Option E: Neurobiology and Behaviour

Question 1

Define stimulus.

Answer 1

A change in the internal or external environment that is detected by a receptor and causes a response.

Question 2

Define response.

Answer 2

A change in an organism as a result of a stimulus.

Question 3

Define reflex.

Answer 3

A rapid and unconscious response to a stimulus.

Question 4

What is the role of receptors in the response of animals to stimuli?

Answer 4

• Specialised cell or nerve ending - Detects a specific stimulus and transforms into electric nerve impulse - Detects internal and external stimuli

Question 5

What is the role of sensory neurons in the response of animals to stimuli?

Answer 5

-Carries nerve impulses from the receptor to the central nervous system.

Question 6

What is the role of of the relay neurons of animals to stimuli?

Answer 6

• Carries nerve impulse from the sensory neuron to the motor neuron - Links up with other relay neurons to carry information up and down the spinal cord.

Question 7

What is the role of motor neurons in the response of animals to stimuli?

Answer 7

• Carries nerve impulses from the central nervous system to the receptor

Question 8

What is the role of synapses in the response of animals to stimuli?

Answer 8

• Connect neurons together - Control how information is passed from one neuron to another - Uses chemicals as neurotransmitters to diffuse across the synaptic cleft

Question 9

What is the role of effectors in the response of animals to stimuli?

Answer 9

• Muscle or secretory gland - Carries out a response to the stimulus.

Question 10

Draw and label a diagram of a reflex arc for pain withdrawal reflex.

Answer 10

Question 11

How can animal responses be affected by natural selection, using two examples?

Answer 11

Natural selection describes the process by which the frequency of an inheritable characteristic changes as a result of environmental agents. Beneficial characteristics are more likely to be passed on to the next generation, as they will increase survival rates. For example, the blackcap (Sylvia atricapilla) exhibits behavioural variation in its migration patterns from its summer breeding grounds in Germany. Historically, most blackcaps migrated south to Spain (warmer climate) with a minority migrating west to the UK (closer, but colder). With a rise in global temperatures, more blackcaps are now migrating west to the UK (more favourable survival prospects) - beneficial gene of choosing to go west. The house sparrow (Passer domesticus) will chirp and gape as a fledgling in order to be fed by its parents In a nest of chicks, those which chirp louder and gape more obviously are more likely to be fed more and survive longer Hence the alleles responsible for chirping and gaping are passed to offspring increasing prevalence of the behaviour.

Question 12

What four different types of human sensory receptor are there?

Answer 12

Mechanoreceptor Chemoreceptor Thermoreceptor Photoreceptor

Question 13

What is the stimulus of mechanoreceptors and what types of receptor are there?

Answer 13

Stimulus: mechanical movement; pressure; forces; sound waves Types: Stretch receptors in muscles are used to position muscles in coordinated movements. Located in ears, skin and arteries.

Question 14

What is the stimulus of chemoreceptors and what types of receptor are there?

Answer 14

Stimulus: (dissolved) chemicals detected by taste buds (in the tongue and mouth);
(airborne) chemicals detected by (olfactory) receptors;
chemicals/ions/pH in blood (for example CO2/glucose) detected by chemoreceptors (in carotid artery/medulla oblongata);
neuroreceptors detect neurotransmitters;

Type: Taste and smell receptors on the tongue (taste buds) and in the nose.

Question 15

What is the stimulus of thermoreceptors and what types of receptor are there?

Answer 15

Stimulus: Change in temperature (hot/cold) Type: Hypothalamus measures temperature of blood for temperature homeostasis.

Question 16

What is the stimulus of photoreceptors and what types of receptor are there?

Answer 16

Stimulus: Light; visible light Type: Roads and cones in the retina

Question 17

Label a diagram of the structure of the human eye.

Answer 17

See diagram.

Question 18

Annotate a diagram of the retina to show the cell types and the direction in which light moves.

Answer 18

See Diagram

Question 19

Compare rod and cone cells.

Answer 19

Similarities: Both types of cells are photoreceptors and both are found in the retine. Differences - Rod cells are found outside the fovea whereas cone cells are found in the fovea - Rod cells are highly sensitive and are used in dim light whereas cone cells are less sensitive and are used in bright light - In rod cells, several rods attach to a single bipolar cell whereas there is one cone cell per bipolar cell. - There is one type of rod cell that detects all wavelengths but in monochrome whereas there are three types of cones absorbing maximally at blue, green and red regions of the spectrum creating a colour image.

Question 20

What are the three processes of visual processing?

Answer 20

• contralateral processing - convergence - edge enhancement

Question 21

How does contraleteral processing work?

