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207 > ch 3a- sensory contribution > Flashcards

ch 3a- sensory contribution Flashcards

1
Q

sensory systems important for control of movement

A

visual, vestibular, somatosensory

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2
Q

describe how sensory feedback works (loop)

A

loop:
Integration (brain/CNS= decision making)—-> signal to effectors (e.g muscles) to produce an action –> movement is sensed by sensory receptors (e.g. eyes or muscle spindles) –> feedback is sent back to brain/CNS for integration and decision making again

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3
Q

Visual sensory feedback

A
  • self and object motion
    -position of limbs relative to body
    -position of limbs/body in relation to environment
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4
Q

Vestibular sensory feedback

A

-self motion
-head position

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5
Q

Somatosensory feedback (proprioception)

A

-muscle length (muscle spindles)
-muscle force (golgi tendon organs)
-joint angles (joint receptors)
-pressure under feet and contact with the environment

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6
Q

Mediating factors that may affect visual feedback

A

-ambient light
-contrast
-peripheral vs. central visual field

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7
Q

Most neurons have 4 functional components that generate signals to transmit information

A
  1. Local input (receptive) component
  2. Trigger (summing) component
  3. Long range conducting (signalling) component
  4. Output (sensory) component
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8
Q

affarent neurons

A

carry info towards CNS and brain. associated w sensory neurons

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9
Q

efferent neurons

A

carry info away from the CNS and brain. associated with motor neurons

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10
Q

interneurons

A

connect other neurons. abundant in the brain

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11
Q

two factors related to the signal transmitted by a neuron

A
  1. number of action potentials
  2. time intervals between action potentials
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12
Q

what determines intensity of sensation or speed of movement?

A

frequency of individual action potentials (firing rate)

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13
Q

What information does the nervous system extract from its receptors?

A

-modality
-intensity
-duration
-location

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14
Q

MODALITY

A

what is the stimulus?
(sight, touch, taste, or smell)
–> each of theses modalities has sub modalities

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15
Q

Somatosensory system receptors that detect different sub-modalities

A

-cutaneous mechanoreceptors (touch e.g. Pacinian corpuscle= vibration and pressuren)
-thermal receptors (temperature)
-nocireceptors (pain)
-muscle mechanoreceptors (e.g. muscle length sensed by muscle spindles)

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16
Q

INTENSITY

A

how much we feel stimulus depends on the strength of the stimulus

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17
Q

intensity is encoded by

A
  1. frequency of actions: frequency coding
  2. number of sensory receptors activated: called population coding
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18
Q

strong stimulus results in

A

activation of more receptor endings OR activation of more sensory neurons

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19
Q

threshold

A

intensity at which stimulus can be perceived

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20
Q

sensory threshold

A

stimulus intensity is detected on 50% of trials

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21
Q

DURATION

A

how long you perceive a stimulus depends on how long the stimulus is present and intensity of the stimulus

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22
Q

as a stimulus persists, you

A

adapt/become desensitized

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23
Q

LOCATION

A

where is the stimulus? (depends on the receptive field of the sensory neuron)

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24
Q

receptive field of sensory neuron

A

the spatial area in the sense organ where stimuli excite or inhibit the neuron

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25
Q

sensory receptive fields provide info about

A

spatial location of a stimulus and spatial resolution of the sensory system

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26
Q

greater spatial resolution means…
where is an example of an area on your body w/ a lower threshold (greater spacial resolution)

A

you can discriminate smaller stimuli
ex. hands

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27
Q

How to test for touch sensations

A

the two-point discrimination test

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28
Q

the two point disrcimination test determines

A

the location at which two closely spaces stimuli can be perceived as separate

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29
Q

“labelled line” concept

A

sensory afferents carry info about a single type of receptor from a specific part of the body. nervous system “knows” what info is being carried by what neurons.

30
Q

What is proprioception?

A

the sensation of limb, trunk, and head position

31
Q

sources of proprioceptive info

A

-muscle spindles (length)
-golgi tendon organs (force)
-joint receptors (angle)
-vestibular system
-cutaneous receptors (mechanoreceptors)
-visual info/optic flow

32
Q

muscle spindles are:

A

spindle shaped receptors in the muscle belly of skeletal muscles

33
Q

What are muscle spindles composed of?

