BioKnowledgy A.3 Perception of stimuli

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Essential idea: Living organisms are able to detect changes in the environment.

A.3 Perception of stimuli

The image show the delicate sensory hairs in the (rat's) inner ear. Sound causes vibrations in the air, which in turn causes the sensory hairs to move. The movement of sensory cells stimulates impulses in neurons which the brain interprets as sound.

By Chris Paine

http://www.bioknowledgy.info/ http://www.sciencemag.org/sites/default/files/styles/article_main_large/public/images/sn-RatEarHair.jpg?itok=YI2_5wou

UnderstandingsStatement Guidance

A.3.U1 Receptors detect changes in the environment. Humans’ sensory receptors should include mechanoreceptors, chemoreceptors, thermoreceptors and photoreceptors.

A.3.U2 Rods and cones are photoreceptors located in the retina.

A.3.U3 Rods and cones differ in their sensitivities to light intensities and wavelengths.

A.3.U4 Bipolar cells send the impulses from rods and cones to ganglion cells.

A.3.U5 Ganglion cells send messages to the brain via the optic nerve.

A.3.U6 The information from the right field of vision from both eyes is sent to the left part of the visual cortex and vice versa.

A.3.U7 Structures in the middle ear transmit and amplify sound.

A.3.U8 Sensory hairs of the cochlea detect sounds of specific wavelengths.

A.3.U9 Impulses caused by sound perception are transmitted to the brain via the auditory nerve.

A.3.U10

Hair cells in the semicircular canals detect movement of the head.

Applications and SkillsStatement Guidance

A.3.A1 Red-green colour-blindness as a variant of normal trichromatic vision.

A.3.A2 Detection of chemicals in the air by the many different olfactory receptors.

A.3.A3 Use of cochlear implants in deaf patients.

A.3.S1 Labelling a diagram of the structure of the human eye.

Diagram of human eye should include the sclera, cornea, conjunctiva, eyelid, choroid, aqueous humour, pupil, lens, iris, vitreous humour, retina, fovea, optic nerve and blind spot.

A.3.S2 Annotation of a diagram of the retina to show the cell types and the direction in which light moves.

Diagram of retina should include rod and cone cells, bipolar neurons and ganglion cells.

A.3.S3 Labelling a diagram of the structure of the human ear.

Diagram of ear should include pinna, eardrum, bones of the middle ear, oval window, round window, semicircular canals, auditory nerve and cochlea.

A.3.U1 Receptors detect changes in the environment.

A.3.A2 Detection of chemicals in the air by the many different olfactory receptors.

Olfactory receptors – sensing smell

http://www.savingstudentsmoney.org/psychimg/stangor-fig04_020.jpg

n.b. only volatile chemicals, those that vapourise easily, generate a response in olfactory receptors

Receptor cells possess cilia which project into the air in the nose. olfactory receptor proteins are located in the membrane of the cilia. Different olfactory receptors respond to different chemicals

Olfaction occurs inside the upper part of the nose.

The combination of impulses reaching the brain allows us to recognise many different types of smell

A.3.S1 Labelling a diagram of the structure of the human eye.

A.3.S2 Annotation of a diagram of the retina to show the cell types and the direction in which light moves.

A.3.U4 Bipolar cells send the impulses from rods and cones to ganglion cells. AND A.3.U5 Ganglion cells send messages to the brain via the optic nerve.

A.3.U2 Rods and cones are photoreceptors located in the retina. AND A.3.U3 Rods and cones differ in their sensitivities to light intensities and wavelengths.

Rod Cells Cone Cells

Many rod cells feed into one ganglion: all their action potentials are combined into a single impulse at the synapse. This means

each ganglion has a large receptive field, but low acuity (low ability to detect differences).

Rod cells are activated in low light conditions, but ‘bleached’ in high light intensities.

They do not detect colour.

Rods are distributed throughout the retina.

Cone cells feed into their own ganglion.This gives a small receptive field for each ganglion, leading to high visual acuity – small differences are easily detected.

There are three types of cone cells, receptive to different wavelengths (red, green, blue). These are only active in sufficient light.

Cone cells are concentrated in the fovea.

images adapted from http://www.fujifilmusa.com/products/digital_cameras/exr/eyes/page_03.html

A.3.U6 The information from the right field of vision from both eyes is sent to the left part of the visual cortex and vice versa.

Sex Linkage X and Y chromosomes are non-homologous.

