Co-ordination & Response (Edexcel IGCSE Science (Double Award): Biology)

The diagram shows three types of neurone.

(i) Give the names of these neurones.

(3)

(ii) Explain the role of these neurones in the withdrawal reflex of a finger from a hot object.

(3)

A teacher uses this method to estimate the speed of a nerve impulse.

• Students stand in a circle and hold hands

• Student A in the circle starts a timer and at the same time squeezes the hand of student B on his left

• When student B feels his hand being squeezed, he immediately squeezes the hand of the student on his left

• This process continues around the circle of students until student A feels his hand being squeezed and he stops the timer

(i) Explain what other measurements the teacher would need to make in order to calculate the speed of a nerve impulse.

(2)

(ii) Describe whether the teacher’s method is likely to give an accurate estimate of the speed of a nerve impulse.

(2)

Humans can control their internal environment.

State the term used to describe the control of an organism’s internal environment.

Coordination uses hormones and nerves.

Some responses are simple reflex arcs.

Describe the structure and functioning of the withdrawal reflex of a finger from a hot object.

Humans use their skin to regulate their body temperature. The diagram shows a section through the skin with two structures labelled A and B.

Changes take place in the skin when a person moves from a warm environment to a cold environment.

(i) Explain the changes that take place in structure A as a person enters a cold environment.

(2)

(ii) Explain the changes that take place in structure B as the person enters a cold environment.

(3)

The diagram shows the position of some hormone producing glands in the female body.

Which of these structures is the adrenal gland?

The adrenal gland is an organ that secretes adrenaline.

State what is meant by the term organ.

Adrenaline is released into the blood when there is danger.

The list gives the effects of adrenaline on different parts of the body.

• dilates the pupil in the eye

• increases heart rate

• narrows small arteries in the intestine

• converts glycogen into glucose in the liver

Explain the advantages of these effects to a person in danger.

Neurones transmit nerve impulses. The diagram shows a neurone.

(i) This neurone is involved in the withdrawal reflex of a finger from a hot object.

The neurone transmits electrical impulses from the central nervous system to the effector.

Draw a circle on the diagram to show the part of the neurone where the impulses are transferred to the effector.

(1)

(ii) What is the name of this type of neurone?

(1)

(iii) Explain the advantage of a withdrawal reflex when a finger touches a hot object.

(2)

Some neurones do not have a myelin sheath.

A scientist investigates the impulse speed for neurones with different diameters. She does this for neurones with a myelin sheath and neurones without a myelin sheath.

The graph shows the scientist’s results.

(i) Which conclusion is supported by the graph?

(1)

(ii) A neurone with a myelin sheath has a diameter of 1.0 μm. 

Use the graph to determine the speed of an impulse in this neurone in m per s.

(1)

(iii) The neurone is 90 cm long.

Calculate the time taken (in seconds) for an impulse to travel along this neurone.

Give your answer in standard form.

(3)

The photograph shows a small animal called a woodlouse.

JMK, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

Woodlice often live under pieces of dead wood in dark, humid conditions.

Design an investigation to find out if light intensity affects the speed at which woodlice move.

Include experimental details in your answer and write in full sentences.

The diagram shows the structure of a human eye.

(i) Which of these is the structure labelled X?

(1)

(ii) When looking at a close object, which row of the table shows the state of the ciliary muscles and suspensory ligaments?

(1)

(iii) Explain how structure Y in the diagram controls the light entering the eye when someone walks into a dark room.

(2)

Multiple sclerosis is a condition that can slow down the speed at which electrical impulses travel along neurones.

The time taken for the blink reflex to occur can be used to help diagnose if someone has multiple sclerosis.

The blink reflex causes the eyelid to close.

Air is blown on to the eye and the time taken for the eyelid to close is recorded.

The diagram shows the reflex pathway.

The speed the impulse moves along the reflex arc consisting of all three neurones in a person without multiple sclerosis is 77 metres per second.

