IB Biology/Option E - Neurobiology and Behavior

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Option E: Neurobiology and Behaviour[edit]

Introduction and Examples of Behaviour[edit]


State that behaviour in animals is related to the environmental context

State that innate behaviour develops independently of the environmental context, whereas learned behaviour reflects conditions experienced by individuals during development.

Explain the role of natural selection in the development of behaviour patterns

  • An organism may develop a certain behaviour which makes it better suited to its environment. For example, a learned behaviour allows the species to obtain food with ease. Possessing a certain behaviour will increase the likelihood of a species and its offspring to survive, and thus more and more of a species will develop this behaviour.

Explain using species of birds or animals one example of each of the types of behavior: migration, grooming, communication, courtship and mate selection.

  • Migration: Arctic tern, swallow, white stork, blue whale
  • Grooming: Rhesus monkeys will groom one another. This is a sign of respect as lower ranking members will groom higher ranking ones. Also, grooming may be addictive for the monkeys due to the release of endorphins while grooming
  • Communication: bird songs, alarm responses and hierarchal dominance patterns in wolves and red deer
  • Courtship: male display (ex: peacock, mallard duck, great crested grebe, blue footed boobie)
  • Mate selection: territory and song (birds) or combat (stags)

Explain the need for quantitative data in studies of behaviour

  • Studies of animal behaviour usually begin with careful observations from researchers. These careful observations allow us to understand the natural history of a species and often lead to the formation of a hypothesis. From here we can test the hypothesis by collecting quantitative data. Then according to this data we can then establish confidence levels for the data by statistical tests.

Perception of Stimulus[edit]


State that sensory receptors act as energy transducers

  • Sensory receptors act as energy transducers. All sensory receptors convert energy from the stimulus into the electrical energy of a nerve impulse. Animal's behaviour is the response that the animals make to the environment and involves perception of stimuli from this environment. They then use sensory receptors and thus all energy transducers.

State that human sensory receptors are classified as mechanoreceptors, chemoreceptors, thermoreceptors, or photoreceptors.

  • Human sensory receptors are classified as mechanoreceptors, chemoreceptors, thermoreceptors, or photoreceptors.

Describe what is meant by by each of the terms mentioned before with reference to one named example of each type of receptor

  • Mechanoreceptors: Perceive mechanical energy in the form of movement or sound, etc. An example is hair cells in the inner ear which send nerve impulses to the brain when sounds make them vibrate.
  • Chemoreceptors: Perceives chemical substances. Nerve cells in the nostrils send impulses to the brain when chemicals bind to them.
  • Thermoreceptors: Perceive temperature. Warm and cold endings in the skin send messages to the brain of the spinal cord.
  • Photoreceptors: Perceive light. Rod and cones in the eyes send messages to the brain when they absorb light.

Draw the structure of the human eye


Annotate diagrams of the human retina

Diagram of retina.JPG

Distinguish between rod and cone cells

  • **Rods function well in dim light, while cone cells function well under bright light. Rod cells absorb all types of light and give monochrome vision whereas cone cells absorb red, blue, and green, and give off colour vision (sensitivity to wavelengths). **Rods group together and send impulses to the same neuron while cones have their individual neurons. Cones give greater visual accuracy than rods. Rods are more widely dispersed through the Retina while cones are concentrated. Rods deal with the pigment rhodopsin, while cones deal with the pigment iodopsin.

Outline how visual stimuli are processed in the retina and the visual cortex

  • Bipolar cells in the Retina combine the impulses of rod and cone cells and pass them on to sensory neurons of the optic nerve (Ganglion cells). The left and right optic nerves meet at a structure called the optic chiasma. Here, all the neurons that are carrying impulses from the right field of vision split and bring the impulses to both hemispheres of the brain, and vice versa. As a result, the left optic nerve carries information from the right half of the field of vision and vice versa. The impulses are processed first by the thalamus, and then carried to the visual cortex where the information is processed into images.

Identify the structures of the human ear.


Perception of Sound 1. Eardrum When sound waves reach the eardrum at the end of the outer ear, they make it vibrate. The vibration consists of rapid movements of the ear drum, towards and away from the middle ear. The role of the eardrum is to pick up sound vibrations from the air and transmit them to the middle ear.

