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7/27/2019 The Nervous System and Reflex Arc
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GCSE Biology 1A Human Biology
KEYWORDS(Write these into your journal book and find the definition as part of your weeks homework)
Gland, Hormone, Impulse, Nervous system, Effector, Stimulus,
Receptor, Neurone, Synapse
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GCSE Biology 1A Human Biology
Name the hormonesUsing 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 glandFSH, LH (stimulates the release and maturity of
follicles during menstruation)
Thyroid glandThyroxine(regulates the rate of metabolism)
Adrenal gland - corticosteroids and catecholamines includingcortisol and adrenaline and small amounts of testosterone(regulates stress levels)
Pancreaspeptides (regulates the production of shorter activedigestive enzymes)
Ovaryoestrogen, progesterone and small amounts oftestosterone (regulates the growth of eggs and stabilises the
growing foetus during pregnancy)
Testistestosterone (plays a key role in the health and well-beingof the man)
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GCSE Biology 1A Human Biology
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 glandsand 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)
LEARNING OBJECTIVES
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GCSE Biology 1A Human Biology
Identification 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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GCSE Biology 1A Human Biology
CONTROL SYSTEMS
There are two main control systems in your body.1. Nervous systemwhich has two main sections
central or CNS that is made up of the spinal cord and brain and functions tocoordinate all actions of the body
peripheral 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 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 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 system works in actions that do not require a fastresponse (fight or fight response)
Sympathetic nervous system works in actions that do require a fastresponse (rest and digest response)
2. Endocrine systemwhich is a system of glands that release anumber of signalling chemicals known as hormones.
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Say what? NERVOUS SYSTEM
CNS PNS
ANSSNS
Parasympathetic Sympathetic
Nervous system releases electrical
impulses that are quick but the
effects are short lived and it involves
the CNS (either just spinal cord orboth spinal cord and brain) messages
are carried by neurones
Endocrine 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 system
The nervous system is made up of three mainparts;
The brain The spinal cord
Nerve fibres
It detects stimuli such as light, sounds,temperature, pressure, pain and co-ordinates
the bodies response.
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GCSE Biology 1A Human Biology
Parts of the nervous system
For example;
If you smell something burning
Your nose (receptor) detects the stimulus
(smell)
Nerve fibres send the message to the brain
Yourbrain then sends a message to move
your body away or to put out the fire!
SIMPLES RIGHT!
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GCSE Biology 1A Human Biology
Lets look at some bits more closely
RECEPTORS Receptors are sensors on the body that detect stimuli
They convert stimuli into electrical signals (messages) called
impulses.
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GCSE Biology 1A Human Biology
EFFECTORS
An effector is any part of the body that produces the response.
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 hormone into the blood
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NERVE FIBRES
Nerve fibres are bundles of nerve cells (neurones)that pass on electrical signals (impulses) to thebrain.
From the brain, nerve fibres send impulses toeffectors (muscles).
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GCSE Biology 1A Human Biology
NEURONES
There are three types of neurones1. Sensory neuronecarries impulses from the
receptors to the spinal cord.
2. Relay Neuronecarries impulses to and fromthe spinal cord and the brain
3. Motor Neuronecarries impulses from the brainto the effector
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GCSE Biology 1A Human Biology
Multiple-choice quiz
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GCSE Biology 1A Human Biology
SYNAPSES
Where two neurones meet, there is a tiny gap calleda synapse.
Signals cross this gap using chemicals.
One neurone releases the chemical into the gap.The chemical diffuses across the gap and makes the
next neurone transmit an electrical signal.
http://www.bbc.co.uk/schools/gcsebitesize/science/aq
a/human/thenervoussystemrev2.shtml
Watch 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.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev2.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev2.shtml7/27/2019 The Nervous System and Reflex Arc
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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 upto 500 trillion synapses.
presynaptic
cell
postsynaptic
cell
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GCSE Biology 1A Human Biology
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
GCSE Bi l 1A H Bi l
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GCSE Biology 1A Human Biology
Continuing the impulseThe neurotransmitters diffuse across the synaptic cleft and
bind with receptors on the next neurone, triggering anotherimpulse.
nerveimpulse
receptor
synaptic
cleft
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GCSE Biology 1A Human Biology
The stick drop test!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 just abovethe 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:
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 theautomatic response (not dropping a hot object, deliberately breathing more slowly,
etc.). Are there some reflex actions over which we have no control?
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GCSE Biology 1A Human Biology
REFLEX ARC
When your body needs to react to something veryquickly (to protect itself) it uses a reflex 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/aq
a/human/thenervoussystemrev3.shtml
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.shtml7/27/2019 The Nervous System and Reflex Arc
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GCSE Biology 1A Human Biology
ANSWERS
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
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GCSE Biology 1A Human Biology
The sequence of a reflex arc
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GCSE Biology 1A Human Biology
REFLEX ACTION
The way the iris in oureye adjusts the sizeof the pupil in
response to bright ordim light is also areflex action.
http://www.bbc.co.uk/schools/gcsebitesize/science/aq
a/human/thenervoussystemrev3.shtml
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.
GCSE Biology 1A Human Biology
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.shtml7/27/2019 The Nervous System and Reflex Arc
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The iris reflex
GCSE Biology 1A Human Biology
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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
GCSE Biology 1A Human Biology
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GCSE Biology 1A Human Biology
REFLEX ACTION
GCSE Biology 1A Human Biology
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PASS 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 theimpulse (zap) gets passed to them.
GCSE Biology 1A Human Biology
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NERVE PATHWAY Have a go at completing this worksheet
GCSE Biology 1A Human Biology
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NERVE PATHWAY answers
SENSORY NEURONETakes impulses from
the sense organ to the
relay neurone.
RELAY NEURONE
Takes impulses to
the brain and from
the brain.
MOTOR NEURONE
Takes impulses from
the relay neurone to
the effector.
BRAIN
Receives impulses
from the spinal
cord and sends out
new impulses.
SENSE ORGAN/RECEPTOR
Senses stimuli
from our
surroundings.
EFFECTOR
The muscle that
receives the
impulse from
motor neurone.
SPINAL CORD
Where the
relay neurones
are found.
GCSE Biology 1A Human Biology
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NERVOUS SYSTEM answers
REFLEX PROTECTION GIVEN
BLINKING To eye
COUGHING Stops us choking
SNEEZING Removes blockages from the
nose
PUPILS CHANGE SIZE Protects the retina
4a) 37m
55m/s
= 0.67s
4b) RT = d
s
= 20m
40m/s
= 0.5s
4c) sensory receptor in eyesensory neurone
relay neurone - brainmotor neurone - effector
4d) i) brain, ii) takes too long
iii) Stimulus sensory neurone
relay neurone motor neurone
effector
GCSE Biology 1A Human Biology
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Glossary (1/2)
accommodation
The reflex reaction that keeps thelens the 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 electricalimpulses.
GCSE Biology 1A Human Biology
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GCSE Biology 1A Human Biology
Glossary (2/2)
neurotransmitterA 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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GCSE Biology 1A Human Biology
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)