the nervous system and reflex arc (gcse)

8/4/2019 The Nervous System and Reflex Arc (GCSE)

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GCSE Biology 1A Human Biology

KEYWORDSKEYWORDS(Write these into your journal book and find the definition as part of your weeks homework)

Gland, Hormone, Impulse, Nervous system, Effector, Stimulus,Gland, Hormone, Impulse, Nervous system, Effector, Stimulus,

Receptor, Neurone, SynapseReceptor, Neurone, Synapse


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Name the hormones Using Figure 2 on

page 24 of the Student Book, write downthe names of the hormones secreted by the

glands shown on the diagram.

Time: 10 minutes

Working Groups: Your choice of 1, 2 or 3

STARTER


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STARTER continued

Name the hormones Have you thought of

any others?

Time: 10 seconds to add them to your list


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STARTER answersPituitary gland FSH, LH (stimulates the release and maturity of

follicles during menstruation)

Thyroid gland Thyroxine(regulates the rate of metabolism)

Adrenal gland - corticosteroids and catecholamines includingcortisol and adrenaline and small amounts of testosterone(regulates stress levels)

Pancreas peptides (regulates the production of shorter activedigestive enzymes)

Ovary oestrogen, progesterone and small amounts of testosterone(regulates the growth of eggs and stabilises the growing foetusduring pregnancy)

Testis testosterone (plays a key role in the health and well-beingof the man)


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I AM LEARNING TO understand how the body is controlled

I WILL LEARN THAT

The nervous system enables humans to react to their

surroundings and coordinate their behaviour.

Receptors detect stimuli which include light, sound, changes in

position, chemicals, touch, pressure, pain and temperature. Information from receptors passes along cells (neurones) in

nerves to the brain. The brain coordinates the response.

Many processes in the body are coordinated by chemical

substances called hormones. Hormones are secreted by glands andare transported to their target organs by the bloodstream.

I CAN

Explain how the body controls its functions and responses

through hormones (chemicals) and nerves (electrical impulses)

LEARNING OBJECTIVES


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Identification of the density of nerve endingsIdentification of the density of nerve endings

AIM: To investigate the sensitivity of different areas of the skin.Method:

1. Working in pairs, one student looks in a different direction,

while another student touches them on the back of the hand with

either one or two pieces of blunt pencil about 1 cm apart.2. The blindfolded student has to say whether it was one point or

two points that touched them.

3. Place a cross on the hand for each point felt.

Results:

Map the density of sensory receptors by drawing it into your book.

Conclusion:

Are the receptors in groups? Or randomly placed? What can you

say about the density of the receptors identified?


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CONTROL SYSTEMSCONTROL SYSTEMS

There are two main control systems in your body.1.1. Nervous systemNervous system which has two main sections

central or CNScentral or CNS that is made up of the spinal cord and brain and functions tocoordinate all actions of the body

peripheral or PNSperipheral or PNS that is made up of the bodies nerves and functions toconnect the CNS to the rest of the body through neurones. PNS is further

divided into somatic or SNSsomatic or SNS which is associated with the voluntary control of body movements

and is made up of all neurones, sense organs, skin, skeletal muscles

Autonomic or ANSAutonomic or ANS which is associated with the involuntary control of bodymovements such as reflex and controls such things as heart rate, body temperature,digestion etc. The ANS is further divided into

Parasympathetic nervous systemParasympathetic nervous system works in actions that do not require a fastresponse (fight or fight response)

Sympathetic nervous systemSympathetic nervous system works in actions that do require a fast response(rest and digest response)

1.1. Endocrine systemEndocrine system which is a system of glands that release anumber of signalling chemicals known as hormones.


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Say what?Say what? NERVOUS SYSTEMNERVOUS SYSTEM

CNSCNS PNSPNS

ANSANSSNSSNS

ParasympatheticParasympathetic SympatheticSympathetic

Nervous systemNervous system releases electrical

impulses that are quick but the

effects are short lived and it

involves the CNS (either just spinalcord or both spinal cord and brain)

messages are carried by neurones

Endocrine systemEndocrine system releases chemical signals that are slow to

react but the effects are long lasting. This does not involve the

CNS. Messages are carried by the blood.


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Parts of the nervous systemParts of the nervous system

The nervous systemnervous system is made up of three mainparts;

The brain The spinal cord

Nerve fibres

It detects stimulistimuli such as light, sounds,temperature, pressure, pain and co-ordinates

the bodies response.


