Nov. 10 Flashcards
sensation
brain’s interpretation or perception of the environment
categories of senses
special and somatic
Special senses include
HE'S TV hearing equilibrium smell taste vision
Somatic senses include
TPTP touch pain temperature proprioception
proprioception
sensation of one’s own body
physiology of sensation forms the
neural basis of sensory signaling processing, transduction and processing
transduction is carried out by
sensory organs
processing is carried out by
CNS
Role of sensory organs
convert some form of energy into electrical signals/ convert physical and chemical attributes of stimulus into electrical signals
example of:
i) specialized sensory organ
ii) simple sensory organ
i) retina
ii) sensory nerve terminals for touch
Trace sensory stimulus to sensation
SPAC
Sensory stimuli
Potential change of sensory receptor membrane
AP firing by sensory neurons, which project to
CNS for integration/processing
sensory receptors cells can be
nerve terminals or specialized cells
General pathway of a sensory system
SPeCTaCular Sensory receptor Primary sensory neuron CNS Thalamus Cortex
types of stimuli
TECM thermal electromagnetic chemical mechanical
photoreceptors may refer to
photoreceptor molecules or photoreceptor cells
sensory receptors convert stimuli into
receptor potentials
receptor potentials
electrical signals in the form of graded potentials which photoreceptors convert from stimuli
do sensory receptor cells fire action potentials?
only some, such as taste and olfactory receptor cells.
photoreceptors don’t
olfactory receptor cells are also called
olfactory neurons, since they, like some other receptor cells are neuronal in nature
taste cells are ________ cells
epithelial
How do receptors that do not fire AP’s encode messages?
amplitude of receptor potential is a form of coding, but is still eventually converted into AP firing before message enters CNS
In the visual system, AP firing begins with the
third relay station of signal transduction
hair cells are used for
balance and hearing
thermoreceptor function
respond to temp change, mediate temp sensation, mediate nociceptive (pain) stimulation
chemoreceptor function
nociceptive stimulation, taste, olfaction
modality of stimulus
light, chemical, temperature, etc
sub-modalities
taste: sweet, bitter, acid, salty, umami
vision: color vision
four characteristics of sensory stimuli that must be distinguished
- modality
- intensity
- location
- timing
how do sensory receptors and sensory receptor cells encode modality?
depends on:
type of receptor activated
labeled line coding (which neuronal pathways are stimulated)
threshold for photoreceptors
one photon
adequate stimulus
the one the receptor is designed for (light for photoreceptors)
why does a punch cause one to perceive light
punch probably activates mechanosensitive channels in photoreceptor cells which produces the same membrane potential as the adequate stimulus would (does not activate rhodopsin)
why do chillipeppers cause you to feel heat?
capsasin activates both taste receptor cells and nerve endings which produce thermal sensation
for sensation, reaching threshold means:
the stimulus must be great enough to activate enough neurons in order for their convergence to be large enough for the brain to detect
another example of a tuning curve exemplified by cochlear cells
frequency versus stimulus magnitude: the lower the magnitude needed for a response at a certain frequency, the more sensitive the cell to said frequency
tuning curve concept applied to taste cells
taste cell responds best to particular molecule or class of molecules, but is still able to bind some other chemicals with similar structure
How is intensity encoded?
- the more receptors activated, the bigger the receptor potential
- when receptor potential is transduced into AP, the frequency and number of AP’s
How is timing encoded?
Different ways:
- continuously firing APs during stimulus
- receptor cells can respond only when stimulus is turned on or turned off
tonic receptors/receptor cells
fire AP’s continuously during stimulus
another word for tonic receptors/receptor cells
slowly adapting
absolute refractory period in tonic receptor cells might be
less than 1 ms (for cells firing AP’s up to 1 kHZ, i.e. 1 AP per ms)
phasing receptor cells
only respond transiently to stimulus (when turned on or off)
phasing receptor cells are also called
fast adapting receptor cells
How is location encoded?
Depends on which receptors are activated
ex. diffnt visual stimuli stimulate diffnt parts of retina
location of sound determined by
comparing signal perceived by the two ears
