Download - 5.ElectricalSignals
-
7/27/2019 5.ElectricalSignals
1/42
1 of 42 Boardworks Ltd 2006
-
7/27/2019 5.ElectricalSignals
2/42
2 of 42 Boardworks Ltd 2006
-
7/27/2019 5.ElectricalSignals
3/42
3 of 42 Boardworks Ltd 2006
Reflexes and reaction times
Reaction times are how long it takes for the muscles to
respond from the start of a stimulus. In sprint races, reaction
times can determine who wins the race.
Why did Burrell
win the race?9.764
9.783
Carl Lewis
Leroy Burrell
Runner Sprint time (s)
In 1991, Leroy Burrell beat team mate Carl Lewiss world
record for the 100m sprint. But who was quickest?
-
7/27/2019 5.ElectricalSignals
4/42
4 of 42 Boardworks Ltd 2006
On the starting blocks
Pressure sensors are also put in
the starting blocks.
This prevents the runner locatedfurthest from the starter from
hearing the start signal last.
To understand you need to know the reaction time of each
runner. Sprint races are timed from the moment the starters
gun is fired. The actual gun is normally silentthe bang
comes from speakers behind the starting blocks.
-
7/27/2019 5.ElectricalSignals
5/42
5 of 42 Boardworks Ltd 2006
Pressure-time graph
-
7/27/2019 5.ElectricalSignals
6/42
6 of 42 Boardworks Ltd 2006
Gaining the advantage
-
7/27/2019 5.ElectricalSignals
7/42
7 of 42 Boardworks Ltd 2006
Scientists have found that it is physically impossible to reactin less than 0.1 seconds. If a runners reaction time is less
than 0.1 seconds then they must have deliberately started
before the signal was heard.
How can pressure-time graphs identify false-starts?
Fairer races
0.05 0.20.150.1
time (sec)
p
ressure
-
7/27/2019 5.ElectricalSignals
8/42
8 of 42 Boardworks Ltd 2006
Is there a correlation?
-
7/27/2019 5.ElectricalSignals
9/429 of 42 Boardworks Ltd 2006
The importance of fast reactions
What kind of factors slow down reaction times?
tiredness
alcohol
drugs
old age
!
Fast reactions can help you to avoid accidents. For example,
at 30mph a car can travel 9m before the driver is able to
respond to the hazard and start braking.
-
7/27/2019 5.ElectricalSignals
10/4210 of 42 Boardworks Ltd 2006
Detecting external stimuli
-
7/27/2019 5.ElectricalSignals
11/4211 of 42 Boardworks Ltd 2006
The brain can respond to touch, smell or taste stimuli in just
0.1 seconds, but sound and vision take longer.
How fast are electrical signals?
Nerve impulses
travel at up to
320mph and
take just
0.02 seconds
to reach the
brain.
-
7/27/2019 5.ElectricalSignals
12/4212 of 42 Boardworks Ltd 2006
Interpreting signals
How can you find your reaction time?
1. Extend your arm over the edge of a tableand have a partner hold a ruler between
your fingers at the 0cm mark.
2. The partner drops the ruler catch itbetween your fingers and thumb as
quickly as possible.
3. Repeat the test 10 times, recording the
results and calculate the mean (average)
distance. Then convert the distance into a
reaction time.
-
7/27/2019 5.ElectricalSignals
13/4213 of 42 Boardworks Ltd 2006
-
7/27/2019 5.ElectricalSignals
14/4214 of 42 Boardworks Ltd 2006
What types of reflexes do you know?
Common reflexes
-
7/27/2019 5.ElectricalSignals
15/4215 of 42 Boardworks Ltd 2006
Reflexes are fast, automatic protective
biological control systems that link a
stimulus to a response.
Many reflexes such as sneezing and focusing
your eyes occur naturally, but other reflexes
can be learned, i.e. conditioned responses.
Reflex reactions happen without you
having to think about them they are
involuntary. This is because thecentral nervous system (CNS) sends
electrical signals to the muscles before
the brain can pick up the message.
What are reflexes?
-
7/27/2019 5.ElectricalSignals
16/4216 of 42 Boardworks Ltd 2006
The central nervous system (CNS) is made up of the brain
and spinal cord.
What is the central nervous system?
cerebralcortex
cerebellum
brainstem
cerebral
hemisphere
spinal cordouter view cross-section
-
7/27/2019 5.ElectricalSignals
17/4217 of 42 Boardworks Ltd 2006
The cerebral cortex is the outer layer of the brain and
controls voluntary movements. Voluntary movements take
longer than reflex movements because more electrical
impulses have further to travel.
Trained sports people seem to move faster than the brain
can respond. They do this by anticipating what will happen
instead of waiting for a message from their senses.
The brain and movement
cerebral cortex initiates actions
cerebellum fine tunes muscle control
brainstem co-ordinates reflexes
-
7/27/2019 5.ElectricalSignals
18/4218 of 42 Boardworks Ltd 2006
What can go wrong?
-
7/27/2019 5.ElectricalSignals
19/4219 of 42 Boardworks Ltd 2006
What are neurones?
Neurones are specialized cells that conduct
electrical impulses through the body.
nerve
nerve fibre
A nerve is a bundle of many nerve
fibres enclosed within a protective
sheath. Nerve fibres are the long
axons of neurones together with
any associated tissues.
