Transcript Aromatherapy

The Special Senses
Taste
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We have about 10,000 taste buds on our tongue
and a few others scattered throughout the upper
respiratory system. If you run your finger across
your tongue you will feel a slightly rough surface.
These are the taste buds. Look at this slide
carefully to see the fungiform and vallate buds
Each bud contains up to 100 epithelial cells,
which act as supporting cells, receptor cells and
basal cells
Taste buds
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Supporting cells form the bulk of the taste
bud and these insulate receptor cells (which
are also called gustatory cells) from each
other. Long microvilli called gustatory
hairs project from the tip of each cell
through a taste pore bathed in saliva and
out onto the epithelial surface. The basal
cells act as stem cells to replace those cells
which are destroyed when eating hot food
Tasting
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We have 4 basic tastes and these are sweet, sour, salty and
bitter. Some people have tried to map taste to different
areas of the tongue but it is not accurate
When a chemical from our food is dissolved in saliva it
can diffuse into the taste pore and come into contact with
the gustatory hairs. This creates a neurotransmitter
response, which generates an action potential in
associated nerve fibres. The different taste sensations are
achieved because of the different times it takes to generate
nerve impulses. Nerve fibres then transmit the message to
the brain, as we can see in this slide. Incidentally, chili
peppers taste hot to us because pain receptors in the
mouth are activated. And yes, 80% of taste is smell.
Smell
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This slide is an electron micrograph of a
small section of lavender. You can see the
oil sac in the plant surrounded by thorns.
When a person crushes the leaf they very
quickly can smell the delightful odour of
lavender. But how do we smell things?
The sense of smell in us
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As it turns out we may be able to distinguish
between 10,000 aromas but yet we only have
about 700 genes for smell.
There may be sex and genetic differences in our
capacity to smell not only different odours but the
concentration of different odours. Its interesting
that babies can smell their mother and there is
some evidence that mothers can smell their
babies;
Aromas and memory
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Most aromas can evoke strong memories and the Proust
effect describes the way that a smell can recall a memory.
If you were to place an aroma under the nose of a
blindfolded person then it probably would evoke powerful
memories
Aromas can also influence physiological memory. An
experiment on healthy young males showed that if you
injected them with insulin and simultaneously exposed
them to an aroma then naturally their blood glucose fell.
After 4 days of this if you gave them the aroma only then
their blood glucose also fell! So aromas clearly have
some physiological effects
Aromas and gender
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It has been shown that females have greater
sensitivity to aromas than males. Some recent
research suggests that females choose mates on
the basis of smell. Whilst other research
indicates that females can detect emotions
associated with smell better than males (females
can detect and distinguish tissues that have been
placed under male and female armpits during
scary movies)
Aromas and our senses
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Aromas can assist concentration. Some
Japanese industrialists use the citrus smell
to stimulate workers in the morning and
floral aromas around midday to help
concentration. They use woody aromas in
the afternoon to alleviate tiredness.
However, our sense of smell declines with
age
Olfactory structures
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The organ of smell is composed of millions
of ciliated pseudo stratified columnar
epithelial cells located around a bend
(sniffing improves air flow over these
cells). Cilia are enclosed in mucus and this
captures odour molecules. You can see
these cells in this slide
Olfactory cells
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There are actually 3 types of olfactory epithelia
and these are basal cells, supporting cells and
olfactory sensor cells. So the olfactory epithelia
are really neuroepithelia and these are the only
nerve cells that are known to be regenerated.
Some modern research is looking at the basal
cells as a way of regenerating other nerve cells.
You can see the sensor cells in this slide as small
bulbs amongst the cilia
Sensing aromas
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Air is swept over olfactory receptors in the nose. Odour
molecules bind to receptors cells and are dissolved by
special proteins. These proteins are the result of about
700 genes. Dissolving and binding of the aroma causes
chemical changes in the cells resulting in an electrical
current transferred through axon.
Filaments of the olfactory nerves synapse with mitral
cells. It is not known how the individual nerves transmit
individual signals that differentiates different odour
molecules but it is assumed that the glomeruli contain
some sort of programmed file
The eye
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The eye is certainly a complex structure
and about 70% of all our body receptors
are found in the eye so the brain must be
busy processing a lot of visual information.
