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th
6 IJSO
2009
BIOLOGY
Responding Part 1
1
Notes to Teachers:
Learning Objectives:
The five senses - the meaning of the terms stimuli and respond (0.25 hr)
The eye - mechanism of vision: function of rods and cones, color vision (0.5 hr)
The ear - the structure of the ear, the mechanism of hearing: the role of the organ
of Corti, investigation on senses (0.75 hr)
The sensory functions of skin (0.5 hr)
The structure and functions of different types of neurone (0.5 hr)
Nerve impulse - generation and transmission of nerve impulse, the role of
sodium and potassium ions, production of resting and action potentials, all-ornothing nature of the action potential, concept of threshold (1.5 hrs)
Central nervous system - the organization of the nervous system into the central
and the peripheral nervous system, structure and functions of human brain,
spinal cord, and medulla (2 hrs)
Autonomic nervous systems - the control of involuntary activities by the
sympathetic and parasympathetic nervous systems with reference to their
antagonistic actions (1 hr)
Reflex action and voluntary actions (0.25 hr)
How muscles move (0.25 hr)
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Learning Outcomes
After studying this topic students should be able to:
describe the various senses in our body
define the terms stimulus and respond
explain the roles of various parts of eyes in detecting light
state and compare the functions of rods and cones
explain the roles of various parts of ear in hearing
perform investigation on senses e.g. sensitivity of skin of different body
parts, hearing range of different ages
explain the sensory functions of skin
state the structure and functions of the neurons
state the nature of nerve impulse
describe the mechanism of generation and conduction of nerve impulse.
describe the mechanism of synaptic transmission
aware the complex organization of the nervous system
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Learning Outcomes (cont’d)
After studying this topic students should be able to:
identify the various parts of the human brain and spinal cord
state the functions of various parts of the central nervous system
state the role of the autonomous nervous system
explain the functioning of a spinal reflex and the types of neurons
involved
state the significance of reflexes
cite examples of reflex action, conditional reflex and voluntary action and
outline their importance in everyday life
describe the role of joints and muscles in locomotion
use the sliding-filament hypothesis to explain muscle contraction
investigate how fast our muscles react
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Responding
Contents
-Understanding of how our bodies’ senses help
us respond to our environment
-Describe the various senses in our body
-Define the terms stimulus and respond and
how they relate
-Describe how nerves carry messages
-Explain how muscles move arms and legs
-Investigate the senses
-Investigate how fast our muscles react
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Case study: A boy is reading …..
@#$^*??
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Some terms
1.
2.
3.
4.
5.
6.
Stimuli
Responses
Receptors
Sense organs
Effectors
Coordination
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A. The process of coordination
Stimuli  receptors
nervous system
effectors -> response
endocrine system
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Sense, stimulus, receptor and
sense organ
Sense
Stimulus Energy
1.sight
Light
2.Hearing Sound
3.Taste
Sense
organ
Electromagnetic
Photoreceptor
Eye
Mechanical
deformation
Mechanoreceptor
Ear
Chemoreceptor
Taste
bud
Mechanoreceptor,
Skin
Chemical Chemical
in food
4.Touch Touch,
pain..