A

–>Intrafusal muscle fibers: nuclear bag (dynamic bag1 and static bag2) and chain fibres
–>Sensory neuron endings: group 1a and group 2 affarents
–>Motor neuron endings: static and dynamic gamma motor neurons

34
Q

sensory neuron endings

A

wrap around central regions of intrafusal fibres. carry sensory info from spindle to spinal cord

35
Q

motor neuron endings

A

activate polar contractile regionals of intrafusal fibres. unique because they have efferent parts

36
Q

detect muscle length

A

muscle spindles
static muscle POSITION
sensed by mostly group 2 afferents

37
Q

detect CHANGES in muscle lenth

A

dynamic= limb/muscle MOVEMENT
sensed by 1a afferents

38
Q

gamma motor neurons elastic band analogy

A

gamma motor neurons tighten the muscle spindle to make it more sensitive to change in length

39
Q

Alpha-gamma coactivation

A

both extrafusal and intrafusal muscle fibers contract

40
Q

How is muscle stretch detected?

A

in an unstretched muscle, action potentials are generated at a constant rate.
in a stretched muscle, muscle spindle is activated and rate of action potentials is increased

41
Q

If only alpha motor neurons were activated?

A

Only extrafusal muscle fibers contract.
Muscle spindle becomes slack and no action potentials are fired.
Unable to signal further changes in length.

42
Q

For voluntary contractions, spindles and muscle fibers….

A

are activated the same amount and only gamma motor neurons connected to the activated muscle(s) are used

43
Q

Eccentric contractions generate very strong..

A

1a afferent activity because lengthening is paired with gamma drive
(lengthening AND gamma drive increase 1a afferent activity individually so together the firing is even stronger)

44
Q

Feedback from muscle spindles is used to

A

-regulate muscle activity through the alpha motor neuron
-elicit the stretch reflex
-signal higher centres about muscle length (and limb position)

45
Q

3 types of potentials

A
  1. receptor potential
  2. synaptic potential
  3. action potential
46
Q

receptor potential

A

-sensory receptors detect specific form of energy, disturbs resting membrane potential due to influx of ionic current (sensory transduction) –> drives membrane potential to receptor potential
-graded signal; spreads passively and decreases w distance

47
Q

synaptic potential

A

-neurotransmitter release via synapse alters membrane potential of post synaptic neuron
-graded signal; spreads passively

48
Q

action potential

A

-neurons propagate signals via action potentials that spread along their axons
all on none!!! (stronger signals cause more frequent action potentials, but each is the same size)

49
Q

greater spacial resolution: small or large receptive field?

A

smaller receptive field: more sensitive= greater spacial resolution

50
Q

group 2 afferents sense?

A

static muscle position

51
Q

1a afferents sense?

A

dynamic (changes in muscle/limb movement)

52
Q

dynamic gamma motor neurons increase sensitivity to…

A

detect muscle length changes (which are signalled by 1a afferents)

53
Q

static gamma motor neurons increase sensitivity to…

A

detect static muscle length (which is signalled by group 2 afferents)

54
Q

main driver of 1a firing?

A

dynamic changes in muscle length

55
Q

1a afferents also wrap around…

A

static bag 2 and chain fibers so they ALSO sense static muscle length but main driver of firing is dynamic CHANGES in muscle length

56
Q

highest spindle density muscles?

A

extraocular

57
Q

whenever the muscle is actively contracted, the muscle spindle is as well; in other words…

A

brain sends a command via alpha and gamma motor neurons at the same time

58
Q

describe monosynaptic stretch reflex

A

muscle is stretched, muscle spindles detect this change in length. The muscle contracts in response to the stretch. Monosynaptic pathway causes the stretch (1a afferent connects to alpha motor neuron controlling antoagonist muscle). A disynaptic pathway is used to inhibit antagonist muscle (1a afferent connects to an inhibitory interneuron in the spinal cord which connects to an alpha motor neuron)

59
Q

real life example of a monosynaptic stretch reflex

A

step on uneven terrain; ankle joint rotates unexpectedly which stretches the muscles around it. Spindle feedback results in greater muscle activity of the muscle stretched and increased joint stability

60
Q

GTOs

A

-tiny receptors located at muscle-tendon junction
-sensory info relayed via group 1b afferents
-senses muscle load/force
-no efferent connections

61
Q

how do GTOs create an action potential?

A

under force/load, collagen fibrils pinch the axon of a 1b afferent => graded receptor potentials= action potential

62
Q

FA 1

A

Meissener’s endings (shallow)

63
Q

SA 1

A

Merkel’s disks (shallow)

64
Q

FA 2

A

Pacini ending (deep)

65
Q

SA 2

A

Ruffini endings (deep)

66
Q

ascending sensory tracts

A
  1. dorsal column
  2. spinocerebral tracts
67
Q

dorsal column

A

transmits touch, vibration, and CONSCIOUS proprioceptive info to supraspinal centres

68
Q

spinocerebellar tracts

A

UNCONSCIOUS proprioceptive info to the cerebellum.
transmits muscle spindle and GTO input

69
Q

gamma motor neurons are responsible for muscle —–

A

stretch

70
Q

alpha motor neurons are responsible for muscle —-

A

contraction

207 (12 decks)

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