Study this slide carefully so that you are
familiar with the terms iris, pupil, sclera
and lacrimal caruncle. This last one
produces a white oily substance during the
night
The eyelids
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I’m sure that you know where your eyelids
are but did you know that they close about
15 times a minute? In stressed people they
close about 40 times a minute and this
“blink rate” test is a good pointer to how
stressed people are. Look carefully at this
slide and note the lacrimal gland and canal.
The lacrimal gland produces tears which
are spread by blinking.
Eye muscles
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Movement of each eyeball is controlled by
6 eye muscles, which you can see in this
slide. You can also see the conjunctiva,
which is a transparent mucus membrane
covering the white of the eye and over the
eyelids. The whole membrane produces
mucus to stop the eye from drying out.
This can become inflamed and infected
resulting in conjunctivitis.
Structure of the eyeball
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Study this slide carefully to ensure that you know
the terms ciliary body, cornea, iris, pupil, lens and
retina. The posterior segment of the eye is filled
with a clear gel called the vitreous humor whilst
the anterior portion is filled with aqueous humor.
This has a composition similar to blood plasma.
Aqueous humor forms and drains continually
through a sinus leading to the venous system. If
the drainage is blocked then pressure will build
leading to glaucoma. Cataracts result from
thickening of the lens
Eye colour
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Eye colour is usually is lighter at birth and
becomes darker as the pigment production
develops over 4 months. The pigment that
gives eye its colour is actually two types of
melanin. We can loose eye colour as we
get older and one eye can have a different
colour because of nerve damage. This slide
is a microscope section of the iris and you
can clearly see pigment deposits.
How do we see?
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This is obviously very complex and we will only
touch on it briefly. Light firstly passes through
the cornea. This is well supplied with nerve
endings and only a slight touch will result in the
eye blinking to protect the rest of the eye. The
coloured iris absorbs light and stops it from
scattering. It’s round central opening called the
pupil allows light to enter the eye. The iris
actually has muscle layers which can expand or
contract the pupil. The lens focuses the light onto
the retina
The retina
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The retina is a multi-layer structure with 3 types
of neurons. The light receptor cells are rods and
cones. Rods are used in dim light and for
peripheral vision whilst cones provide very
accurate and fine colour vision. Both rods and
cones produce an electrical current when light
hits them and this passes to the bipolar cells,
which in turn activates the ganglion nerve cells
and a message is sent to the brain
The Ear
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The mechanism for both hearing and balance is
relatively simple, although the structures are
complex. Fluids are stirred and that stimulates
mechanoreceptors of the ear. Sound vibrations
move fluids to stimulate receptors and movement
of the head disturbs fluids that surround the
balance organs. To achieve this the ear is divided
into outer, middle and inner ear.
The outer ear
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The outer ear consists of auricle and external
canal. The auricle directs sound into the canal,
which is about 2.5cm long. The canal is lined
with hair sebaceous glands and sweat glands,
which produce cerumem or ear wax. It’s job is to
trap foreign bodies
The outer ear (tympanic
membrane)
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Sound waves hit the tympanic membrane, which is thin
connective tissue covered externally by skin and
internally by mucosa. When you look at this slide you
will note that the the eardrum is shaped like a flattened
cone with the apex penetrating the middle ear. The
eardrum transfers sound waves to the middle ear bones
The middle ear
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The Middle air is an air filled cavity. It is bounded laterally by the
eardrum and medially by a bony wall with two openings. These
openings are the superior oval window and the inferior round
window. The round window is closed by the secondary tympanic
membrane. The mastoid antrum is a canal in the posterior tympanic
cavity and this permits communication with mastoid air cells in the
mastoid process. Note the anterior auditory tube (it used to be called
the Eustachian tube. Normally this tube is flat and closed but if you
yawn or swallow then it opens briefly to permit air pressure to
equilibrate with external air pressure. This is essential for eardrum
vibration. If pressures are unequal then the ear drum bulges causing
hearing difficulties
Middle ear bones
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Three bones called ossicles are in the middle ear
(hammer, anvil and stirrup) and these transmits
the vibration of the eardrum to the oval window
which in turn sets the fluids in motion which in
turn excites the hearing receptors
The inner ear (Vestibule)
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The vestibule is the central cavity and its lateral
wall is the oval window. It has 2 sacs (utricle and
saccule). These contain equilibrium receptor
regions called maculae. Each of these ducts has
an enlarged swelling at one end called ampulla
which also houses an equilibrium receptor. These
receptors respond to rotational movements of the
head. The cochlea (snail) is a small bony chamber
about half the size of a split pea. It contains the
spiral organ of Corti which is the receptor for
hearing
How do we hear?
