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Nerves + Eyes
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Cards (26)
Stimulus
- This is the
change
in
environment
which will
bring
about a
response
Receptor
- This detects the
change
in the
environment
it is usually one of the
sense organs.
Effector
- Brings about the response : is usually a muscle which
contracts
of a
gland
which
secretes
a
hormone.
Example of Receptors:
Ear
Eye
Nose
Temperature
Receptors
Pressure
Receptors
Pain
Receptors
The
brain
and
spinal cord
make up our
central nervous system
(CNS).
There are
3
types of neurones -
sensory
neurones,
relay
neurones and
motor
neurones.
Impulses from receptors pass along
sensory neurones
until they have reached the
brain
and
spinal cord.
Relay neurones
in the
brain
and
spinal cord
pass
impulses
from
sensory
neurones to
motor
neurones
Impulses pass to
effectors
(muscles or glands) along
motor neurones.
A
reflex action
is a rapid
automatic
response to a
stimulus
(for example when a bright light shines in the eye the
pupil
gets
smaller
).
The
brain
is not involved - you cannot stop the reflex and often are not
even
aware
it is happening
Reflex actions
help to protect the body from damage.
Energy
always needs to be
converted
to
electrical energy
as that is how
messages
are
passed.
A
synapse
is a
gap
between
two neurones.
Impulses arriving at a
synapse
cause the end of an axon to secrete a chemical, called a
neurotransmitter.
This chemical
diffuses
across the gap and attaches to
receptors
on the
membrane
of the second neurone (the
post-synaptic
membrane).
Fovea
- The region of the
retina
with the
greatest
number of
cones.
Suspensory ligaments
- hold the lens in place.
Cornea
-
protects
the
eyes’ surface
and
focuses light rays.
lens
-
focuses light
on the
retina
Iris
- regulates the amount of
light
entering the eye.
Ciliary Muscles
-
Change
the
shape
of the
lens.
Optic Nerve
- consists of many neurones which carry impulses from the retina to the brain.
Retina - Senses
light
and consist of
rod
and
cone
cells.
Blind spot
- The region where the
optic nerve
leaves the
eye
- there is no
rods
and
cones
here ad therefore no
image
is formed.
Rod Cells:
Work well in
dim
light
Cannot distinguish between different
colours
Image produced is
black
and
white
Found all over the
retina
Cone Cells
:
Work well in
bright light
There are
3
types that are sensitive to
red
,
green
and
blue
Colour
produced in an
image
Found
concentrated
in a region of the
retina
called the
fovea