topic 11: special senses

Question 1

what are the five special senses

Answer 1

-smell
-hearing
-sight
-taste
-balance

Question 2

structure of taste buds

Answer 2

taste buds are the organs responsible for taste
they are chemoreceptors consist of taste cells surrounded by supporting cells.
projecting from the upper surface of each taste bud are hair like processes

facial nerves: carry taste information from the taste buds from the front part of the tongue to the brain
glossopharyngeal nerve: carries taste buds from the taste buds on the back part of the tongue to the brain

Question 3

and explain how the sense of taste is created.

Answer 3

chemicals enter the taste buds and touch the hair like structures, activating the taste cells. cells send signal to the brain to create sense of taste. nerve carrying the information to the brains are glossopharyngeal -9 and facial -7

Question 4

Describe how olfactory receptor cells work with nervous system to create sense of smell.

Answer 4

• The nerves carrying information to the brain are
  cranial nerve IX (9 - glossopharyngeal) & VII (7 -
  facial) (from the taste buds-taste cells to the brain)

Question 5

Describe how olfactory receptor cells work with nervous system to create sense of smell.

Answer 5

The sense of smell is known as olfaction. It is achieved by
olfactory epithelium covering the nasal cavities
* The receptor cells are also chemoreceptors.
* Each olfactory receptor cell has receptors on its surface that
are sensitive to specific odour molecules.
* When an odorant comes into contact with the receptors that
match its shape, it triggers a chemical reaction within the
receptor cell.
* The chemical reaction in the olfactory receptor cell
generates an electrical signal (nerve impulse), which is then
transmitted along the olfactory nerve (cranial nerve I).
* The signal is transmitted to olfactory bulbs of the forebrain,
where they are interpreted as smell.

Question 6

List the major components of the three layers of an eyeball.

Answer 6

Outer fibrous layer (Sclera)
o Sclera
o Cornea

• Middle layer (Uvea)
  o Iris
  o Ciliary body
  o Choroid (the pigmented
  vascular layer)
• Inner nervous layer
  (Retina)
  o Retina

Question 7

Being able to label the following structure on a picture of an eyeball: Sclera, Cornea, Iris, Ciliary body, lens, suspensory ligament, Choroid, Retina, vitreous body.

Question 8

Name the two muscles on the iris which contol the size of the pupil diameter.

Answer 8

• The contraction of radial
  or circular smooth
  muscles control the size
  of the pupil diameter

Question 9

Describe the structure of anterior and posterior chamber.

Answer 9

• Iris divides the space between lens
  and cornea into anterior and
  posterior chambers.
• A & P chamber are filled with
  aqueous humour, the fluid secreted
  by the ciliary body
• Vitreous body is a clear jelly-like
  structure behind the lens

Question 10

Describe the functions of aqueous humour and vitreous body

Answer 10

• Aqueous humour and vitreous
  body are providing nutrients to
  structures in the eye and
  maintaining the shape of the eye.

Question 11

What are the muscles that control the thicknees of the lens?

Answer 11

Ciliary body
Contain ciliary muscles
attaching to suspensory
ligaments of lens to control
the thickness and shape of
the lens

Suspensory ligament
a continuation of the
ciliary body, suspending
the lens

Question 12

Describe the two main photoreceptor cells (rods and cones) in retina.

Answer 12

Mainly contains photoreceptor cells rods and
cones.
* Rods account for 95% and cones 5% of the total
photoreceptor cells in the dog and cat.
* Rods cells function well under dim light but not
sensitive to color, thus responsible for light of
differing intensity seen in black & white and used in
night vision
* Cones cells are functioning well under bright light
and responsible for color vision

Question 13

Describe the circulation of aqueous humour.
(and function)

Answer 13

Both the chambers contain a watery
fluid, the aqueous humour, secreted
into the posterior chamber by the
ciliary body.
It flows over the surface of the lens,
circulates through the pupil to drain
into the canal of Schlemm in the
anterior chamber.
The aqueous humour is a source of
nutrients for the lens and the cornea,
which are non-vascular.

