article outline
- receptors
senses per se
- smell
- equilibrium
- sight
- lateral line
-
- cranial
nerves
- bibliography
From whence do we
sense? Receptors, receptors, that's the thing. According to Hickman, Roberts
& Larson (Integrated Principles of Zoology, 11th ed, page
736), "Sense organs are specialized receptors designed for detecting
environmental status and change."
Status, for
example, may be the issue for a terrestrial animal on its feet keeping
conscious of its balance in relation to the center of the earth. i.e., a
skateboarder, will know if he is some quite obtuse angle from a vertical normal
to the surface on which he rolls his board.
Even when a fish
does not touch the bottom of the sea or ocean (or dwell on the bottom as is the
habit of selachians such as manta rays), the fish has to know if its ventral
surface indeed faces the center of the earth, and consequently have its dorsal
surface face the sunlight (though it be many dozens of meters distant from
both) by means of its membranous labyrinth in its innner ear, so that it can
make most of its counter-shading so as not to be visually conspicuous to either
predators or prospective prey.
Proprioceptors,
Cutaneous Receptors, and Chemoreceptors (such as the terminal nerve, and the
chemical receptors part of the vomeronasal organ and the olfactory system)
among other receptors are involved in receiving sensory stimuli.
Receptors are
cells which became more complex, active and advanced in development compared to
other cells.
They act as
transducers. Receptor cells convert energy from one form to another. According
to Bemis, Walker etc., receptors are quite sensitive to VERY SLIGHT changes in
energy ensuing from specific environmental signals, such as smell, taste,
sound, pressure or light, but I say that though some signals indeed be
energy-tweak based, other signals have got to do more to particulate presence
of MATTER, (such as taste and smell) rather than energy going around per se (of
course, aromatic particles, going about do disperse due to their KINETIC
energy). The physical aspect indicating the stimulatory character of odor
particles is more their concentration rather than their energy of movement, or
velocity therefrom.
Furthermore,
minute-ness need not be an aspect of what would be sensorily received. Sure
enough, man has devised floods of stimuli which now and then are not exactly
what even are own animal bodies are meant to handle. Communists in India and
other countries from decades back have suffered blinding interrogations whereby
their eyes just couldn't take extreme wattages of bulbs flooded into their
brave eyes. But in the normal world, outside man's perversion, not even thunder
or volcano explosions deafen animals. Only man was stubborn in enough to
expressly institude habitats volcanoside (as had been the case in Mount Thera).
Of course, man drags innocent vertebrates into whatever reckless addresses he
may choose.
The sense of smell
is the most minutae-sensitive of all senses. Even we people can detect vapours
of synthetic cleaning compounds present in very low pressures (like even less
than micro-atmospheres). Sharks can pick up an odor a kilometer away (and then
act accordingly). People only conquer such distance within a moment's space in
communicating by means of the tools we've technologically devised, as the well
as the logos of our information-posting. Felis like man
unequipped (i.e., a leftist or oppositionist thrown into solitary confinement)
and unlike shark is more bound to detect stimuli bodily if stimuli are within
the periphery of about the size of a room.
According to
Wilson-Pauwels (page 16), the olfactory epithelium, tracts, bulbs and pertinent
brain areas comprise the olfactory system.
In squalus, in
heptanchus maculatus and vertebrates in general, olfactory sensations are
carried caudad by the olfactory peduncles/tracts to the forebrain's olfactory
lobes (J. Frank Daniel).
Before even cutting
the shark, we see its two nares. Each is itself divided into two holes by a
superficial flap of skin and a deeper ridge (Bemis, etc., p. 185). An incurrent
naris, rostro-lateral in orientation, takes in water so that such may reach the
olfactory sac. The other hole, the excurrent naris, is medially located.
Although the incurrent and excurrent openings are right beside each other what
allows their water flow to be so antonymical to each other is the valve along
the caudal margin of the excurrent naris--- thin and flaplike only though this
valve be.
TO DO:
REMOVE SKIN AND
OTHER TISSUE AROUND OLFACTORY SAC ON SIDE OF SHARK HEAD!
ALSO CUT AWAY THE
CHONDROCRANIUM’S ANTORBITAL PROCESS AND THE NASAL CAPSULE, FOR THESE CONCEAL
THE OLFACTORY SAC!
