Proprioception

Question 1

define proprioception

Answer 1

The sense of the relative position of the neighbouring parts of the body

Question 2

what is contained with in the joint capsule that act as receptors ?

Answer 2

Ruffini
Paciniform
golgi-type
free nerve ending

Question 3

what is the evidence that the joint capsule has minimum input into proprioception?

Answer 3

Hip replacement… there is still evidence of normal sense of join capsule after the replacement

Question 4

what do the muscle spindle receptors consist of?

Answer 4

• Bundle of thin muscle fibres contained within a capsule
• Situated in parallel with main ‘extrafusal’ muscle, but generate no useful force.
• Wrapped around by a pair of sensory axons that muscle stretch.
• Gamma motor neurons cause active contraction of spindle (alpha motor neurons innervate the main body of muscle)

Question 5

what does the muscle spindle detect?

Answer 5

static length of muscle (position)

Rate of change of muscle stretch (velocity)

Question 6

joint angles cal be calculated through what (related to muscle spindles)

Answer 6

changes in muscle length signalled by spindles

Question 7

which part of the spindle in non-contractile ?

Answer 7

central part

Question 8

when the muscle is stretched what in the sensory axons are activated?

Answer 8

stretch-sensitive ion channels

Question 9

what do the primary endings of the muscle spindle do?

Answer 9

signal position and velocity. It is transmitted by 1a afferents. they are sensitive to vibrations

Question 10

what do the secondary endings in the muscle do?

Answer 10

position only. via group 2 afferents

Question 11

The gamma fibres are the contractile element of the spindle…

Answer 11

they have no useful force output and are purely intended to keep spindle taught.

Question 12

Explain the process of alpha-gamma co-activation

Answer 12

1. 1a spindle continuously fires to signal muscle length
2. contraction of main muscle causes spindle to slacken - this causes a drop in firing rate and a loss of sensitivity
3. gamma activation contracts the spindle to keep it taught, thus maintaining sesnitivity

Question 13

How do we know spindles are important for sensation

Answer 13

1. Muscle vibrations
   - 80-100 Hz vibration selectively activates 1a afferents. which produces illusions of muscle stretch. In the calf, these vibrations produce a strong sway response
2. Muscle conditioning effects
   - significantly affects joint position sense.
   - due to muscle becoming slack/taut, thus affecting spindle output

Question 14

What effect does the golgi tendon organ have on joint rotation sense.

Answer 14

it indirectly contributes to it.

Signals force and heaviness

Question 15

where is the golgi tendon organ situated

Answer 15

between muscle and tendon

Question 16

what happens to the 1b afferent axon when the golgi tendon organ is stretched

Answer 16

it is compressed by collagen fibres and its of firing increases

Question 17

in the absence of vision, what happens to movement?

Answer 17

• movement accuracy degrades over time

Question 18

proprioception is ___ order of magnitude more sensitive for balance than the vestibular system. Why?

Answer 18

1 order of magnitude

and because muscles provide better information/feedback

Question 19

what is the link between proprioception, ageing and falls?

Answer 19

ankle proprioception declines with age however the proprioception-falls link in not strong