IB DP Biology Option A: Neurobiology and behaviour (Core topics) : A.3 Perception of stimuli HL Paper 3

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Question

A cataract is a clouding of the lens in the eye, resulting in blurred vision.

[Source: Cataract in Human Eye, Rakesh Ahuja, MD (https://en.wikipedia.org/wiki/Cataract#/media/File:Cataract_in_human_eye.png)]

Explain the use of a local anesthetic during surgery to remove the cataract.

[2]
b.

Describe red-green colour blindness.

[2]
c.
Answer/Explanation

Markscheme

a. reduction/elimination of pain

    OR

    to block sensory perception

b. blocks synaptic transmission between «sensory neurons and CNS»

    OWTTE

c. allows patient to remain aware

d. prevent reflex causing blinking/eye movement

    OWTTE

[Max 2 Marks]

b.

a. sex/X-linked «genetic trait»

b. results from absent/defective cone cells

c. cannot distinguish between red and green

[Max 2 Marks]

c.

Question

The diagram shows the mechanism of action of the psychoactive drug cocaine.

Suggest how cocaine might influence the brain.

[2]
a.

Dopamine acts as a slow-acting neurotransmitter. Outline one function of slow-acting neurotransmitters.

[2]
b.

Outline the structure of a reflex arc.

[3]
c.

State the type of receptor that detects odours.

[1]
d.
Answer/Explanation

Markscheme

a. «cocaine» is an excitatory drug  OWTTE
OR
excitatory influence on the brain 

b. increase the concentration/level of dopamine in the synapse  OWTTE

c. prolonged effect/continuous stimulus of dopamine on the brain/postsynaptic neuron 

d. addiction/dependence on high levels of dopamine for the same effect/addiction

a.

a. they contribute to memory/learning 

b. they modulate fast synaptic transmission «in the brain» 

c. by causing the release of secondary messengers in the postsynaptic neuron

b.

a. receptor cell  

b. sensory neuron passes stimulus 

c. to interneuron/relay neuron 

d. which transmit response to motor neuron 

e. effector

Award marking points for a clearly annotated diagram.
eg:

c.

olfactory «receptor»
OR
chemoreceptor

d.

Question

Graph 1 shows the range of light wavelengths detected by the three types of cone cells in normal colour vision. Graph 2 shows the range of light wavelengths detected by a person with one form of colour blindness. Each line shows a different type of cone cell.

Deduce, with a reason, the difference in colour perception between people with normal colour vision and those with this type of colour blindness.

[2]
a.

Explain how sounds of different wavelengths are distinguished by the ear.

[3]
b.
Answer/Explanation

Markscheme

difference in colour perception:

a. cannot distinguish red and green 

reason:

b. green and red cones detect very similar wavelengths
OR
peak of altered green shifts to the right
OR
range of altered green wider «than normal green»

a.

a. «movement of eardrum and ossicles» causes vibration of cochlear fluid 

b. hair cells in different position «along the basal membrane» have hair/cilia of different length  OWTTE

c. different hair/cilia vibrate at different wavelengths 

d. «different hair cells send different» nerve signals in the auditory nerve

b.

Question

Approximately 350 000 people worldwide have received cochlear implants. Outline the use of cochlear implants in patients with hearing problems.

[3]
a.

State the part of the ear that is responsible for detecting movement of the head.

[1]
b.

Describe the role of bipolar cells in the eye.

[3]
c.
Answer/Explanation

Markscheme

a. microphone outside the ear pick up sounds 

b. sound waves converted to electronic/digital signals 

c. electronic impulses sent to electrode in cochlea 

d. «electrode» directly stimulates auditory nerve 

e. signals «generated by implant» sent to brain which recognizes signals as sound

a.

semicircular canals

b.

a. transmit the signals from the photoreceptors «rods and cones» to the ganglion cells 

b. groups of/more than one rod cell synapse with one bipolar cell 

c. one cone cell synapses with one bipolar cell 

d. once light is absorbed bipolar cell depolarizes 

e. activates/depolarizes a ganglion cell

c.

Question

State the function of the bones in the middle ear.

[1]
b.

Explain the role of the hair cells in the cochlea.