-
7/27/2019 5.ElectricalSignals
20/4220 of 42 Boardworks Ltd 2006
What do neurones look like?
The axons of most neurones are wrapped in an insulating
lipid layer called the myelin sheath. Why is this important?
Thin projections called dendrites extend from the cell body
and connect with other neurones, allowing electrical impulses
to pass from one to the other.
Neurones are elongated cells consisting of a cell body and
long, thin axon.
myelin
sheath
axon
dendrites
cell
body
-
7/27/2019 5.ElectricalSignals
21/4221 of 42 Boardworks Ltd 2006
What are sensory neurones?
Sensory neurones transmit messages from sense
receptors, such as the eye or nose, to the brain or spinal
cord.
cell body
nerve impulse
from sense organnerve impulse
to CNS
-
7/27/2019 5.ElectricalSignals
22/4222 of 42 Boardworks Ltd 2006
What are motor neurones?
Motor neurones transmit messages from the brain and
spinal cord to the muscles and glands.
cell body
muscle
-
7/27/2019 5.ElectricalSignals
23/4223 of 42 Boardworks Ltd 2006
A reflex arc
-
7/27/2019 5.ElectricalSignals
24/4224 of 42 Boardworks Ltd 2006
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
-
7/27/2019 5.ElectricalSignals
25/4225 of 42 Boardworks Ltd 2006
The release of neurotransmitters
When a nerve impulse arrives at the end of one neurone it
triggers the release ofneurotransmittermolecules from
synaptic vesicles.
synaptic
vesicle
neurotransmitter
molecules
-
7/27/2019 5.ElectricalSignals
26/4226 of 42 Boardworks Ltd 2006
synaptic
cleft
Continuing the impulse
The neurotransmitters diffuse across the synaptic cleft and
bind with receptors on the next neurone, triggering another
impulse.
nerveimpulse
receptor
Th f fl
-
7/27/2019 5.ElectricalSignals
27/4227 of 42 Boardworks Ltd 2006
The sequence of a reflex arc
T f l ?
-
7/27/2019 5.ElectricalSignals
28/42
28 of 42 Boardworks Ltd 2006
True or false?
-
7/27/2019 5.ElectricalSignals
29/42
29 of 42 Boardworks Ltd 2006
Th i i fl
-
7/27/2019 5.ElectricalSignals
30/42
30 of 42 Boardworks Ltd 2006
The iris reflex
I id th
-
7/27/2019 5.ElectricalSignals
31/42
31 of 42 Boardworks Ltd 2006
Inside the eye
lensfocuses light
on retina
iris
regulates amountof light entering eye
retinasenses light
optic nervetransmits impulses to
the brain
ciliary muscleschange shape of the lens
corneaprotects eye surface and
focuses light rays
suspensory ligamentshold lens in place
Wh t i bi l i i ?
-
7/27/2019 5.ElectricalSignals
32/42
32 of 42 Boardworks Ltd 2006
Animals with binocular vision have eyes close together.
This provides an overlapping field of view and enhanced
depth perception.
What is binocular vision?
monocular
field of
vision
binocular
field of
vision
Predators tend to have binocular vision because they need
to judge distances and anticipate the movement of prey.
no field
of vision
Wh t i l i i ?
-
7/27/2019 5.ElectricalSignals
33/42
33 of 42 Boardworks Ltd 2006
What is monocular vision?
Animals with monocular vision have eyes spaced apart,
providing a very wide field of view.
Animals like the
horse have acombination of
monocular and
binocular vision.
monocular
field of
vision
binocular
field of
vision
Prey animals tend to
have monocular vision
because they need to
see predatorsapproaching from any
direction.
no
field of
vision
A d ti
-
7/27/2019 5.ElectricalSignals
34/42
34 of 42 Boardworks Ltd 2006
Accommodation
Correcting sight
-
7/27/2019 5.ElectricalSignals
35/42
35 of 42 Boardworks Ltd 2006
Correcting sight
What is colour blindness?
-
7/27/2019 5.ElectricalSignals
36/42
36 of 42 Boardworks Ltd 2006
What is colour blindness?
Colour blindness (dichromatism) means that a person has
difficulty distinguishing between red and green.
If you have normal vision
you can see an eye in the
image. If you are colourblind you can only see
either red or orange
spots.
Colour blindness is caused by a lack of receptors in the retina
and affects about 7% of men and 1% of women.
What can you see in the circle?
-
7/27/2019 5.ElectricalSignals
37/42
-
7/27/2019 5.ElectricalSignals
38/42
38 of 42 Boardworks Ltd 2006
Glossary (1/2)
-
7/27/2019 5.ElectricalSignals
39/42
39 of 42 Boardworks Ltd 2006
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 electrical
impulses from the CNS to muscles and glands.
neurone A specialized cell that carries electricalimpulses.
Glossary (2/2)
-
7/27/2019 5.ElectricalSignals
40/42
40 of 42 Boardworks Ltd 2006
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.
Anagrams
-
7/27/2019 5.ElectricalSignals
41/42
41 of 42 Boardworks Ltd 2006
Anagrams
Multiple choice quiz
-
7/27/2019 5.ElectricalSignals
42/42
Multiple-choice quiz