AQA Science Biology Nerves and Hormones Booklet

8/13/2019 AQA Science Biology Nerves and Hormones Booklet

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B1.2 Nerves and Hormones

Summary

The nervous system and hormones enable us to respond to external changes. They also

help us to control conditions inside our bodies. Hormones are used in some forms of

contraception and in fertility treatments.

You should be able to:

evaluate the benefits of, and the problems that may arise from, the use of hormones to

control fertility, including In Vitro Fertilisation (IVF)

Key terms

Central nervous system

Brain

Spinal cord

Stimulus / stimuli (plural)

Receptor

Impulse

Neurones

Nerve

Sensory neurone

Relay neurone

Motor neurone

Effector

Synapse

Reflex action

Muscle

Gland

Secrete

Saliva

Homeostasis

Enzymes

Hormones

Menstrual cycle

Ovary

Womb

Uterus

Embryo

Follicle stimulating

hormone (FSH)

Oestrogen

Artificial

Fertility

Oral contraceptive

In-vitro fertilisation (IVF)

The nervous system

What makes up the nervous system?

What does the nervous system do?

What are the cells of the nervous system called?

What carries the messages to and from the brain?

What is the difference between sensory and motor neurons?

What is the same?

What is the synapse?

Which type of reaction bypasses the brain?


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The nervous systemThe nervous system enables humans to react to their surroundings and coordinate their

behaviour.

Central nervous system = brain plus spinal cord.

Stimuli = changes in the environment.

Receptors = cells that detect stimuli

Nerve impulse = electrical message that passes along a neurone.

Neurones = nerve cells.

Neurones are highly specialised cells:Very long so nerve impulses can travel quickly to different parts of the body.

Branched ends to form connections with many other neurones.

Insulating sheath to maintain the nerve impulse.

Nerve = a bundle of neurones connected to brain or spinal cord.

Sensory neurone = nerve cell that transmits nerve impulse from a receptor to the central

nervous system.

Relay neurone = neurone in the central nervous system.

Motor neurone = nerve cell that transmits nerve impulse from the central nervous system

to an effector.

Effector = a structure that the nervous system causes to responda muscle or gland.


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Label this diagram

Synapses

Synapses = junctions between nerve cells.

When a nerve impulse arrives at the end of a neurone, chemicals are released.

These diffuse across the synapse, and cause a new nerve impulse in the next neurone.

Receptors

Receptors and the stimuli they detect include:

receptors in the eyesthat are sensitive to light

receptors in the earsthat are sensitive to sound

receptors in the earsthat are sensitive to changes in positionand enable us to

keep our balance

receptors on the tongue and in the nosethat are sensitive to chemicals and enable

us to tasteand to smell


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receptors in the skinthat are sensitive to touch, pressure, painand to

temperaturechanges.

Light receptor cells, like most animal cells, have a nucleus, cytoplasm and cell

membrane.

Information from receptors passes along neurones in nerves to the spinal cord and the

brain.

The brain coordinates the response.

Reflex actions

Reflex actions are automatic and rapid.

They are simple responses to stimuli that often protect the body from harm.

They often involve sensory, relay and motor neurones.

The pathway starting with a stimulus and resulting in a response does not require

conscious control by the brain.

In a simple reflex action:

Impulses from a receptor pass long a sensory neurone to the central nervous system

There is a synapse between a sensory neurone and a relay neurone in the central

nervous systemA chemical is released at the synapse between the sensory neurone and a relay neurone.


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This causes an impulse to be sent along the relay neurone

A chemical is then released at the synapse between a relay neurone and motor neurone

in the central nervous system

This causes impulses to be sent along a motor neurone to the effector

This is either a muscle or a gland

A muscle responds by contractingA gland responds by releasing (secreting) chemical substances eg salivary gland

releases saliva.

Questions

What is the difference between a sense organ and a receptor?

What two parts make up the central nervous system?

List the three types of neurones.

What is a reflex action?

Put these in order to show how a reflex action works

EffectorMotor neuroneRelay neuroneResponseReceptorSensory neuroneStimulus


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Label the pathway for a reflex arc

1.

2.

3.

4.

5.

6.

7.

