lecture 10 and 11 sensory physiology

Question 1

sensory information

Answer 1

conscious or sub-conscious awareness of the internal or external environment

Question 2

general somatic sensation

Answer 2

pain, temperature (thermal), tactile (eg. touch,pressure), proprioception (sense of limb in space)

Question 3

special senses

Answer 3

smell, taste, vision, hearing, balance

sensory input- sensation-perception

Question 4

sensory receptors are located

Answer 4

-at the end of a primary afferent neuron

or

-seperate receptor cell that signals to the primary afferent neuron

Question 5

stimulus

Answer 5

energy or chemical that activates a sensory receptor

Question 6

adequate stimulus

Answer 6

type of stimulus that is unique to sensory receptor

Question 7

mechanoreceptors

Answer 7

respond to mechanical stimuli (pressure, stretch)

Question 8

thermoreceptors

Answer 8

respond to temperature stimuli (cold,hot)

Question 9

photoreceptors

Answer 9

respond to light wavelengths

Question 10

chemoreceptors

Answer 10

respond to binding of chemicals

Question 11

nociceptors

Answer 11

respond to pain (heat, mehanical, chemical)

Question 12

sensory transduction

Answer 12

stimulus translate into an electrical response

• involves opening or closing of ion channels directly or through a second messenger
• becomes a graded potential called receptor potential

Question 13

receptor potential

Answer 13

• magnitude of a receptor potential will decrease with distance from its origin
• if the afferent neuron is depolarized to threshold, AP will continue to fire and propagate to CNS
• increase in graded potential magnitude = increase in AP frequency
• increase in graded potential magnitude= increase neurotransmitter release at the afferent neuron’s central axon terminal
• does not determine amplitude of the AP

Question 14

adaptation

Answer 14

• leads to a decrease in receptor sensitivity
• decrease in AP frequency in afferent neuron
• 2 types : slow adapting and rapidly adapting receptors

Question 15

slow adapting (tonic) receptors

Answer 15

maintain a persistent or slow decaying receptor potential during constant stimulus

• little adaptation in response to a prolonged stimulus
• better at gaging the intensity of a stimulus than fast adapting

Question 16

rapidly adapting (phasic) receptors

Answer 16

• quickly cease responding
• gage the change of a stimulus intensity better than slow adapting receptors

Question 17

primary sensory coding

Answer 17

• conversion of a stimulus energy into a signal that conveys the relevant sensory information to the CNS
• important characteristics of stimulus : type, intensity and location

Question 18

stimulus types (modalities)

Answer 18

modality: temperature, taste

submodalities : cold and hot/ sweet or salty

Question 19

factors that effect stimulus intensity

Answer 19

1. frequency of AP in a single afferent neuron
2. summation : receptors on other branches of the same afferent neuron are activated
3. recruitment : receptors on other branches of nearby afferent neurons are activated

Question 20

summation coding (summation)

Answer 20

more receptors activated in the same afferent neuron as there is more pressure on the skin→ more AP’s

Question 21

population coding (recruitment)

Answer 21

neurons next to each other are recruited as stimulus increases and is sensed by primary sensory neurons

Question 22

stimulus location

Answer 22

AP will travel to CNS via a distinct pathway that is associated with that particular modality and body location

Question 23

acuity

Answer 23

how precise we can locate and discern one stimulus from an adjacent one

→ greater convergence, less acuity

→greater size of receptor, less the acuity

→density of the sensory unit

→amount of overlap in nearby receptive fields

Question 24

receptive field overlap

Answer 24

best respond to stimuli applied to center of receptive field due to high receptor density

-if stimulus acts on the periphery of the receptive field → cant differentiate intesity or location precisely

Question 25

lateral inhibition

Answer 25

enables localization in a stimulus

-enhances the contrast between the center and periphery of a stimulated region

Question 26

central control of afferent information

Answer 26

• reticular formation and cerebral cortex have descending inhibitory pathways
• via indirect synpase on axon terminal of primary afferent neuron
• via indirect synapse through interneurons

Question 27

afferent sensory pathways carry what kind of info

Answer 27

conscious and not conscious information

• ascending pathways convey information about a single type of sensory information (eg. mechanreceptors →touch/pressure)
• pass through brainstem→thalamus→specific area on the cerebral cortex

Question 28

second order neurons

Answer 28

the interneuron that the afferent neuron synapses onto

Question 29

cortical association areas

Answer 29

-cortical association areas are outside the primary cortical sensory and motor areas

-regions closer will process information in a simple way

-regions further away will process information in more complicated ways

Question 30

factors that affect perception

Answer 30

1. sensory receptor mechanism
2. emotions, personality and experience
3. not all information entering the CNS gives rise to conscious sensation
4. we lack suitable receptors for many types of potential stimuli
5. drugs (hallucinations)
6. mental illness

two people can be exposed to the same stimulus and have different perception from it

Question 31

phantom limb

Answer 31

-damaged neuronal networks

-

Question 32

somatosensory cortex includes

Answer 32

pre central gyrus

post central gyrus

Question 33

motor cortex

Answer 33

coordinates our bodily movements

• primary motor area
• primary sensory area
• secondary motor and sensory areas (middle)
• anterior speech area (broca’s area)
• primary auditory area (more inside) secondary auditory area
• posterior speech area (wernickes area)
• primary visual area (more posterior) secondary visual area