Lecture 10: Sensory Afferent Division

Question 1

what is modality?

Answer 1

the form of energy that activates a particular sensory receptor

ex. mechanical force, chemicals, etc.

Question 2

what is an adequate stimulus?

Answer 2

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

Question 3

what is sensation?

Answer 3

information carried by action potentials to the CNS

Question 4

what is perception?

Answer 4

conscious awareness of a sensation (requires stimulation of activity in the brain and interpretation)

Question 5

what are the 5 receptor classes through which stimuli are sensed?

Answer 5

1. photoreceptors
2. chemoreceptors
3. thermoreceptors
4. mechanoreceptors
5. nociceptors

Question 6

photoreceptors:

Answer 6

sense vision

their adequate stimulus is: photons of light

Question 7

chemoreceptors:

Answer 7

sense taste and smell

their adequate stimulus is: chemicals (ions, O2, etc.)

Question 8

thermoreceptors:

Answer 8

sense touch

their adequate stimulus is: temperature

Question 9

mechanoreceptors

Answer 9

sense touch and hearing

their adequate stimulus is: vibration, pressure, sound

Question 10

nociceptors

Answer 10

sense pain

their adequate stimulus is: mainly chemical, but could also be pretty much any of the other options too

Question 11

what is sensory transduction?

Answer 11

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)

Question 12

reminder of what the thalamus does

Answer 12

-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

Question 13

what are sensory projection pathways?

Answer 13

the journey of sensory info from the PNS to CNS usually involves 3 orders of neurons

Question 14

what are the 3 orders or neurons?

Answer 14

-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

Question 15

how are receptor potentials similar to post synaptic potentials (EPSPs, IPSPs)?

Answer 15

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

Question 16

how are receptor potentials different from post synaptic potentials?

Answer 16

they’re not triggered by neurotransmitters binding (triggered by activation of a sensory receptor)

Question 17

what is an example of receptor potential

Answer 17

-pacinian corpuscles

Question 18

what are pacinian corpuscles

Answer 18

-mechanoreceptors found in the skin and joints
-they convert mechanical energy (pressure and vibration) to a nerve impulse
***know the diagram!!!

Question 19

sensory coding

Answer 19

sensory receptors can transmit 4 types of information

Question 20

what 4 ways do sensory receptors transmit info?

Answer 20

1. modality
2. intensity
3. duration
4. location

Question 21

transmission through modality

Answer 21

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)

Question 22

transmission through intensity

Answer 22

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

Question 23

transmission through duration

Answer 23

a. how long the stimulus lasts
b. phasic v. tonic receptors

Question 24

transmission through location

Answer 24

a. encoded by which fibers are sending signals to the brain
i. receptive fields
ii. lateral inhibition

Question 25

what are receptive fields

Answer 25

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)

Question 26

know the receptive overlap and convergence diagram

Answer 26

:)

Question 27

what is lateral inhibition?

Answer 27

the ability of excited neurons to inhibit neighboring neurons

** know the diagram :)

Question 28

what is sensory adaptation?

Answer 28

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

Question 29

sensory adaptation mechanism, why is it important (3 reasons)

Answer 29

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

Question 30

phasic v. tonic receptors

**know diagram :)

Answer 30

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)