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COM Neuro 3 > Cutaneous Senses - Karius > Flashcards

Cutaneous Senses - Karius Flashcards

1
Q

Sensory afferent neuron channels

A

open and close in response to a stimulus

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2
Q

Example of sensory afferent neuron

A

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

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3
Q

What does opening of sensory afferent neuron channel do?

A

produces local response similar to subthreshold response

gets you closer to threshold

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4
Q

Generator Potential

A

slight depolarization due to the opening of sensory afferent neurons

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5
Q

What does a strong and long generator potential cause?

A

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

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6
Q

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

A

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

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7
Q

Best known receptor for touch

A

pacinian corpuscle

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8
Q

What happens at the pacinian corpuscle?

A

axons come together and is used as the starting point

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9
Q

Structure of the pacinian corpuscle

A

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

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10
Q

What happens to pacinian corpuscle when we could something?

A

the membrane and fluid layers to deform

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11
Q

What happens when the pacinian corpuscle layers deform?

A

open mechanosensitive Na+ channels on membrane and influx of sodium

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12
Q

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

A

the sodium stops firing

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13
Q

What if the stimulus is maintained?

A

action potentials gradually die as adaptation occurs

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14
Q

Why does adaptation occur?

A

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

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15
Q

What is most of the adaptation a result of?

A

changes in the periphery altering the afferent

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16
Q

Afterdischarge

A

reformation of nerve ending when stimulus is removed

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17
Q

What is associated with afterdischarge

A

Persistence of the sensation

ex. sunglasses on forehead even though I took them off

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18
Q

Sensory unit

A

sensory nerve and all it’s branches and skin associated

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19
Q

Receptive Field

A

area where stimulation produces activation of neuron

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20
Q

How to code for the stimulus intensity?

A

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

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21
Q

How much change needs to happen before you notice it

A

10% for conscious recognition

22
Q

Strength and Intensity relationship

A

Perceived intensity = K(measured intensity)^A

*K and A are constants

23
Q

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

A

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

24
Q

What are the pathways to the brain?

A

Dorsal Columns, Spinothalamic tract, spinoreticulothalamic system, spinocerebellar tract

25
Q

Dorsal Columns

A

proprioceptive and discriminative (fine touch)

26
Q

Spinothalamic Tract

A

Pain, temperature, and crude touch

27
Q

Presynaptic Inhibition components

A

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

28
Q

End result of pre-synaptic inhibition

A

reduced NT release from inhibited pre-synaptic terminal

29
Q

Inhibitory NT released

A

GABA which activates chloride

30
Q

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

A

hyperpolarize and allow less calcium to enter and less NT release

31
Q

Where does pre-synaptic inhibition occur?

A

between neighboring receptors at the first synapse in the pathway

32
Q

Purpose of pre-synaptic inhibition

A

increase brain’s ability to localize the signal

33
Q

Where is the pre-synaptic inhibition important

A

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

34
Q

How is the sensory cortex arranged?

A

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

35
Q

How many layers in the somatosensory cortex?

A

6

36
Q

How are the neurons in the somatosensory cortex arranged?

A

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

37
Q

What occurs at layer IV in a column

A

sensory information is received via the thalamus

38
Q

Neighboring column information

A

receive from same part of the body but different sensory modality

39
Q

Somatic Sensory Area 1 - (S1)

A

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

40
Q

Somatotopic Representation for S1

A

toes medial and head lateral

41
Q

Somatic Sensory Area 2 (S2)

A

wall of lateral fissure

receives input from S1

42
Q

What is S1 involved with

A

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

43
Q

What is S2 involved with

A

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

44
Q

Relationship between S1 and S2

A

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

45
Q

Importance of Parieto-temporal occipital (PTO) cortex

A

required for high-level interpretation of sensory input

receives input from S1 and S2

46
Q

Functions of PTO cortex

A

makes you aware of your surroundings

naming objects

47
Q

Why do babies first explore things with their mouth?

A

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

48
Q

What happens if one part of the body is amputated

A

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

49
Q

What if an area of cortex is lost

A

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

50
Q

Doctrine of specific nerve energies

A

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

51
Q

Law of Projections

A

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

COM Neuro 3 (3 decks)

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