Sense Organs Flashcards by Daisy Brooks

Which cranial nerve supplies the ears?

Vestibulocochler nerve CN8

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What are the 3 parts of the ear?

Outer
Middle
Inner

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Which part of the ear connects to the nasopharynx and how?

Middle ear via the Eustachian tube

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Name the three parts of the outer ear

Auricle / pinna
External auditory canal
Tympanic membrane (ear drum)

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What is the auricle / pinnacle made from and what does it do?

Flap of elastic cartilage covered by skin that traps and directs sound waves

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What is the tympanic membrane?

Semi-transparent partition between external auditory canal and middle ear

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What does the tympanic membrane do?

Converts sound waves into mechanical vibration

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What is the middle ear

Small air-filled cavity in the temporal bone

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What does stapes attach to?

It attaches to the ‘oval window’ which connects to the cochlea

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What is the name of the small muscle in the middle ear and what does it do?

Stapedius
Dampens large vibrations and is inner ages by the facility nerve

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What is another name for the inner ear?

Labyrinth

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What are the names of the two parts of the inner ear?

Outer bony labyrinth
Inner membranous labyrinth

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3 parts of the bony labyrinth and their functions

3 semi-circular canals & vestibule - receptors for balance

Cochlea - heading

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What fluids are found in the labyrinth

Perilymph & endolymph

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Where is the cochlea and describe its shape

Anterior to the vestibule
Spiralled hollow chamber

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What is in the cochlea?

Epithelial cells line with hair cells, topped with 40-80 cilia each called stereocilia

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What are stereocilia?

Receptors for hearing that extend into the endolymph

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How does hearing in the inner ear work?

Fluid movement (vibration) causes stereocilia movement which initiated and electrical impulse

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What does the vestibulocochlear nerve do?

Cranial nerve XIII provides sensory info for hearing and balance

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Describe the structure of the vestibulocochlear nerve

2 parts - vestibular fibres and cochlear fibres

Vestibular fibres have nerve branches that synapse with receptors for balance

Cochlear nerve provides hearing

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Where in the brain does the vestibulocochlear nerve connect to?

Brainstorm

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What are the 4 steps of sound sensation?

Sound wave
Mechanical vibration
Fluid waves
Nerve impulse

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Stages of how sound travels (sound physiology)

The pinna concentrates the waves and directs them along the auditory canal
Vibrations transmitted though the middle ear by the 4 auditory ossicles
Stapes rocks the oval window sending fluid waves in the cochlear perilymph
Pressure waves transmitted to cochlea causing round window to bulge
Pressure wave into endolymph
Vibration of hair cells
Bending stereocilia hair cells generates action potential
Nerve impulse along vestibulocochlear
Vestibulocochler impulse to cerebrum

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What is pitch and how is it measured?

Frequency of sound waves Hz (hertz)

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What is volume and how is it measured?

Amplitude of sound waves (dB) decibels

Prolonged exposure to what sound level causing hearing loss

90dB

What is white noise?

Background noise the brain ignores Can be used to mask other sounds

Where is the Eustachian tube?

Connects nasopharynx to the middle ear

What are the roles of the Eustachian tube?

Equalise pressure between middle ear and atmosphere Drain mucus

Why are middle ear infections more common in children?

Eustachian tube is more horizontal in children

Which parts of the inner ear aid balance by providing info about the head position?

Semi-circular canal and vestibules

How is info about head movement relayed for balance

Dense layer of calcium carbonate extends over and rests on the stereocilia called the otolithic memebrane

What is the otolithic memebrane?

Dense layer of calcium carbonate crystals

What causes movement in the perilymph and endolymph?

Change in head position Bend hair cells and stimulate sensory nerve endings

Which part of the brain makes postural adjustments to maintain balance?

Cerebellum

What feeds back to the cerebellum to make postural adjustments

Vestibular - ear Visual Proprioceptors - skeletal muscles

Which nerve supplies the eye

Optic nerve - cranial nerve II

What are the 3 layers of the eyeball?