[3]
c.
Answer/Explanation

Markscheme

amplify/transmit the sound/vibrations

b.

a. hair cells located within the organ of Corti
OR
hair cells are mechanoreceptors

b. hairs/cilia of hair cells move/vibrate with the movement of the liquid/fluid in the cochlea

c. amount of movement is proportional to the amplitude/loudness of the sound

d. frequency/wavelength/pitch distinguished by different hair cells/according to position of hair cells/length of hairs/cilia

e. hair cells transmit impulses to auditory nerve/brain

c.

Question

Explain how colour in the environment is detected by the eyes and relayed to the brain in humans.

Answer/Explanation

Markscheme

Detected by the cones
OR
Cones are photoreceptors

They are located in the retina/concentrated in the fovea

Three types of cones that absorb different wavelengths of «visible» light

Cones absorb light passing impulse to bipolar cell

Bipolar cells connected to ganglion cells

There is one to one connection of cones to bipolar cells
OR
One to one connection of bipolar cells to ganglion cells

Relayed to the optic nerve

Right field of vision «of both eyes» is sent to the left part of the brain (Vice versa)

Information is passed to the visual cortex/occipital lobe

Question

 Label the numbered parts of the reflex arc.

[2]
a.

 State the type of human sensory receptor that detects motion, gravity and stretch.

[1]
b.

 State the part of the brain responsible for coordination and balance, especially during athletic competition such as the Olympics.

[1]
c (i).

 Outline control of heart rate by the medulla oblongata.

[2]
c (ii).
Answer/Explanation

Markscheme

Award [1] for every two correct up to [2 max].
I: sensory/afferent neuron;
II: interneuron/relay neuron;
III: motor/efferent neuron;
IV: effector/muscle;

a.

mechanoreceptor

b.

cerebellum

c (i).

a. (autonomic nerve signals from medulla oblongata) can override pacemaker;
b. parasympathetic stimulation decreases heart rate;
c. parasympathetic/vagus nerve runs from the medulla oblongata to the heart;
d. sympathetic nerves from medulla (travel down spinal cord where) synapse with other nerves before going to heart;

c (ii).

Question

Explain how the ear converts sound waves in the air to the nerve impulses sent to the brain.

Answer/Explanation

Markscheme

a. sound waves cause the eardrum to vibrate;

b. the eardrum transmits these vibrations to the bones (of the middle ear);

c. the bones (ossicles) amplify the vibrations;

d. the bones cause movement / vibration of the oval window;

e. (the oval window) causes movement of the fluid in the inner ear/cochlea:

f. causes movement of the hairs (of hair cells);

g. triggers action potential/nerve impulse;

h. transmitted to brain by the auditory nerve;

i. round window equalizes pressure in the inner ear;

Question

Label the following diagram of the eye.

[2]
a.

Outline how the pupil reflex can be used to indicate brain death.

[2]
b.

The diagram below shows a synapse where the neurotransmitter is dopamine and some of the processes that take place during nerve transmission.  

Explain the effect of cocaine on neurotransmission at a synapse.

[3]
c.
Answer/Explanation

Markscheme

I iris
II vitreous humour
III choroid
IV fovea (do not accept yellow spot)
Award [1] for every two correct answers.

a.

a. pupil normally constricts when light is shone on it;
b. light detected in the retina and impulse sent to brain;
c. lack of (motor) response indicates no brain processing taking place/brain death;

b.

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

c.

Question

The diagram shows the structure of the human ear.

Label structures I and II

I.  …………………………………………………….

II.  ……………………………………………………. 

[1]
a (i).

Outline how sounds are perceived in the cochlea, including the name of the cell type involved.

[1]
a (ii).

Identify a function of the parts of the brain by using numerals II to V to complete the chart. Hypothalamus has been completed for you.

[2]
c.

Discuss how the pupil reflex can be used as a test for brain death.

[2]
d.
Answer/Explanation

Markscheme

I: pinna;
II: ear drum / tympanic membrane; (both needed)

a (i).

cilia/hair/hair bundles of hair cells vibrate with (cochlear) liquid/fluid movement

a (ii).

Award [1] for any two correct responses.

c.

a. pupil reflex is controlled by autonomic nervous system/brain/midbrain; (do not accept medulla)
b. light shone into the eye would normally cause pupil contraction;
c. no pupil reflex indicates that synapses are not functioning;
d. can indicate brain death but not necessarily / OWTTE;

d.

Question

Explain how sound is perceived by the ear.