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The sense of
sight is the sense which most handles organism-sized sources of stimuli (i.e., bodies of mass,
even other organisms, which reflect light).
Detection and
perception of organism-sized stimuli facilitates the capture of prey, or even
mere vegetative feeding.
For the sense of
vision, animals have photoreceptor cells, which according to Roger M. LeBlanc
(cf. Vision in Fishes: Ali, general editor) use the energy of quanta of
light as transducers, converting such into neural signals.
Vertebrates have
rods and cones, but not every single vertebrate has got cones to receive the
stimuli from light rays. Rods work great in dim lighting. Cones are more
known for picking up color.
Here I have
marked on the sheep brain its optic chiasma, as well as cranial nerve II (the
optic nerve).
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The way vision is
processed UNTIL it gets on its way out of eyeball is quite an electrical
activity. The receptor, the horizontal cell and the bipolar cell are the
neurouns that form the receptive field (RF) in the ganglion cell (Tsuneo
Tomita, "Microelectrode study of the physiology of neurons in the fish
retina" from Ali, Vision of Fishes).
Eyes are composite
bodies of mass normally exposed to a medium which is a fluid mixture (such as
common air or sea water). Different parts the eye has, but those different
parts are different too from the surrounding medium, and thus the cornea and
lens are in a position to refract the light waves which they receive from the
medium. The eyes is a very moist organ, however, so the cornea doesn't really
bend light with an index of refraction so different from water's own value of
1.33.
According to Munz,
"The lens is usually spherical and protrudes through the pupil." Munz
contrasts the way that elasmobranchs (such as Squalus) have a protractor muscle
to pull forward the eye lens very slightly so as to accomodate vision whereas
bony fish have retractor muscles tug the opposite way (Fish Physiology page 3)
For us humans, the
visual pathway (Cranial Nerves: Wilson-Pauwels, Akesson, Stewart,
Spacey) goes from the optic canal to the optic nerve, then optic chiasma to
suprachiasmatic nucleus of the hypothalamus, then to the optic tract, cerebral
peduncle, lateral geniculate body, pretectal area, rimary visaual cortex right
calarine fissure, cut left cortex, and so on.
What are the
primary sources of incoming stimuli?
Electromagnetic
and electrical stimuli are not one and the same thing.
In fact electrical
stimuli are more akin to mechanical stimuli than to electromagnetic stimuli.
For the sense of
equilibrium , the inner ear, especially the otoliths within it, play the key
role; the same otoliths are also needed for perceiving sound (cf. J. Tomas, J.
Geffen, p. 1384, Journal of Fish biology). Calcium carbonate (same stuff
which makes which makes grand limestone formations) normally comprise otoliths.
CaCO3 forms into network solid clusters of aragonite mineral. When
some other mineral is formed from precipitating calcium carbonate, the fish
becomes abnormal in development.
What kind of
receptors do animals have? Animals have chemical receptors such as olfactory
cells for smell and taste buds for taste.
Animals also have
electrical, temperature-sensitive and mechanical receptors.
Tonic receptors
are receptors which are always active.
The felis has sinus hairs
in the form of whiskers , such are sensitive to touch and presssure, Merkel's
disks, Meissner's corpuscles, Pacinian corpuscles and Eimer's organs as well as
Ruffini endings also all are sensitive to touch and pressure, and are found in
many animals, especially terrestrial vertebrates.
But since whiskers
are an advanced forms of sense organ, they are not really needed for the
survival of the cat in the house or on the streets. Or am I mistaken, and do
whiskers pick up a gush of wind so as to notify a cat if a motor vehicle is
charging towards it?
Reference:
The optic and
olfactory nerves have got special sensory (special afferent) aspects to them.
The optic and olfactory nerves are not quite like the other ten cranial nerves
in that they are both rather more of extension of the brain. Some scholars thus
see the structure of the retina as a model for the structure of the brain itself.
Neither cat nor
shark nor any monkey has got the extent of sense of touch that man does. Still,
the cat has a much more tactile sense than sharks, reptiles or most animals.
Domesticated Dogs and cats have highly advanced tactile sense: say, when
compared to reptiles.
Felis has the most
advanced tactile sense of animals which aren't people.
