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Flashcards in Sensory Physiology Deck (59):
1

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

channels
stimulus

2

Starting an AP
for example, touch receptors have a _______ that is _____

Na channel
opened with deformation of the cell membrane

3

Starting an AP
Opening of channels produces a _________, similar to _____

local response
sub threshold response or epsp

4

Starting an AP
sub threshold response in sensory neurons is called

this depolarization is caused a "generator potential"

5

Starting an AP
getting an AP from stimulus

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

6

Starting an AP
where does the AP go

back to the spinal cord/brain

7

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

Pacinian Corpuscle

8

The Pacinian corpuscle is comprised of

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

9

when we touch something, what happens to the pacinian corpuscle

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

10

what happens when the stimulus is maintained on a pacinian corpuscle

the action potentials gradually die away as adaptation occurs

11

The adaptation in a pacinian corpuslce is due to

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

12

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

changes in the periphery (directly altering the afferent)

13

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

action potentials as the ending "reforms"
this is known as an afterdischarge

14

Afterdischarge is associated with

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

15

Sensory unit

the sensory nerve and all its branches

16

Receptive field

the area from which stimulation produces activation of the neuron

17

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

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

18

The number of ______ also increases with increased

receptors firing

19

The number of ______ also increases with increased

receptors firing

20

Just noticeable difference

the smallest difference that can be detected
a change of about 10% is usually required for conscious recognition of the change

21

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

Weber Fechner Law
Perceived intensity =log(measured intensity)

22

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

perceived intensity =K(measured intensity)^A

where K and A are constants

23

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

type of sensory receptor

24

K and A for muscle senses s

both are close to 1
meaning - our perceived intensity matches th actual intensity very closely

25

K and A for cutaneous senses

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

26

Sensory pathway to the brain for proprioceptive and discriminative touch

Dorsal columns

27

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

spinothalamic tract

28

Spinoreticulothalamic system

nociceptive

29

In sensitive parts of our bodies, stimulus activates

more than one receptor due to overlap of receptive fields

30

Presynaptic inhibition is what kind of synapse?
What is the end result?

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

Presynaptic inhibition - describe

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

Presynaptic inhibition occurs between

neighboring receptors at the first synapse in their pathway
this increases the brains ability to localize the signal

33

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

modify or respond to the stimulus

34

The sensory cortex is arranged

somatotopically

35

The somatosensory cortex is neocortex so it has

six layers

36

neurons in the somatosensory cortex are arranged in

columns

37

Each column deals with

one sensory modality in on part of the body

38

Sensory information arrives at its respective column in layer

IV (via the THALAMUS)

39

Somatic Sensory Area 1 (S1)

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

40

Somatic Sensory Area 2 (S2)

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

41

Somatic Sensory Area 2 (S2)

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

42

S1 is involved in

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

S1 feeds the processesed information to

S2

44

Somatic sensory area 2 (S2) is required for

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

45

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

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

46

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

the amount of cortex devoted to association areas

47

PTO association area

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

PTO functions in

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

49

How the cortex can be changed by sensation

modification of input
plasticity

50

plasticity

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

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

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

52

Plasticity - if an area of the cortex is lost

those afferents will innervate neighboring (remaining) columns

53

What's the trade off in that plasticity

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

What you feel law

the doctrine of specific nerve energies

55

doctrine of specific nerve energies states:

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

doctrine of specific nerve energies means

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

57

Where you feel it law

law of projections

58

law of projections states

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

law of projections means

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.