2009 6 th ijso biology responding part 1 1. notes to teachers: the five senses - the meaning of the...
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2009 6th IJSO BIOLOGY
Responding Part 1
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Notes to Teachers:
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-or-nothing 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)
Learning Objectives:
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Learning Outcomes
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
After studying this topic students should be able to:
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Learning Outcomes (cont’d)
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
After studying this topic students should be able to:
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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. Stimuli2. Responses3. Receptors4. Sense organs5. Effectors 6. 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 Receptor Sense organ
1.sight Light Electromagnetic Photoreceptor Eye
2.Hearing Sound Mechanical deformation
Mechanoreceptor Ear
3.Taste Chemical in food
Chemical Chemoreceptor Taste bud
4.Touch Touch,
pain..
Mechanical deformation
Mechanoreceptor,
chemoreceptorSkin
5.Smell Chemical in air
chemical chemoreceptor nose
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Skin – touch receptor, thermoreceptor(heat, cold receptor), pain receptor, pressure receptor
EpidermisB. DermisC. Subcutis/HypodermisD. Blood and Lymph VesselsE. Stratum Germinativum
1.Hair Shaft2.Stratum Corneum3.Pigment Layer4.Stratum Spinosum5.Stratum Basale6.Arrector Pili Muscle7.Sebaceous Gland8.Hair Follicle9.Papilla of Hair10.Nerve Fiber11.Sweat Gland12.Pacinian Corpuscle13.Artery14.Vein15.Sensory Nerve ending (for touch)16.Dermal Papillary17.Sweat Pore18.Acidic Fluids/>
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Eye
pupil
iris
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Eye
Wikipedia file
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Wikipedia file
Rods and cones in retina
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photochemical reaction
Under light, retinene undergoes isomeric change, rhodopsin breaks down to scotopsin and retinene (both colourless)
Bleaching of visual pigments nerve impulse
Light
Rhodopsin Scotopsin + retinene (colourless)
(purple) Dark Nerve impulse
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Differences between rods and conesRods ConesPeriphery of retina Concentrated at centre
Large number in yellow spot
High visual sensitivity
Low
Low visual acuity High
-detect dim light
-night vision
-cannot detect colour
-only detect strong light
-day vision
-detect colour
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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
Wikipedia file
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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
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Accommodation – near / distant objects
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Pupil reflex
Wikipedia file
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Short sight and its correction
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Long sight and its correction
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Ear
Wikipedia file
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Organ of corti – sensory hair cell
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Mechanism of hearing
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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 and loudness of the sound are detected.
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taste buds - chemoreceptors
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Chemoreceptors in nose
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Distribution of taste buds sensitive to different tastes
1 . Bitter 2. Sour 3. Salty 4. Sweet
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6th IJSO BIOLOGYPART 1.2
Nerves
Function of nervous system
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Chasing by a dog
Stimulus Light
Receptor Photoreceptors
Coordinating system ??
Effector ??
Response Skeletal muscles contract Running
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Human nervous system
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Mammalian nervous system
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Mammalian nervous system
Central nervous systemPeripheral nervous system
Autonomic nervous system
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Neuron(e) 神經元
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Neuron(e) 神經元
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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
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3 types of neurones
Motor neurone
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Sensory neurone – olfactory sensory neurone
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Nerves – sensory/motor/mixed
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Nerve
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Spinal cord
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Functions of spinal cord
1. relays these sensory impulses to the brain2. 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
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White matter and grey matter
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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 lobeGrey 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 cerebrumFunctional 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 learned2.Usually faster Usually slower3.Stereotyped response Different responses4.Control centre is in medulla Control centre is in cerebrum or spinal cord5.A receptor is involved A receptor may not be involved / may be initiated spontaneously.
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Pain receptor in skin sensory neurone interneurone motor neurone biceps contracts, withdraw the hand
Withdraw reflex
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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. 63
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stretch receptor in patellar tendon sensory neurone motor neurone extensor muscle contracts, leg jerk forward
Knee jerk reflex
Wikipedia file
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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 file65
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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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