Control in the human body

Internal conditions that are controlled include:

The water content of the body:

Water leaves the body:

via the lungs when we breathe out

via the skin when we sweat to cool us down.

Excess water is lost via the kidneys in the urine

The ion content of the body:

Ions are lost via the skin when we sweat

Excess ions are lost via the kidneys in the urine

Temperature:

To maintain the temperature at which enzymes work best.

Enzymes are protein molecules that control reactions inside and outside cells.

They are sensitive to changes in temperature and work best at body temperature37oC.

Blood sugar levels:

To provide the cells with a constant supply of energy.

We take in sugars as carbohydrate in our food.

Hormones

Many processes within the body are coordinated by chemical substances called

hormones.

Hormones are secreted by glands.


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They are transported to their target organs by the bloodstream.

Hormones regulate the functions of many organs and cells.


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Menstrual cycle

The monthly release of an egg from a womans ovaries

The changes in the thickness of the lining of her womb

These are controlled by hormones secreted by the pituitary gland and by the ovaries.

They are involved in promoting the release of an egg.

Follicle stimulating hormone (FSH):Secreted by the pituitary gland

Causes eggs to mature in the ovaries.

It also stimulates the ovaries to produce hormones including oestrogen.

Oestrogen:

Secreted by the ovaries.

Inhibits the further production of FSH.

Brings about the release of LH.

Luteinising hormone (LH):

Stimulates the release of eggs from the ovary


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5. Oestrogen causes

4. Oestrogen inhibits 1. FSH released release of LH from

production of FSH from pituitary pituitary

Oestrogen FSH LH

2. Causes egg to mature

in ovary

3. Causes release of

oestrogen by ovary 6. LH causes release

of an egg from the ovary


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The use of artificial fertility controlling hormones

Hormones can be synthesised artificially.

These are very similar to human hormones, and can be used to affect the way the body

works.

Some people are concerned about the use of hormones that control fertility.

Oral contraceptives

Oral contraceptives contain hormones to inhibit FSH production so that no eggs mature.

Oral contraceptives may contain oestrogen and progesterone to inhibit egg maturation.

The first birth-control pills contained large amounts of oestrogen.

These resulted in women suffering significant side effects

Progesterone-only pills lead to fewer side effects.

Birth-control pills now contain a much lower dose of oestrogen, or are progesterone only.

Some religions do not encourage the use of hormones that prevent conception.

Fertility drugs

Fertility drugs can be given to women whose own level of FSH is too low to stimulate

eggs to mature.

They contain FSH and LH.

This stimulates eggs to mature.

This increases the chances of getting pregnant.

These drugs are also used in in-vitro fertilisation(IVF) treatment.

IVFinvolves giving a mother FSH and LH to stimulate the maturation of several eggs.The eggs are collected from the mother and fertilised by sperm from the father.

The fertilised eggs develop into embryos.

At the stage when they are tiny balls of cells, one or two embryos are inserted into the

mothers uterus (womb).

Objections to IVF

Some people believe that the human population is growing too quickly anyway.

Fertility drugs can result in multiple pregnancies, which can be dangerous to the mother.

Excess embryos may be used for embryo research, and many people disagree with this,

because embryos have the potential to become a living human.


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Look through the facts about IVF below.

Highlight the facts you already know in yellow.

Highlight the facts you are most surprised by in pink.

Scientific: Infertility is the inability to get pregnant (conceive). 1 in 7 couples in the UK has trouble conceiving. IVF is successful in only 22% of cases (chances increase with 2 or more cycles). IVF involves: i) removing some of the womans egg cells, ii) fertilising them with sperm to

create embryos in a laboratory, and iii) implanting the embryos in the woman to carry

pregnancy.

Legal Clinics must decide if couples will be suitable parents before providing treatment. Choosing the sex of a baby using IVF is currently illegal. Since 2005, eggs and sperm cannot be donated anonymously. If one partner removes their consent to use their eggs/sperm, the embryos must be destroyed.

Political From April 2005, the UK government advised that all eligible couples should receive one cycle of

treatment on the NHS. Waiting times for treatment vary across the UK. In England and Wales, the suggested age limit for women receiving IVF is 40 years old.