5.Smell
Receptor
Mechanical
deformation
Chemical chemical
in air
chemoreceptor
chemoreceptor nose
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Skin – touch receptor, thermoreceptor
(heat, cold receptor), pain receptor, pressure receptor
Epidermis
B. Dermis
C. Subcutis/Hypodermis
D. Blood and Lymph Vessels
E. Stratum Germinativum
1.Hair Shaft
2.Stratum Corneum
3.Pigment Layer
4.Stratum Spinosum
5.Stratum Basale
6.Arrector Pili Muscle
7.Sebaceous Gland
8.Hair Follicle
9.Papilla of Hair
10.Nerve Fiber
11.Sweat Gland
12.Pacinian Corpuscle
13.Artery
14.Vein
15.Sensory Nerve ending (for touch)
16.Dermal Papillary
17.Sweat Pore
18.Acidic Fluids/>
Wikipedia file
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Eye
pupil
iris
Wikipedia file
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Eye
Wikipedia file
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Rods and cones in retina
Wikipedia file
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photochemical reaction
Light
Rhodopsin
(purple)
Scotopsin + retinene (colourless)
Dark
Nerve impulse
Under light, retinene undergoes isomeric change,
rhodopsin breaks down to scotopsin and retinene
(both colourless)
 Bleaching of visual pigments
 nerve impulse
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Differences between rods and cones
Rods
Cones
Periphery of retina
Concentrated at centre
Large number in
yellow spot
Low
High visual
sensitivity
Low visual acuity
-detect dim light
-night vision
-cannot detect colour
High
-only detect strong light
-day vision
-detect colour
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Wikipedia file
Each cone synapses with only one bipolar neurone  low visual
sensitivity / tightly packed  high visual acuity
Many rod synapses with one bipolar neurone  high visual
sensitivity / less tightly packed  low visual acuity
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trichromatic theory of colour vision
Sensation of any given colour is
determined by the relative frequency
of impulses reaching the brain from
each type of cone
stimulate both green and red cones
 yellow
-Colour blindness
-Red-green colour blindness
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Ishihara test charts
Wikipedia file
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Accommodation –
near / distant objects
Wikipedia file
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Pupil reflex
Wikipedia file
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Short sight and its correction
Wikipedia file
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Long sight and its correction
Wikipedia file
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Ear
Wikipedia file
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Organ of corti – sensory hair cell
Wikipedia file
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Wikipedia file
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Mechanism of hearing
Wikipedia file
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Mechanism of hearing
- pinna collects sound waves
- eardrum is set into vibrations
- ear ossicles amplify the vibration
- vibrations of oval window set the fluid in inner ear
into motion
- pressure waves in fluid set the basilar membrane
into vibrations.
- hairs of sensory hair cells in the Organ of Corti to
brush against the tectorial membrane
- hairs bend and this shearing force causes the
excitation of sensory hair cells
- excites the auditory nerve (the auditory part of VIIIth
cranial nerve) and initiates action potential.
- The auditory nerve conducts the action potential to
auditory cortex of cerebrum where the pitch, quality
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and loudness of the sound are detected.
taste buds - chemoreceptors
Wikipedia file
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Chemoreceptors in nose
Wikipedia file
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Distribution of taste buds sensitive
to different tastes
1 . Bitter
2. Sour
3. Salty
4. Sweet
Wikipedia file
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th
6
IJSO BIOLOGY
PART 1.2
Nerves
Function of nervous system
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Chasing by a dog
Wikipedia file
Stimulus
Light
Receptor
Photoreceptors
Coordinating system
??
Effector
??
Response
Skeletal muscles contract Running
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Human
nervous
system
Wikipedia file
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Mammalian nervous system
Wikipedia file
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Mammalian nervous system
Central nervous system
Peripheral nervous system
Autonomic nervous
system
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Neuron(e) 神經元
Wikipedia file
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Neuron(e) 神經元
Wikipedia file
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Structure of a neurone
1.Cell body – controls cellular activities
found in grey matter (灰質)
2.Nerve fibre – in white matter(白質)
-dendrons 樹突
-axon 軸突
-myelin sheath surrounded by Schwann cell
plasma membrane, for insulation and
increase the rate of conduction of nerve
impulse
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Myelinated VS unmyelinated nerve fibre
Wikipedia file
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3 types of neurones
Motor neurone
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Sensory neurone – olfactory
sensory neurone
Wikipedia file
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Nerves – sensory/motor/mixed
Wikipedia file
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Nerve
Wikipedia file
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Spinal cord
Wikipedia file
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Wikipedia file
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Wikipedia file
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Wikipedia file
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Functions of spinal cord
1. relays these sensory impulses to the brain
2. relay the motor impulses from the brain to
the limb muscles (e.g. leg muscles) via the
spinal nerves to effect coordinated movement
and to keep body in equilibrium posture.
3. a passage for nerve fibres to allow the
2-way conduction of nerve impulses to and
from the brain and the limb muscles (e.g. leg
muscles).
4. The spinal cord is the site for control of
somatic reflexes (e.g. withdrawal reflex)
which are involuntary actions.