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Parts of the nervous systemParts of the nervous system

For example;

If you smell something burning

Your nose (receptorreceptor) detects the stimulusstimulus

(smell)

Nerve fibresNerve fibres send the message to the brainbrain

Yourbrainbrain then sends a message to move

your body away or to put out the fire!

SIMPLES RIGHT!SIMPLES RIGHT!


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Lets look at some bits more closelyLets look at some bits more closely

RECEPTORSRECEPTORS Receptors are sensors on the body that detect stimuli

They convert stimuli into electrical signalselectrical signals (messages) called

impulses.


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EFFECTORSEFFECTORS

An effectoreffector is any part of the body that produces the responseresponse.

Here are some examples of effectors:

a muscle contracting to move the arm

a muscle squeezing saliva from the salivary gland

a gland releasing a hormonehormone into the blood


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NERVE FIBRESNERVE FIBRES

Nerve fibres are bundles of nerve cells (neurones)(neurones)that pass on electrical signals (impulses)(impulses) to thebrain.

From the brain, nerve fibres send impulses toeffectorseffectors (muscles).


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NEURONESNEURONES

There are three types of neuronesThere are three types of neurones

1.1. Sensory neuroneSensory neurone carries impulses from thereceptors to the spinal cord.

2.2. Relay NeuroneRelay Neurone carries impulses to and fromthe spinal cord and the brain

3.3. Motor NeuroneMotor Neurone carries impulses from thebrain to the effector


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Multiple-choice quiz


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SYNAPSESSYNAPSES

Where two neuronesneurones meet, there is a tiny gap calleda synapsesynapse.

Signals cross this gap using chemicalschemicals.

One neuroneneurone releases the chemical into the gap.The chemicalchemical diffuses across the gap and makes the

next neuroneneurone transmit an electrical signal.

http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/then

Watch this video on synapses then draw a flow chart of the processWatch this video on synapses then draw a flow chart of the process
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev2.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev2.shtml


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What is a synapse?A synapse is a junction between two neurones across which

electrical signals pass. The human body contains up to 500trillion synapses.

presynaptic

cell

postsynaptic

cell


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The release of neurotransmittersWhen a nerve impulse arrives at the end of one neurone it

triggers the release ofneurotransmittermolecules fromsynaptic vesicles.

synaptic

vesicle

neurotransmitter

molecules

GCS i 1A i


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Continuing the impulseThe neurotransmitters diffuse across the synaptic cleft and

bind with receptors on the next neurone, triggering anotherimpulse.

nerveimpulse

receptor

synaptic

cleft

GCSE Bi l 1A H Bi l


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The stick drop test!The stick drop test!METHOD:METHOD:

1. Working in pairs, one student holds a metre rule vertically at the zero end, betweenthe thumb and forefinger of another student, so that the 50 cm mark is level with thetop of the forefinger.

2. Without warning, the first student drops the rule and the second student attempts tocatch it between the thumb and forefinger, noting the distance on the ruler justabove the forefinger.

3. Repeat several times, so that a mean can be calculated.

4. Then change around so that everyone gets a turn. Write a report of the experiment.

CONCLUSION AND DISCUSSION:CONCLUSION AND DISCUSSION:

What was the accuracy of the measurements, the calculation of means and the controlof variables?

Identify the parts of the body involved. What senses are being used? Can we trainourselves to react more quickly? Does practice make perfect?

Can we alter reflex actions? think of a situations where it is possible to alter the

automatic response (not dropping a hot object, deliberately breathing more slowly,etc.). Are there some reflex actions over which we have no control?

GCSE Bi l 1A H Bi l


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REFLEX ARCREFLEX ARC

When your body needs to react to something veryquickly (to protect itself) it uses a reflex arcreflex arc(spinal reflex).

Instead of sending impulses from the receptorSpinal cord brain spinal cord effector

It sends impulses from the receptorspinal cord effectorYup it bypasses the brain!

http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/then

GCSE Bi l 1A H Bi l
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtml


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ANSWERSANSWERS

Electrical impulses along neurones, chemical(neurotransmitters) across the synapse.

The microscopic gap between two neurones.

By chemicals called neurotransmitters.

To pass the impulse onto the correct motorneurone.

Glands or muscle that produce the

effect or make a response.