Nonethless, so
clear it is that such advanced tactile sense has the end only of the domestic cat
being an extensively touched animal rather than an extensively touch-performing
animal. Moreover, when a cat touches something, it more of pushes it, rather
than to touch the thing per se so as to examine texture. Non-human mammals tend
to have paws and hooves (ungulates constituting the latter case) rather than
our palms, which are so advanced, we may even use them to relieve stress
ensuing from too much word-processing by squeezing on a yuppie rubber stress
ball.
People are the
animals best equipped in using touch cognitively (even blind people). Although
the tactile sense is a general sensory modality cutaneously distributed up and
down the mammalian body, we people have noted via homunculus schematics that
our face, feet-soles and hands are all the more sensitive to being touched than
our, say, the pot belly, or a couple of inches up and away from the smalls of
our backs.
The reason why
face and extremities are so sensitive to touch is due to innervation. The face
has, of course, the facial nerve, and even the trigeminal nerve.
No animal touches
the way that man does; monkeys arent' to be compeared to people when it comes
to touching. I guess that we people have the hand of God, being made in His
image.
The non-human
tactile sense is, like the human tactile sense, a general sensory rather a
special sensory one.
A domesticated cat
can roll a ball of yarn (they've been doing that for at least the latter part
of the previous century. But cats have only been able to do that thanks to
people . Cats may "touch" food, their containers and garbage forms,
but such objects for cats to touch and avail of were constructs of man.
To be cat means
not be just an animal, but to be by default associated with the habitats of
people. Even a cat on the streets has its existence confined wthin the streets
OF PEOPLE. Felis humani. Felis homini.
Middle-class man
and cat both act with tact. Proletarian man and dog both act with resolve and
brazen efficiency, at best. It is more with the "What up, dog?" kind
of man that I identify with.
Tactile sense is a
physiological matter. The sense of tact is a disposition of behavior summed up
as "Why do?" or "Why bother go there?" A qui vadis? rather than a quo
vadis? mentality (the latter being the dog's, or that of the unwrinkled
achiever).
hence, later down
the previous century, middle-class people hanging out in socializing bars
proudly y-cleped the males among them as "cats."
The shark however
is not so welcome in the human home in alive form in the way that cat is. A
shark TOUCHES nothing. in that it doesn't really make a habit of touching
anything for the sake of touching. The shark doesn't go "Ooh! I want to
touch this!" I even doubt if the shark will keep its rostrum in gentle
contact with, say some panel of a sunken ship---- for like a third of a minute
or some other ponderous amount of time.
It is terrestrial
vertebrates such as koalas, kitties and monkeys which are more bound to fiddle
with objects: in sum, bipeds or at least quadruped vertebrates given enough to
an upright position.
Man is the man
animals that loves to touch., No animal touches the way man does. Man's hands
are not just sensorially enhanced. Well man's hands are so sensorially enhanced
that touch thereabouts
Arabs and Greeks
from centuries ago have studied the sense organs. There was Khazali. Khazali
did lavish diagrams and treatises on the eye, although due to religio-legal
constraints, he and other Arabs did not have much of a hand in dissecting
organs themselves, but Khazali, Avicenna any numerous other Arabs zealously
translated and studies Greek science and philosophical texts, to an extent
unbecoming of Extension School students, moreso the vocational flock of the
Health Careers Program.
According to Olav
Sand, lateral line organs are epidermal sense organs. According to Homeberger
and Walker, the lateral line and electroreceptive organs of sharks, besides
numerous aquatic amniotes and larval amphibians are innervated by SPECIAL
somatic sensory nerves. The lateral line organs are no longer construed as
being innervated by nerves component to the standard among dozen vagus,
glossopharynegeal and facial nerves, but are rather appreciated as being
innervated by six lateral line nerves, which are in their own right recognized
as separate and distinct cranial nerves. After all, they come from not the
exact same neurogenic placodes, and they end up not in the brain nuclei
becoming of any of the dozen pan-vertebral cranial nerves.
The six lateral
line nerves no longer seen as mere derivative of the pan-vertebral cranial
dozen may be dichotomized into preotic and postotic groups.
The cochlea is
efferently innervated (H. Spoendlin).
How are the senses
related to the cranial nerves?
