Special senses

Question 1

What are the special senses?

Answer 1

Chemical senses- taste (gustation), smell (olfaction)
Vision
The ear- hearing, equilibrium

Question 2

Where are the taste buds found?

Answer 2

Taste buds on the tongue are located on papillae

There are four types

Question 3

What are taste buds made up of?

Answer 3

Taste receptor cells (gustatory cells)
Microvilli through pore, bathed in saliva
Dissolved molecules bind and induce receptor cells to generate impulses in sensory nerve fibres

Question 4

What types of taste are there?

Answer 4

Sweet
Sour 
Salty
Bitter
Umami- glutamate (MSG)

Question 5

Which cranial nerves are involved in the taste pathway?

Answer 5

VII (Facial n.) – anterior 2/3 of tongue

IX (Glossopharyngeal n.) – posterior 1/3 tongue and pharynx

Question 6

What is the olfactory epithelium in the roof of the mouth made up of?

Answer 6

Involved in the sense of smell
Pseudostratified columnar epithelium
Has millions of bipolar neurons- olfactory receptor cells
Only neurons undergoing replacement throughout adult life

Question 7

How do we detect smell?

Answer 7

Olfactory cilia bind odour molecules
Mucus captures and dissolves odour molecules
Each receptor cell has an axon- bundled into filaments of olfactory nerve, enter olfactory bulb

Question 8

Describe the function of the olfactory bulb

Answer 8

Olfactory bulb is in the forebrain
In bulb, nerves synapse with mitral cells (neurons in clusters of glomeruli)
Mitral cells send signals via olfactory tract

Question 9

How does the brain recognise smell?

Answer 9

Approximately 1000 types of cell receptors
Convergence of many receptor cell signals onto one glomerulus registers a signature pattern
Brain recognises the pattern, sent to the olfactory area and limbic area

Question 10

What is anosmia and what are the possible causes?

Answer 10

Absence of the sense of smell
Caused by: trauma, colds or allergies producing excessive mucus, polyps causing blockage, zinc deficiency, amiodarone use

Question 11

What are the three parts of the ear?

Answer 11

Outer external ear
Middle ear (ossicles for hearing)
Inner ear (labyrinth) for hearing and equilibrium

Question 12

Describe the function of the tympanic membrane and the ossicles

Answer 12

TM causes ossicles in air filled middle ear to move: malleus (hammer), incus (anvil), stapes (stirrup)
Ossicles form a lever system that amplifies and transmits the vibratory motion of the TM to fluids of inner ear cochlea via oval window

Question 13

What three parts make up the inner ear?

Answer 13

Cochlea- hearing
Vestibule- equilibrium
Semicircular canals- equilibrium
Filled with perilymph and endolymph fluids

Question 14

How does the spinal organ of corti assist in hearing?

Answer 14

Vibration of stirrup at oval window starts traveling waves displacing basilar membrane
Sensory hair cells stimulated
Nerve ending of cochlear nerve division of VIII (Vestibulo-cochlear n.)

Question 15

What is the function of the semi-circular canals?

Answer 15

Each canal lies in one of the three planes of space
Sense rotational acceleration of the head
Duct with ampulla housing a small crest
Hairs project into jellylike cupula and basilar cells synapse with fibres of vestibular nerve

Question 16

What are the accessory structures of the eye?

Answer 16

Eyebrows
Eyelids or palpebrae- upper and lower separated by palpebral fissure, corners- medial and lateral canthi
Eyelashes

Question 17

Describe the anatomy of the eye

Answer 17

Lacrimal apparatus is responsible for tears- contain mucus, antibodies and lysozyme
Lacrimal gland in orbit of eye
Tears pass out into nasolacrimal duct
Empty into nasal cavity (sniffles)

Question 18

Describe the muscular control of the eye

Answer 18

Six muscles control the movement of the eye
Four rectus muscles (straight), two oblique muscles (curved)
Controlled by the ocularmotor and tochlear cranial nerves

Question 19

Describe the retina

Answer 19

Develops as part of the brain
Two layers- outer thin pigmented layer containing melanocytes to prevent pigment scattering; inner thicker neural layer which plays a direct role in vision

Question 20

How do photoreceptors pass information to the brain?

Answer 20

Photoreceptor neurons signal bipolar cells, which signal ganglion cells to generate action potentials
Axons run on internal surface to optic nerve which runs to brain