Answer 21

-Pigment molecules in the rods and cones detect the light stimulus - Bipolar neurons transfer electrical information from rod or cone cells to axons of ganglion cells - Ganglion cell axons enter the optic nerves through the blind spot. - Left and right optic nerves meet at the optic chiasma in the brain - Axons from the half of the retina closest to the nose cross over to the opposite side of the brain - Thus, information from the left visual field goes to the right visual cortex of the brain and vice-versa. - This is called contralateral processing. - This allows the image to have depth and be in 3D.

Question 22

How does convergence work?

Answer 22

• There are about 100x more photoreceptor cells in the retina than axons in the optic nerve. - Bipolar cells in the retina combine impulses from groups of rods and cones and pass the signal to a single ganglion cell. - The further from the fovea the larger the number of photoreceptor cells that are grouped together. - About 10% of the axons in the optic nerve come from the cones in the fovea. - The bipolar cells relay these signal to the optic nerve via the ganglion cells.

Question 23

How does edge enhancement work?

Answer 23

Signals from rods and cones follow both vertical and lateral pathways. Photoreceptors stimulate opposing bipolar cells but inhibit adjacent bipolar cells, which is known as lateral inhibition. This makes light spots lighter and dark spots darker, with the contrast greatest at the edges, known as edgy enhancement.

Question 24

Label a diagram of the ear.

Answer 24

See diagram.

Question 25

How is sound perceived by the ear?

Answer 25

a. sound waves/vibrations in air cause ear drum/tympanic membrane to vibrate;
b. vibrations amplified by middle ear bones/ossicles/malleus, incus, stapes;
c. causes oval window/fluid in cochlea to vibrate;
d. stimulates mechanoreceptors/hair cells in the cochlea;
e. auditory nerve passes nerve impulse to brain;

Question 26

Distinguish between Innate and Learned behaviour.

Answer 26

Innate Behaviour: Behaviour that normally occurs in all members of a species despite natural variation in environmental influences.

Learned Behaviour: Behaviour developed as a result of experience, either by personal trial and error or from another individual. There are several different types of learned behaviour.

Question 27

Distinguish between Taxis and Kinesis.

Answer 27

Taxis: Locomotion of an organism in a particular direction in response to an external stimulus. A positive taxis is towards the stimulus whereas a negative taxis is away from the stimulus.

Kinesis: The movement of an organism in response to a stimulus such that the rate of movement depends on intensity not the direction of the stimulus.

Both are innate behaviour.

Question 28

Design experiments to investigate innate behaviour in invertebrates, including either a taxis or a kinesis.

Answer 28

Kinesis is a change in activity rate in response to a stimulus

Woodlice have gills for respiration that will tend to dry out in dry conditions

Step 1: Place a woodlouse in a dry petri dish and mark its movements every 30 seconds
Step 2: Repeat for a second woodlouse placed in moist conditions
Step 3: Compare the rate of movement for the two woodlice (should be more in dry dish - want to find a way out of dry environment)

Question 29

Discuss how the process of learning can improve the chances of survival.

Answer 29

animals learn to avoid dangerous situations / predators;

animals learn how to hunt/obtain food;

animals learn to adapt to changing environments;

Question 30

Outline Pavlov’s experiments into conditioning of dogs.

Answer 30

• Pavlov was a Russian scientist who conducted experiments into classical conditioning
• Dogs normally salivate (unconditioned response) in anticipation of being fed (unconditioned stimulus)
• Pavlov sounded a bell (neutral stimulus) prior to feeding a dog
• After many repetitions, the dog came to associate the bell with food and began to salivate when the bell was rung (conditioned response)
• Pavlov described this as a conditioned reflex - the stimulus that prompted the response had been changed (Known as classical conditioning)

Question 31

Define classical conditioning.

Answer 31

Classical conditioning: the modification of behaviour in an animal in response to a repeated stimulus such that the stimulus and response become associated.

Question 32

Outline the role of inheritance and learning in the development of birdsong in young birds

Answer 32

• inheritance plays role as basic song is the same for all members of a species;
• birds raised in isolation still sing but song lacks complexity/sounds different from song heard in the wild / more complex songs develop when there is social interaction; y
• oung birds learn details of songs/dialects from fathers/other birds;
• (development of birdsong) is a form of motor learning/ability to learn is genetic/inherited;

Question 33

Some presynaptic neurons ____(a)____ postsynaptic transmission and others ____(b)_____ postsynaptic transmission.

Answer 33

(a) - excite
(b) - inhibit

Question 34

Explain how psychoactive drugs affect the brain and personality.

