Biology Journal 3/17/2014

Suppose that you are driving on the freeway and notice that the car in front of you has stopped. You react by slamming on the breaks. But, this “reaction time” process has taken up a certain amount of time. What nervous system processes needed to happen? Describe it, including what your motor neurons, sensory neurons, and relay neurons did during that process.

Biology Journal 3/18/2014

The back of your eye is full of specialized neurons called rods and cones. What kind of neuron do you think these cells are? What do you think would be different about their dendrites?

Biology Journal 3/19/2014

What is the most interesting thing you observed from the eye dissection?

Dissecting a whale eye.

What part of the brain processes the signals from the eyes?

Biology Journal 3/20/2014

The primary visual cortex, which is in the back of the brain

What part separates the visual signals into the left and right sides?The optic chaism

What is the name of the nerve that sends signals from the eyes to the brain?The optic nerve

This is called contralateral processing

E.2 Perception of StimuliE.2.1 Outline the diversity of stimuli that can be detected by human sensory receptors, including:

Mechanoreceptors, chemoreceptors, thermoreceptors, photoreceptorsDetails of how each receptor functions are not required.

E.2.2 Label a diagram of the structure of the human eye. The diagram should include: sclera, cornea, conjunctiva, eyelid, lens, choroid, aqueous humour, pupil, iris, vitreous humour, retina, fovea, optic nerve, blind spot

E.2.3 Annotate a diagram of the retina to show the cell types and the direction in which light moves. Include names of rod and cone cells, bipolar neurons and ganglion cells.

E.2.4 Compare rod and cone cells. Include: use in dim light versus bright light one type sensitive to all visible wavelengths versus three types sensitive to red, blue and green light passage of impulses from a group of rod cells to a single nerve fibre in the optic nerve versus passage from a single

cone cell to a single nerve fibre

E.2.5 Explain the processing of visual stimuli, including edge enhancement and contralateral processing. Edge enhancement occurs within the retina and can be demonstrated with the Hermann grid illusion. Contralateral processing is due to the optic chiasma, where the right brain processes information from the left

visual field and vice versa. This can be illustrated by the abnormal perceptions of patients with brain lesions.

E.2.6 Label a diagram of the ear. Include: Pinna, eardrum, bones of the middle ear oval window, round window, semicircular canals auditory nerve, cochlea

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.

Perception of Stimuli

Name of sensory neuron What it detects Examples

Mechanoreceptors Pressure, texture, vibration

Pain sensors in skin, balance

Name of sensory neuron What it detects Examples

Mechanoreceptors Pressure, texture, vibration

Pain sensors in skin, balance

Chemoreceptors Chemicals Taste buds, smell, CO2 concentration in blood

Name of sensory neuron What it detects Examples

Mechanoreceptors Pressure, texture, vibration

Pain sensors in skin, balance

Chemoreceptors Chemicals Taste buds, smell, CO2 concentration in blood

Photoreceptors Electromagnetic radiation rods, cones

Name of sensory neuron What it detects Examples

Mechanoreceptors Pressure, texture, vibration

Pain sensors in skin, balance

Chemoreceptors Chemicals Taste buds, smell, CO2 concentration in blood

Photoreceptors Electromagnetic radiation rods, cones

Thermoreceptors Temperature Temperature sensors in skin

Pupilopening that lets light in

Scleraprotective outer layer

Conjunctivaprotective outer

layer of pupil, secretes mucus

Eyelidprotection, cleaning

Choroidlayer of light-

absorbing pigment

Aqueous Humortransparent jelly

Irismuscles that control size of pupil; gives “eye color”

Vitreous humortransparent liquid

Retinamostly rod cells

Foveaarea of

concentrated cone cells

Blind Spotno receptor

cells

Optic Nervecarries nerve

impulses to brain

Lensadjusts to focus light

on retina

What do your pupils do in bright light?

What do your pupils do in darkness?