2. Bones of the middle ear There is a series of very small bones in the middle ear, called the ossicles. Each ossicle touches the next one. The first ossicle is attached to the eardrum and the third one is attached to the oval window. The ossicles' role is to transmit sound waves from the eardrum to the oval window. They also act as levers, reducing the amplitude of the waves, but increasing their force, which amplifies sounds by about 20 times. The oval window's small size, compared with the eardrum, helps with amplification. Muscles attached to the ossicles protect the ear from loud sounds, by contracting to damp down vibrations in the ossicles.

3. Oval window This is a membranous structure, like the eardrum. It transmits sound waves to the fluid filling the cochlea. This fluid is incompressible, so a second membranous window is needed, called the round window. When the oval window moves towards the cochlea, the round window moves away from it, so the fluid in the cochlea can vibrate freely, with its volume remaining constant.

4. Hair cells in the cochlea The cochlea consists of a tube, wound to form a spiral shape. Within the tube are membranes, with receptors called hair cells attached. These cells have hair bundles, which stretch from one of the membranes to another. When the sound waves pass through the fluid in the cochlea, the hair bundles vibrate. Because of gradual variations in the width and thickness of the membranes, different frequencies of sound can be distinguished, because each hair bundle only resonates with particular frequencies. When the hair bundles vibrate, the hair cells send messages across synapses and on to the brain via the auditory nerve.

Innate Behaviour[edit]


Define innate behaviour

  • Innate behaviour is behaviour inherited by genes which occurs in all members of a species. An animal in a sense is born with this type of behaviour.

Outline the pain withdrawal reflex and one other human spinal reflex

  • A hand accidentally touches something which causes pain. This will stimulate pain receptors in the skin. The pain receptor passes a message to a sensory neuron which carries it as a nerve impulse to gray matter in the spinal cord. The message is passed via a linking neuron called an associate neuron in the grey matter to a motor neuron. The motor neuron carries the message to a muscle in the arm. The message stimulates the muscle to contract, removing the hand from danger. This is called the reflex arc.

Knee-Jerk Reflex - Stretch receptor to the sensory neuron to the motor neuron to the muscle.

Draw the structure of the spinal cord and its spinal nerves to show the components of the reflex arc

Outline the pupil reflex and one cranial reflex

  • If a bright light is shone in one eye, the pupils of both eyes constrict. Photoreceptor cells in the retina detect the light stimulus. Nerve impulses are sent in sensory neurons of the optic nerve to the brain. The brainstem processes this and send impulses to the muscles of the iris which contract.
  • Sneeze - Irritation in nose,sensory receptor, trigeminal cranial nerve (5th), medulla, motor neuron, muscles (abdominals), SNEEZE!

Draw the gross structure of the brain including the medulla oblongata, cerebellum, hypothalmus, pituitary gland and cerebral hemisphere


State one function for each of the parts of the brain listed before.

  • Medulla oblongata: controls unconscious processes including breathing rate.
  • Cerebellum: helps to coordinate muscle movements and balance.
  • Hypothalamus: controls secretion of hormones in the pituary gland.
  • Pituitary gland: Secretes hormones
  • Cerebal hemispheres: Complex thought processes such as memory, learning, and problem solving.

Discuss the use of the pupil reflex in testing for brain death

  • If light stimulation does not cause the pupils to constrict, then heavy damage to the most basic parts of the central nervous system is likely.

Define taxis and kinesis

  • Taxis: is directional movement away or towards a direct stimilus. Maggots move directly away from a light source.
  • Kinesis: a stimulus produces a change in the the rate of movement or rate of turning. Woodlice moves fast in dry areas, but moves slow in humid areas while turning more.

Explain, using one example of each behaviour, how the responses improve the animal's chances for survival

  • Woodlice live better in humid areas as they dehydrate easily in dry areas because of their gas exchange. The kinesis that they have ensure that they spend more time in humid areas.
  • Fly maggots move away from light. This ensures that they stay inside a dead carcass where there is abundant food and protection from predators.

Discuss the importance of innate behaviour to the survival of animals

  • Innate behaviour are inherited from parents as genes. They develop by natural selection and thus are suited to better adapt a species to its environment. Therefore, they increase an animal's chances for survival.

Learned Behaviour[edit]


Define classical conditioning

  • Classical conditioning is an alteration in the behaviour of an animal as the result of the association of external stimulus.

