Transcript Neurobiology & Behaviour - IB

Neurobiology & Behaviour
HL & SL Option E
Stimulus & Response
• E.1.1. Define the terms stimulus, response, and
reflex in the context of animal behaviour.
Stimulus, response, and reflex
• Stimulus (pl. stimuli)
– A change in external or internal environment that is detected by a
receptor and elicits a response
• Response
– Is a reaction to a stimulus
• Reflex
– Is a rapid, unconscious response
– e.g. - the response to pain
Video
Response of animals to pain stimuli
• E.1.2 Explain the role of receptors, sensory neurones,
relay neurones, motor neurones, synapses and effectors
in the response of animal to stimuli
Pain Reflex Arc
• Receptors receive the stimulus
– Pain, heat, pressure, chemicals
• Receptors
– Generate a nerve impulse in the sensory neurons
• Sensory neurons carry the impulse toward the spinal cord
• The axons of the sensory neuron enters the spinal cord
Pain Reflex Arc
• The axon of the sensory neuron enters the spinal cord in the
dorsal root
• It sends a chemical message across a synapse to a relay neuron
(interneuron)
• Synapse – functional connections between neurons or between
neurons and other types of cells.
• Relay neuron (interneuron) is located in the gray matter
• The motor neuron is located in the ventral root of the spinal cord
Pain Reflex Arc
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It carries the impulse to an effector
An effector is an organ that performs the response
Effectors are muscles or glands
A reflex is an automatic response following a sensory stimulus. It
is not under conscious control and is therefore involuntary (it
does not involve the human brain.)
• E.1.3 Draw and label a reflex arc for a pain withdrawal
reflex, including the spinal cord and its spinal nerves,
relay neuron, motor neuron, and effector
• E.1.4 Explain how animal responses can be affected by
natural selection, using two examples
http://msjensen.cehd.umn.edu/1135/Links/Animations/Flash/0016swf_reflex_arc.swf
Effects of Natural Selection
• Animal behaviour is much more than just single reflex arcs
• Behavioural changes may be so extreme that a new species is
formed
• Review – Black Peppered Moths
Migration in European Blackcaps
• Small warblers
• Migrate between
Germany & Spain
– Breed in Germany in
spring
– Spend the winter in
Spain
Migration in European Blackcaps
• 50 years ago – some blackcap warblers came to UK for winter
• UK blackcaps left to go back to Germany 10 days earlier than the
Spanish blackcaps
• The earlier the birds arrived in Germany, the more choice of
territory they had; the more eggs they laid
• UK warblers have an advantage
Video
Migration in European Blackcaps - experiment
1)
2)
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4)
Eggs collected from UK parent
Eggs collected from Spanish parents
Young reared without parents
All birds in study migrated in the same direction that their
parents had gone
5) Supports the hypothesis – blackcaps are genetically programmed
to fly in a certain direction
6) Change in migration patterns may cause new species
Sockeye Salmon
Video clip
Sockeye Salmon
1) Sockeye salmon were
introduced into Lake
Washington
2) Some migrated to Lake
Cedar
3) River flows quickly –
lake is deep & quiet
4) Different aquatic
environments
Sockeye Salmon – Lake Washington
1) 13 generations of salmon over 60 years
2) River & lake salmon do NOT interbreed
3) 2 different breeding methods
a) Lake salmon spawn on the beach, females lay eggs in the sand
b) Males have heavy bodies & are inefficient at navigating fast
currents in the river
Sockeye Salmon – Cedar Lake
1) Thinner & narrower bodies
2) Females bury their eggs
deep in the sandy river
bottom – not washed away
3) Fish hatched in the river
had little success trying to
spawn on the beach
Comparison of the Sockeye Salmon
1) Variations in the 2 populations were selected for by the 2
different environments
2) Original population diverged into 2 different breeding
populations.
3) The lake conditions favour one set of traits and the river
conditions favour another set of traits
4) Sockeye salmon are now 2 genetically distinct populations