The senses have
got to do with the cranial nerves, but not all cranial nerves are involved with
the senses. Shakrs perhaps typically have ten pairs of cranial nerves, if we go
by Kavita juneja's nerve count for the other shark known as Scoliodon (Recent Trends
in chordates, volume 2, new delhi) CN 0-II have sensory functional components.
The trochlear nerve and the oculomotor nerve both control the eye, and so have
a somatic motor functional component, although the oculomotor has got more
control of the eyeball's movement than does the trochlear nerve. The trigeminal
nerve has at least three branches (opthalmic , maxillary and mandibular) and
these all have general cutaneous sensory componenets.
Special somatic
sensory fibers do comprise the statoacoustic nerve (XIII), which has part of it
come from the ampullae of the anterior vertical and lateral semicrcular ducts
of the inner ear.
The
glossopharyngeal nerve, identified with the third visceral arch and the first
of five definitive gill pouches, is a dorsal root nerve. We see it crossing the
floor of the otic capsule posterior to the inner ear's sacculus. When doing
dissections, we must take care not to confuse the glossopharyngeal nerve with
the statoacoustic nerve, the caudal branch of which is ventrally passed through
by CN IX.
The vagus nerve
(X) is a dorsal root nerve, and is associated with the posteriormost gill
arches. Reference:
Homeberger, Walker
The superficial
orgin of many a cranila nerce is the lateral wall of the myelenbcephalon (which
is the part of the rhombencephalon or hindbrain even more posteripor than the
metenchephaol)
The cranial nerves
pass through holes in the neurochranium of the chondrocchandrium of the
dogfish. The holes are called foramina.
According to
Lazier, the terminal and olfactory nerves both pass through the olfactory
foramen. The optic, oculomototr, trochlear, abducens, auditory/acoustic and
glossopharyngeal nerves pass through pretty muych eponymous foramen. The facial
nerve (VII) passes through the orbital fissure.
According to
Lazier, "the [dogfish] organs of special sense consist of olfactory
organs, the eyes and the acousticolateral system." What comes to mind
Today we will discuss a few aspects of vertebrate sensory systems.
We will focus on
cat and shark.
The squalus is the
spiny dogfish because it has spines on its dorsal fins, as opposed to the
mustelus or smooth dogfish. The squalus acanthias, according to R. Mcneill
Alexander, does not lay its eggs, but keeps embryos in its uterus for almost
two years until such offspring may go about the water themselves. (p. 120, The
Chordates).
In page 122 of R.
Mcneill Alexander's The Chordates (Cambridge University press) we see
the same diagram as we do see in our Bemis, Liem textbook, that is the dogfish
(Sclyliorhinus, rather than our own squalus per se) was experimented with, as
to its electroception.
Dogs have been
known (before the days of constant feeding of for dogs onluy processed dog
food) to be able to bury their bones in the backyard under rthe dirt. Well, the
dogfish Scyliorhinus has been known to dig up for food under the sand at the
bottom of a body water. Aquatic animals produce action potentials; potentials
are potential differences where there is a shift in energy per unit charge
going from one place to another.
Cat and shark are
animals famous for their sensory systems. But The cat (Felis) has indeed a more
advanced sensory system. The cat is more cognitive than the shark. So advanced
is the cat's sensory system to that of the First we study the olfactory.
There's the olfactory bulb up front. Then we follow caudad the olfactory tract.
then we study optic.
The MORE ADVANCED
A SENSORY SYSTEM IS, the more suppressible are the involved organism's impulses
to responsive action. Sense eventually becomes a thing in itself. As our
Liem-Bemis-Walker-Grande text shows, the sharks electroception can get so
crude, that it can be fooled to attack an electrode instead of morsels of food.
The domestic cat felis on the other hand has so advanced a sensory system (even
in relation to its jungle counterparts) Thus the immune system is quite
complementary to the sensory system. The immune system responds (especially in
the case of us people) often without conspicuous announcements in store for the
sensory system. What's the use of sensing without responding?
The more developed
an animal's sensory system is, the LESS USEFUL need be it, for it itself
fulfills the gratification of cognition. To sense something, and not be moved by
it, represents an advancement in development.
Biological
advancement SHOVES ASIDE the compulsion of expression--- whether it be regards
to sense-response or gene presence.
