Human sensory receptors
 receptors detects the
changes in both internal
and external environment
 they transform the stimuli
energy into a nerve
impulse that can be sent
to the central nervous
system (CNS) which in
turn coordinates an
appropriate response.
 receptors are located in
the sense organs such as
the eye, ear, skin, tongue
etc.
Human sensory receptors & stimuli that can detect
Type of receptor
Stimulus detected
Example of receptors
mechanoreceptors
pressure, sound
hair cells in the ear
chemoreceptors
chemical substances
taste buds on the tongue &
olfactory cells along the nose
thermoreceptors
temperature
nerve endings in the skin &
hypothalamus of the brain
photoreceptors
light
rods and cone in the retinas of
the eye
hydroreceptors
humidity
nocireceptors
pain
?
sensory nerve ending in the skin
Human eye
Eye lashes
Sclera
Pupil
Iris
Eye lid
Label the diagram of the human eye below
sclera
choroids
retina
ciliary body / muscles
iris
lens
cornea
fovea
blind spot
optic nerve
pupil
Structure
Function(s)
Sclera
tough outer layer of the eye which overs and protect eyeball.
Choroid
prevents internal reflection of light and nourish retina.
Retina
contains rods and cones which convert light into nerve impulses.
Ciliary Body
a ring of muscle controlling the shape and curvature of the lens.
Iris
controls the pupil size thus controls entry of light.
Pupil
a hole in the iris that lets light into the back of the eye.
Lens
accommodation & focusing of light onto the retina.
Cornea
bends incoming light focusing it on the retina.
Fovea
a tiny area of densely packed cones for detailed and coloured vision.
Blind Spot
exit point of the optic nerve cutting through the retina so no rods or
cones
Optic Nerve
carries the impulses from the rods and cones to the visual center of the
brain.
Annotate the diagram of the retina below
direction of light movement
Axon of the ganglion cell
Ganglion cell
Bipolar cell
Synapse
Rod
Cone
Pigment
Sclera
Compare rod and cone cells
Rod Cells
rod cells more effective in low light
intensity
rod cells detect a broad range of
colours (wavelength)
groups of rod cells pass impulses to a
single nerve fibre
rod cells more sensitive to movement
Cone Cells
cone cells more effective in high light
intensity
cone cells are sensitive to a specific
colours (wavelength)
a single cone cell passes impulses to
a single nerve fibre
cone cells give higher visual acuity
(sharpness )
rod cells respond more slowly to light
cone cells respond more rapidly to light
rod cells spread through retina
cone cells concentrated in centre of retina
(at fovea )
rod cells contains one type of pigment
(rhodopsin)
cone cells contains three types of
pigment (iodopsin)
rod and cone cells are both are photosensitive
Compare rod and cone cells
Cone Cells
Rod Cells
 rod cells more effective in low






light intensity
rod cells detect a broad range of
colours (wavelength)
groups of rod cells pass impulses
to a single nerve fibre
rod cells more sensitive to
movement
rod cells respond more slowly to
light
rod cells spread through retina
rod cells contains one type of
pigment (rhodopsin)
 cone cells more effective in high






light intensity
cone cells are sensitive to a
specific colours (wavelength)
a single cone cell passes
impulses to a single nerve fibre
cone cells give higher visual
acuity (sharpness )
cone cells respond more rapidly
to light
cone cells concentrated in centre
of retina (at fovea )
cone cells contains three types of
pigment (iodopsin)
 rod and cone cells are both are photosensitive
Contralateral processing of visual stimuli
 rod & cone cells in the retina





convert light into nerve
impulses
impulses pass to bipolar cells
bipolar cells pass impulses to
sensory neurons of the optic
nerve
at the optic chiasma, impulses
cross over to the opposite optic
nerve
impulses continue to the
thalamus where optical
information is processed
images form in the visual
cortex of the brain
Edge enhancement
 edge enhancement is a ‘pre-
central nervous system
‘processing of information on
the retina
 it enhances contrast at the
edges (boundaries of different
objects) and provides more
detail to the visual system of
the environment
 in certain regions of the
retina, single ganglion cell
receives information form a
number of rods and cones,
such a region is called
receptive field
 the fewer the rods and cones
that supply a single ganglion
the smaller the receptive field
& the higher visual acuity i.e.
the detailed information one
sees
Label the diagram of the ear below
Middle ear bones
Semi circular canals
Oval Window
Auditory Nerve
Round window
Cochlea
Eustachian tube
Eardrum
Auditory canal
Pinna
How sound is perceived by the ear
 sound waves reaching eardrum cause it to vibrate
 vibrations are passed to bones of middle ear which amplify them
 the bones pushes the oval window which cause a pressure wave in the fluid-
filled cochlea
 As the oval window moves in, the round window moves out, this allows the
fluid in the cochlea to move freely backward & forward
 the vibrations caused by fluid movement pushes the membrane on which
the hair cells (mechanoreceptors) sits, triggering nerve impulses in the
auditory nerves
 the nerve impulse is carried to the auditory cortex in brain through auditory
nerve for interpretation