GCSE Bi l 1A H Bi l
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtml


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The sequence of a reflex arc

GCSE Bi l 1A H Bi l
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtml


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REFLEX ACTIONREFLEX ACTION

The way the iris in oureye adjusts the sizeof the pupil inresponse to bright ordim light is also areflex action.

http://www.bbc

.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemre

shtml

In brightlight

In dim light

Radial muscles of theiris relax.

Circular muscles ofthe iris contract.

Less light enters theeye through thecontracted pupil.

Radial muscles of theiris contract.

Circular muscles ofthe iris relax.

More light enters theeye through the dilatedpupil.

GCSE Bi l 1A H Bi l
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev3.shtml


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The iris reflex

GCSE Biolog 1A H man Biolog


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Inside the eye

lensfocuses light

on retina

iris

regulates amountof light entering eye

ciliary muscleschange shape of the lens

optic nervetransmits impulses to

the brain

corneaprotects eye surface and

focuses light rays

retinasenses lighthold lens in place

suspensory ligaments



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REFLEX ACTIONREFLEX ACTION



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PASS THE ZAPPASS THE ZAP Some volunteers get an A4 sheets on which

the names of parts of the reflex pathway are to

be written.

The students should then arrange themselves

in the correct order.

Using a lightning-shaped zap, each student is

to talk through their bit of the process as the

impulse (zap) gets passed to them.



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NERVE PATHWAYNERVE PATHWAY Have a go at completing this worksheetHave a go at completing this worksheet



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NERVE PATHWAYNERVE PATHWAY answersanswers

SENSORYNEURO

NE

SENSORYNEURONE

Takesimpulsesfro

mthe

senseorgantothe

relay

neurone.

RELAYNEURONE

RELAYNEURONE

Takesimpulsesto

thebrainandfrom

thebrain.

MO

TOR

NEURONE

MO

TOR

NEURONE

Tak

esimpulsesfrom

the

relayneuroneto

the

effector.

BR

AIN

BR

AIN

Re

ceivesimpulses

fro

mthespinalcord

an

dsendsoutnew

im

pulses.

SENSEORGA

N/

SENSEORGA

N/

RECEPTOR

RECEPTOR

Sensesstimuli

fromour

surroundings.

E

FFECTOR

E

FFECTOR

T

hemusclethat

receivesthe

impulsefrom

m

otorneurone.

SPINALCORD

SPINALCORD

Wheretherelay

neuronesare

found.



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NERVOUS SYSTEMNERVOUS SYSTEM answersanswers

REFLEX PROTECTION GIVENBLINKINGBLINKING To eye

COUGHINGCOUGHING Stops us choking

SNEEZINGSNEEZING Removes blockages from the nose

PUPILS CHANGE SIZEPUPILS CHANGE SIZE Protects the retina

4a) 37m

55m/s

= 0.67s

4b) RT = d

s

= 20m

40m/s

= 0.5s

4c) sensory receptor in eye sensory neurone

relay neurone - brain motor neurone - effector

4d) i) brain, ii) takes too long

iii) Stimulus sensory neurone

relay neurone motor neurone

effector



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Glossary (1/2)

accommodation The reflex reaction that keeps the lensthe right shape to focus light on the retina.

CNS The central nervous system, consisting of the brainand spinal cord.

iris The part of the eye that limits the amount of lightentering the eye.

lens The part of the eye that focuses light on the retina.

motor neurone A neurone that carries electricalimpulses from the CNS to muscles and glands.

neurone A specialized cell that carries electrical impulses.



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Glossary (2/2)

neurotransmitter A chemical that diffuses acrosssynapses to continue an impulse in a connecting neurone.

reaction time The time taken to respond to a stimulus.

reflex A fast, automatic protective response.

retina The part of the eye that contains light receptors.

sensory neurone A neurone thatcarries electricalimpulses from sense organs to the CNS.

synapse The gap between two connecting neurones.

GCSE Biology 1A Human BiologyLEARNING OBJECTIVES


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I AM LEARNING TO understand how the body is controlled

I WILL LEARN THATThe nervous system enables humans to react to their

surroundings and coordinate their behaviour.

Receptors detect stimuli which include light, sound, changes in

position, chemicals, touch, pressure, pain and temperature. Information from receptors passes along cells (neurones) in

nerves to the brain. The brain coordinates the response.

Many processes in the body are coordinated by chemical

substances called hormones. Hormones are secreted by glands and

are transported to their target organs by the bloodstream.

I CAN

Explain how the body controls its functions and responses

through hormones (chemicals) and nerves (electrical impulses)

the nervous system and reflex arc (gcse)

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