ANATOMY & PHYSIOLOGY OF THE
SENSESANATOMY & PHYSIOLOGY 2013-2014
Are There Additional Human Senses?• Proprioception = sense of body position (i.e. what is your body doing right now)• Equilibrium = balance• Acceleration• Nociception = sense of pain• Temperature• Satiety• Thirst• Micturition• Amount of CO2 and Na in blood
Senses
• Means by which an organism obtains information for perception• Sensation is part of the Somatic Division of the Peripheral Nervous System • However integration and perception require the Central Nervous System• Five major senses
OpthalamoceptionGustaoceptionAudioceptionOlfacaoceptionTactioception
Sensory Transduction
•All of our senses receive input with specialized cells/nerves called transducers• The transducers convert stimuli into
action potentials•Action potentials (APs) are electro-
chemical messages that are conveyed along nerves• These messages are ultimately received
and “understood” by the various cortices of the brain
Examples of Transduction
Audition = convert kinetic energy of sound waves into action potentialsGustation = generate action potentials from binding of proteins to specific receptorsOpthalamoception = convert radiant energy into action potentials
Anatomy of the Eye
Changing Views About the Physiology of the Eye
• Platonic view: Extramission (light emanates from the eye)• Aristotelian view: Intramission
(light enters the eye)• Galen: Optical pneuma flows from the brain
into the eye via hollow optical nerves• Kepler: first to suggest the centrality of the
retina (over a crystalline lens) in vision
Ophthalmoception (Sight)• GOAL: Light stimuli transduced into an Action Potential (AP)• HOW: Our eyes act as converging lenses, focusing this light to
their transducing structures• When light strikes the transducers, the photosensitive proteins
rhodopsin & photopsin change 3D shape• This conformational change in shape triggers an AP which then
travels to the occipital lobe of the brain via the optic nerve
Phototranducers
•RODS•Concentrated on periphery of retina•125 million cells in retina•Most sensitive to light•Scotopic (night) vision
•CONES•Responsible for color vision•Work best in more intense light•4.5-6 million in retina
Hermann Grid Illusion
•Lateral Inhibition: Stimulation of adjacent rods causes rods at vertices to be shut off
Color Afterimages• opponency process =The optic nerve encodes color in
three separate channels; one for intensity of lightand two for color. • photopsin may take as long as 45 minutes for it to
change back to its original form. During that period of time, the photopsin is said to be photobleached and it sends a constant stimulus to the brain. • Eventually, the brain becomes desensitized to the
constant stimulation from that color photoreceptor and the brain does not see that color. • However, due to the opponency process, the
complimentary color appears as an “afterimage”.
Colorblindness• “Normal” color vision is trichromatic: red, blue, green
color receptors (cones). • Color “blindness” or deficiency comes from a lack or
absence of one or more of these types of cones
Audioception (Hearing)
Audioception (transduction of sound)
•Mechanical stimuli transduced into an Action Potential• Our ears funnel and relay vibrations,
directing these compression (sound) waves to their transducing structures, the cilia• The sloshing of the cochlear fluid
causes cilia to deflect (fold over)• Deflection triggers an AP directed to
the temporal lobe of the brain via the auditory nerve
McGurk Effect Explanation
• Processing of audition is highly reliant upon visual input as well as auditory input• However, as auditory processing
is 5x faster than visual processing, there can be a “disconnect” between the two senses
Shepard Rissert Tone: Explained
• Overlapping tones at octaves produce vibrations in the inner ear that are the same sine wave and hence sound like the same tone
Conductive Hearing Loss
•Conductive hearing loss (CHL) is usually the result of some disturbance in the outer or middle ear structures • It is often due to fluid buildup in the middle ear
from colds, allergies (serous otitis media), a perforated eardrum, or earwax (cerumen) that has partially blocked the auditory canal• This type of hearing loss can usually be treated
with antibiotics or simple as it is a mechanical blockage of the sound waves
Sensorineural Hearing Loss
• Sensorineural hearing loss (SNHL) is the result of damage to the inner ear (cochlea) or nerve pathways (auditory nerve) from the ear to the brain •Causes: age, severe head trauma, genetic or
hereditary deformations, or drugs that are toxic to hearing. •Much more difficult to correct than CHL as it is an
issue with transduction—cochlear implants may restore hearing to some
Anatomy of the Skin
Tactioception (touch)
•Mechanical/Temp/Pain stimuli transduced into AP• Transducing structures are specialized nerves•mechanoreceptors: Detect pressure, vibrations & texture• thermoreceptors: Detect hot/cold•nocireceptors: Detect pain•proprioreceptors: Detect spatial awareness
• This triggers an AP which then travels to various locations in the brain via the somatosensory nerves
Density of Different Receptors
Density and Distribution of Different Receptors
Anatomy of the Nasopharygeal & Buccal Cavities
Physiology of the Skin
• ___________________________ stimuli AP
• Transducing structures are specialized nerves: –_______________________________:
Detect pressure, vibrations, and texture –_______________________________:
Detect hot/cold –_______________________________:
Detect pain –_______________________________:
Detect spatial awareness
Anatomy of the Skin
• This triggers an AP which then travels to the brain via the _____________________________Prosthetics
o How is DARPA revolutionizing the field of prosthetics?
Gustaoception (taste) & Olfacaoception (smell)• Chemical stimuli transduced into AP• Sensitive regions in our tongues & noses
respond to chemicals, processing them in their transducing structures• Taste buds: Detect sweet (OH-), sour (H+), salt
(metal ions), and bitter (N-rich alkaloids) in food• Cilia: Detect odorants in the air
• Each transducer is specialized to interpret a particular chemical (taste or smell)• This triggers an AP which then travels to the
temporal lobes of the brain via gustatory & olfactory nerves
Olfactory & Gustatory Illusions
• Similar to afterimages, once a molecule has bound to a receptor, it will continue to send action potentials• However, eventually the neuron
will enter a refractory period during which it cannot send a message
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