the nervous system

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


Name the hormones – Using Figure 2 on page 24 of the Student Book, write down the 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


STARTER continued

Name the hormones – Have you thought of any others?

Time: 10 seconds to add them to your list


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 including

cortisol and adrenaline and small amounts of testosterone (regulates stress levels)

Pancreas – peptides (regulates the production of shorter active digestive enzymes)

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

Testis – testosterone (plays a key role in the health and well-being of the man)


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 and are transported to their target organs by the bloodstream.

I CANExplain how the body control’s its functions and responses through hormones (chemicals) and nerves (electrical impulses)

LEARNING OBJECTIVES


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?


CONTROL SYSTEMSCONTROL SYSTEMSThere 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 to coordinate all actions of the body

• peripheral or PNSperipheral or PNS that is made up of the bodies nerves and functions to connect 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 body

movements 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 fast

response (fight or fight response)» Sympathetic nervous systemSympathetic nervous system works in actions that do require a fast response

(rest and digest response)

2.2. Endocrine systemEndocrine system – which is a system of glands that release a number of signalling chemicals known as hormones.


Say what?Say what? NERVOUS SYSTEMNERVOUS SYSTEM

CNSCNS PNSPNS

ANSANS SNSSNS

ParasympatheticParasympathetic SympatheticSympathetic

Nervous systemNervous system releases electrical impulses that are quick but the effects are short lived and it involves the CNS (either just spinal cord 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.


Parts of the nervous systemParts of the nervous system

The nervous systemnervous system is made up of three main parts;

• The brain• The spinal cord• Nerve fibres

It detects stimulistimuli such as light, sounds, temperature, pressure, pain and co-ordinates the bodies response.


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

• Your brainbrain then sends a message to move your body away or to put out the fire!

SIMPLES RIGHT!SIMPLES RIGHT!


Lets look at some bits more closelyLets look at some bits more closelyRECEPTORSRECEPTORS

• Receptors are sensors on the body that detect stimuli

• They convert stimuli into electrical signalselectrical signals (messages) called impulses.


EFFECTORSEFFECTORSAn 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


NERVE FIBRESNERVE FIBRES• Nerve fibres are bundles of nerve cells (neurones)(neurones)

that pass on electrical signals (impulses)(impulses) to the brain.

• From the brain, nerve fibres send impulses to effectorseffectors (muscles).


NEURONESNEURONESThere are three types of neuronesThere are three types of neurones1.1. Sensory neuroneSensory neurone – carries impulses from the receptors to the

spinal cord.2.2. Relay NeuroneRelay Neurone – carries impulses to and from the spinal cord

and the brain3.3. Motor NeuroneMotor Neurone – carries impulses from the brain to the effector


Multiple-choice quiz


SYNAPSESSYNAPSESWhere two neuronesneurones meet, there is a tiny gap called

a 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/thenervoussystemrev2.shtml

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


What is a synapse?A synapse is a junction between two neurones across which electrical signals pass. The human body contains up to 500 trillion synapses.

presynaptic cell

postsynaptic cell


The release of neurotransmittersWhen a nerve impulse arrives at the end of one neurone it triggers the release of neurotransmitter molecules from synaptic vesicles.

synaptic vesicle

neurotransmitter molecules


Continuing the impulseThe neurotransmitters diffuse across the synaptic cleft and bind with receptors on the next neurone, triggering another impulse.

nerve impulse

receptor

synaptic cleft


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, between

the thumb and forefinger of another student, so that the 50 cm mark is level with the top of the forefinger.

2. Without warning, the first student drops the rule and the second student attempts to catch it between the thumb and forefinger, noting the distance on the ruler just above 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 control

of variables?

Identify the parts of the body involved. What senses are being used? Can we train ourselves 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?


REFLEX ARCREFLEX ARC• When your body needs to react to something very

quickly (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 receptor spinal cord effector…Yup it bypasses the brain!



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 motor

neurone.• Glands or muscle that produce the effect or make a response.


The sequence of a reflex arc


REFLEX ACTIONREFLEX ACTION

The way the iris in our eye adjusts the size of the pupil in response to bright or dim light is also a reflex action.


In bright light

In dim light

•Radial muscles of the iris relax.

•Circular muscles of the iris contract.

•Less light enters the eye through the contracted pupil.

•Radial muscles of the iris contract.

•Circular muscles of the iris relax.

•More light enters the eye through the dilated pupil.


The iris reflex


Inside the eye

lensfocuses lighton retina

irisregulates 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


REFLEX ACTIONREFLEX ACTION


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.


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


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NERVOUS SYSTEM… NERVOUS SYSTEM… answersanswers

REFLEX PROTECTION GIVEN

BLINKINGBLINKING To eye

COUGHINGCOUGHING Stops us choking

SNEEZINGSNEEZING Removes blockages from the nose

PUPILS CHANGE SIZEPUPILS CHANGE SIZE Protects the retina

4a) 37m 55m/s = 0.67s4b) 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


Glossary (1/2)accommodation – The reflex reaction that keeps the

lens the right shape to focus light on the retina.

CNS – The central nervous system, consisting of the brain and spinal cord.

iris – The part of the eye that limits the amount of light entering the eye.

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

motor neurone – A neurone that carries electrical impulses from the CNS to muscles and glands.

neurone – A specialized cell that carries electrical impulses.


Glossary (2/2)

neurotransmitter – A chemical that diffuses across synapses 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 that carries electrical impulses from sense organs to the CNS.

synapse – The gap between two connecting neurones.


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 and are transported to their target organs by the bloodstream.

I CANExplain how the body control’s its functions and responses through hormones (chemicals) and nerves (electrical impulses)

LEARNING OBJECTIVES

the nervous system

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