What number do you see?

Chromosome images from Wikipedia:http://en.wikipedia.org/wiki/Y_chromosome

A.3.A1 Red-green colour-blindness as a variant of normal trichromatic vision. AND Review: 3.4.A2 Red-green colour blindness and hemophilia as examples of sex-linked inheritance.

X and Y chromosomes are non-homologous.

What number do you see?

5 = normal vision2 = red/green colour blindness

Sex LinkageA.3.A1 Red-green colour-blindness as a variant of normal trichromatic vision. AND Review: 3.4.A2 Red-green colour blindness and hemophilia as examples of sex-linked inheritance.

Red-Green Colour Blindness How does it work?

The OPN1MW and OPN1LW genes are found at locus Xq28.

They are responsible for producing photoreceptive pigments in the cone cells in the eye. If one of these genes is a mutant, the pigments are not produced properly and the eye cannot distinguish between green (medium) wavelengths and red (long) wavelengths in the visible spectrum.

Because the Xq28 gene is in a non-homologous region when compared to the Y chromosome, red-green colour blindness is known as a sex-linked disorder. The male has no allele on the Y chromosome to combat a recessive faulty allele on the X chromosome.

A.3.A1 Red-green colour-blindness as a variant of normal trichromatic vision. AND Review: 3.4.A2 Red-green colour blindness and hemophilia as examples of sex-linked inheritance.

The Ear and Hearing

A.3.U7 Structures in the middle ear transmit and amplify sound. AND A.3.U8 Sensory hairs of the cochlea detect sounds of specific wavelengths. AND A.3.U9 Impulses caused by sound perception are transmitted to the brain via the auditory nerve.

http://www.cengage.com/biology/discipline_content/animations/hearing.html

http://newt.phys.unsw.edu.au/jw/hearing.html

eardrum/tympanic membrane is moved by sound waves;eardrum causes movement of the bones of the middle ear;bones of the middle ear (malleus, incus and stapes) amplify sound (by 20x);bones of the middle ear on the oval window;causing movement of fluid within the cochlea;hair cells are mechanoreceptors;different hair cells respond to different wavelengths/pitch of sound;hair cells release a chemical neurotransmitter when stimulated;sounds/vibrations are transformed into nerve impulses/action potentials;carried by auditory nerve to brain;round window releases pressure/dissipates sound;this allows the fluid in cochlea to vibrate;

A.3.A3 Use of cochlear implants in deaf patients.

How do cochlear implants work?

https://youtu.be/zeg4qTnYOpw

http://kidshealth.org/EN/images/illustrations/cochlearImpant_420x315_rd1_enIL.jpg

A cochlear implant is a surgically implanted device that helps to correct hearing loss associated with damaged cochlea hairs.Its function is to generate electrical signals from sound vibrations and transmit them to your auditory nerve

Watch the video to see how it works:

How do cochlear implants work?

https://youtu.be/zeg4qTnYOpw

http://kidshealth.org/EN/images/illustrations/cochlearImpant_420x315_rd1_enIL.jpg

A cochlear implant is a surgically implanted device that helps to correct hearing loss associated with damaged cochlea hairs.Its function is to generate electrical signals from sound vibrations and transmit them to your auditory nerve

Watch the video to see how it works:

Nature of science: Understanding of the underlying science is the basis for technological developments - the discovery that electrical stimulation in the auditory system can create a perception of sound resulted in the development of electrical hearing aids and ultimately cochlear implants. (1.2)

Early research into the cochlear and research involving

the electrical stimulation of it inspired the development

of hearing aids and cochlear implants.

Read more: http://biomed.brown.edu/Courses/BI108/BI108_2001_Groups/Coch

lear_Implants/history.html

A.3.U10 Hair cells in the semicircular canals detect movement of the head.

https://commons.wikimedia.org/wiki/File:Anatomy_of_the_Human_Ear_en.svg

Detecting movement and maintaining balance

2. Movement of the head causes the fluid in the canals, if the canal is aligned with the movement3. Movement of the fluid is detected by hair cells in the cupula (wide base of each canal)4. If the hairs are triggered they in turn stimulate nerve impulses which are transmitted to the brain by

the Vestibular nerve5. The brain deduces the direction of head movement from the combination of impulses

1. The three semi-circular canals, are at right angles to each other - they are each orientated in a different plane

Bibliography / Acknowledgments

BioKnowledgy A.3 Perception of stimuli

Education