Detection of the environment by mammals

Detection of the environment by mammals
title Detection of the environment by mammals

15.2 Detection of the environment by mammals
content 15.1 Irritability 15.2 Detection of the environment by mammals 15.3 The eye, how it works 15.4 How is the image formed and interpreted as sight 15.5 How does the eye focus near and distant objects 15.6 Eye defects 15.7 The structure and functions of the ear 15.8 How do we hear 15.9 How do we detect changes of movement and keep our balance? 15.10 Production of smell and taste 15.11 Detection of touch and heat

15.1 Irritability Irritability stimuli receptors nervous system
ability to detect stimuli and carry out responses stimuli receptors detected by any change in the external or internal environment of the body nervous system endocrine system The process of coordination electrical impulses hormones The way an organism reacts after detecting a stimulus responses effectors carry out

15.2 Detection of the environment by mammals
sense organ stimulus sensation detected by sends out results in transmitted to nerve impulse brain

Movement of the body, balance
15.2 Detection of the environment by mammals sense organ stimulus sensation Eye Ear Nose Tongue Skin Light Sight Sound Hearing Movement of the body, balance Movement Chemicals in air Smell Chemicals in food Taste Touch, pain, pressure Texture, pain, pressure Temperature Heat or cold

15.3 The eye, how it works Eyes detect light and form images
of objects. Why can you see me ?

Side view of the human eye
Structures around the eye eyeball bone of ‘orbit’ of eye Side view of the human eye eye muscles allows eyeball to move in various directions upper eyelid orbit lower eyelid

Structures around the eye
eyebrows Let’s observe the front part of the eyes of your classmates !!! upper eyelid eyelashes lower eyelid There are eyelashes prevent objects from entering eyes eyebrows prevent sweat from running into eyes upper and lower eyelids protect eyes by closing them Do you know how these structures protect the eyes ?

vertical section through the eyeball
Internal structures of the eyeball The wall of the eyeball - 3 layers Outer layer Sclera sclera vertical section through the eyeball white, tough cover made of fibres functions protects delicate inner layers provides surfaces for attachment of eye muscles maintains the shape of the eyeball

Internal structures of the eyeball Outer layer Cornea sclera vertical section through the eyeball cornea transparent curved surface covered and protected by a thin layer of cells — conjunctiva functions allows light to pass through (transparent) refracts light into eye (curved surface) conjunctiva

Internal structures of the eyeball Outer layer Conjunctiva sclera vertical section through the eyeball cornea protects the cornea conjunctiva

Internal structures of the eyeball Middle layer Choroid choroid vertical section through the eyeball contains black pigment which absorbs light and reduces the reflection of light inside the eye contains numerous blood vessels which supply nutrients and oxygen to the eye

Internal structures of the eyeball Inner layer retina Retina vertical section through the eyeball contains rods for black and white vision, and cones for colour vision rods — contain a pigment, visual purple, which is sensitive to low light cones — require brighter light to function

Internal structures of the eyeball Inner layer retina Retina vertical section through the eyeball yellow spot two special regions yellow spot and blind spot at yellow spot — sharpest vision; most concentrated with cones and no rods blind spot optic nerve at blind spot — no cones or rods; the place where optic nerve leaves the eye

Internal structures of the eyeball Inner layer retina Optic nerve vertical section through the eyeball a collection of nerve fibres (connect to each of rods and cones) function transmits nerve impulses to the optic centre in the cerebral cortex optic nerve

Internal structures of the eyeball Inner layer retina Optic nerve vertical section through the eyeball stimulated by light rods cones send off nerve impulses travel along optic nerve for interpretation optic nerve optic centre

Internal structures of the eyeball The iris and pupil Iris vertical section through the eyeball iris front part of choroid contains colour pigment (brown for Chinese) made up of radial and circular muscles pupil function regulates the size of the pupil and hence the amount of light entering the eye a circular hole in the centre of iris

Internal structures of the eyeball
The iris and pupil To prevent too much light from entering the eyeballs radial muscles relax which may damage or over-stimulate the retina narrow pupil (pupil constricts) circular muscles contract eye in bright light

Internal structures of the eyeball
The iris and pupil More light is allowed to enter the eye helping a clear image to form at low light intensity radial muscles contract wide pupil (pupil dilates) circular muscles relax eye in dim light

Internal structures of the eyeball The lens, suspensory ligaments and the ciliary body Lens vertical section through the eyeball lens behind iris transparent and elastic biconvex shape function refracts and focuses light onto the retina

Internal structures of the eyeball The lens, suspensory ligaments and the ciliary body Suspensory ligaments vertical section through the eyeball lens connected to ciliary body function holds lens in position suspensory ligaments

