Sensory Systems

Sensory Systems:

Sensory Systems 9 th Grade Biology Woodinville Montessori School Alaine Davis

What are Receptors?:

What are Receptors? Sensory receptors detect stimuli such as light, sounds, and skin temperature Receptors send information to the CNS where it is interpreted When sensory information reaches your brain, you experience a sensation A sensation is an awareness of a stimulus When the brain integrates the information it forms a perception A perception is a meaningful interpretation of sensory data

Humans have 5 Types of Sensory Receptors:

Humans have 5 Types of Sensory Receptors Pain receptors – dendrites of sensory neurons detect pain Thermoreceptors – detect heat and cold; found in the skin and some internal organs Mechanoreceptors – found in the skin and the inner ear; detect touch, pressure, stretch, and motion. Chemoreceptors – sensitive to certain chemicals; found in nose and taste buds Photoreceptors – receptive to various wavelengths of light; found in the retina

The Visual System:

The Visual System Consists of the eye , optic nerves , and the brain The occipital lobe is where the majority of visual processing occurs Visual defects may be caused by injury, illness, or problems with any part of the visual pathway A person with perfect eyes and nerves, but damage in the part of the brain that processes visual input will be functionally blind Visual processing must be learned in infancy by being exposed to visual stimuli

Eye Didn’t Know That!:

Eye Didn’t Know That! In sighted individuals, more than half of the sensory input to the brain is visual The giant squid has the largest eyeball on the planet, with a diameter of 18 inches (about the size of a beach ball) An ostrich’s eye weighs more than its brain Your eyelashes fall out and are replaced every 5 months Human beings can distinguish between 500 different shades of gray www.eyedidntknowthat.info

External Anatomy of the Eye:

External Anatomy of the Eye Cornea – the tough, bulging covering in front of your eye, it helps focus light on the retina Iris – a pigmented muscle that controls how much light reaches the interior of the eye Pupil – dark opening in the center of the eye; it is a hole that lets in light Sclera – the white of the eye

Inside the Eye:

Inside the Eye

Rods and Cones:

Rods and Cones Rods C o n e s Detect brightness (shades of gray) Detect colors Found at the periphery of the retina Found in the center of the retina None in the fovea Plentiful in the fovea Can function well in low light levels Need moderate or high level of light Only one kind Three different kinds

There are 3 Different Types of Cones:

There are 3 Different Types of Cones

Colorblindness:

Colorblindness Colorblindness is usually a genetic trait (located on the X-chromosome, therefore much more common in males than females) About 8% of males and 0.5% of females are affected Colorblindness is most often caused by one or more types of cones being absent or nonfunctioning—most often the “green” cone type In rare cases, an individual is born without any functioning cones at all; this person would truly see the world like a black-and-white movie

Are You Colorblind?:

Are You Colorblind?

The Optic Chiasm:

The Optic Chiasm

The Auditory System:

The Auditory System The receptors of the auditory system process sound waves This system consists of the outer ear , middle ear , inner ear , and brain Deaf individuals often have nonfunctioning cochleas Hearing loss is frequently due to exposure to loud noises, which damages parts of the inner ear

Anatomy of the Auditory System:

Anatomy of the Auditory System

Anatomy of the Auditory System:

Anatomy of the Auditory System

The Middle Ear: Focus on Ossicles:

The Middle Ear: Focus on Ossicles The ossicles are the bones of the middle ear They are the smallest bones in the body The ossicles consist of the malleus (hammer) incus (anvil) stapes (stirrup)

The Inner Ear:

The Inner Ear

The Cochlea:

The Cochlea The cochlea is a spiral tube containing hair cells As the hair cells are moved by sound vibrations, they cause action potentials to be fired

Frequency and the Cochlea:

Frequency and the Cochlea Different regions of the cochlea have hair cells that respond to different sound frequencies The auditory nerve sends this information to the brain for interpretation

Summary of Sensory Systems:

Summary of Sensory Systems There are five types of sensory receptors: pain, thermo-, chemo-, mechano - and photo- The visual system consists of the eye, optic nerves, and the brain Important parts of the eye: cornea, pupil, sclera, iris, lens, retina, fovea The auditory system consists of the outer ear, middle ear, and inner ear Outer ear: pinna and auditory canal; tympanic membrane separates outer ear from middle ear Middle ear: the ossicles , which are the malleus , incus , stapes Inner ear: semicircular canals, cochlea