The special senses

Question 1

Sense organs are;

Answer 1

Information on your surroundings

processed in the CNS

Question 2

5 special senses;

Answer 2

Senses
Somatosensory system (pressure, warmth, vibration, limb position)
Sight (Visual system)
Hearing (Auditory system)
Taste (Gustatory system)
Smell (Olfactory system)

Question 3

Eye; Vision is the dominant sense in humans
How are they protected?

Answer 3

by orbit and cushion of fat

Question 4

Accessory Structures

Eyebrows
Eyelids or palpebrae

Answer 4

eyelids allow to blink

Question 5

Eyelashes

Answer 5

keeping airborne dirt, dust, lint and other debris from reaching the delicate eye tissues

Question 6

Conjunctiva

Answer 6

transparent mucous membrane

Question 7

Lacrimal apparatus

Answer 7

Lacrimal gland: Responsible for tears (PNS)
mucus, antibodies and lysozyme
nasolacrimal duct —> nasal cavity

Question 8

Extrinsic Eye Muscles

Answer 8

Movement

Question 9

Eye ball; 3 tissues/tunics

Answer 9

1) Fibrous Layer (Outer)
2) Vascular layer
3) Nervous tissue layer (inner most)

Question 10

1) Fibrous Layer (Outer) - is made out of what 2 things, colour?

Answer 10

Sclera: white of the eye
Cornea: front of the eye (transparent)

Answer 11

Choroid
Dark: melanin containing cells
Absorbs light

Question 12

2) Vascular layer (has a LOT of blood vessels in it)

Answer 12

Choroid

Dark: melanin containing cells
Absorbs light
Ciliary body
Cilliary muscles
Change thickness of Lens

Iris
Coloured part of eye
Highly vascularised
Pupil size controlled by muscles of the iris
Light passes through pupil

Question 13

3) Nervous tissue layer (inner most)

Answer 13

Retina

Outer Pigmented retina
Prevents light reflection

Inner sensory retina

Question 14

Why is the Cornea transparent?

Answer 14

light needs to pass through it (this is the outer layer of the eyeball)

Question 15

How many chambers are there in the eye?

Answer 15

2 =

Anterior Segment / cavity (FRONT) + Posterior segment/cavity (BACK)

Question 16

What is the anterior cavity made up of?

Answer 16

ANTERIOR CHMABER
chamber between cornea and iris

POSTERIOR CHAMBER
chamber between iris and lens

AQUEOUS HUMOR: Fills Anterior Segment
Watery liquid, replaced continuously
Filtered through ciliary body and returned to blood via venous synus
Nutrients
Refracts light
Maintains pressure

Question 17

Posterior segment/cavity COMPOSITION?

Answer 17

VITREOUS CHAMBER

VITREOUS HUMOR: in posterior segment
Jellylike
Maintains pressure and refracts
Forms in embryo and doesn’t circulate

Question 18

What is humor?

Answer 18

the liquid in the eye

Question 19

For vision, what happens in the eye?

Answer 19

1. The iris allows light into the eye
2. Focused by the cornea, lens, and humors onto the retina
3. The light striking the retina produces action potentials that are relayed to the brain via optic nerve

Question 20

What are the two layers of the retina?

Answer 20

a) Outer thin pigmented layer
b) Inner thicker neural/sensory layer

Question 21

a) Outer thin pigmented layer

Answer 21

Melanocytes (prevent light scattering), contains melanin

Question 22

b) Inner thicker neural/sensory layer - neurons

Answer 22

Three main type of neurons:
Photoreceptors
Rods
Cones
Bipolor cells
Ganglion cells

Question 23

Macula; length? [region of posterior retina]

Answer 23

5.5mm
High-resolution, color vision (lots of rods and cones)
Within this is the fovea (1.5mm)
Where light is most focused when the eye is looking directly at an object
Highest density of cones

Question 24

Optic disc properties; [region of posterior retina]

Answer 24

Blood vessels enter the eye
Axons from the retina meet, pass through the layers and exit the eye as the optic nerve
No photoreceptors

Question 25

What happens when light gets to the retina?

