1. The Senses

2. Senses
What is a sense?
How many senses do we have? Name them.

4. Non-Traditional Senses
Balance and equilibrium : Equilibrioception
Acceleration
Thermoception: sensing heat or the cold
Proprioception: sensing parts of our body
Walking in the dark, typing without looking
Nociception: sensing pain
Internal senses:
Hunger, lungs, brain monitoring CO2/O2, salt levels in blood, etc…

5. Non-Traditional Senses
Chronoception : feeling the passage of time
Familiarity / recognition memory
Non-human (animal) senses
Some are analogous to ours, but better/worse
Smell of dog/shark
Echolocation
Bat sonar
Magnetoception
Internal compass of migratory birds
More at:

7. Senses
The sensory receptors are cells that capture all information about the environment that is processed by the brain.
They are an integral part of the sensory organs which are:
Eye : sight
Ear : hearing
Skin : touch
Tongue : taste
Nose : smell

8. Sensory Organ  Sensory Signal
The path followed by a sensory signal always follows the same path:
Sensory receptor captures information (stimulus)
A “transformer “ changes info into a nervous impulse
Sensory neurons send info to the brain for analysis

9. The Eye – Sight
The eye is a complex organ that is sensitive to light.

10. Parts of the Eye Eyeball is covered by 3 membranes:
Sclera (outside layer)
Choroid (middle)
Retina (inside layer)

12. The Sclera
The sclera- thick opaque (white) outside layer that protects the eye and give it its shape
The thick layer becomes thinner and transparent forming the cornea at the front of the eye.

14. Choroid Layer A blood vessel rich layer that turns into the iris
The iris is the coloured part of the eye which is composed of two groups of muscles that control the amount of light entering the eye
The pupil is the opening formed by the iris which widens in the dark and contracts in bright light

16. Heterochromia Iridum

17. Pirates and Eyepatches
It takes several minutes for the human eye to adjust to darkness…

18. The Retina
The Retina – is a pink-beige coloured membrane that contains specialized nerve cells called photoreceptors sensitive to light
The retina covers 2/3rds of the inside of the eyeball and ends in a jagged edge.
This makes it susceptible to detaching

20. Photoreceptors
Cones
Rods

21. Cones There are about 20x less cones than rods
They are concentrated in the center of the retina in a spot (a cone filled pit) approx 2mm in diameter called the macula
Cones are responsible for color and very detailed vision but need lots of light for this.
(you see less color detail in when it gets dark)

22. The retina
The macula

24. Cones There are 3 types of cones: Red – detect red
Green – detect green
Blue – detect blue
Red and some green = orange
All three stimulated equally results in white color

25. Macular Degeneration

27. Rods
Rods are detect contrast (not color) therefore are important for night vision
The farther away from the macula you go the more dense the rods become.
Rods cover the retina except in the macula and the “blind spot”.
The blind spot is where the optic nerve leaves the eye and there are NO photoreceptors.