Sensory Physiology Flashcards

1
Q

Starting an AP

Sensory neurons have _______ that are opened or close in response to______

A

channels

stimulus

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2
Q

Starting an AP

for example, touch receptors have a _______ that is _____

A

Na channel

opened with deformation of the cell membrane

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3
Q

Starting an AP

Opening of channels produces a _________, similar to _____

A

local response

sub threshold response or epsp

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4
Q

Starting an AP

sub threshold response in sensory neurons is called

A

this depolarization is caused a “generator potential”

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5
Q

Starting an AP

getting an AP from stimulus

A

if the stimulus is strong enough or lasts long enough, the generator potentials will cause the afferent neuron to come to threshold and generate an AP

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6
Q

Starting an AP

where does the AP go

A

back to the spinal cord/brain

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7
Q

One of the best studied of the receptors that responds to touch

A

Pacinian Corpuscle

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8
Q

The Pacinian corpuscle is comprised of

A

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

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9
Q

when we touch something, what happens to the pacinian corpuscle

A

all the layers of the membrane are deformed–> opening of mechanosensitive Na channels on the membrane and influx of Na–>generation of an AP back to the CNS

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10
Q

what happens when the stimulus is maintained on a pacinian corpuscle

A

the action potentials gradually die away as adaptation occurs

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11
Q

The adaptation in a pacinian corpuslce is due to

A

redistribution of fluid in the corpuscle so that the force is no longer transmitted to the nerve ending.

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12
Q

Much, but not all of the adaptation that occurs is the result of

A

changes in the periphery (directly altering the afferent)

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13
Q

In some cases of the receptor adaptation, the removal of the stimulus triggers

A

action potentials as the ending “reforms”

this is known as an afterdischarge

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14
Q

Afterdischarge is associated with

A

the persistence of the sensation after the stimulus eliciting the discharge has been removed (phantom glasses)

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15
Q

Sensory unit

A

the sensory nerve and all its branches

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16
Q

Receptive field

A

the area from which stimulation produces activation of the neuron

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17
Q

The number of ____ is one way of coding the intensity of a stimulus

A

Number of action potentials. (with greater intensity, we see more action potentials - with further increases we may se patterned discharges like doublets or triplets)

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18
Q

The number of ______ also increases with increased

A

receptors firing

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19
Q

The number of ______ also increases with increased

A

receptors firing

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20
Q

Just noticeable difference

A

the smallest difference that can be detected

a change of about 10% is usually required for conscious recognition of the change

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21
Q

The Relationship between perceived strength and actual (measured) intensity - Oricinaly described as

A

Weber Fechner Law

Perceived intensity =log(measured intensity)

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22
Q

The Relationship between perceived strength and actual (measured) intensity - New data suggests the following formula

A

perceived intensity =K(measured intensity)^A

where K and A are constants

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23
Q

The Relationship between perceived strength and actual (measured) intensity - K and A vary depending on

A

type of sensory receptor

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24
Q

K and A for muscle senses s

A

both are close to 1

meaning - our perceived intensity matches th actual intensity very closely

25
Q

K and A for cutaneous senses

A

more variability

meaingin - what we perceive may diverge from the actual rather substantially

26
Q

Sensory pathway to the brain for proprioceptive and discriminative touch

A

Dorsal columns

27
Q

sensory pathway to the brain for thermal, nociceptive, and crude touch

A

spinothalamic tract

28
Q

Spinoreticulothalamic system

A

nociceptive

29
Q

In sensitive parts of our bodies, stimulus activates

A

more than one receptor due to overlap of receptive fields

30
Q

Presynaptic inhibition is what kind of synapse?

What is the end result?

A

axo-axonal synapse (the post-synaptic cell is a pre-synaptic terminal)
End result of pre-synaptic transmission: reduced neurotransmitter release from the inhibited pre-synaptic terminal

31
Q

Presynaptic inhibition - describe

A

Start with a a normal chemical synapse with NT release from A to B
add another neuron that synapses on the presynaptic terminal (A)
when activated neuron C releases GABA
which activates Cl entrance into neuron A
causing the presynaptic terminal of A to hyper polarize, and allow less Ca to enter
leading to less NT release
reducing the probability of AP in neuron B

32
Q

Presynaptic inhibition occurs between

A

neighboring receptors at the first synapse in their pathway

this increases the brains ability to localize the signal

33
Q

Regardless of which pathway is used, every synapse along the way represents a chance to

A

modify or respond to the stimulus

34
Q

The sensory cortex is arranged

A

somatotopically

35
Q

The somatosensory cortex is neocortex so it has

A

six layers

36
Q

neurons in the somatosensory cortex are arranged in

A

columns

37
Q

Each column deals with

A

one sensory modality in on part of the body

38
Q

Sensory information arrives at its respective column in layer

A

IV (via the THALAMUS)

39
Q

Somatic Sensory Area 1 (S1)

A

post central gyrus
brodmann;s 1, 2, 3
first stop for most cutaneous senses
Somatotopic representation - toes medial, head lateral

40
Q

Somatic Sensory Area 2 (S2)

A

wall of lateral (Sylvian)fissure
receives input from S1
somatotopic representation - not as detailed as S1

41
Q

Somatic Sensory Area 2 (S2)

A

wall of lateral (Sylvian)fissure
receives input from S1
somatotopic representation - not as detailed as S1

42
Q

S1 is involved in

A

the integration of the information for position sense as well as size, shape discrimination

(I know the characteristics of the object in my hand, but not what the object is)

43
Q

S1 feeds the processesed information to

A

S2

44
Q

Somatic sensory area 2 (S2) is required for

A

cognitive touch
stereognosis
comparisons between two different tactile sensations
determining whether something becomes a memory

45
Q

Describe damages to S1 and S2 and how they affect each other

A

Because of the wiring, damage to S1 will impair the functioning of S2
Damage to S2 will not impair the function of S1

46
Q

One of the greates differences between human brains and the brains of other species is

A

the amount of cortex devoted to association areas

47
Q

PTO association area

A

the parieto temporal occipital association cortex is required for high level interpretation of sensory inputs - so it receives that input from the different sensory cortical areas, including S1 and S2

48
Q

PTO functions in

A

analysis of the spatial coordinates of self/surrondign objects
naming of objects
other functions related to other aspects of cognition

49
Q

How the cortex can be changed by sensation

A

modification of input

plasticity

50
Q

plasticity

A

early in life many of our experiences enable us to refine the map that is genetically coded in the cortex
this includes anatomically eliminating synapses as well as strengthening others

51
Q

plasticity - if an area of the body is amputated or otherwise denervated

A

afferent input from remaining parts of the body will reinnervate the cortex

52
Q

Plasticity - if an area of the cortex is lost

A

those afferents will innervate neighboring (remaining) columns

53
Q

What’s the trade off in that plasticity

A

gain - the ability to detect the signal from the part of the body that the signal is coming from
given up - some of the precision bc now activating the column that is dedicated to something else

54
Q

What you feel law

A

the doctrine of specific nerve energies

55
Q

doctrine of specific nerve energies states:

A

stimulation of a sensory pathway at any point leads to the perception of a sensation that is dictated by the nature of the receptor that started the pathway

56
Q

doctrine of specific nerve energies means

A

If I stimulate the cortical column that receives input from a pascinin corpuscle, you will perceive the sensation of light touch

57
Q

Where you feel it law

A

law of projections

58
Q

law of projections states

A

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

59
Q

law of projections means

A

that if the cortical column I stimulated receives input from a pacinian corpuscle in your left index finger, you perceive the touch as occurring on your left index finger.