NEUROBIOLOGY AND BEHAVIOUR Option E IB Biology Miss Werba

OPTION E – NEUROBIOLOGY & BEHAVIOUR STIMULUS and RESPONSE E.2 PERCEPTION of STIMULI E.3 INNATE and LEARNED BEHAVIOUR E.4 NTs and SYNAPSES E.5 THE HUMAN BRAIN E.6 FURTHER STUDIES IN BEHAVIOUR J WERBA – IB BIOLOGY 2

THINGS TO COVER Definitions of stimulus, response & reflex Role of the following in response to stimuli: Receptors Relay neurons Motor neurons Synapses Effectors Draw & label a diagram of a flex arc for a pain withdrawal reflex How natural selection can affect animal behaviour J WERBA – IB BIOLOGY 3

INTRODUCTION OF TERMS Command term = DEFINE Stimulus: A change in the environment that is detected by a receptor Response: A change in an organism resulting from a stimulus Reflex: A rapid and involuntary (unconscious) response to a stimulus

THE RESPONSE TO STIMULI Command term = EXPLAIN Receptors: specialized cells designed to generate a neural signal when stimulated transform stimuli into electrical nerve impulses eg. thermal energy into action potentials Sensory neurons: transfer the nerve impulse to the CNS enter the dorsal root of the spinal cord Relay neurons: (interneurons or connector neurons) transfer the nerve impulse within the CNS

THE RESPONSE TO STIMULI Command term = EXPLAIN Motor neurons: transfer nerve impulses from the CNS to an effector exit from the ventral root of the spinal cord Effectors: (muscles or glands) produce a response to the stimulus Synapses: junctions between two nerve cells synaptic transmission of a signal requires chemical neurotransmitters

THE RESPONSE TO STIMULI Command term = EXPLAIN Sensory neurons: receptor organs CNS Relay neurons: motor neurons sensory neurons Motor neurons: effectors CNS

THE PAIN WITHDRAWAL REFLEX Command term = DRAW and LABEL Reflexes are rapid and unconscious responses eg. The response to pain Reflexes are the product of natural selection (evolution): Rapid and unconscious responses allow for danger avoidance with minimal harm to the organism – so pain is a good thing! The pain reflex is a spinal reflex Means that it is moderated by the spinal cord rather than the brain. Shorter paths therefore faster responses and no conscious decisions needed!

THE PAIN WITHDRAWAL REFLEX Command term = DRAW and LABEL

THE PAIN WITHDRAWAL REFLEX Command term = DRAW and LABEL

THE PAIN WITHDRAWAL REFLEX Command term = DRAW and LABEL

NATURAL SELECTION & BEHAVIOUR Command term = EXPLAIN Natural selection is Charles Darwin’s theory of Evolution. It’s the process by which the frequency of an inheritable characteristic changes as a result of environmental selection pressures. These beneficial inheritable traits are called adaptations. They can include instinctive behaviours, such as migrating, foraging, hunting, communication, etc.

NATURAL SELECTION & BEHAVIOUR Command term = EXPLAIN Examples are the best way to explain natural selection and its effect on behaviour. Examples: Blackcap migration patterns Butterfly mate preference Any other example that you wish to use is fine too 

E.1.4 EXAMPLE 1: BLACKCAPS Scientific name: Sylvia atricapilla (S. atricapilla) Common name: the blackcap bird Breeds during the Summer in Germany .

E.1.4 EXAMPLE 1: BLACKCAPS Normal behaviour: chicks hatch and fly SW towards Spain for Winter (to avoid harsh Winter conditions) Alternate behaviour: some chicks hatch and fly NW towards UK Advantage of alternate: It’s closer and birdfeeders provide easy sources of food Birds can return to Germany faster and be more reproductively successful

E.1.4 EXAMPLE 1: BLACKCAPS Natural selection: genes for NW migration passed on to offspring; population begins to change over time Experimental evidence: they swapped the eggs in the nests of the two groups, and the NW chicks that hatched still flew NW when they migrated for the Winter

EXAMPLE 2: BUTTERFLIES Scientific name: Heliconius cydno (H. cydno) Common name: the Heliconius butterfly Heliconius butterflies exhibit mate preference for butterflies with particular colour markings.

E.1.4 EXAMPLE 2: BUTTERFLIES Normal behaviour: huge range of colours and individuals mate with any other variant Alternate behaviour: Yellow butterflies developed preference for yellow mates Advantage of alternate: Yellow pigment may be easier to see May be occupying a particular niche that the colour suits

E.1.4 EXAMPLE 2: BUTTERFLIES Natural selection: Yellow butterflies are becoming reproductively isolated through sexual selection. Will likely result in speciation over time. Experimental evidence: observations show preferential mating, hybrids are not as well adapted to the local niches

Sample questions Q1 True or false? 1. The difference between sensation and perception is whether information about a stimulus reaches the central nervous system. 2. Once transmission along a neuron starts it can't be stopped without damaging the neuron. 3. Sensory nerve cells act as the decision-making cells to sum up all signals for certain stimuli. 4. Neurons often have many short dendrites and a long axon. 5. A sensory neuron of the peripheral nervous system take nerve impulses from sensory receptors to the motor neurons 6. Nerve impulses go from sensory neurons in sense organs directly to the muscles and glands that respond. 7. A nerve impulse is the way a sensory neuron receives information. 8. In humans, transmission of nerve impulses across a synaptic cleft is carried out by neurotransmitters. 9. The central nervous system consists only of the brain. 10. Information about touch detected on the left side of the body is transmitted to the brain in the dorsal columns of the spinal cord. J WERBA – IB BIOLOGY 20

Sample questions A1 F T J WERBA – IB BIOLOGY 21

Sample questions Q2 Identify the mean time until the laying of the first eggs in the control group of Zebra finches. [1] Calculate the percentage decrease between the mean time until the laying of the first eggs in pairs of Zebra finches exposed to intra-colony sounds and in pairs exposed to extra-colony sounds. Show your working. [2] Evaluate the effect of the recorded colony sounds on the reproductive pattern of laying eggs in Zebra finches. [3] J WERBA – IB BIOLOGY 22

Sample questions Q3 Q4 Define the terms stimulus and reflex. [1] Explain the role of the neurons used in the pain withdrawal reflex. [3] J WERBA – IB BIOLOGY 23

Sample questions A2 15 days [1] (4 days /13 days) × 100 = 31% or 30.8% or 30.77%; [2] both types of sound decreased mean time to egg laying; extra-colony sound decreased time more than intra-colony; both types of sound increased (mean) number of eggs laid; same (increase in) egg number with intra- and extra-colony sound; no information on sample sizes/number of pairs/egg size; competition (implied/perceived) leads to earlier egg laying [3] J WERBA – IB BIOLOGY 24

Sample questions A3 stimulus: change in environment; reflex: rapid, unconscious /involuntary response; 2 A4 sensory neurons receive information from receptors; transmit nervous impulses to the central nervous system; relay neurons in the central nervous system transmit the information from sensory neurons to motor neurons; motor neurons send impulse to effector; 3 max J WERBA – IB BIOLOGY 25