Senses

• The Sense Organs detect environmental stimuli and transform them into nerve impulses (message).

• The message travels to the area of the brain responsible for that type of sensory information.

• “Sensory adaptation,” allows for filtering of stimuli considered not important.

Eyes

• The position of the sense organs is critical to the organisms ability to perceive its environment.

• Eyes; in front of the face, allows the ability to perceive distance (binocular vision - use both eyes to create image) by brain interpreting focus point (via turning off the eyes and muscle movement).

  • Eyes on the sides of the head (monocular vision) allow prey animals to view more of their environment and more awareness of movement.

Sensory Adaptation

• Constant exposure to a specific stimuli can eventually cause adaptation to it.

• In order for this stimuli to cause an effect, a greater stimuli must occur as the threshold for it has usually increased.

  • E.g; The smell of an outhouse or farm “dissipates” as you “get used to it.”

• Sometimes the ability to adapt or filter out unnecessary extra stimuli is not possible for some individuals.

• The over stimulation due to hypersensitivity can be weakening or confusing.

• Sometimes information processing gets “remixed” and what we sense is not really what we perceive.. Like optical illusions.

  • Optical illusions may look like they move due to the slight movement of the eye on various points of object.

Eye Structures

• Fat & Bone: Protection and support.

• Muscle(s): Movement and support.

• Conjunctiva: Clear layer over sclera, helps lubricate the eye by producing mucus and tears and helps to prevent the entrance of microbes into the eye.

• Lacrimal Glands: Produce tears.

• Eye Lids, Lashes & Eyebrows: Prevents sweat, dust and debris entering the eye.

• Sclera:

  • The white of the eye.

  • Helps maintain shape, supports and protects. 

  • Attachment point for muscles, so you can move your eye around.

• Choroid Layer:

  • The soft tissue inside the eye that contains blood vessels.

  • Contains a black (lack of pigment provides better night vision) pigment to help prevent stray light from bouncing around inside the eye. 

  • Nourishes retinal cells & other cells within the eye. 

• Cornea:

  • The transparent cover of the front of the eye - refracts change direction/bends) light toward the pupil. 

  • Protects the eye. 

  • Protected by the layer of cells (conjunctiva = epithelial cells).

• Iris:

  • Muscular coloured part of the eye. (What creates the colour of someones eyes)

  • Contains photoreceptors that are sensitive to the amount of light striking the eye.

• Pupil:

  • The opening centre front of the eye.

  • The size determines the amount of light tat enters the eye.

    • Dark: The pupil is bigger so more light enters the eye.

    • Light: The smaller, so less light enters the eye.

  • Not a structure, only a hole. (Controlled by the iris)