18 reflexes Flashcards

1
Q

name 3 types of movements

A

involuntary
voluntary
rhytmic

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2
Q

What 2 rough mechanisms maintain posture?

A

feedback

feedforward (anticipation)

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3
Q

Where must the centre of mass be to maintain balance?

A

within our foot area

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4
Q

What do postural muscles need?

A

maintain tone to maintain a constant state of partial
contraction

corrective reflexes

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5
Q

What do proprioceptors sense?

A

muscle length and tension

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6
Q

Which other organ helps with stability?

What reflexes does this involve?

A

the eyes and their saccades

vestibulo-ocular reflex
optokinetic reflex

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7
Q

What 4 origins may sensory feeback arise from?

A

(vestibulo-ocular reflex and optiokinetic reflex)
visual system
vestibular system

(somesthesia)
skin receptors
prorioreceptors

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8
Q

Name 2 proprioception organs

A

Muscle spindle fibres

Golgi tendon organs

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9
Q

What do muscle spindles measure, and what is their structure?

A
measure length (dynamic and static changes, for rate of change too)
in parallel to muscle fibres
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10
Q

What do golgi tendon organs measure and how are they arranged?

A

measure tension

in series with muscle fibres

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11
Q

what are the 2 main regions of the muscle spindle fibre?

A

central region

polar regions

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12
Q

What comprises the central region of muscle spindles?

A

non-contractile fibres

primary and secondary sensory afferent endings

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13
Q

What innervates the polar regions of muscle spindles and what is their function?

A

Gamm motor neurones

doesn’t contribute to overall force, but adjusts the sensitivity of the spindle

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14
Q

In muscle spindles, what is the function of secondary afferents?

A

innervate the eds of the central region and respond to static length

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15
Q

In muscle spindles, what is the function of primary afferents?

A

innervate central region and respond to velocity of lengthening

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16
Q

What elements do secondary afferents of muscle spindles have?

A

anulospiral elements

17
Q

What elements to primary afferents of muscle spindles have?

A

splay endings

18
Q

What is tonic signalling?

A

1 - extrafusal muscle fibres at resting length
2 - sensory neuron is tonically active
3 - spine integrates function
4 - alpha motor neurons to extrafusal fibres receive tonic input
5 - extrafusal fibres maintain a certain level of tension even at rest

19
Q

What is the problm with stretching a muscle accidentally?

A

it will contract

This might be a muscle next to the spindle, pushing on the spindle fibres

20
Q

What maintains spindle function when muscles contract?

A

alpha-gamma co-activation

21
Q

How does alpha-gamma co-activation work?

A

alpha and gamma motor neurones fire

muscle contracts

stretch on centres of intrafusal fibres unchanged, firing rate of afferent neuron remains constant

22
Q

What is the Servo-loop hypothesis?

A

when the muscle i s stretched, the gamma mn enable the contracted muscle to stay at the desired length

there was a theory that gamma neurones were controlling muscle length, by controlling alpha neurones, but this doesn’t really hold up anymore

23
Q

What is the practical implication of the servo-loop hypothesis?

A

we can maintain muscle stiffness when piling on loads

24
Q

Are reflexes context dependent?

25
How can feeedofrward mechanisms work?
gamma mn control feedback gain of spinal loops via feedforward mechanisms from higher motor centres
26
Where to reflexes go through?
ventral horns for the motor bit, the ascending tract pat won't bother with this as its' job is to stimulate somatic sensation
27
What effect do golgi tendon organs have on alpha motor neurones?
inhibit them (glycinergic)
28
What will the golgi tendon organ do in an overload situation?
the tension will increase massively, and the golgi tendon will inhibit contraction to save the muscle