Internal structures of the eyeball The lens, suspensory ligaments and the ciliary body Ciliary body vertical section through the eyeball ciliary body lens made up of ciliary muscles function regulates the curvature of the lens by contraction and relaxation of the ciliary muscles suspensory ligaments control bending of light entering the eye

Vertical section through the eyeball
Internal structures of the eyeball The aqueous humour and vitreous humour Aqueous humour Vertical section through the eyeball transparent liquid between cornea and the lens more watery anterior chamber filled with aqueous humour functions refracts light into the eye maintains the convex shape of the cornea supplies nutrients to the conjunctiva, cornea and lens

Internal structures of the eyeball The aqueous humour and vitreous humour posterior chamber filled with vitreous humour vertical section through the eyeball Vitreous humour transparent liquid between the lens and retina more jelly-like functions refracts light into the eye keeps the eyeball spherical in shape

Examination of a model of the eye
Carry out Practical 15.1 Examination of a model of the eye

Dissection of an ox’s eye
Carry out Practical 15.2 Dissection of an ox’s eye

15.4 How is the image formed and interpreted as sight?
Do you remember which structures can refract the light? Light from the object is refracted and focused onto the retina cornea lens aqueous humour vitreous humour focus the light here is an object The image formed is real, inverted and smaller than object

15.4 How is the image formed and interpreted as sight?
Do you remember which structures can refract the light? cornea lens aqueous humour vitreous humour focus the light Let’s demonstrate the formation of image first

To demonstrate the formation of an inverted image on the retina
Carry out Practical 15.3 To demonstrate the formation of an inverted image on the retina

Light from the object is refracted and focused onto the retina
The image is formed real,inverted and smaller than object

The image will be detected by rods and cones which cause nerve impulses

Nerve impulses are transmitted along optic nerve to the optic centre in the cerebral cortex of the brain

The optic centre in the brain interprets the nerve impulses and ‘sees’ an upright image of the object in brain

15.5 How does the eye focus near and distant objects?
by controlling the thickness of lens thicker (near object) thinner (distant object) Accommodation The ability of the eye to focus objects at different distances onto the retina

To demonstrate the need for accommodation
Carry out Practical 15.4 To demonstrate the need for accommodation

Focusing on near objects
This is why the eyes become tired after too much reading! Circular ciliary muscles contract Tension in suspensory ligaments reduces Light is refracted more by the lens side view light rays from near object (diverging) Light is focused on the yellow spot Lens becomes more convex

Focusing on distant objects
This is how the eyes are when resting! Circular ciliary muscles relax Tension in suspensory ligaments increases Light is refracted a little by the lens light rays from distant object (parallel) Light is focused on the yellow spot Lens becomes less convex side view

Examples of eye defects
Short sight see nearby objects clearly but not distant objects Long sight see distant objects clearly but not nearby objects Colour blindness cannot see some or all colours

Short sight The image of distant object is formed in front of the retina because of two reasons: can be corrected by concave lens Lens too convex Eyeball too long cause (lens too convex) and correction of short sight cause (eyeball too long) and correction of short sight

Long sight The image of nearby object is formed behind the retina because of two reasons: can be corrected by convex lens Lens not convex enough Eyeball too short causes (lens not convex enough) and correction of long sight causes (eyeball too short) and correction of long sight

Carry out Practical 15.5 Demonstration of the causes of short and long sight and their corrections, using a model of the eye

Colour blindness Colour blindness
reduced number of / some defects in one or more of the 3 types of cone cells inherited Human beings seldom have total colour blindness. Red-green colour blindness is the most common form. normal eyesight with colour blindness

Testing for colour blindness using charts
Carry out Practical 15.6 Testing for colour blindness using charts

15.7 The structure and functions of the ear
Please don’t bark at me ! Ear detects sound. It also helps to detect movement. Why can you hear me barking?

Ear is divided into 3 parts:
structure of the ear outer ear middle ear inner ear

Outer ear structure of the ear middle ear outer ear inner ear

Outer ear Ear pinna function ear pinna
piece of cartilage covered with skin function collects and directs sound waves into the canal

Outer ear Ear canal functions ear pinna
lined with hairs and glands (secretes waxy substances) ear canal functions directs sound waves towards the eardrum trap foreign particles by waxy substances

Outer ear Eardrum function ear pinna
a thin and elastic membrane at the end of ear canal ear canal function converts sound waves into mechanical vibrations eardrum

Middle ear Structure of the ear middle ear outer ear inner ear

Middle ear Ear bones function 3 ear bones behind eardrum
held by ligaments ear bones function amplify and transmit vibrations from the eardrum to the membrane at the oval window

