concretion is attached to the wall of the vacuole via a thin stalk and he suggested that the organelle functions as a statocyst.”
“More recently, a brief note and a more thorough study indicated a rather complex structure of the Muller vesicle, involving an invaginated cilium and other fibrillar structures. The invaginated cilium, the tip of which protrudes to the cell surface, has also been reported in a recent SEM study on Loxodes . Finally, it has been shown that the Muller bodies of Laxodes contain barium and those of Remanella brunnea, strontium; they are likely to consist of the sulfates of these metals.”
Essentially the Müller vesicle is acting like a girl on a swing. But, imagine the entire ceiling moving, the girl hanging on the swing will change direction if the ceiling is the suspended fuselage of a plane making violent turns.
What Nature has designed in the Müller vesicle is a miniature accelerometer to detect a gravity force change by swinging one way or another, the weighted swing essentially reacting to the change in gravity direction.
“Due to the asymmetric attachment of the body to the dorsal wall of the vesicle and due to the limitation in free movement set by the vesicle wall, the Muller body can take only one of the two possible positions for any of the four ways the cells usually orient themselves. If the cells are swimming head down or if they glide horizontally with their ciliated side downwards, the Müller body falls to the anterior right side of the vesicle nearly directly beneath the ciliary tube. If, conversely, the ciliate swims head up or if it glides horizontally on the underside of a surface, the body will be found in the posterior left side of the vesicle. Observations on turning cells show that the shift in position of the body takes place well within one second. During the movement, the stalk does not seem to bend. The total free path of the body is 3-4 microns, leading to a change of roughly 90 degrees in the angle between the stalk and the ciliary tube.”
“The fact that the Müller body takes one position within its vesicle when the cell is either oriented head down or with the ciliated side down and another position when the cell is either oriented with its head up or its ciliated side up is consistent with the observed behavior of Loxodes. If cells are placed in oxygen containing water, they will swim straight downwards. If they change orientation during their descent, they will tumble until the anterior end is directed downwards again. Once at the bottom, however, they will glide horizontally along it without an excessive frequency of tumbling. Therefore this orientation seems as acceptable to them as swimming downwards, given the O2 tension of the environment. In an anoxic environment exactly the opposite is the case; the cells tend either to swim upwards or to glide along the underside of objects.”
“It is a general observation that the presence of modified or unmodified cilia is nearly always a feature of sensory cells or organelles It is now generally believed that the transduction of the (mechanical) sensory input is not due to the cilium itself, which merely acts as a lever, but that it takes place at the base of the cilium. Here the mechanical stress on the cell membrane is believed to change the conductance. leading to a depolarization or a hyperpolarization. ”
” The change in membrane potential is then propagated along the surface of the cell leading to a nervous impulse or to a reversal or an increased frequency of ciliar motion. Our observations are consistent with this. The stalk supporting the Müller body seems rigid during the motion of the body and at the same time it is anchored to the posterior kinetosome by the microtubules. The kinetosome must therefore follow the movements of the slatolith. On the other hand, the ciliary tube is anchored to the wall of the vesicle. Consequently, any movement of the Müller body must lead to a deformation of some structure at the base of the ciliary tube, which then presumably transduces that mechanical signal into an electrical one. A likely candidate for this structure is the surface membrane adjacent to the
ciliated kinetosome, but this is not really known. It seems likely, although entirely conjectural, that all the cilia of the kinety to which the Müller vesicles belong have a role as mechanoreceptors since they are immotile and held like bristles. If this is so, the Müller vesicle represents only a further development of a more primitive mechanoreceptor. The proportionality of Müller vesicle numbers to surface area in different species is consistent with the idea that the signal from the vesicles propagates as a membrane depolarization, but that the signal is dampened as it spreads over the surface. It is an important aspect of loxodid behavior and of its adaptive significance, that the geotaxis is modified by the environment, viz., that the ciliates tend to swim up or down according to the oxygen, tension. This requires that another receptor (presumably for oxygen,) can reverse the response to a given position of the Müller body.”
Please notice the highlighted descriptions of the authors, specifically, like, anchored and surface membrane they hint of the force of stretched tension attachments within these descriptions. What is happening here, what is Nature telling us, revealing in her ancient subtlety of shape design?
Nature is revealing inside a ciliate creature, as if behaving like a miniature submarine that can self sense its motions seeking out the nutrient rich layer at the correct oxygen tension within a defined density of light penetration into the correct zone of life-sustaining opportunity. The shape of this creature can bend to turn, rapidly pivoting into the light shaft of its opportunity by aligning into the gravity vector. Nature is revealing to us the über importance of gravity sensing as the primal orientation signal processing to align the direction of motion of a shape based intelligence system, based on suspended tension/compression shape a la floating Snelson tension membrane inside this tiny creature flitting inside a murky puddle.
What we learn as we try to comprehend a brain concussion is the enormously old, one billion year heritage that sensing gravity within a gravity based accident of deceleration is first sensed via the vestibular system into a shape based sensing apparatus designed under floating tension/compression, which is the city architecture of our massively interactive brain shape. It is following this ancient Müller vesicle trace as it reveals itself in our modern 2013 brain anatomy.
Like a precious code, the ancient signalling is the essence of back tracking into navigating the priority of the logic of the problem of brain concussion. Within this tiny puddle with swimming ciliate loxodes, we learn to appreciate the basics of Nature, how to trace the first sensing motion of gravity when a brain concussion occurs, to address the current question: what sense has the oldest core signaling priority within a hierarchy of signalling status?