Why viruses
continue to hit this late stage of Earthly life is an inevitable manifestation
of the protracted insurgence of the abiotic against people and their cows----
expression is in the manifesto of viruses, and we people in our late mode of
civilization have lunged into a chronic disposition of non-expression.
The more useful
some sensory phenomenon is, the more we may suspect it be crude or primitive.
The more advanced
a property is, the more SEVERED it may be made from its original conception.
Thus an advanced form of Coca-Cola need only have Coke at its banner name, need
neither caffeine, nor sugars infused into it, AND NEED NOT EVEN KEEP A
SEMBLANCE of the original taste, once Lysol-ic lemon goes into the new product.
We will start with
the shark (squalus acanthias, which we have right here in our SC 4th floor
labs). Squali may also be procured from Nebraska Scientific. The squalus
acanthias is an elasmobranch, a selachian. It is a shark not given into growing
so much as three feet long.
What do we mean by
sensory? Sensory system allows for reception of stimuli. There's reception of
stimuli from the external environment: exteroception. There's consciousness of
internal conditions: interoception
One form of
exteroception is hearing. To hear the animal has got to have ears. Hearing is
different for felis and homo than it is for squalus and other chondrichthyans
besides teleosts. Sound is sound, which is a longitudinal propagated wave,
causing alternating compressions and rarefactions of matter as medium. But
felis and squalus receive sound by different media (we people have got radio).
Sound is louder and water, although air allows for more enriching subtle
variations in sound modulation, which make the cat's meow so adorable. Air is
the medium best suited for the propagation of animal voice. Sure dolphins can
make sounds, and other aquatic vertebrates such as whales can use echolocation,
but the contours of sound have enhanced possibilities of quality in the fluid
medium for sound that is air.
Hearing for felis
and homo (quote Bemis Walker p. 415, 2001) is the detection of airborne pressure waves.
Electroreception
is more becoming of aquatic rather than terrestrial vertebrates. Aquatic
vertebrates may both detect and GENERATE electric fields. On land, it is man
that is the vertebrate that generates electric fields, but not with his body
alone, but with his implements and technology. For some small glee, people may
rub their combs vigorously and see how the static charge they produce causes
hair to rise from its natural draping placement will rise due to an F = qE
greater than the F = mg due to hair's inertia and gravity's force per unit mass
on the surface of our Earth.
Let's talk about
photoreception. Metazoans need to detect CHANGES in light. Animals receiving
light have cells geared for photorecpetion. Sharks, unlike cats or people,
never developed tear glands, since the eyes of the shark qare not bound to dry
up. The squalus has only got immovable upper and lower eyelids, although some
sharks do have a nictitating membrane. May we compare the ears of our cat
specimens with the lateral lines of our sharks? The sensory system deals with
both the external environment a Sensory Squalus
Let's check out
the ampullae of Lorenzini, the openings of which are pores on the snout through
which jellylike material may be squeezed right out of. The ampullary organ has
a receptor opening. The organ is an invagination beneath the skin surface at
the end of which are found receptor cells. Past the bottom of receptor cells, a
lateralis nerve wires up.
The Squalus, like
fishes and larval amphibians, has a lateral line system. The cat does not. The
motor and sensory fibers REMAIN separate in Squali & other elassmobanchs
(Smeets 1983 page 23) Liem The forebrain is the prosencephalon, which branches
into the telencephalon and the diencephalon. The Olfactory and optic senses are
both prosencephalic, but the olfactory is telencephalic whereas the optic is
diencephalic. To study the sensory system of All animals have sensory systems,
but what advances do vertebrate All organisms respond to the environment,
sensing is a level advanced above mere response. To sense means to detect We've
got the olfactory sac, then the olfactory bulb. What olfactory things are we
looking for?
According to
Biemis etc. we people cannot sense SMALL changes in electric fileds in the way
that aquatic vertebrates sych as Squalus can. Of corse, humans are the only
animals to subject each other to GREAT currents of electricity, or om a more
productive tone, grand mangnitudes of Voltage (i.e. Tesla
Does a shark even
care what it's food tastes like? Should it bite into something its tongue may
find odd, would it spit out the food? Is the cat conspicuously
taste-selective?.... considering that cats rummage through garbage anyways. We know
pigs eat anything, even filth. But what about dogs? We know cows go crazy when
people incompetently feed them feeds which are derivative from cow flesh
itself, but that goes to show that the cow cannot discrimnate taste enough so
as top prevent itself from swallowing stuff that might turn it into a mad cow.
