Sensory Lab

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Sensory Lab
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Nonhuman Senses

• Infrared imaging
• Electrosense
• Vomerolfaction
• Ultrasound detection
• Infrasound detection
• Magnetoreception
• Cutaneous chemosense

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Sensory Pathway
1. Stimulus is detected by a sensory neuron or
specialized receptor cells. The receptor cell
converts stimuli into an electrical signal.
2. This action potential is now sent to the CNS
for integration.
3. A signal is then sent to the effectors
(specific muscle groups).
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Reflexes

• Functions that should happen while you are free
  to think about other matters!!

Best known Tendon Reflex Patellar
Reflex Other Reflexes to test today Blink
Reflex Light Reflex
Grasp reflex in infants
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Patellar Reflex

• The tendinous attachments of muscles have special
  sensory receptors
• Attachment receptors respond to stretch stimuli
• Receptors relay info to the CNS
• Nerve impulses pass up to the spinal cord and
  through a synapse to the a motor neuron and then
  to a nearby musclereflexive response impulses
  never reach the brain!!

You will quantify the strength of the patellar
reflex in response to different stimuli.
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Specific Reflexes

• Blink Reflex
• As an object comes near the eye the eyelids
  rapidly close to protect the eye. You will
  observe this reflex reaction.
• Light Reflex
• The iris contracts and relaxes controlling the
  amount of light allowed through the pupil. You
  will measure the dilation of the irises under
  various light conditions.

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Chemosense Taste

• EXPERIMENT
• Locate the various types of taste receptors
• Diagram the surface of the tongue and identify
  the regions where the taste sensations are most
  strongly experienced.
• Determine your threshold for salt and sugar using
  concentrations of varying intensities.
• Record your observations and compare your
  threshold with other members of the class

Sour
Umami
Salty Sweet
Fattiness
Bitter
RINSE YOUR MOUTH BETWEEN TASTES!!
Calcium
Piquance
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Chemosense Smell

• Smell receptors are located in upper portion of
  nasal cavity
• Characteristics
• Sense of smell shows high degree of adaptation
• Certain odors mask others

Experiment

1. Close your eyes and distinguish the odors
2. Smell the camphor until the odor can no longer be
   detected and then try to distinguish between oil
   of cloves and oil of peppermint. (Repeat with
   alcohol as masking agent, and compare the ability
   of the two substances to affect your ability to
   distinguish.)

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Cutaneous Sensations Touch

• Experiments
• Distribution of receptors
• Mark your palm, back of hand, back of arm and
  back of neck
• Using an aesthesiometer, stimulate each ink spot
  with a minimal and CONSISTENT stimulus. Locate
  those areas with the highest concentration of
  sensitivity (touch receptors) and try to quantify
  the differences between body parts.
• With a pithing needle locate the distribution
  of pain receptors in the same area you did with
  the touch receptors
• Also locate the distribution of temperature
  receptors using one each of cold and warm glass
  rods.

• Just a touch of information
• A given neuron can have a small or large receptor
  field over which a stimulus can affect it
• Sensitive areas (ex. fingers) contain the
  highest density of touch receptors

DONT WATCH!!!
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Cutaneous Sensations

• Experiment
• Warning!!
• Make sure the intensity isnt too strong (no one
  should feel too much pain!)
• Use consistent intensity throughout the entire
  experiment

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Cutaneous Sensations Touch

• Experiments
• Tactile Discrimination
• Determine a persons ability to distinguish two
  distinct stimuli using a compass.
• Make sure the two areas are applied
  simultaneously.
• Quantify the differences in tactile ability among
  different parts of the body.

DONT WATCH!!!
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Cutaneous Sensations Temperature, intensity, and
thermal adaptations

• Experiments
• Survey areas on the ventral and dorsal surfaces
  of forearm with a cold glass rod
• --Determine whether there are differences in
  intensity of cold in different areas.
• Set up three beakers
• Hot water, room temperature water, cold water.
• Place one index finger in the hot and one in the
  cold water, then place both in the room
  temperature water.
• Compare the sensations.

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Mechanoreception - Hearing
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Sound waves enter ear through auditory meatus
Tympanic membrane moves back and forth
Movement of tympanic membrane is transmitted to
ossicles
Ossicles vibrate against membrane (oval window)
Oval window sets fluid of the cochlea into
motion
Ion channels open and cause a receptor potential
along auditory nerve
Specific portions of the basilar membrane (in the
cochlea) move in response to the movement of the
cochlear fluid
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Deafness
Conduction Deafness Due to abnormalities of
the auditory canal, tympanic
membrane, or ossicles
Nerve deafness Due to abnormalities
of the cochlea and neural mechanisms
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Mechanoreception - Hearing
Experiments Webbers Conduction - Deafness
test Place the handle of a vibrating tuning
fork on the mastoid process. When sound can no
longer be heard move the fork to the front of the
ear. Localization of Sound Attempt to locate
the position of a time clock held in different
positions Repeat with one ear closed record
the position of the clock when you could and
could not locate it.
Cochlear Implant
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Mechanoreception - Balance
Balance is determined by the movement of fluid,
the endolymph, in the labyrinth (a complex set of
tubing in the inner ear) Movement of the
endolymph causes nerve impulses which are signals
to the brain indicating motion, direction of
motion, etc.
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Mechanoreception - Balance

• Experiment
• Whirl until dizzy
• Attempt to quickly strike the outstretched
  finger of partner with your finger
• Record the direction in which you over-corrected
  your attempt to make contact

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Vision
Visual Acuity

• Blind Spot

?
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Myopia and Hypermetropia
Myopia Occurs when the lens is too convex or
the eyeball is too long Hypermetropia Occurs
when the eyeball is too short, the lens is too
flat, or there is a corneal imperfection,
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Astigmatism
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Other Vision Experiments

• Accommodation
• Eye Dominance
• Afterimages

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In your lab report

• Abstract
• Experimental (brief, but include all)
• Results/Observations
• Discussion w/ study questions
• Next week Muscles