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✓
describe the human central nervous system (brain and spinal cord as areas of coordination) and the peripheral nervous system, which together serve to coordinate and
regulate body functions
Coordination of muscles, Voluntary movement e.g.
walking, Non-voluntary movement e.g. balance
Peripheral
Central
Intelligence, Language, Memory, Emotion, Visual
and sensory processes
Spinal Chord
✓
✓
classify sense organs as groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals
compare and contrast the way in which different sense organs enable an individual to respond to the environment
Stimuli
Change in the environment
Receptor
Cells that detect stimuli
Nerve Impulse
Electrochemical messages that pass along neurone
Effector
A structure that nervous system cause to respond, a
muscle or a gland
It is a rapid “involuntary” (autonomic) response due to
a stimulus
Autonomic very rapid action not under conscious
control
Region between the
Reflex Arc
Involuntary
action
Synapse
✓
✓
conduct simple experiments to deduce the stimulus-response pathway that controls a person's response to a stimulus, and depict it diagrammatically, with reference to
sense organs and effector organs (muscles and glands)
investigate a variety of simple reflexes, and explain the significance of a simple reflex arc (including sensory, relay and motor neurones) as a means of automatically
and rapidly integrating and coordinating stimuli with responses, modelling transmission at a synapse
1.
s
R
S
R
M
E
R
Another view of the 3 types of neurons, notice
the difference in location of the cell body in each
•Stimulus
•Receptors
•Sensory
Neurone
2.
•Relay Neurone
•Motor
Neurone
3.
•Effector
•Response
Receptor cells sense the
stimulus & send impulses
along the sensory neuron
to the spinal cord.
Impulses pass to the relay
neuron through the
synapse by
neurotransmitters.
The impulses travel along
the motor neuron to the
effector organ generating
a response which is either
a muscle contraction or a
gland secretion
SRSRMER
Transmission at the synapse
Synapses are regions between the end of a neuron and the start of another one
Transmission of impulses
Along the Neuron
At Synapses
Electrical Signal
Chemical Signal (Neurotransmitters)
When the impulses reach the end
of the axon it causes a chemical to
be released.
They are called neurotransmitters.
They diffuse across the gap and
stimulate the impulse to continue in
the next neurone
Convey impulses
from the CNS to
the effector organ
Transmit impulses from
receptors in sensory
organs to the CNS
Examples of a reflex action
Receptor
Effector
Withdrawak reflex
skin
Muscles of the arm
Iris reflex
Retina
Muscles of the iris
Blinking Reflex
Retina
Muscles of the eye lid
Sneezing, knee jerks, etc.
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✓ apply knowledge of the structure and function of the eye to explain changes in the eye in response to light levels (pupil reflex) and close
and distant vision (accommodation)
✓ investigate how the blind spot affects vision and describe the function and distribution of rods and cones
Blind spot
Part of the retina in front of the optic nerves which lacks rods and
cones
Ciliary body A ring of muscle that controls the shape of the lens to allow
focusing
Lens
Transparent, curved surface on the front of the eye, refracts light
to focus it
Fovea
An area of the retina containing high concentration of cones,
where light is usually focused and colors are detected
Iris
A colored ring of circular and radial muscles that controls the size
of the pupil
Optic Nerve Transmits electrical impulses from the retina to the brain
Pupil
A hole in the center of the iris that controls the amount of light
reaching the retina
Retina
A light sensitive layer made of rods and cones
Suspensory Attaches the lens in place
ligaments
How do we see?
1. Receptors cells in the retina are sensitive to light.
2. When light falls on receptor cells (rods and cones) they send an electrical impulse along the optic nerve to the brain.
3. The brain sorts out all the impulses from each receptor cell and builds up an image.
Fovea
Blind Spot
Rods
Cones
The part of the retina where
the cones are tightly packed.
Image formed is small and
inverted
The spot of the retina where the optic
nerve leaves
No receptor cells
If light falls, no impulses will be sent
to the brain
Sensitive to dim light
Do not respond to
colors
120 million, a group
share one nerve
connection
Sensitive to bright light
Distinguish between
different colors
6 millions, each has its
own nerve connection
Focus Reflex “The process of accommodation
The fatter the lens, the
more it will bend the light
Fat lens
Focus Reflex “Accomodotion”: a response to different light intensities
The thinner the lens, the
less it will bend the light
Very near to the eye
Flying away
Getting closer
Fat lens (near objects)
contracted ciliary muscle
thin lens
Looking at the
bird
Thin lens, far object
Relaxed ciliary muscles