Outline Pavlov's experiments on conditioning of dogs

  • Ivan Pavlov observed that dog's secreted saliva when they saw or tasted food. The sight or taste of meat is called the unconditioned stimulus and the secretion of saliva is called the unconditioned response. Pavlov then gave a neutral response by ringing a bell whenever he served the dogs food. The sound of the bell eventually came to become the conditioned stimulus as dogs would secrete saliva at its sound. The dogs associated the sound of the bell with the arrival of food. The secretion of saliva due to the conditioned stimuli is called the conditioned response.

Define operant conditioning

  • Operant conditioning is behaviour which develops as a result of the association of reinforcement with a particular response on numerous occasions.

Outline Skinner's experiments into operant conditioning

  • Skinner created a ‘skinner box’, into which a rat (or pigeon) could be placed, and on pressing a lever food would be delivered to feed the rat. A hungry rat would be placed in the box, and it would eventually press the lever by accident, and learn to associate the pressing of the lever with the reward of food. The food reward is the reinforcement and pressing the lever is the operant response. The more quickly the reinforcement is given, the faster operant conditioning develops. When the response is not given invariably, the conditioning develops more strongly.

Define imprinting

  • Imprinting is a learning a response to a stimulus during a sensitive period of development.

Outline Lorenz's experiment on imprinting in geese

  • Lorenz removed half of the eggs that a female goose had laid and incubated them. When they hatched, he observed them for a time, so that he was the first moving object which the goslings saw. The goslings then associated him with their mother, and so followed Lorenz around, and on maturity even attempted to mate with humans. The birds which hatched with the female goose developed normally. The goslings are able to filter external stimuli to identify the moving object as a sign stimulus, and the ability to identify the sign stimulus is called the innate releasing mechanism. Imprinting allows animals to learn to respond to significant stimuli in their environment and ignore others. Imprinting is species-specific (innate) behaviour.

Discuss how the process of learning improves the chances of survival

  • Birds can avoid tasting black and orange caterpillars, Monarch butterflies.
  • Grizzly bears can learn how to catch salmon.
  • Goslings learn who their mother is and avoid predators by staying with her

Social Behaviour[edit]


List three examples of animals that show social behaviour

  • Ants, honey bees, and termites.

Describe the social organization of honey bee colonies

  • There are three castes of honey bees which have different tasks. The single queen bee of a colony has to lay eggs. The worker bees do jobs that maintain the colony. The drones do nothing to help the colony to survive. However, if they successfully mate with virgin queens, they spread the genes of the colony to new colonies. Workers eject drones from the colony at the end of the season during which virgin queens are available.

Discuss the role of altruistic behaviour in social organizations using two examples

  • Wolves - In a pack of wolves, there is a dominant male and female which are the sole reproducers, and the other members of the pack hunt and bring back food for the breeding pair.
  • Naked Mole Rats - There exist breeding males and females, the diggers (who dig tunnels and provide food) and protectors who offer their lives when facing a predator. The concept is that the sacrificers will indirectly pass on their genes by protecting the mating pair.

AHS The ANS (Autonomic Nervous System)[edit]


The ANS consists of sympathetic and parasympathetic neurons.

The roles of the sympathetic and parasympathetic system are largely antagonistic towards one another - that is, the parasympathetic nerves might stimulate a bodily function that will be inhibited by the sympathetic nerves.

The ANS serves the heart, blood vessels, smooth muscles and digestive system.

Their comparative effects can be explained as follows:

Parasympathetic Nerves Largely concerned with calming and returning the body’s emphasis to self-maintenance functions. Originate in the lower brain and at the base of the spinal cord. Stimulate the salivary glands. Constricts the pupil. Slows the heart.

Sympathetic Nerves Correlates with arousal and energy generation, focusing on specific functions. Originate from the middle region of the spinal cord. Inhibit salivary gland secretion. Dilates the pupil. Accelerates the heart.

Discuss the relationships between the influence of the conscious part of the brain and automatic reflexes as shown by bladder or anus control, meditation and yoga - this basically means that it is possible for a person to override automatic reflexes (for example, by concentration).