Answer 34

a. psychoactive drugs may increase/decrease post synaptic transmission;
b. can affect mood/behaviour;
c. increase / decrease the release of neurotransmitters;
d. delay the breakdown of neurotransmitters;
e. interfere with storage/re-uptake;
f. mimic the action of neurotransmitters / block receptors;
g. reduce the effect of excitatory neurotransmitters / increase the effect/release of
inhibitory neurotransmitters;

Question 35

List three examples of excitatory psychoactive drugs

Answer 35

1. Nicotine
2. Cocaine
3. Amphetamines

Question 36

List three examples of inhibitory psychoactive drugs

Answer 36

1. Benzodiazepines
2. Alcohol
3. Tetrahydrocannabinol

Question 37

Explain the effects cocaine in terms of their action at synapses in the brain

Answer 37

dopamine initiates depolarization of post-synaptic membrane;
cocaine binds to (transporter) carrier proteins/proteins in pre-synaptic membrane;
cocaine blocks reabsorption (of dopamine);
cocaine causes dopamine build up in synaptic cleft/space;
so stimulus continues/cocaine is excitatory;

Effect:

1. Increased energy and alertness
2. More talkative
3. Constricts blood vessels
4. Elevates body temperature
5. Increases heart rate and blood pressure
6. Increases pleasurable feelings
7. Suppresses appetite

Question 38

Explain the effects of THC in terms of their action at synapses in the brain

Answer 38

THC binds to cannabinoid receptor; blocks release of (excitatory) neurotransmitter; therefore it is inhibitory; euphoria/anxiety/short-term memory loss/impaired coordination/pain relief; extended use leading to social dysfunction/addiction;

Question 39

Discuss the causes of addiction.

Answer 39

Dopamine Secretion

Dopamine affects the brain processed that control emotional response and feelings of pleasure. Thus, anything that increases activity at dopamine synapses, and hence the feelings of pleasure, is likely to be repeated.

Social Factors

These can play a key role. Drugs may provide an ‘escape’ from poverty and social deprivation. Peer pressure in ‘gangs’. Or it may be cultural, used in religious or shamanic context. People with mental health problems.

Genetic predisposition

Susceptibility to drugs of any sort (nictoine, sleeping tablets, anti-depressants, psychoactive drugs) varies from person to person. Desensitisation to a drug can take a long time in some people and in other people a single dose is sufficient. There appear to be family traits which implies a genetic component however further research needs to be done to identify the genes involved.

Question 40

Explain the effect of the interaction between the activites of excitatory and inhibatory presynaptic neurons at synapses on the CNS.

Answer 40

a. (many) excitatory and inhibitory presynaptic neurons may be connected to
postsynaptic neuron;
b. impulses from excitatory neurons increase release of excitatory
neurotransmitter (in synaptic cleft);
c. impulses from inhibitory neurons increase release of inhibitory
neurotransmitter in (synaptic cleft);
d. effects of neurotransmitters combine/cancel each other to alter (probability of)
action potential/firing in postsynaptic neuron;
e. presynaptic neurotransmitters act at same time / add up in (very) short interval; by

Question 41

Draw and label a diagram of a reflex arc for a pain withdrawal reflex

Answer 41

Question 42

How do excitatory drugs affect the brain.

Answer 42

chemical substance that acts primarily upon the central nervous system;

increase postsynaptic transmission; can cause chemical dependency / lead to substance abuse / addictions;

stimulants produce psychomotor arousal/more alertness;

by acting like neurotransmitters / interfering with breakdown of neurotransmitter;

can affect the transmission of optic signal in the thalamus/optical cortex; example given;

Question 43

Explain how the cochlea functions during hearing.

Answer 43

a. bone/ossicle/stapes contacts oval window of cochlea; b. ossicle vibrations are transmitted to cochlear fluid via the oval window; c. cochlear fluid vibrations cause movement of (basilar) membrane (in precise areas); d. movement depends on membrane width and thickness in specific area; e. movement causes shearing motion of hair bundles projecting from hair cells attached to membrane; f. stimulated hair cells generate action potential that arrive in the brain via auditory nerve;

Question 44

State the typr of receptors that detect sound and an example of these receptors.

Answer 44

Mechanoreceptors and hair cells of cochlea.

Question 45

Explain the processing of visual stimuli.

Answer 45

• both retinas receive information/stimuli from left and right fields of vision;
• left and right optic nerves cross in optic chiasma;
• neurons from both eyes carrying impulses from left field of view go to right hemisphere / vice versa / right field of vision is processed in left side of brain / vice versa;
• neurones from the optic nerve synapse (in the lateral geniculate nucleus) with neurones to the (primary) visual cortex; allowing brain to have perception of depth, distances and sizes;