The time taken for the blink reflex to occur in a person with multiple sclerosis is 0.0050 s.

The total length of the neurones in the reflex arc for the person with multiple sclerosis is 25 cm.

(i) Calculate the difference between the speed of impulse for the person with multiple sclerosis and for the person without multiple sclerosis.

Give your answer in metres per second.

(3)

(ii) The speed of an impulse along the axon of the motor neurone for someone without multiple sclerosis is 120 metres per second.

Suggest why the speed of the impulse calculated along all three neurones is less than the speed of the impulse along only the motor neurone.

(2)

The diagram shows a section through the human eye.

(i) Describe the role of structures A, C and D in focusing light from a near object onto the retina.

(4)

(ii) Bright light can damage the retina.

Explain how a reflex involving structure B protects the retina from this damage.

(3)

There are tear glands that release liquid into the eye.

This liquid contains an enzyme called lysozyme that breaks down cell walls.

(i) Suggest why the liquid contains lysozyme.

(2)

(ii) Suggest why the liquid is maintained at pH 7

(2)

Nerve tissues that communicate with muscles contain a receptor called the nicotinic acetylcholine receptor.

The diagram below shows how a nerve impulse passing along neurone X is passed to a motor neurone.

The motor neurone in the diagram is connected to the diaphragm, a muscle involved in breathing.

Identify the type of neuron represented by neurone X?

Describe the series of events that would need to occur within the structures covered in part (a) in order for the diaphragm to contract.

Anatoxin is a neurotoxin that is also known as ‘Very Fast Death Factor’ because when it is injected into mice it induces paralysis and death within a few minutes.

Anatoxin is similar in shape to the neurotransmitter that usually binds to the nicotinic acetylcholine receptor.

Suggest how anatoxin can lead to death.

A group of scientists wanted to investigate the control of blood glucose in mice.

They fed one group of mice with a normal diet and another group with a ‘high fat’ diet containing a high level of both fat and sugar for three weeks beforehand. They then measured the blood glucose levels of the mice over a period of 2 hours directly after a meal. Their results are shown below.

Explain the change in blood glucose levels for the normal diet mice during the first 90 minutes after the meal.

After the first 90 minutes the normal diet mice show an increase in blood glucose despite no more food being eaten.

Suggest why blood glucose increases despite no more food being consumed.

Suggest an explanation for the results shown in part (a) for the mice on a high-fat diet.

After carrying out the investigation detailed in part (a) the scientists gave the high fat diet mice supplements of a drug called a DDP-4 inhibitor in their drinking water. Inhibitors reduce or prevent the activity of specific enzymes; the enzyme inhibited by the DDP-4 inhibitor is known as DDP-4.

The functional DDP-4 enzyme works by inactivating another enzyme known as GLP-1. The results of this in the body are shown below.

Suggest and explain how the administration of DDP-4 inhibitors might affect the blood-glucose levels of the high fat diet mice.

A group of students wanted to investigate geotropism in bean seedling roots.

The set-up of their experiment is shown in the diagram below.

The students used the following method:

• Measure the starting length of the roots of 5 bean seedlings

• Pin the 5 bean seedlings to a cork mat as shown in Apparatus A

• Place Apparatus A in a dark cupboard for 3 days

• After 3 days, measure the length of the root in each seedling and make a drawing of each seedling

The students' teacher told them that their method was incomplete and that they needed to set up a control experiment (which will be referred to as Apparatus B) for comparison.

Describe how Apparatus B could be set up so to provide the students with a control experiment.

Explain why the seedlings in the experiment in part (a) were placed into a dark room?

The students carried out their experiment using 10 bean seedlings split across two sets of apparatus; Apparatus A and Apparatus B (the control).

The results of the student’s investigation are shown in the table below.

Complete the table to calculate the mean change in length for the bean seedlings in Apparatus A and Apparatus B.

The diagram below shows the appearance of the seedlings at the end of the 3 days.

Explain the appearance of the seedlings in the diagram.