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Brain
Wikipedia file
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Wikipedia file
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White matter and grey matter
Wikipedia file
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Function of brain
- forebrain, midbrain / brain stem (腦幹)
and hindbrain
forebrain - cerebrum, thalamus
(丘腦) and
hypothalamus (下丘腦)
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Cerebrum (大腦)
cerebral cortex – frontal, parietal, temporal
and occipital lobe
Grey matter on outer surface, white matter
inner surface
Cerebral cortex is highly folded to
increase the surface area for holding
more neurones for more complicated
coordination.
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Functional area of cerebrum
Functional
area
Functions
Sensory
centre
receives sensory impulse from various receptors of
sense organs and produce sensation e.g. skin sensation
(pain / pressure…), vision, audition, vestibular
sensation (movement of head), taste and olfaction.
Association
centre
site for other integrative functions e.g. emotion,
language, learning, memory, planning, judgment,
motivation, intelligence, etc.
processes impulses from the sensory cortex, medulla
or cerebellum and relay them to the motor centre in
the cerebral cortex.
Motor centre
It sends motor impulse to the skeletal muscles of
hands or legs to initiate voluntary movement and
other skeletal muscles to maintain balance.
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Hypothalamus osmoregulation, temperature regulation,
lactation and controlling the activities of
other endocrine glands.
Midbrain –
controls cranial reflexes (腦反射) e.g. pupil
reflex
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Hindbrain – cerebellum (小腦)
(1) It receives impulses
- from semi-circular canals, utriculus and sacculus
about the position of head.
- from the proprioceptors (stretch receptors) in muscles,
tendons and joints about the
muscular movement
- from motor centre of cerebral cortex.
(2) After processing the information received, the
cerebellum
- coordinate the muscular activities to perform precise
body movements.
- coordinates reflexes in the body to maintain
equilibrium.
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Hindbrain – medulla oblongata (延腦)
(1) cardiovascular centre - controls cardiovascular
function e.g. heart beat rate
respiratory centre - controls respiratory
function e.g. ventilation rate
vasomotor centre - controls vasomotor function e.g.
blood pressure
(2) It is also the control centre for many involuntary
actions e.g. swallowing, sneezing, coughing,
blinking of eyes.
(3) It helps to maintain the equilibrium state of the
body.
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Brain damage
What body functions would be affected if
brain damage occurred in:
(i) the occipital lobe
(ii) the cerebellum
(iii) the medulla oblongata?
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Reflex action
Quick, inborn, automatic, stereotypic
Spinal cord / medulla / midbrain
Significance:
1. Homeostatis
2. prevent body from damage
3. Conduct body function
4. Conditioned reflex
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Reflex VS voluntary action
Reflex actions
Voluntary
actions
1. Inborn / need not learn
Not inborn / can be learned
2.Usually faster
Usually slower
3.Stereotyped response
Different responses
4.Control centre is in medulla Control centre is in cerebrum
or spinal cord
5.A receptor is involved
A receptor may not
be involved / may
be initiated
spontaneously.
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Withdraw reflex
Pain receptor in skin  sensory neurone
 interneurone  motor neurone 
biceps contracts, withdraw the hand
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(ii) this reflex is automatic / not involve the
cerebrum until after the event.
Interneurone to brain can transmit sensory
impulse to the sensory area of cerebrum where the
sensation of pain is produced.
Withdrawal of the stimulated hand occurs before
sensation of pain is experienced. WHY?
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(ii) this reflex is automatic / not involve the
cerebrum until after the event.
Interneurone to brain can transmit sensory
impulse to the sensory area of cerebrum where the
sensation of pain is produced.
Withdrawal of the stimulated hand occurs before
sensation of pain is experienced. WHY?
It takes a shorter time for the impulses
transferred to the effector (biceps) than
to the cerebrum. It is the cerebrum that
gives the sensation of pain.
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Knee
jerk
reflex
Wikipedia file
stretch receptor in patellar tendon  sensory
neurone  motor neurone  extensor
muscle contracts, leg jerk forward
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Conditioned reflex (條件反射) - Pavlov
Smell of food ->
(natural stimulus)
salivation (natural reflex)
Bell sound ->
(conditioned stimulus)
Salivation (conditioned
reflex)
Wikipedia file
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Conditioned reflex VS voluntary
actions
Conditioned reflex actions
Voluntary actions
1. A stimulus is necessary
A stimulus may not be
for producing response
necessary
2.Usually faster
Usually slower
3.Stereotyped
different responses
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