Economic

In 2005, the cost of one cycle of IVF was 2771. Drugs to support the treatment cost an extra 1000. In 2005, only 25% of IVF treatment was funded by the NHS.

Social Some pro-life supporters disagree with destroying embryos that are not used in treatment. Some religious leaders believe we shouldnt interfere with natural reproduction. Many women are waiting until they are older to have children, when their fertility is lower, and it is

more difficult to conceive. Designer babies is a term used by the media. It describes an embryo chosen for specific

characteristics or genetic traits.


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Nervous system

Complete the sentences.

Receptors in the eyes are sensitive to ___________________

Receptors in the ears are sensitive to ___________________

Receptors in the ____________ are sensitive to changes in position

Receptors in the _____________ and ___________ are sensitive to chemicals that

enable us to taste and smell

Receptors in the skin are sensitive to t________________, p_______________ and

p_______

Complete using the following terms

Automatic Brain Cell Membrane Cytoplasm Motor Nucleus Neurones

Rapid Relay Sensory

Light receptor cells like most animal calls have a _______________, _______________

and ________ __________________ .

Information from receptors passes along __________________ (cells in nerves) to the

______________

The brain coordinates the response.

Reflex actions are ___________ and _________rapid.

They involve ____________, ____________ and ______________ neurones


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Nervous System Key WordsMatch the term to the definition

Central nervoussystem

An automatic response to a stimulus that does notinvolve conscious thought.

Effectors Connects a motor and a sensory neurone in thecentral nervous system and is involved in a reflex arc.

Motor neurone Carries the nerve impulse from the central nervoussystem to an effector.

Nerve Electrical message that passes along a neurone.

Nerve impulse Changes in the environment.

Neuron A specialised nerve cell.

Receptor A junction between 2 neurones.

Reflex A bundle of neurones.

Relay neurone The brain and the spinal cord.

Stimulus Carry out the response and are either muscles orglands.

Sensory neurone This carries the nerve impulse from the receptor to thecentral nervous system.

Synapse Specialised cells that detect stimuli.


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Homeostasis and hormones

The nervous system and hormones enable us to respond to external changes. They alsohelp us to control conditions inside our bodies. Hormones are used in some forms ofcontraception and in fertility treatments. Plants also produce hormones and respond to

external stimuli.

Four things that need to be kept constant in the body are:

1.

2.

3.

4.

How does water leave the body?

What is lost when we sweat?

Why is it important that our body temperature is kept constant?

Complete the sentences with these word: Bloodstream Glands Hormones

Many processes within the body are coordinated by chemical substances called.

These are secreted by and are usually transported to their targetorgans by the

Insulin is produced in the.

Oestrogen is produced in the .

FSH is produced in the .

LH is produced in the .

What are the two functions of FSH in the menstrual cycle?

What effect does oestrogen have on the production of FSH?


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HormonesThe human menstrual cycle is controlled by hormones.

Name the gland which produces:

FSH ..

Oestrogen ..

GCSE question


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Control in plants

Summary

Plants produce hormones and respond to external stimuli.

You should be able to:

evaluate the use of plant hormones in horticulture as weed killers and to encourage the

rooting of plant cuttings.

Key terms

Auxin

Phototropism

Gravitropism

Geotropism

Stimulus

Inhibit

Agriculture

Horticulture

Weeds

Control in plants

Plants are sensitive to light, moisture and gravity:

Their shoots grow upwards:

towards the light

against the force of gravityTheir roots grow downwards:

towards moisture

in the direction of the force of gravity.

Plants produce hormones to coordinate and control growth.

Auxin controls phototropism and gravitropism (also called geotropism).

The response to light is called phototropism.The response to gravity is called geotropism.The response to moisture is called hydrotropism.

The responses of plant roots and shoots to light, gravity and moisture are the result of

unequal distribution of hormones, causing unequal growth rates.


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Hormones

The ways in which a plant responds to these stimuli is coordinated by hormones.

Hormones also control the growth of a plant.

One plant hormone is called auxin.

Auxin is made by cells in the tips of the roots and shoots.

It speeds up growth in shoots and slows down growth in roots.

Unequal distribution of hormones causes unequal growth rates in different tissues.

