Proprioception

Question 1

What is proprioception?

Answer 1

The sense of knowing what the orientation of the body is in space

Question 2

What information does the brain use in proprioception?

Answer 2

Muscle length

Question 3

Where does the information for the muscle length come from?

Answer 3

The spindle

Question 4

Muscle spindles lie _____ to the muscle fibres

Answer 4

Parallel

Question 5

Anything inside the spindle is…?

Answer 5

Intrafusal

Question 6

Anything outside the spindle is…?

Answer 6

Extrafusal

Question 7

Fluid around the spindle is called

Answer 7

Endolymph

Question 8

What type of ending do type Ia fibres have?

Answer 8

Anulospiral

Question 9

What type of ending do type II fibres have?

Answer 9

Flower spray

Question 10

Pulling apart of anulospiral endings does what?

Answer 10

Activates action potentials in the axon

Question 11

Where are group II endings embedded?

Answer 11

In the equatorial regions of the bag fibres

But have anulospiral endings largely confined to nuclear chain fibres

Question 12

Group Ia sensory endings relay information on the _____ phase of muscle stretch

Answer 12

Dynamic

Question 13

Group II endings relay information on the _____ phase of the muscle stretch

Answer 13

Static

Question 14

Group Ia fibres give us information on what?

Answer 14

When the stretch is occurring

Question 15

Group II fibres give us information on what?

Answer 15

When the muscle is at its final length

Question 16

Muscle spindles are only useful when they are _____

Answer 16

Under tension

Question 17

When the muscle contracts what is activated?

Answer 17

Gamma-motor neurones co-activated with alpha-motorneurones

Spindle shortens in register with extrafusal fibres

Question 18

Why do you get alpha-gamma co-activation?

Answer 18

So that you don’t get unloading of the spindle and therefore tension is maintained

Question 19

What happens to gamma-motorneurones in the presence of serotonin?

Answer 19

Increased activity

Question 20

What happens to gamma-motorneurones in the presence of NA?

Answer 20

Decreased activity

Question 21

By slightly stimulating the gamma-motorneurone with serotonin, what happens?

Answer 21

The intrafusal fibres can be made slightly stiffer

Question 22

Stiffer materials transmit stretches _____

Answer 22

Better

Question 23

By inhibiting the gamma-motorneurones with NA, what happens?

Answer 23

The intrafusal fibres can be made more elastic and floppy

Question 24

Do elastic materials transmit stretches well and why?

Answer 24

No

Because they themselves stretch

Question 25

Tendon Jerk Reflex

Answer 25

Only monosynaptic reflex Primary sensory endings (Ia) are activated and send action potentials along the limb to the spinal cord It has a single synapse with the homonymous muscle's a-neurone and produces an action potential in it The muscle contracts in opposition to the stretch and the limb jerks

Question 26

Jendrassik's manoeuvre

Answer 26

Causes excitation in upper segment of the spinal cord (C5) Excitation spills over the rest of the spinal cord Spill over effects the gamma-motorneurone pool, which makes the intrafusal fibres stiffer and more sensitive

Question 27

Tonic vibration reflex

Answer 27

On flexion, group II afferents frequency decreases | Vibrator applied to tendon drives the Group II afferents in muscle so they discharge at much higher frequency

Question 28

The Stretch Reflex

Answer 28

Opposes the lengthening of a muscle Polysynaptic refelx Spindle Ia makes excitatory connections on homonymous and synergistic muscle Ia's also act through inhibitory interneurones that innervate antagonistic muscles When muscle stretched, Ia firing rate increases Causes contraction of the homonymous and synergist muscles and relaxes antagonistic muscles Reflex counteracts the stretch, enhancing the springiness of the muscle

Question 29

Homonymous muscle

Answer 29

Muscle that the spindle is in

Question 30

Synergistic muscle

Answer 30

Muscles that help the main muscle contraction

Question 31

Where is proprioceptive information processed?

Answer 31

At the level of the spinal cord

Question 32

What does the somatosensory cortex do?

Answer 32

Higher level processing such as touch information

Question 33

What is the central pathway for proprioceptive information?

Answer 33

Dorsal Column - Meidal Lemniscal System