Lecture 10: Sensory Afferent Division Flashcards
what is modality?
the form of energy that activates a particular sensory receptor
ex. mechanical force, chemicals, etc.
what is an adequate stimulus?
the specific modality that a sensory responds best to
generally each receptor responds best to 1 modality (specialization)
sometimes other modalities can “trick” sensory neurons into responding
ex.) menthol and capsaicin
what is sensation?
information carried by action potentials to the CNS
what is perception?
conscious awareness of a sensation (requires stimulation of activity in the brain and interpretation)
what are the 5 receptor classes through which stimuli are sensed?
- photoreceptors
- chemoreceptors
- thermoreceptors
- mechanoreceptors
- nociceptors
photoreceptors:
sense vision
their adequate stimulus is: photons of light
chemoreceptors:
sense taste and smell
their adequate stimulus is: chemicals (ions, O2, etc.)
thermoreceptors:
sense touch
their adequate stimulus is: temperature
mechanoreceptors
sense touch and hearing
their adequate stimulus is: vibration, pressure, sound
nociceptors
sense pain
their adequate stimulus is: mainly chemical, but could also be pretty much any of the other options too
what is sensory transduction?
when sensory receptors receptors convert the energy of a sensory stimulus into a change in membrane potential called a receptor potential
adequate stimulus (stim. energy is converted to receptor potential )—> sensory neuron (receptor potential is coded into action potential) —> CNS (processes sensory information through decoding)
reminder of what the thalamus does
-a collection of nuclei that pass and process information between the cerebral cortex and the PNS/spinal cord/brainstem
-all sensory info (except smell) pass through the thalamus before reaching the cortex
what are sensory projection pathways?
the journey of sensory info from the PNS to CNS usually involves 3 orders of neurons
what are the 3 orders or neurons?
-1st order: (afferent neuron) receives the stimulus at receptors
-2nd order: is in the spinal cord and brainstem and ends in the thalamus
-3rd order: begins in the thalamus and ends in the cortex
how are receptor potentials similar to post synaptic potentials (EPSPs, IPSPs)?
they are…
1. graded potentials
2. caused by the opening and closing of ion channels
3. short lived
4. can lead to the generation of action potentials
how are receptor potentials different from post synaptic potentials?
they’re not triggered by neurotransmitters binding (triggered by activation of a sensory receptor)
what is an example of receptor potential
-pacinian corpuscles
what are pacinian corpuscles
-mechanoreceptors found in the skin and joints
-they convert mechanical energy (pressure and vibration) to a nerve impulse
***know the diagram!!!
sensory coding
sensory receptors can transmit 4 types of information
what 4 ways do sensory receptors transmit info?
- modality
- intensity
- duration
- location
transmission through modality
a. important for the brain to be able to determine what kind of sensory information it is receiving
b. labeled line coding - the brain perceives information from a specific sensory tract as the adequate stimulus for the receptor (even if a different stimulus activates it)
transmission through intensity
a. the brain can distinguish intensity by
i. which fibers send the signals
ii. how many fibers are sending signals
iii. how fast fibers are sending signals
transmission through duration
a. how long the stimulus lasts
b. phasic v. tonic receptors
transmission through location
a. encoded by which fibers are sending signals to the brain
i. receptive fields
ii. lateral inhibition
what are receptive fields
an area monitored by a single sensory receptor
if a stimulus falls within the receptive field, the receptor will be activated (if it is an adequate stimulus)
important for localization:
-can be large or small
-can overlap
-can converge (multiple 1st order neurons converge into a single 2nd order neuron)
know the receptive overlap and convergence diagram
:)
what is lateral inhibition?
the ability of excited neurons to inhibit neighboring neurons
** know the diagram :)
what is sensory adaptation?
a change in the sensitivity of your perception of a sensation
examples:
-adapting to hot or cold water after submerging briefly
-eyes adjusting to varied lighting
-adapting to the smell of your own house
-the feeling of clothes on your body
sensory adaptation mechanism, why is it important (3 reasons)
is a property of all sensory receptors
it is important for cells to adapt because…
constant excitation can lead to cell death
it is energetically expensive
it allows us to focus on new and important stimuli
phasic v. tonic receptors
**know diagram :)
phasic receptors adapt quickly and inform when the stim. is on an off
tonic receptors: are more informative about the duration of a stimulus (more frequent waves)