It's people, even prepubescents not yet sexually mature, who can get so picky
with taste so as to reject whole classes of food. What is the purpose of the
sense of taste, then, for non-humans?
The sense of taste
must be then quite an advanced thing, especially if it entails tasting not just
AGAINST poisons or toxins, The sense of taste of humans is so advanced that the
anti-toxin taste buds at the base of our tongue have been relegated so
posteriorly, whereas the anterior two thirds innervated by one of the cranial
nerves is all for the pleasure of taste. Pleasure is an advanced sensation,
multi-faceted, which humans and domesticated cats may indulge in.
The nose of the
shark has got two nares. Each one has got two sub-
According to R.
Mcneill Alexander, dogfish, like other sharks, have heterocercal tails:
"The posterior end of the vertebral column turns upwards and extends into
the dorsal lobe of the fin (pp. 100-1, Chordates, 1975)."
Shark eyelids
don't move (and hence are like the residents of hell from Jean Paul Sartre's
drama Huis clos). Well, real people, even dead ones do get to close their
eyelids, although it's still true that "L'enfer, c'est les autres [hommes]!"
One of the first
things we may examine is squalus is its upper and lower eyelids. Notice how
simple and few are the elements (not even four things are out there when we
view what's there laterally. It's not as complicated as in a terrestrial
vertebrate such as a rabbit or a cat, where there would be tear glands or
Harderian glands. Actually, many sharks do have nictitatng membranes (Fish
Physiology, Hoar, volume 5) Sharks can also move their eyeballs, as six
innervated muscles fo support our squalus eyeball. although the squalus might
not remarkable y exhibit retinomotor skills. We don;'t do any vivisection for
Bio E100, but others who have done so have noted that they could shut off the
dogfish's electric sense by the cutting the cranial nerves innervating the
ampullae of Lorenzini. The ampullae of Lorenzine is one of the first thigbs we
see on the surface of our shark.
The mission of
this lab project is to rehash familiar resources on shark anatomy study into a
format which takes advantage of current digital camera photography.
So many sensory
mechanisms vertebrates and other chordates and have that we won't get to see a
lot of them today in our lab.
Squalus has
lateral line and neuromasts associated with it, as do lampreys, hagfish,
selachians and teleosts (although lampreys and hagfishes have their lateral
line neuromasts stick out from their integument, wheras selcahinas and teleosts
have neuromasts both on their integumentary surface and inside sunken canals)
(Alexander, 1975, page 121).
We've got sensory
features, even entire sensory organs not present in cat or shark
Snakes, for
example, limbless tetrapods they are, have pit organ cells which detect EM
radiation of longer wavelength than the red we people see.
What kinds of
eneteroception need we note of? Accoridng to Bemis, internal chemoreceptors
continuous;ly monitor some facets of what goes beneath the integument of the
vertebrate organism itself.
Questions
- What is the
major sensory nerve of the face?
Questions
- What are
that nerve's three major divisions?
-
-
-
-
-
Answers
- trigeminal
nerve
The trigeminal (V)
nerve's 3 divs are
- ophthalmic
(V1
-
- maxillary (V2
-
- mandibular
(V3
-
-
-
-
-
Davison's manual
was for mammals, with special reference to cats. So Davison's statements about
sensory system should be seen as relevant to the felis rather than the squalus
of our lab. Davison tells us that Sensory nerves' endings everywhere throughout
the mammalian skin (limbs, urogenital portals, as well as the integument framed
around mammalian sight and smell organs)
class list
references
bibliography
- Sir R.
Mcneill Alexander, The Chordates, Cambridge University Press,
1975
- Ali, M.A., Vision
of Fishes
- Hoar, Fish
Physiology
- Bemis,
Walker, Grande, Liem
- J. Frank
Daniel, The Elasmobranch Fishes
- E.L.
Lazier, Anatomy of the Dogfish, Stanford University OPress, 1940, 1947
- Cranial
Nerves: clinical Wilson-Pauwels, Akesson, Stewart, Spacey
- Homeberger,
Walker
- ?
- ?
- ?