Question 14

Describe the process of image formation

Answer 14

Light rays pass through the
cornea, lens, vitreous body and
strike the retina.
Photoreceptor cells (rods and
cones) are activated in the retina.
Nerve impulses generated by
photoreceptor cells travel along
the optic nerve (II) and is carried
to the brain (visual cortex) where
it is interpreted as an image.

Question 15

Compare myopia vs hyperopia.

Answer 15

• Animals with short sightedness (myopia) or long
  sightedness (hyperopia), their lens
  accommodation process is abnormal.
• Which means the shape of the lens cannot be
  adjusted normally.
• As such, for myopia, the image falls in front of
  retina.
• And the animal cannot see objects far away clearly.
• For hyperopia, the image falls behind of retina.
• For animals with this condition, distant objects are
  usually seen more clearly than close ones

Question 16

What are the functions of meibomian glands (tarsal glands)?

Answer 16

Opening directly on to the edge of the eyelid, producing oily tears.
* These tears float on the surface of the watery tear film and help
prevent evaporation.

Question 17

Describe the flow pathway of tears.

Answer 17

Tears are produced in tear
(lacrimal) gland
* disperse across corneal
surfaces,
* enters the tear duct
(lacrimal canaliculi) at
punctum
* enter the nasal cavity
* Via nasolacrimal duct

Question 18

Describe the structures (including components) of external (outer) ear

Answer 18

Pinna, outer portion of the ear,
contain mainly elastic cartilage
and skin
* The external auditory canal,
carry the sound wave to
tympanic membrane (ear
drum)

Question 19

Describe the structures (including components) of middle ear

Answer 19

Ear drum is a paper-thin
membrane which belongs to
middle ear. It vibrates when
sound wave strikes it.

The middle ear is a small air-filled
cavity.
* Within the middle ear are three
tiny bones called the ossicles:
malleus, incus, and stapes.
* These bones are connected in a
chain and work together to amplify
and transmit sound vibrations from
the external ear to the inner ear. (cochlea)
* When sound reaches the middle
ear, the eardrum starts vibrating,
and this vibration is passed on to
the ossicles.

The end of stapes is attached
to membrane of oval window
of the cochlea

Eustachian tube connects the
middle ear cavity with the
pharynx, which balances air
pressure on the two sides of
the ear drum.

Question 20

structures of the inner ear

Answer 20

The inner ear is a small, fluid-filled cavity located deep within the
skull. It consists of two primary components:

• Cochlea:
• The cochlea is a coiled, snail-shell-shaped structure that plays a crucial
  role in the process of hearing.
• It is lined with specialised sensory cells called hair cells, which are
  responsible for converting sound vibrations into electrical signals.
• These hair cells are sensitive to different frequencies of sound and
  transmit the information to the brain through the auditory nerve

(Vestibulocochlear nerve - Cranial nerve VIII)
* Vestibular System:
* The vestibular system is another part of the inner ear, responsible for
maintaining balance and equilibrium.
* It comprises three semicircular canals and the otolith organs (utricle and
saccule).
* These structures contain fluid and sensory hair cells that detect the
movement and position of the head, helping us stay balanced and
oriented in space.

Question 21

Perception of Sound - Hearing

Answer 21

Sound waves, picked up by the pinna and transmitted
down the ear canal to the tympanic membrane and
auditory ossicles.
* The vibrations of stapes push and pull the membrane
on the oval window.
* Inside the cochlea, the sound vibrations cause the
fluid inside cochlea to move, bending the hair cells.
* This bending generates electrical signals (nerve
impulses), which are then sent to the brain’s auditory
cortex via the vestibulocochlear nerve (Cranial nerve
VIII).
* The brain interprets these signals as sound, allowing
us to hear and perceive different pitches and tones

Question 22

Explain how balance is maintained by the structure in the ear (vestibular system)?

Answer 22

• The vestibular system is responsible for
  our sense of balance.
• It consists of 3 tiny, fluid-filled tubes
  (semicircular canals) in inner ear.
• When an animal move its head, the fluid
  in the semicircular canals shifts, moving
  the hair cells that line the canal.
• Which allow the hair cells to predict loss
  of balance and send signal to brain via
  vestibulocochlear nerve (Cranial nerve
  VIII) to adjust the movement and help us
  maintain our balance.