Option E: Neurobiology and Behavior

E.2.1 Outline the diversity of stimuli that can be detected by human sensory receptors, including mechanoreceptors, chemoreceptors, thermoreceptors and photoreceptors.

A wide range of stimuli can be detected by diverse receptorsin humans.

Each receptor is specific to its stimulus and adapted to suit its function.

• Mechanoreceptors - changes in pressure, e.g. touch, pain, and tension receptors - changes in texture, e.g. touch receptors in skin - changes in vibration, e.g. inner ear for hearing and balance

• Chemoreceptors - chemical solutes, e.g. taste in tongue, CO2 concentration in the blood - chemical vapors, e.g. smell in the nose

• Photoreceptors - electromagnetic radiation e.g. rod and cone cells in the retina

• Thermoreceptors - changes in temperature - thermoreceptive nerve endings in skin

E.2.2 Label a diagram of the structure of the human eye.

E.2.3 Annotate a diagram of the retina to show the cell types and the direction in which light moves.

The lens is responsible for focusing the image to the retina.

E.2.3 Annotate a diagram of the retina to show the cell types and the direction in which light moves.

• The lens focuses light onto the retina.

• Light directly hits the fovea, with densely- packed rods and cones.

• All information is processed by retina and converted to nerve impulses, which is carried to the brain by the optic nerve.

• Blind spot is where there are no rod and cone cells. This is where optic nerve meets retina.

• Your brain fills in the rest!!

The Blind Spot

Move closer or further away, the imageof the dot falls on the retina and so isperceived.

This illusion shows us that the blind spot of the righteye falls within the leftpart of the retina - which is responsible for collecting stimuli from the rightvisual field.

Visual Fields = the range over which an eye can detect visual stimuli

Light from your _____ visual field falls onto the ______ side of the retina and vice versa.

Stimuli from both left retina are processed in the left visual cortex of the occipital lobe. Therefore, both sides of the brain process images from both eyes.

E.2.3 Annotate a diagram of the retina to show the cell types and the direction in which light moves.

E.2.3 Annotate a diagram of the retina to show the cell types and the direction in which light moves.

1. Light reflects of choroid and hits rods and cones.

2. Pigments in rods and cones break down.

3. This stimulates an action potential.

4. Synapses pass impulses from photoreceptors to bipolar neurons and then to the ganglia.

5. Ganglia carry the impulse via the optic nerve to the occipital lobe.

E.2.4 Compare rod and cone cells.

Rod Cells Comparison Cone CellsDominant in ______ light conditions (“bleached” in bright light)

Light brightnessDominant ________ light conditions (not activated in dim light)

_____ type Diversity _______ types

Throughout _______ Distribution Concentrated around ________

Responsive to ____ visible wavelengths

Wavelength sensitivity

Short – ________Medium – greensLong – _______

______: many rods connect to one ganglion

Receptor: ganglion ratio _______(even 1:1)

_________ Visual acuity _________

Receptive Fields and Processing Stimuli

A receptive field is the area of the retina over which a single ganglion collects stimuli.

Many rod cells feed into one ganglion.- Gives a large receptive field and low acuity.- Differences in light within the receptive field are not likely to be perceived with clarity.

Cone cells feed into their own ganglion cells.- Gives many small receptive fields and high acuity.- Different types of cone cells detect different wavelengths of light and can perceive small details.

E.2.5 Explain the processing of visual stimuli, including edge enhancement and contralateral processing.

The retina is the first step in visual perception.

The brain receives information about where the biggestareas of contrast are in the receptive field, and this is processed into an image.

It also allows the brain to fill in the gaps in thereceptive field, such as in the + and o illusion.

This is an example of edge enhancement.

E.2.5 Explain the processing of visual stimuli, including edge enhancement and contralateral processing.

• When light falls onto a receptor, it is stimulated.

• If light also falls onto its neighboring receptors, they inhibit each other. The gray spots on the grid are the result of lateral inhibition in your retina.

• Areas of white next to each other cause inhibition of receptors in between, giving the illusion of being slightly darker.

E.2.5 Explain the processing of visual stimuli, including edge enhancement and contralateral processing.

E.2.5 Explain the processing of visual stimuli, including edge enhancement and contralateral processing.

• Images are focused by the cornea and lens.• An inverted image is focused to the retina.• Both eyes send visual information to both sides of the brain by optic chiasm = information from the inner halves of the retina (nasal retina) are crossed over.

E.2.5 Explain the processing of visual stimuli, including edge enhancement and contralateral processing.

• The optic tract carry the visual nerve impulse to the visual cortex in the occipital lobe. This is called contralateral processing.

• This means that both sides of the brain are responsible for processing information from both eyes.

E.2.5 Explain the processing of visual stimuli, including edge enhancement and contralateral processing.

• Both eyes have a right and left visual field.

• The right side of each retina collects light from the left visual field and vice versa.

E.2.5 Explain the processing of visual stimuli, including edge enhancement and contralateral processing.

Retina receives stimuli with edge enhancement ↓Retinal ganglia carry nerve impulses through the optic nerve to the brain. ↓The nasal ganglia cross over at the optic chiasmthrough contralateral processing. ↓The right side of visual cortex processes images on both right retinas (hence both left visual fields). ↓The visual cortex constructs images in the brain

E.2.5 Explain the processing of visual stimuli, including edge enhancement and contralateral processing.

• Because the two eyes are apart, the images are slightly different.

• This stereoscopic vision leads to the production of a 3D image and depth perception.

• The inverted image that hits the retina is also corrected.

E.2.5 Explain the processing of visual stimuli, including edge enhancement and contralateral processing.

E.2.6 Label a diagram of the ear.The ear is an example of mechanoreceptors in action:vibrations in the air are converted into action potential.

E.2.7 Explain how sound is perceived by the ear, including the roles of the eardrum, bones of the middle ear, oval and round windows, and the hair cells of the cochlea.

Sound waves collected by pinnaEar drum vibrated by air pressure changes

(due to sound waves)Middle ear bones stimulated, enhancing sound by 20xOval window transmits vibrations to cochleaTiny hairs in cochlea act as receptors for individual

wavelengthsAction potential generated in the cochleaAuditory nerve transmits AP to brainRound windows of cochlea dissipate sound