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/>

Wikipedia file 10

Eye

pupil

iris

Wikipedia file 11

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

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 file22

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 file26

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

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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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

Wikipedia file

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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 systemPeripheral nervous system

Autonomic nervous system

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Neuron(e) 神經元

Wikipedia file36

Neuron(e) 神經元

Wikipedia file37

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 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

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 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

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

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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