Bio Notes
February 12, 2009
CHAPTER 42
Sensory Receptors Classified by Location of Stimuli
o
Exteroceptors
o
Receive stimuli from outside environment
How to determine the type of food source, friendly associations (pleasant
or painful), hot or cold etc…
o
Interoceptors
o
Detect changes within the body
o
Changes in pH, body temp, chemical composition of blood, osmotic pressure
o
The person is unaware of messages sent to CNS until signal internal conditions
E.g. thirst in diabetes insipidus
•
Hyperglycemia- higher level of glucose in the blood- that changes
the osmotic pressure in the body and the body has to rectify that
Sensory Receptors Classified by Type of Energy
•
Thermoreceptors
: respond to heat and cold-
o
Receptors in antennae locate prey, or ticks identifying an endothermic prey
o
Mammals
External: skin, tongue, ear, eye
Changes in temp via receptors/nerve endings on body surface signal
internal thermorecptors in hypothalamus
•
Homeostatic mechanisms ensure constant internal body
temperature
•
Electroreceptors
o
Used by predatory fishes to detect prey
Respond to electrical potential
•
Electric fields from muscle activity of prey
•
Feedback signals from electric organs (other animals)
o
Electromagnetic receptors
Detect Earth’s magnetic field
•
Some animals orient by magnetic fields
•
Migratory animals (birds) navigate via magnetic fields
•
Nociceptors
o
Pain receptors
Free nerve endings (dendrites) of certain sensory neurons transmit signal
•
Three types respond to extreme conditions
o
Strong tactile stimuli (1. mechanical)
o
Temperature extremes (2. thermal)
o
Certain chemicals (3. others)
•
The release of neurotransmitters
glutamate
and
substance P
(enhances signal of
glutamate
) enhances the signal via interneuron
to the spinal cord, hypothalamus and finally the brain centers (pain
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awareness)
•
Mechanoreceptors
o
Transduce mechanical energy
Activated when they change shape (mechanical push or pull)
Allow animals to feel, hear, maintain balance (head up, feet down)
Operation of internal organs (presence food in stomach etc)
o
Include:
Gravity (statocysts)
•
In invertebrates:
o
Statocysts tilts in response to movement; correct abnormal
orientation
o
Sensory hair cells bend one or more statoliths (granules of
sand or calcium carbonate that change position as animal
moves)
o
Receptor potentials and action potentials inform CNS of
change in position
Sensory (touch)
Movement and tension (propriorectors, hair cells, and lateral line
organs)
•
In mammals:
o
Receptors in the skin (hair in a hair follicle)
o
Displacement of hair (motion) leads to movement of
receptor in deeper hair follicle and receptor potential
o
Encapsulated endings-
Merkel Discs
(adapt slowly),
Meissner
(adapts quickly (action to impulse is quick but
not sustained)), and
Ruffini corpuscles
(adapt slowly
(helps adapt to pain))
o
Pacinian Corpuscle
responds to very deep touch and
pressure caused by rapid movement of tissue; Action
Potential ceases (e.g. surgery)
•
Propriorectors

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- Spring '10
- Martin
- Photoreceptor cell, hair cell, hair cells
-
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