The auxin diffuses away from the stimulus.

It affects the growth of cells in different ways.

In the shoots: it causes increased cell growth

This causes the shoot to curve towards the stimulus.

In the roots:it inhibits cell growth.

This causes the root to curve away from the stimulus.


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Geotropism and Auxin

Commercial Uses of Hormones

Plant growth hormones are used in agriculture and horticulture.

Agriculture= large scale business involving cultivating of soil, to produce crops,

and raise livestock.

Horticulture= small scale cultivation of fruits, vegetables, flowers, or ornamental

plants typically in a garden.

Chemicals are synthesised that are similar to plant hormones.

Some people are concerned about these chemicals entering the food chain and causingtoxic effects.

Weed killers

Chemicals that are used that are specific to the weeds eg dandelions.

They cause the weed to grow very quickly.

The weed cannot sustain this rate of growth and dies.

This also kills other wild plant species that are not weeds.

Rooting powdercontains auxin.

It is applied to cuttings to stimulate the growth of roots.

Large numbers of plants can be produced quickly, so more money can be made.

Hormones control fruit ripening.

Producers use chemicals to slow down the ripening of fruits, such as bananas, duringtransport.

Just before sale, ripening can then be speeded up using different chemicals and a

warmer temperature in the storerooms.


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GCSE Questions

Q1. The photograph shows a girl waiting to cross a road.

Lionel Lassman

(a) Name two different sense organs she would use to detect when it is safe to cross theroad.

1 ..................................................................................................................................

2 ..................................................................................................................................(2)

(b) Which sense organ contains receptors that help the girl to keep her balance?

..................................................................................................................................... (1)


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(c) (i) Complete the sentence.

A car driver automatically brakes if a child dashes out into the road.

This is called a ...................................................................................... action.(1)

(ii) Draw a ring around the correct answer to complete the sentence.

In the nervous system, information passes along cells called

effectors

neurones

synapses

.

(1)

(Total 5 marks)

Q2. Some organs in the human body contain receptor cells. The receptor cells detect differentstimuli in the environment.

(a) Complete the table by writing the name of the correct organ in each box.

The first one has been done for you.

Receptor for stimulus Organ containing the receptor cells

Taste tongue

Light

Smell

Temperature

(3)

(b) Your body needs to keep an internal temperature of around 37 C.

Which two statements describe how your body cools itself down if your temperature goesabove 37 C?

Tick ( ) two boxes.


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Statement Tick ( )

Sweat is released from the sweat glands in the skin

Less blood flows to the capillaries in the skin

More blood flows to the capillaries in the skin

The sweat glands stop releasing sweat

(2)

(d) Complete the sentences.

Your body reduces the amount of glucose in your blood using a hormone. This

hormone is called ................................................................ .

It is produced in the .............................................. .(2)

(Total 8 marks)

Q3. Reflex actions are rapid and automatic.

(a) Name the following structures in a reflex action.

(i) The structure that detects the stimulus.

...........................................................................................................................(1)

(ii) The neurone that carries impulses to the central nervous system.

...........................................................................................................................(1)

(iii) The neurone that carries impulses away from the central nervous system.

...........................................................................................................................(1)

(iv) The structure that brings about the response.

...........................................................................................................................(1)


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(b) Describe what happens at a synapse when an impulse arrives.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(c) Some people have a condition in which information from the skin does not reach the brain.

Explain why this is dangerous for the person.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 8 marks)

Q4. A person accidentally touches a hot pan.

Her hand automatically moves away from the pan.

The diagram shows the structures involved in this action.


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(a) Describe fully how the structures shown in the diagram bring about this reflex action.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(6)

(b) (i) The nerve pathway in this reflex action is about 1.5 metres in length. A nerve

impulse travels at 75 m s1

.

Use this information to calculate the time taken for this reflex action to occur.

Show clearly how you work out your answer.

...............................................................................................................

...............................................................................................................

Time intervals ....................................... s(2)


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(ii) The actual time interval is longer than the interval you have calculated in part (i).

Suggest an explanation for the difference.

...............................................................................................................

...............................................................................................................(1)

(Total 9 marks)

AQA Science Biology Nerves and Hormones Booklet

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