2.4 Co-ordination & Response

Figure 1 shows a human brain with four regions labelled A - D. 

Figure 1

Identify regions A - D and give an example of a role of each region.

Ancient scientists including Aristotle (4^th Century BCE) believed that the brain's main function was to allow excess heat to be radiated from the body. This has since been disproved by other scientists.

Suggest and explain an aspect of the brain's appearance that caused Aristotle to put forward this theory of the brain's function. 

Higher Tier only

In 1975, a woman standing on a railway station platform was hit from behind by the open carriage door of a moving train. Sadly, she sustained a serious injury to the back of her head and was blinded instantly.

Explain why the woman lost her sight after this incident. 

Higher Tier only

Sophisticated scanning techniques like CT and PET have allowed doctors to visualise brain function and diagnose disease, as an alternative to the use of invasive procedures like surgery. This has allowed information to be gathered much more safely and quickly in hospitals.

Contrast the techniques of CT and PET for providing information on brain function. 

A measles infection can cause inflammation of the brain.

Figure 1 shows a brain.

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..................................... people

Figure 1 shows a neurone found in the human nervous system.

Figure 1

State the name of the type of neurone seen in Figure 1 and describe its role in the nervous system.

(2)

(ii)

Label the dendrites on Figure 1.

(1)

The optic nerve is responsible for carrying electrical impulses to the brain from the eye

The eye responds to changes in the environment, such as changing light levels. Figure 2 shows a section of the eye.

Figure 2

State the structure and function of parts A, B and C in Figure 2.

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Astigmatism is an eye condition that causes blurred vision and short-sightedness.

Explain, in terms of light entering the eye, how short-sightedness is caused.

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(ii)

Suggest what type of lens could be used to correct astigmatism and explain how this would work.

(3)

The nervous system contains important structures called synapses. 

Explain how a signal is transmitted at a synapse.

Some painkillers work by reducing the ability of synapses to transmit signals.

One scientist investigated the effect of different painkillers on the amount of pain felt by the patient. They tested paracetamol, ibuprofen and a placebo (sugar tablet containing no medication).

The results are shown in Figure 3 below.

Figure 3

State why the scientist decided to use a placebo in the experiment. 

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(ii)

A student concluded that paracetamol was the most effective painkiller.

Evaluate this conclusion.

(4)

The human nervous system is responsible for detecting and responding to changes in our environment. 

Describe how impulses in the reflex arc are transmitted in order to decrease the chances of getting hurt when accidentally touching a hot saucepan. 

Two students decided to investigate the speed of transmission of electrical impulses in the nervous system. 

They decided to test how caffeine affected their reaction times. Student A drank a 330ml caffeinated sports drink while Student B drank a 330ml glass of water. They tested their reaction times every 5 minutes by dropping a ruler between their fingers and timing how long it took to catch the ruler.

The results of their experiment are shown in Table 1 below.

Table 1

Impulses in neurones in the reflex arc can travel at 120 metres per second. 

The sensory neurone in a single reflex arc is 76mm long.

Use the equation:    

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Higher Tier only

Advances in brain scanning mean that signs of MS can be picked up much earlier than in previous years. 

Magnetic Resonance Imaging (MRI) scans are the most effective way to detect changes in the brain tissue that highlight MS. The paler the appearance of the tissue, the greater the damage to the myelin sheath. 

Figure 1 shows an MRI scan comparing a brain of a person without MS to a brain of a person that has MS.

Figure 1

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(2)

Describe the differences between the structures and functions of a sensory neurone and a motor neurone.

The speed of a nervous impulse travelling along a myelinated axon is around 150 metres per second. 

A sensory impulse generated in a man's toe travels 1.5 metres along myelinated axons to his central nervous system, crossing 4 synapses on its journey.

The average time required for a synapse to transmit an impulse is 2 milliseconds, (or 2 × 10^-3 seconds).

Calculate the overall time taken for the nervous impulse to reach the man's central nervous system.

Suggest and explain how the time taken to transmit the impulse would differ if the impulse were to travel along unmyelinated axons. 

Figure 1 shows an eye.

Figure 1

A student was given the hypothesis ‘People with brown eyes are more likely to be short-sighted than people with blue eyes.’

Devise a plan to test this hypothesis.

Figure 1 shows a picture seen through healthy eyes and the same picture seen through eyes affected by cataracts.

Figure 1 

Figure 2 shows the estimated number of people with cataracts in the world between 1980 and 2020.

Describe the change in the estimated number of people with cataracts between 1980 and 2020.

The effect of age on focusing distance was investigated.

Volunteers of different ages had their eyes tested.

Each volunteer was asked to read words from a book. The book was moved closer to their eyes.

When the words became out of focus, the distance was recorded.

Figure 1 shows the results.

Figure 1

(3)

.......................................... mm

(1)

(2)

Which part of the eye detects coloured light?

Figure 2 shows light rays entering the eye of a person with normal vision.

Figure 2

Figure 3 shows light rays entering the eye of a person with an eye defect and two lenses that can be used to correct eye defects.

Figure 3

Figure 1 shows the number of neurones in the brain of different animals.

Figure 1

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........................................ neurones

(3)

Figure 2 shows a sensory neurone.

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(2)

Explain how impulses are transmitted at synapses.

Figure 1 shows a diagram of the human eye.

Figure 1

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(2)

Eye tests can detect some brain tumours.

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(2)

Figure 1 shows part of a reflex arc in the spinal cord.

Figure 1

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(2)

A scientist investigated the reaction times of five students using a computer program.

The computer screen showed a blue square at the start.

As soon as the blue square turned yellow, each student had to press a key on the keyboard as fast as possible.

Figure 2 shows the results for the five students.

Figure 2

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