Perception of stimuli

Option A3

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


A.3.U1 Receptors detect changes in the environment

Types of human sensory receptors

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

Rods and cones in the retina

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

Rods and cones absorb different wavelengths

Different wavelengths effect the rods and cones

How light intensity affects the activity of rods and cones

Different effects of light intensity on rods and cones

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

Impulse carried from bipolar and ganglion cells

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

Impulse carried from ganglion cell to optic nerve to brain

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

Contralateral Processing

Contralateral processing explained

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

Magnification of sound by the middle ear

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

How does the eardrum vibrations move sensory hairs?

How eardrum vibrations move hair cells

Relationship between location of sensory hairs and frequency/wavelength

Different sensory hairs different vibrations

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

How the nerve impulse in generated in the auditory nerve

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

Motion and the semicircular canals

How do the semicircular canals detect direction and acceleration of the head?

How do semicircular canals detect direction of head motion


A.3.A1 Read-green color blindness as a variant of normal trichromatic vision

Red-green colourblindness graphs and explanation

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

Diagram of the sense of smell

How does the sense of smell work?

Explanation of the sense of smell

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

How a cochlear implant works


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

Structure of human eye labelled

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

Draw and annotate the structure of the retina as shown in the diagram below.

Structure of the retina

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

Structure of the human ear
Back to top of page

Valid XHTML 1.0 Strict Valid CSS!