Answer/Explanation

Markscheme

eardrum moved by sound waves;
eardrum/tympanic membrane causes movement of the malleus/bones of the middle ear/ossicles;
bones of the middle ear/malleus, incus and stapes/hammer, anvil and stirrup amplify/magnify movement;
bones of the middle ear/stapes push on the oval window;
causing movement of fluid/vibration within the cochlea/inner ear;
hair cells are mechanoreceptors;
which release a chemical neurotransmitter when stimulated;
sounds/vibrations are transformed into nerve impulses/action potentials;
carried by auditory nerve to brain;
round window releases pressure so fluid in cochlea can vibrate;

Question

Identify the parts of the brain indicated on the diagram below.

[2]
a.

Outline the unconscious control of the heart rate.

[3]
b.

Describe different aspects of the processing of visual stimuli.

[3]
c.
Answer/Explanation

Markscheme

I. cerebral hemisphere / cerebrum;
II. hypothalamus;
III. cerebellum;
IV. medulla oblongata;
Award [1] for any two of the above.

a.

heart can contract without nervous stimulation/myogenic contractions;
SA node is pacemaker/generates heart beat/initiates each cardiac cycle;
epinephrine/adrenalin speeds up the heart rate;
autonomic/sympathetic and parasympathetic nervous system control;
sympathetic speeds up heart rate;
parasympathetic/vagus nerve slows heart rate (back to normal/resting rate);

b.

edge enhancement is greater perception at edges of light/dark areas;
caused by processing in two types of ganglion cell in retina;

contralateral is processing left field of view in right side of brain / vice versa;
cross over between left and right sides in the optic chiasma;

convergence is combining impulses from groups of (rod/cone) cells;
done by bipolar cells in retina;

c.

Question

Label the diagram of the ear.

Answer/Explanation

Markscheme

I eardrum / tympanic membrane
II cochlea
III auditory/vestibulocochlear nerve
IV semicircular canals
Award [1] for every two correct.

Question

The diagram below represents the human eye. State the names of structures I, II, III and IV.

I. …………………………………………………………

II. …………………………………………………………

III. …………………………………………………………

IV. …………………………………………………………

[2]
a.

Outline the evidence provided by DNA for the common ancestry of living organisms.

[2]
b.

The cladogram below shows the classification of species A to D. Deduce how similar species A is to species B, C and D.

[2]
c.

Suggest two reasons for using cladograms for the classification of organisms.

[2]
d.
Answer/Explanation

Markscheme

I. cornea;
II. lens;
III. vitreous humour;
IV. choroid; (Accept sclera as line is on the border between these two)
Two correct for [1] and four correct for [2].

a.

all living organisms use DNA as genetic/hereditary material;
genetic code is (almost) universal;
idea that mutations accumulate gradually in DNA;

b.

A is most similar to B;
A is equally similar to C and D;
A is least similar to both C and D;

c.

methods used to prepare cladograms use a different approach from traditional classification/taxonomy;
show ancestral relationships;
reflect how recently two groups shared a common ancestry;
cladograms are (objective/accurate because they are usually) based on molecular differences;
they should be considered as a good complement to traditional classification;

d.

Question

Removal of toxic heavy metals from industrial waste water is essential in order to control environmental pollution. Industrial waste water near Yanbu City, Saudi Arabia was found to contain 19 species of microorganisms that could tolerate heavy metals. The accumulation of cadmium ions in the most common of these microorganisms, Aspergillus fumigatus, was investigated.

The graph below shows the effect of pH on the ability of A. fumigatus to absorb cadmium ions from an aqueous solution.

Describe the cadmium ion uptake by A. fumigatus at pH 6.

[2]
a.

Calculate the difference in cadmium ion uptake between pH 4 and pH 5 at 60 minutes.

……………………..%

[1]
b.

Discuss the use of A. fumigatus for the removal of cadmium ions in polluted waters.

[2]
c.

The investigation found that both living and dead A. fumigatus cells were able to absorb cadmium ions. Suggest an advantage of using dead A. fumigatus cells.

[1]
d.
Answer/Explanation

Markscheme

rapid initial uptake (to approximately 75 % uptake);
rate of uptake slows and plateaus (at approximately 85 % uptake after 90 minutes);
only 90 % of cadmium ions absorbed (however long the contact time) / reaches maximum at 120 min;

a.