Outer - sclera Middle - uvea Inner - retina

What is the coloured portion of the eye called and what does it do?

Iris. Controls the amount of light reaching the retina by adjusting the pupil size

What is behind the pupil and why does it do

Lens - further focused light along the cornea

5 eye accessory structures

Eyebrows Eyelids / lashes Conjunctive Lacrimal apparatus - produces tears Blinking

What do tears do

Protect the eye from infection and lubricate movements of the eye

Which cranial nerve controls tears

Trigeminal nerve - CNV

What do tears contain

IgA and lysozymes

Which gland produces tears

Lacrimal gland

3 steps to achieve clear vision

1. refraction of light rays 2. accomodation 3. changing size of pupils

What is refraction

Bending light rays The cornea and lens refract light rays helping to focus the image on the retina

What distance do objects need to be refracted from?

Closer than 6m

What is accommodation

As lens curvature becomes greater its focusing power increases

What happens to the lens when an object is close and what is this called

Ciliary muscle contracts - lens becomes more convex - greater refraction\ Called 'accommodation'

What happens to the lens when an object is far away and what is this called

Ciliary muscle relaxes - flattens the less - less refraction Called 'accommodation'

What does the sympathetic nervous system do to pupil size

Dilates the pupil

What does the parasympathetic nervous system do to pupil size

Constricts the pupil

What is eyeball convergence

MEdial movement of two eyeballs so they are both directed towards the same object

What happens if convergence is not complete

Double vision - diplopia

What is binocular vision?

Both eyes focus on one object which allows for perception of depth and 3D nature

What is the part of the brain where images cross over

Optic chiasma

Why is tunnel vision more common in pituitary tumours

As the optic chiasma sits next to the pituitary gland

Where is the retina and what does it do?

Inner layer of the line Beginning of the visual pathway

What's special about viewing the retina

It's the only place where a nerve can be viewed

What is the optic disc

Where the optic nerve exits the eyeball and causes a blind spot It doesn't contain any rod or cone cells

2 layers of the retina

Pigmented layer Photoreceptors

2 types of photoreceptors

Rod cells and cone cells

Difference between rod cells and cone cells

Rod cells - 120mil See in dim light, no colour Cone cells - 6 mil Three types -blue, red and green Cones regenerate quickly, rods take longer

What is the macula lutea

Yellow spot at the centre of the retina

What is the favea centralis

Small depression in the macula lutea that has only cone cells Area of highest visual acuity

What are photo-pigments and what are they derived from

Transmembrane proteins Vitamin A

Where is the most vitamin A stored

In the pigmented layer of the retina

What is vitamin A derived from?

Retinoids

3 types of retionoids

Retinol Retinal Retinoic acid

What happens to vitamin A in the retina

Vitamin A in the form of retinal blinds to a protein called opsin to produce photopigments

What are carotenoids

Precursors to vitamin A

How many smell receptors are there and what are they contains in?

10-100 million olfactory epithelium

3 parts of the olfactory epithelium

1. olfactory receptors - neurons attached to olfactory hairs 2. supporting cells - physical support 3. basal cells - stems cells that produce olfactory receptors

How is smell processed

Chemical sense Olfactory glands produce mucus Secretion helps dissolve the odorant

Which nerve is involved in smell

Olfactory nerve - CN1

What is the connection between smell and emotion

Some of the axons in the olfactory tract project into the limbic system

When it comes to smell what does adaptation mean

Decreased sensitivity to odours is rapid Prevents us smelling bad odours

What is another name for taste

Gustation

Which cranial nerve is connected to the tongue

Hypoglossal nerve CNXII

What do taste buds contain x 3

Gustatory receptor cells - detect taste Basel cells - stem cells Supporting cells

4 nerves invloved in taste

Facial nerve - anterior 2/3 tongue Glassopharyngeal nerve - taste and sensation Trigemial nerve - tongue Vagud nerve - throat and epiglottis