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Sound is a pressure disturbance originating from a vibrating object.
The pressure wave hits the tympanic membrane. It vibrates at the
same frequency. The distance the membrane moves in is proportional
to the sound intensity. The vibration is transferred to the ossicles.
This sets fluid in motion in scala vestibuli (Cochlea) much like a
wave moving back and forward. This makes the basilar membrane
swing in response and the cochlear duct oscillates in time. The spiral
organ of Corti has about 16,000 hearing receptor cells called cochlear
hair cells. Notice that nerve fibres are twisted around these cells and
vibration of the cells causes excitation of the nerve fibres and a sound
message to the brain. Sound direction is worked out by the mid brain
Balance
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Keeping our balance relies on vision, information from stretch receptors in
muscles and tendons as well as the ear. Under normal circumstances
equilibrium sensors in the vestibular apparatus sends signals to the brain that
initiate reflexes. But if the system is damaged then our body can adapt so it
is difficult to say exactly which receptors are responsible for what. But we
do have sensors in the ear that respond to both static and dynamic balance.
The sensory receptors for static equilibrium are macule (spots) in each
saccule and utricle wall. They monitor the position of the head in space.
They respond to straight line acceleration. Each macule is a flat epithelial
patch containing supporting cells and scattered receptor cells called hair cells.
The hair cells have numerous long supporting microvilli and are embedded in
the otolithic membrane which is a jelly like mass studded with tiny stones.
The function of the stones is to add weight and inertia. As we move the hairs
of these cells move and this depolarises the cells causing a wave of electrical
excitation to the brain
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The maculae are horizontal in the utricle and
when the head is upright the hairs are vertical.
They respond to sidewards motion. In the
saccule the macula is nearly vertical and the hairs
are horizontal so these respond to vertical
movement. The cells release neurotransmitters
continuously but any movement causes an
increase or decrease in the impulse generation by
the vestibular nerve endings coiled around their
base
Dynamic equilibrium
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The receptor for this is the cristae ampullaris. This is minute
elevation of in the ampulla of the semicircular canal. The cristae are
excited by head movement. Since the semicircular canal is in 3
dimensions all rotatory movements of the head disturb the cristae.
Each crista is composed of supporting cells and hair cells. The hair
cells project into a gelled mass called a cupula. Nerve fibres encircle
the base of the hair cells. The cristae respond to changes in velocity
of rotating head. Because of its inertia the fluid in the semicircular
canal goes in the opposite direction deforming cristae and sending a
message to the brain. If the body continues to rotate at a constant rate
the fluid comes to rest. If we are blindfolded we cannot tell if we are
moving at a constant speed after a few seconds
Proprioceptors
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Proprioceptors occur in skeletal muscles, tendons, joints,
ligaments and connective tissue coverings of bones and
muscles. They constantly advise the brain of our
movement by monitoring the degree of stretch of the
organs that they occupy. There are several types including
Ruffini’s Corpuscle, Pacinian corpuscle, muscle spindles
and Golgi tendon organs. In this slide you can see a
muscle spindle. Stretching activates the spindle, which
sends signals to the spinal cord and also to motor neurons
that activate the muscle. The brain is informed and the
muscle spindle relaxes until the next stretch
Stretch and deep tendon reflexes
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The brain needs to be kept informed constantly
about the current state of all skeletal muscles and
of course if muscles are to work efficiently then
they must have healthy tone. Muscle spindles
and Golgi tendon organs keep the brain informed
about muscle equilibrium whilst stretch reflexes,
initiated by muscle spindles monitor changes in
muscle length. All this information is crucial to
normal muscle function, movement and posture.
You can visualise this in this slide.