64 (%) (allow responses in the range of 62 to 66 %)

b.

can remove almost 100 %/98 % cadmium ions at pH 5 therefore very efficient;
A. fumigatus able to remove cadmium ions at pH values tested;
removal of cadmium ions more efficient at higher pH/weak acid;
strongly acidic/very low pH may inhibit/reduce uptake of cadmium ions by A. fumigatus;
pollution causing acidification of water may make removal more difficult;
A. fumigatus common therefore may be convenient/easy to use / OWTTE;
cadmium is not actually removed as it may pass along food chains / be released when A. fumigatus dies / unknown impact on environment;

c.

easier to store/collect/transport dead/dried material;
prevents overgrowth of A. fumigatus;
reduce BOD and allow other organisms to use more resources/live in water;

d.

Question

The diagram below shows a section through the ileum.

The diagram below shows the structure of the retina. Label I and II.

[1]
a (i).

Label I and II.

[1]
a (i).

Distinguish between rods and cones.

[2]
a (ii).

Outline the pupil reflex.

[2]
b.

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

[3]
c.
Answer/Explanation

Markscheme

I: ganglion cell
II: bipolar cell/neuron
(both needed)

a (i).

I: lacteal
II: longitudinal/smooth muscles / muscularis mucosa
(both needed)

a (i).

To award [2 max] responses need to be compared.
Responses do not need to be shown in a table format.

a (ii).

rapid unconscious response to change in light intensity / controls amount of light entering eye to prevent damage to retina/to see in darkness;
in bright light circular muscles in iris contract causing pupil to constrict / in dim light longitudinal/radial muscles in iris contract causing pupil dilation;
constriction by parasympathetic NS / dilation by action of sympathetic NS;

b.

pupil reflex is a brain stem reflex / shows activity in the medulla oblongata;
pupil reflex must be absent in brain death;
pupil reflex is possible in coma victims where motor function is absent;
pupil reflex alone not enough to diagnose brain death;
other criteria include coma/absence of response to pain in all extremities/ absence of brain stem reflexes/lack of respiratory movements;
some cases of coma irreversible / some cases may recover;
doctors need to diagnose damage to decide treatment/long-term life support /organ donation;

c.

Question

Explain how the structures of the human ear allow for sound perception.

Answer/Explanation

Markscheme

eardrum/tympanic membrane vibrates with sound (waves);
movements of eardrum/tympanic membrane amplified by bones of middle ear/stapes;
bones are malleus/hammer, incus/anvil, stapes/stirrup;
movement transmitted to oval window;
creates pressure waves in the liquid within cochlea;
waves travel up to/dissipate at round window;
hairs in cochlea vibrate according to movement (of liquid/waves);
different frequencies detected by different hair cells (on different parts of membrane);
movement of hairs cause action potential/depolarization/hyperpolarization of hair cells;
cause nerve impulses to be transmitted through auditory nerve;

Question

Explain how the structures of the human ear allow for sound perception.

Answer/Explanation

Markscheme

eardrum/tympanic membrane vibrates with sound (waves);
movements of eardrum/tympanic membrane amplified by bones of middle ear/stapes;
bones are malleus/hammer, incus/anvil, stapes/stirrup;
movement transmitted to oval window;
creates pressure waves in the liquid within cochlea;
waves travel up to/dissipate at round window;
hairs in cochlea vibrate according to movement (of liquid/waves);
different frequencies detected by different hair cells (on different parts of membrane);
movement of hairs cause action potential/depolarization/hyperpolarization of hair cells;
cause nerve impulses to be transmitted through auditory nerve;

Question

List two stimuli and the receptors that detect them.

[2]
b.

Outline how pain is perceived and the role of endorphins in this process.

[3]
c.
Answer/Explanation

Markscheme

a. pressure/movement/sound (detected by) mechanoreceptors;

b. chemicals (detected by) chemoreceptors;

c. temperature (detected by) thermoreceptors;

d. light (detected by) photoreceptors;

e. pain (detected by) nocireceptors;

f. stretch/orientation/movement (detected by) proprioreceptors;

b.

a. impulses passed from pain receptors to sensory areas;

b. of the cerebral cortex where pain is perceived / feelings of pain in the areas of the cerebral cortex;

c. endorphins act as painkillers;

d. which block transmission of impulses at the synapses involved in pain transmission;

c.
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