Dilated pupils: when they’re open wide

Constricted pupils: when they’re small

Ever have your eyes get sore from staring at a bright computer screen, TV, or phone?

That’s because you’re iris muscles are sore from constricting for so long!

I’d better check her facebook page again…

Many drugs dilate the pupils because they relax the body’s muscles. This contributes to why vision seems more intense

The lens changes shape to focus an image on the retina.

Nearsighted: The focus of the image falls short of the retina, so its blurry.Farsighted: The focus of the image is beyond the retina, so its blurry.

Rods respond to light intensity. They work well in low light.Cones are receptors respond to colors (blue, green, red). They do not work well in low light.

Your peripheral vision has mostly rods. The focus of your retina (called the fovea) contains mostly cones.

How you see:1. Light stimulates the receptors of the rods and cones.2. Bipolar cells send the action potential from the rod/cone to the ganglion

cells.3. Ganglion cells collect the action potentials from many rods or cones

and send this signal down the retina, toward the optic nerve, where it is sent to the brain.

Direction of light

Choroid

Action Potential

Direction of light

Rod cell

Cone cell

Bipolar cell

Ganglion cell

Direction of nerve signal

contralateral processing

An image is flipped twice in visual processing:1. The lens flips it to

opposite sides of the retina.

2. The optic chaism flips the image back, where it is carried primary visual cortex (back of the brain) to be interpreted.

Do you See what I See?

Which box is darker, A or B?

Edge enhancement: Our photoreceptors inhibit neighboring photoreceptors that are the same color. Thus, when color borders a different color (there is an “edge”), a photoreceptor won’t be inhibited on the edge, making the edge appear. This helps us to see shapes better.

Explanation

How might edge enhancement help us survive?

Retinal Fatigue: Our rods and cones get “fatigued” when being stimulated by the same wavelength of light for a long time, and begin to shut down.

After fatiguing your photoreceptors… Subtle changes in color get “washed out.” When you look at a “blank” screen, colors are inverted.

Explanation

Retinal Fatigue: Your brain is adapted to reading faces. It does this so well that we often see faces in when there are none.

However, his can lead to distressing images when the faces don’t meet our brain’s expectations…

Explanation

Our Devine Savior the Holy Jesus Cheese Sandwich

Auditory Senses

Eardrumvibrated by air pressure changers due to sound

waves

Semicircular Canals

balance (is not involved in hearing)

Cochleatiny hairs respond

to individual wavelengths of

sound, generating action potential

Auditory Nerve

transmits nerve signals

to brain

Eustachian Tubetransmits nerve signals

to brain

Oval Windowtransmits vibrations

from middle ear bones to inner ear

Round Windowdissipates vibrations (lessens and lessens

“old” sounds)

Pinnacollects sound waves

Middle Ear BonesStimulated by ear drum, knock against each other

to magnify sound

E.2.7Explain 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.

Youtube videos

How Vision WorksA simple, short video showing how light enters the eye and how it stimulates signals to go to the brain.https://www.youtube.com/watch?v=gBdyU1b0ADQ

Auditory TransductionComputer generated animation with excellent sounds and narration.http://www.youtube.com/watch?v=PeTriGTENoc

Hearing TestA 5:59 frequency test. Shows the wavelengths, which is nice.https://www.youtube.com/watch?v=H-iCZElJ8m0

Earphone TestA 1:40 frequency test. Shows the progress of wavelength on a graph, which is not as easy to visualize.https://www.youtube.com/watch?v=cvBtQmY2B5I

1. Sound waves are collected by the pinna2. Ear drum vibrates from air pressure changes (due to

sound waves)3. Middle ear bones are stimulated by the ear drum,

enhancing the sound (it is increased by about 20 times)

4. Oval window transmits vibrations from middle ear bones to cochlea

5. Tiny hairs in cochlea are mechanoreceptors for individual wavelengths of sound, and send action potentials

6. Auditory nerve sends signals to brain7. Round windows dissipate “old” sounds

How you Hear