The reflex arc

The nervous system allows the body of animals to respond to the environment.

The diagram shows a reflex arc of a dog stepping on a pin.

Moving a paw away after standing on a pin is an example of a reflex.

Explain how a reflex arc prevents harm to the dog.

Complete the flow diagram to show the order that structures are stimulated in this reflex arc.

One has been done for you.

Choose words from the list.

motor neurone receptor relay neurone sensory neurone

A study recorded the reaction time of people of different ages.

The table shows the mean reaction times for the different age groups.

Which age group had the fastest mean reaction time?

Calculate the percentage increase from the 25–34 age group’s mean reaction time and the 65+ age group.

Give your answer to 3 significant figures.

When drivers are at the UK limit for blood alcohol content it increases their reaction time by 0.12 s.

A 25 year old drives at the UK limit.

Which age group has a mean reaction time closest to this 25 year old driver?

A student draws and labels a diagram of a reflex arc.

The diagram shows their labelled drawing.

What mistake has the student made in their drawing?

Tick (✓) one box.

The spinal cord coordinates nervous responses.

Which other part of the central nervous system coordinates responses?

The body is also controlled by the endocrine system.

Complete the table to show two differences between the nervous system and the endocrine

Oestrogen and testosterone are both hormones.

Write down one role of oestrogen and one role of testosterone in the body.

A person with type 1 diabetes tests their blood sugar level before they eat any food.

The diagram shows their results. The units for blood sugar level are mmol / l.

The person then compares their results with the information in this table.

Explain why the person will need to take insulin.

Draw lines to connect the letters, X, Y and Z, to the correct name of each neurone.

The foot steps on a sharp object. The leg is pulled away from the sharp object.

Explain how the reflex arc in the diagram produces this response.

The body is also controlled by the endocrine system.

Adrenaline and thyroxine are both hormones.

Compare the roles of adrenaline and thyroxine in the body.

A scientist investigates the effect of glucose on insulin levels in the blood.

They drink glucose dissolved in water. They then measure the level of insulin in their blood.

The table shows their results.

Explain the change in blood insulin levels between 90 and 120 minutes.

The diagram shows the central nervous system (CNS).

Complete the sentence to describe the structure of the CNS. Use the diagram.

The CNS is made up of the........ and the........ cord.

Hot objects can burn your skin. Removing your hand from a hot object is a reflex action. The response is a reflex action because it is controlled by a reflex arc.

Suggest two other reasons why the response is a reflex action.

Draw lines to connect each part of the reflex arc to its correct function when responding to a hot object.

A student uses a computer program to measure the reaction times of their friends.

The table shows their results.

Identify the median reaction time for the five friends.

Calculate the mean reaction time for the five friends.

Use the data in the table to suggest one reason why friend D has the fastest reaction time.

Adrenaline is a hormone that speeds up reaction times.

Describe the typical features of hormonal coordination such as adrenaline in the body.

It is important that our body maintains a constant internal environment.

Complete these sentences about maintaining a constant internal environment.

You can use each word once, more than once or not at all.

carbon dioxide embryonic hydrogen insulin

metabolic oestrogen oxygen testosterone

The body needs a constant internal environment so that........ reactions take place at an appropriate rate.

The body needs to maintain........ levels so that aerobic respiration can take place.

Blood sugar levels are controlled by the hormone........

The nervous system helps the body maintain a constant internal environment. It also allows a person to respond to external stimuli.

A person touches a hot pan. Fig. 11.1 shows the reflex arc involved with a response when a person touches a hot pan.

Complete the three boxes in Fig. 11.1 to label the neurones involved in the response.

Draw two arrows on Fig. 11.1 to show the direction the nerve impulse travels along each

neurone in the arm.

Explain how the reflex arc prevents too much damage from the hot pan.

Caffeine is a chemical found in coffee and cola drinks.

A scientist investigates the effect of caffeine on reaction times.

They test two groups.

• Group A contains 5 boys aged 12 years; they are given 150 cm³ of a caffeine-free drink.

• Group B contains 8 boys aged 15 years; they are given 150 cm³ of a caffeine drink.

Both groups are tested before and after taking the drink.

Identify one variable that has been controlled in this investigation.

The cornea is a part at the front of the eye that allows in light.

The cornea can be damaged by injury or disease. Treatment often requires a local anaesthetic. Local anaesthetics stop nerve impulses passing along the sensory neurone.

Use your knowledge of the structure of a reflex arc to explain why a person would not feel pain.

Pregnancy can affect the response of neurones to local anaesthetics.

The graph shows the effect of a local anaesthetic on nerve activity in women.

Time following local anaesthetic injection (minutes)

Look at the data over the first 10 minutes after injection.

Calculate the percentage decrease in nerve activity after 10 minutes when pregnant compared to not being pregnant.

The data in the graph has range bars plotted. These give the highest and lowest values at each point.

Why is this an improvement when presenting this data?

Explain why stem cells taken from embryos are more suitable than those from adult bone marrow.

* Scientists can use embryo stem cell technology for treating damage to the cornea to restore vision.

Read the information in the box.

• Corneal cells are transparent to allow light to pass through.

• Corneal tissue does not have blood vessels in order to remain transparent.

• Corneal transplants from donor tissue are one way to restore vision after damage to the cornea.

• Corneal transplants are at risk of tissue rejection when blood vessels develop in the cornea.

• Scientists are able to genetically engineer donor corneal cells to prevent new blood vessel formation following transplantation.

• The genetically engineered cells produce a protein which prevents the formation of blood vessels.

Describe the main steps involved in genetically engineering donor corneal cells and identify any improvements and risks from this type of treatment.