Answer 25

Light passes through components of anterior cavity and is focused by lens and passes through vitreous humor

Pass between axons, ganglion cells and bipolar cells, to photoreceptors next to pigmented layer

Question 26

Direction of travel of neuronal signal

Answer 26

Photoreceptor cells synapse with bipolar cells, which synapse with ganglion cells : ganglion cell axons run on internal surface and converge at posterior of eye to form optic nerve which exits eye

Question 27

2 types of Photoreceptors:

Answer 27

1. Rod cells
2. Cone cells

Question 28

1. Rod cells - properties

Answer 28

More sensitive to light - vision permitted in dim light but only gray and fuzzy
Only black and white and not sharp
Rhodopsin (opsin & retinal)

Question 29

2. Cone cells (for detailed vision)

Answer 29

High acuity NEED bright light
Colour vision
3 sub-types:
blue, red and green light cones
found in macula lutea,
operate in bright light, colour vision

Question 30

Photo Transduction

Answer 30

1. Retina takes light energy and converts it to electrical energy ( in photoreceptors)
2. Rods operate in dim light, numerous at periphery of retina, fuzzy images
3. Rhodopsin (1) = protein opsin loosely bound to pigment called retinal
   Light= retinal changes shape splits into opsin and retinal.
4. Change in rhodopsin stimulates the rods, resulting in vision
5. Generates a receptor potential  action potential in the attached

Question 31

Neural Pathways

Answer 31

1. Optic nerve leaves eye enters brain at optic
   chiasm
2. Some fibres cross to other side of brain
3. —–> then visual cortex in occipital lobe

Question 33

Why is back of eye dark?

Answer 33

control scatter of light

Question 34

Auditory system

Answer 34

Hearing

Question 35

Parts of THE EAR
3 parts;

Answer 35

Outer (external) ear
Pinna
External auditory canal

Middle ear (ossicles) for hearing)
Tympanic membrane
Malleus (hammer)
Incus (anvil)
Stapes (stirrup)

Inner ear (labyrinth)
Mechanoreceptor for hearing and balance
Vestibular apparatus
Semicircular canals
Cochlea
Organ of Corti

Question 36

MIDDLE EAR

Answer 36

Air filled

Oval and round window connect to inner ear

TM causes ossicles in air filled middle ear to move:
Malleus (hammer) (attached to TM)
Incus (anvil)
Stapes (stirrup) (touches oval window)
Ossicles form a lever system
Amplifies and transmits the vibratory motion of the TM to fluids of inner ear cochlea via oval window

Auditory canal open to pharynx

Question 37

Inner ear - Labyrinth (consists of lot of different cannals)

Answer 37

3 bony chambers

Cochlea - hearing

Vestibule - equilibrium

Semicircular canals – equilibrium

Filled with liquid called perilymph and endolymph fluids

Meconoreceptor cells

Question 38

Cochlea - full of liquid

Answer 38

Shaped like snail shell

2 canals
extends from the oval window to the apex of the cochlea.
from the apex back to the round window
Lined on bottom channel by Basilar membrane

Middle: cochlear canal - contains Organ of Corti
Specialised sensory hair cells : stereocilia
Seated on basilar membrane
Reach to tectorial membrane
Base of Hair cells attached to neuron

Basilar membrane moves/vibrates when sound waves in periplymph move over it

Question 39

Cochlea and organ of corti

Answer 39

Receptor organ for hearing

Question 40

Cochlea

Answer 40

Organ of Corti contains hair cells – move due to pressure waves
Hair cells sit on BM between BM and TM
embedded in TM

Question 41

BM

Answer 41

Basilar membrane

Question 42

TM

Answer 42

Tectorial Membrane

Question 43

Summary of Sound transmission through the ear;

Answer 43

1. Sound waves vibrate tympanic membrane
2. Auditory aussicles vibrate. Amplification
3. Stapes connected to oval window, sends vibrations into cochlea
4. Pressure wave pushes on basilar membrane of cochlea duct. Energy waves dissipate at round window
5. Hair cells bend, transmission of signal
6. Neurotransmitter release activates sensory neurones, action potentials to brain.

Question 44

Auditory pathway

Answer 44

-Vestibulocochlear nerve:
Cochlear nerve - portion involved in hearing
Vestibular nerve is involved in balance.

-The cochlear nerve sends axons to the regions including

-Auditory cortex in temporal lobe

Question 45

EQUILIBRIUM; Vestibular apparatus

Answer 45

static equibilbrium (movement and position)

2 Chambers: Saccule and utricle

Maculae

Hair cells, tips embedded in gelatinous mass weighed down by otoliths (protein and calcium carbonate)

Otoliths moves in relation to gravity bending hairs
Upright : don’t move
Hairs bend when tilted

Depolarises receptor cells - action potentials in associated neurons travel to brain about head position

Question 46

Equilibrium 2

Answer 46

Semi circular canals
Dynamic equilibrium:
Rotational acceleration in 3 planes

3 canals : right angles

Base: ampula
Hair cells embedded in jelly cupula
Floats in endolymph

Movement:
Endolymph tends to move in opposite direction
Cupula and steroclia on hair cells bend
Leads to action potential

Vestibulocochlear nerve to cerebellum