Middle ear Oval window function oval window membrane covered opening
ear bones function transmits vibrations from the ear bones to the inner ear

Middle ear Round window function oval window membrane covered opening
below oval window ear bones function releases the pressure set up in cochlea into the air in the middle ear round window

Middle ear Eustachian tube function oval window
narrow tube connecting the middle ear with the pharynx normally closed by muscles opened by swallowing or yawning ear bones round window function equalizes pressure within the middle ear with the atmospheric pressure Eustachian tube

Middle ear PA > PM eardrum bulges inwards  temporary deafness How the Eustachian tube equalizes pressure on both sides of the eardrum ? descend rapidly PA  swallowing allows air in through Eustachian tube from the mouth PA = atmospheric pressure PM = air pressure in the middle ear PA = PM PM 

Middle ear PA = atmospheric pressure PM = air pressure in the middle ear PA = PM PM  opening mouth allows air to leave through Eustachian tube PA < PM ascend rapidly PA  eardrum bulges outwards  temporary deafness

Inner ear Structure of the ear middle ear outer ear inner ear

Inner ear Semicircular canals function semicircular canals
3 semicircular canals lie in three different planes, at right angles to each other filled with endolymph with ampulla, which contains sensory cell, at the end of each canal function detect direction of head movement

Inner ear jelly-like substance in a membrane sac ampulla
inside ampulla semicircular canals and cochlea ampulla hair attached to sensory hair cell hair cell auditory nerve

Inner ear Cochlea semicircular canals
divided into 3 canals, which are separated by two membranes filled with endolymph and perilymph contains sensory hair cells which detect vibration of lymph of the cochlea and produce nerve impulses cochlea

Inner ear upper and lower canal: middle canal: auditory nerves
filled with endolymph presence of sensory hair cells - react to pressure changes and produce nerve impulse filled with perilymph cochlea cross section of cochlea auditory nerves

Inner ear Auditory nerve function auditory nerve semicircular canals
connects to brain function conducts nerve impulses from the cochlea and the semicircular canals to the brain cochlea where sound and directions of head movements are interpreted

Examination of a model of the ear
Carry out Practical 15.7 Examination of a model of the ear

15.8 How do we hear? We can hear by ear through several steps:
The hearing process

15.9 How do we detect changes of movement and keep our balance?
Do you remember? The semicircular canals detect movement of the head in different planes The detection is done by: 3 semicircular canals located on different planes filled with endolymph ampulla at the end of canals

For example: The head moves in this direction
Endolymph presses against the jelly-like substance and bends it. jelly like substance Endolymph moves in opposite direction. Nerve impulse generated transmits to cerebrum and cerebellum. Sensory hair cells are stimulated. to auditory nerve

15.10 Production of smell and taste
Nose Tongue contains chemical receptors to detect dissolved chemicals Nose Sensation of smell Tongue Sensation of taste Flavour - due to stimulation of both the taste receptors and the smell receptors

Nose Smell receptors — at the membrane lining the upper part of the nasal cavity nerve to brain produce nerve impulses to brain Structures of the smell receptors detected by smell receptors sensory hair cell chemical substance in air mucus layer dissolves in mucus layer

produce impulses to brain
Tongue taste buds Taste receptors - at the upper surface of the tongue similar to nose, the chemicals dissolve before detected Taste bud chemicals dissolve in mucus produce impulses to brain detected by sensory cells

Tongue which are not evenly distributed over the tongue
4 different types of taste buds sour taste bitter taste salty taste sweet taste

15.11 Detection of touch and heat
There are a number of types of receptors : sensation of touch They are unevenly distributed in our body sensation of heat pain receptor Major receptors in the skin touch receptor cold receptor heat receptor pressure receptor hair nerve

Carry out Practical 15.8 Investigation of the ability to sense a stimulus by touch in different regions of the skin

Investigation of the temperature sensing ability of the skin
Carry out Practical 15.9 Investigation of the temperature sensing ability of the skin

Please click to continue...
Concept diagram Irritability involves lead to stimuli responses carried out by detected by nervous system receptors send impulse to send impulse to endocrine system often located in sense organs effectors Please click to continue...

Concept diagram Detection of the environment by mammals light and
objects touch and temperature movement and position by sound by by smell and taste by by eyes ears, eyes and muscle receptors ears Please click to continue... accommodation eye defects structure function

Concept diagram touch and smell and temperature taste taste smell
by by smell receptors in nose taste receptors in tongue (taste buds) touch receptors in skin temperature receptors in skin

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