Neurotransmitters and Synapses[edit]


State that synapses of the peripheral nervous system (PNS) are classified according to the neurotransmitter used, including acetylcholine and noradrenalin. --Synapses of the PNS are classified according to the neurotransmitter used. Cholinergic synapses use acetylcholine and adrenergic synapses use noradrenalin. Most adrenergic synapses are sympathetic and most cholinergic synapses are parasympathetic.


Explain how pre-synaptic neurons can either encourage or inhibit post-synaptic transmission by depolarization or hyperpolarizaton of the post-synaptic membrane.--Pre-synaptic neurons can encourage post-synaptic transmission by depolarization of the post-synaptic membrane. It does this by causing sodium ions or other positively charged ions to enter the post synaptic neuron, helping to depolarize it and cause and action potential. This is called an excitatory synapse. --Pre-synaptic neurons can inhibit post-synaptic transmission by hyperpolarizaton of the post-synaptic membrane. This happens when negative chloride ions move to the post-synaptic neuron, increasing polarization. This is called hyperpolarizaton and makes it more difficult to depolarize a neuron sufficiently to cause an action potential. These synapses are called inhibitory synapses.


Outline how pain is sensed and how endorphins and enkephalins can act as painkillers.--Pain receptors are located in the skin and on organs. Pain signals are sent along these nerve endings along nerve fibers on the spinal cord. The signals pass synapses to neurons that carry them up in an ascending tract to the stem or thalamus of the brain. The signals may pass on in other neurons to sensory areas of the cerebral cortex, causing conscious pain. --Endorphins and enkephalins act as painkillers by stopping the pain signal to the brain. Enkephalins block calcium channels in the membrane of the pre-synaptic neurons. They block the synaptic transmissions, so the message doesn’t reach the brain. Endorphins are released from the pituitary gland to control pain. They are carried to the brain and bind to pain receptors and block the release of the neurotransmitter that is used to transmit pain signals to the brain.


Outline the symptoms of Parkinson’s disease and the involvement of dopamine.--Parkinson’s is from the death of neurons in a certain part of the brain called the substanti negra. These neurons release dopamine at synapses that control muscle contradictions. The synapses at which dopamine are released are inhibitory. Muscle contractions cannot be controlled properly without dopamine and this leads to the symptoms of Parkinson’s. The early symptoms of Parkinson’s are feeling shaky and tired and the loss of concentration. Eventually the body becomes stiff because the antagonistic muscles cannot relax. Uncontrollable shaking affects the hands and other parts of the body and movements become very slow.


Explain that psychoactive drugs affect the brain and personality by either increasing or decreasing synaptic transmission.--psychoactive drugs affect the brain and personality by either increasing or decreasing synaptic transmission. They do this by 1) some act as neurotransmitters and bind to receptors for that neurotransmitter in post-synaptic membranes. They block the receptor, preventing the neurotransmitter from having its usual effect; 2) some have the same effect of a neurotransmitter, but unlike the neurotransmitter, they are not broken down when they bind to the receptors, so the effect lasts much longer; and finally 3) some interfere with the breakdown of neurotransmitter in synapses and prolong the effect of the neurotransmitter.


Discuss the behavioral effects of the excitatory psychoactive drugs nicotine, cocaine and amphetamines.--The behavioral effect of the excitatory psychoactive drug nicotine are said to be calming and thus an increase in the nicotine levels reduces the craving for it. The behavioral effect of the excitatory psychoactive drug cocaine is alertness, increased energy, and talkativeness. The behavioral effect of the excitatory psychoactive drug amphetamines has a similar effect of cocaine, but usually last longer. Users frequently become aggressive and hyperactive. One amphetamine is ecstasy and it usually fosters feelings of empathy, openness and caring. It lowers feelings of aggression and increases sexual behavior.

Discuss the behavior effects of the inhibitory psychoactive drugs benzodiazepines, cannabis and alcohol.--The behavioral effect of the inhibitory psychoactive drug benzodiazepine is a feeling of relaxation and reduction of anxiety. High doses cause drowsiness, slurred speech, and loss of muscle coordination. The behavioral effect of the inhibitory psychoactive drug cannabis is an increases intensity of sensual perception and the feeling of emotional well-being and allows clear thinking of complex ideas. The behavioral effect of the inhibitory psychoactive drug alcohol is said to reduce inhibitions, making people more talkative and confident. It impairs reaction times and fine muscle coordination. In large quantities it causes loss of memory, slurred speech, loss of balance and poor muscle coordination.