Cutaneous Senses - Karius

Question 1

Sensory afferent neuron channels

Answer 1

open and close in response to a stimulus

Question 2

Example of sensory afferent neuron

Answer 2

Touch receptors have a sodium channel that opens with deformation of cell membrane

Question 3

What does opening of sensory afferent neuron channel do?

Answer 3

produces local response similar to subthreshold response

gets you closer to threshold

Question 4

Generator Potential

Answer 4

slight depolarization due to the opening of sensory afferent neurons

Question 5

What does a strong and long generator potential cause?

Answer 5

afferent neuron to come to threshold and cause action potential sent to the brain and spinal cord

Question 6

What if no sensory afferent neuron is sent to the brain?

Answer 6

the brain doesn’t know to do anything this is different than special senses and NT

Question 7

Best known receptor for touch

Answer 7

pacinian corpuscle

Question 8

What happens at the pacinian corpuscle?

Answer 8

axons come together and is used as the starting point

Question 9

Structure of the pacinian corpuscle

Answer 9

alternating layers of membrane with fluid between them surrounding the nerve ending

Question 10

What happens to pacinian corpuscle when we could something?

Answer 10

the membrane and fluid layers to deform

Question 11

What happens when the pacinian corpuscle layers deform?

Answer 11

open mechanosensitive Na+ channels on membrane and influx of sodium

Question 12

What happens when the stimulus is removed and no more deformation is occurring?

Answer 12

the sodium stops firing

Question 13

What if the stimulus is maintained?

Answer 13

action potentials gradually die as adaptation occurs

Question 14

Why does adaptation occur?

Answer 14

redistribution of the fluid in the corpuscle so force is no longer transmitted

Question 15

What is most of the adaptation a result of?

Answer 15

changes in the periphery altering the afferent

Question 16

Afterdischarge

Answer 16

reformation of nerve ending when stimulus is removed

Question 17

What is associated with afterdischarge

Answer 17

Persistence of the sensation

ex. sunglasses on forehead even though I took them off

Question 18

Sensory unit

Answer 18

sensory nerve and all it’s branches and skin associated

Question 19

Receptive Field

Answer 19

area where stimulation produces activation of neuron

Question 20

How to code for the stimulus intensity?

Answer 20

number of action potentials- greater intensity causes more action potentials
number of receptors firing- increases with increased intensity

Question 21

How much change needs to happen before you notice it

Answer 21

10% for conscious recognition

Question 22

Strength and Intensity relationship

Answer 22

Perceived intensity = K(measured intensity)^A

*K and A are constants

Question 23

What are K and A dependent on in the strength and intensity relationship

Answer 23

Type of sensory receptor
Muscle senses - both are closer to 1- match closely
Cutaneous senses - more variability

Question 24

What are the pathways to the brain?

Answer 24

Dorsal Columns, Spinothalamic tract, spinoreticulothalamic system, spinocerebellar tract

Question 25

Dorsal Columns

Answer 25

proprioceptive and discriminative (fine touch)

Question 26

Spinothalamic Tract

Answer 26

Pain, temperature, and crude touch

Question 27

Presynaptic Inhibition components

Answer 27

axo-axonal synpase and post-synaptic cell is a pre-synaptic terminal

Question 28

End result of pre-synaptic inhibition

Answer 28

reduced NT release from inhibited pre-synaptic terminal

Question 29

Inhibitory NT released

Answer 29

GABA which activates chloride

Question 30

What does chloride do to the original neuron of pre-synaptic inhibition?

Answer 30

hyperpolarize and allow less calcium to enter and less NT release

Question 31

Where does pre-synaptic inhibition occur?

Answer 31

between neighboring receptors at the first synapse in the pathway

Question 32

Purpose of pre-synaptic inhibition

Answer 32

increase brain's ability to localize the signal

Question 33

Where is the pre-synaptic inhibition important

Answer 33

in sleep because there is so much stimulation that doesn't need to go to the cortex

Question 34

How is the sensory cortex arranged?

Answer 34

somatotopically- different areas get more stimulation than others (hands and brain)

Question 35

How many layers in the somatosensory cortex?

Answer 35

6

Question 36

How are the neurons in the somatosensory cortex arranged?

Answer 36

in columns and each column deals with one sensory part of the body

Question 37

What occurs at layer IV in a column

Answer 37

sensory information is received via the thalamus

Question 38

Neighboring column information

Answer 38

receive from same part of the body but different sensory modality

Question 39

Somatic Sensory Area 1 - (S1)

Answer 39

post central gyrus Brodmann's 1, 2, 3 First stop for most cutaneous senses

Question 40

Somatotopic Representation for S1

Answer 40

toes medial and head lateral

Question 41

Somatic Sensory Area 2 (S2)

Answer 41

wall of lateral fissure | receives input from S1

Question 42

What is S1 involved with

Answer 42

information for position, sense, size, and shape discrimination ex. feel a remote in pocket - feel it in hard cold but don't know what it is

Question 43

What is S2 involved with

Answer 43

cognitive touch comparisons between 2 different tactile sensations determining weather something becomes a memory ex. being able to identify "this is a remote"

Question 44

Relationship between S1 and S2

Answer 44

S1 influences S2 so if there is damage to S1, it will impair functioning of S2 BUT damage to S2 will not damage S1

Question 45

Importance of Parieto-temporal occipital (PTO) cortex

Answer 45

required for high-level interpretation of sensory input | receives input from S1 and S2

Question 46

Functions of PTO cortex

Answer 46

makes you aware of your surroundings | naming objects

Question 47

Why do babies first explore things with their mouth?

Answer 47

might have 2 different columns that are doing the same thing so they put fingers and toes in their mouth to distinguish one *oh thats my finger* and eliminate another *oh this is not my toe*

Question 48

What happens if one part of the body is amputated

Answer 48

neurons in that area die and afferent input from remaining parts of the body will reinnervate the cortex

Question 49

What if an area of cortex is lost

Answer 49

afferents will innervate neighboring columns-- the brain will know something is happening but don't know what the input is

Question 50

Doctrine of specific nerve energies

Answer 50

no matter where in a specific sensory pathway the stimulation was turned on- the brain know what it is

Question 51

Law of Projections

Answer 51

no matter where along the path we stimulate it, the perceived sensation is always referred back to the area of the body where the receptor is located