Download Option E: Neurobiology and Behaviour

Option E:
Neurobiology and
Behaviour
E.1 Stimulus and Response
Definitions
A
stimulus is the change in the
environment (internal or external)
that is detected by a receptor and
elicits a response.
 A response is a change in an
organism produced by a stimulus
 A reflex is a rapid, unconscious
response to a stimulus
Response to a stimulus (pain
withdrawal reflex)
 Receptor
is nerve endings in skin
that detect stimulation
 Sensory Neurons carry impulses to
control center
 Relay neuron in the CNS connect
sensory neuron to motor neuron
 Motor neuron sends response
message to effector organ(muscle)
 Effector –( Muscle ) contracts,
causing desired response.
Pain Withdrawal reflex
Pain Withdrawal reflex and The
Reflex Arc
Hand touches something
which causes pain.
 Pain receptor passes
message to sensory
neuron that runs through
the white matter on the
dorsal root of the spinal
cord to the grey matter
 Interneurone in gray
matter transfers impulse
from sensory neuron to
motor neuron

Motor neuron leaves
ventral root of spinal
cord and carries
message to muscle in
arm
 This message
stimulates the muscle
(effector) to contract
removing it from
danger
 This is the response


Knee jerk reflex is
another example of
a spinal reflex
Natural Selection and Behavior
Certain behaviors benefit an organism to
survive in its environment
 Possessing genes that allow these behaviors
to manifest are useful in that environment
 This is natural selection a.k.a. “Survival of
the Fittest”
Eg: Peppered moth
Dark moths survive in dark tree bark. If the
colour of tree bark changes to light, more
light-colored moths survive. The color of the
moth is determined by genes but survival is
determined by environment.

Natural Selection determines
animal response
 European
Blackcaps
– Live in Germany in summer
– Spain vs. UK migration for winter
– UK birds return 10 days sooner & have
more choice of territory
 Sockeye
Salmon
– Lake Washington
– Lake vs. creek environment
– Lake males are heavy to hide in the
deep waters, stream males are sleek to
swim in the current.
– No crossbreeding even though river
connects to lake