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SfM topics > Sensory Receptors 2 > Flashcards

Sensory Receptors 2 Flashcards

1
Q

what are proprioceptors?

A

mechanoreceptors that signal body or limb position

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2
Q

function of muscle spindles

A
  • these monitor the LENGTH and rate of change of muscle lengths
  • control reflexes and voluntary movements (tell us how short or long muscles are)
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3
Q

function of golgi tendon organs

A
  • Monitor TENSION on tendons. (monitors muscle tension)

- Tension is produced by muscle contraction so they prevent the muscle from ripping itself apart

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4
Q

function of joint receptors

A

monitor joint angle, rate of angular movement and tension on the joint

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5
Q

what 3 things are proprioceptors responsible for?

A
  1. send sensory info to the brain to control voluntary movement
  2. muscle spindles and golgi tendon organs provide sensory information for spinal cord reflexes
  3. provide sensory info to perceive limb and body position and movement in space (kinaesthesia)
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6
Q

what are the most contractile skeletal muscle fibres?

A

extrafusal muscle fibres (cause the contraction)

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7
Q

what is contained within a capsule inside the extrafusal fibres?

A

intrafusal muscle fibres (with specialised sensory and motor innervation)

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8
Q

what do alpha motor neurones do?

A

make muscles CONTRACT, they act on extrafusal fibres

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9
Q

what do gamma motor neurones do?

A

contract END parts of the fibre only, they act on intrafusal fibres, more specifically on the muscle SPINDLES

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10
Q

what are the 2 kinds of intrafusal fibres?

A
  1. nuclear bag fibres (bag shaped and nuclei collect together)
  2. nuclear chain fibres (nuclei lined up in a chain)
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11
Q

what do both nuclear bag fibres and nuclear chain fibres have wrapped around them?

A

sensory nerves

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12
Q

what is the property of muscle fibres in terms of cellular structures?

A

muscle fibres are always multinucleate

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13
Q

what are the 2 kinds of endings on afferent (sensory) nerves wrapped around fibres in intrafusal fibres?

A
  1. Primary ending (type 1a) spiral around the centre of intrafusal fibres to form annulospiral endings (around nuclear bag fibre)
  2. Secondary endings (type 2) spiral around the ends of intrafusal fibres to form flower-spray endings (around nuclear chain fibre)
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14
Q

what part of the intrafusal fibres contain the contractile sarcomeres?

A

ends of the intrafusal fibres (central area has no contractile material)

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15
Q

what do gamma motor neurones innervate?

A

ends of the intrafusal fibres which contract

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16
Q

which are smaller in diameter, gamma or alpha motor neurones?

A

gamma motor neurones

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17
Q

what does muscle stretch stimulate?

A

spindle stretch receptors

18
Q

what does a stretch cause in terms of action potentials?

A
  • stretch sensitive ion channels open
  • this creates a local generator/ endplate potential
  • this leads to APs in the afferent fibres
19
Q

what is action potential proportional to?

A

proportional to velocity of stretch (i.e. how fast the muscle stretches affects number of APs fired)

20
Q

do muscle spindles lie in parallel with muscle fibres?

A

yes

21
Q

what is the effect of stretching an agonist on the spindle?

A

increases spindle discharge (lots of APs fired because of big stretch due to size of gradient potential size)

22
Q

what is the effect of shortening the agonist? (contracting it)

A

reduces spindle discharge

23
Q

what informs the brain about joint position?

A

info from both spindles and joint receptors

24
Q

what happens to GTO (golgi tendon organ) when the muscle is stretched and when it contracts?

A

muscle stretched: GTO becomes very small (little APs)

muscle contracts: GTO is elongated/stretches (lots of APs fired)

25
Q

how do muscle spindles lie in proportion to extrafusal muscle fibres?

A

lie in parallel

26
Q

how to GTOs lie in proportion to extrafusal muscle fibres?

A

lie in series/ groups

27
Q

what does a muscle contraction cause the GTO to do?

A

stretch (and Ib sensory axons fires AP)

28
Q

what does isometric length mean?

A

activated muscles remain the same length during a contraction

29
Q

what would happen if there were no gamma motor neurones?

A
  • during a muscle contraction, the muscle spindle would become floppy and spindle discharge would stop
  • brain would not be informed about muscle length (preventing muscle use)
30
Q

role of extrafusal fibre

A

makes the actual contraction, motor part of the muscle (innervated by alpha motor neurones)

31
Q

role of GOT

A

senses and controls muscle tension, prevents muscle from ripping itself apart

32
Q

role of muscle spindle

A
  • lets the brain know about muscle length (innervated by gamma motor neurones)
  • if they don’t work, they become floppy and brain doesn’t know about action of muscle
33
Q

what occurs to muscle spindle during a contraction?

A

muscle spindle poles are contracted so it shortens to match the shortening of the muscle (muscles become shorter= spindles become shorter)

34
Q

where does the muscle spindle send information about muscle length to?

A

to the brain

35
Q

what makes the muscle spindle an appropriate length for a new muscle length for the next contaction?

A

gamma firing (gamma motor neurones)

36
Q

what are the main afferent/sensory neurones which attach to intrafusal fibres?

A

Type 1a

37
Q

what would happen if only alpha motor neurones fired and not gamma?

A

Contraction would still happen and shortening of muscle would occur BUT spindle would stay the same length and become floppy, so sensory 1a firing decreases in intrafusal fibres. (little APs)

38
Q

when are the most APs fired?

A

-when both alpha and gamma motor neurones work on the extrafusal fibres and the spindle (in the intrafusal fibres)

39
Q

describe what happens when both alpha and gamma neurones fire simultaneously.

A
  1. alpha motor neurones fire causes extrafusal fibre contraction
  2. gamma motor neurone fire causes intrafusal fibre ends to contract and so stretch the spindle (central sensory elements)
  3. this restores tension and resets sensitivity of the central sensory part of the intrafusal fibres at a new muscle length
40
Q

what is essential for normal voluntary movements?

A

alpha-gamma coactivation

41
Q

what do muscles, tendons and joints proprioceptors do together?

A
  • inform the brain on the movements and position of body in space
  • act automatically to control movements via spinal cord reflexes

SfM topics (21 decks)

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