18 reflexes

Question 1

name 3 types of movements

Answer 1

involuntary
voluntary
rhytmic

Question 2

What 2 rough mechanisms maintain posture?

Answer 2

feedback

feedforward (anticipation)

Question 3

Where must the centre of mass be to maintain balance?

Answer 3

within our foot area

Question 4

What do postural muscles need?

Answer 4

maintain tone to maintain a constant state of partial
contraction

corrective reflexes

Question 5

What do proprioceptors sense?

Answer 5

muscle length and tension

Question 6

Which other organ helps with stability?

What reflexes does this involve?

Answer 6

the eyes and their saccades

vestibulo-ocular reflex
optokinetic reflex

Question 7

What 4 origins may sensory feeback arise from?

Answer 7

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

(somesthesia)
skin receptors
prorioreceptors

Question 8

Name 2 proprioception organs

Answer 8

Muscle spindle fibres

Golgi tendon organs

Question 9

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

Answer 9

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

Question 10

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

Answer 10

measure tension

in series with muscle fibres

Question 11

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

Answer 11

central region

polar regions

Question 12

What comprises the central region of muscle spindles?

Answer 12

non-contractile fibres

primary and secondary sensory afferent endings

Question 13

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

Answer 13

Gamm motor neurones

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

Question 14

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

Answer 14

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

Question 15

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

Answer 15

innervate central region and respond to velocity of lengthening

Question 16

What elements do secondary afferents of muscle spindles have?

Answer 16

anulospiral elements

Question 17

What elements to primary afferents of muscle spindles have?

Answer 17

splay endings

Question 18

What is tonic signalling?

Answer 18

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

Question 19

What is the problm with stretching a muscle accidentally?

Answer 19

it will contract

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

Question 20

What maintains spindle function when muscles contract?

Answer 20

alpha-gamma co-activation

Question 21

How does alpha-gamma co-activation work?

Answer 21

alpha and gamma motor neurones fire

muscle contracts

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

Question 22

What is the Servo-loop hypothesis?

Answer 22

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

Question 23

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

Answer 23

we can maintain muscle stiffness when piling on loads

Question 24

Are reflexes context dependent?

Answer 24

yes

Question 25

How can feeedofrward mechanisms work?

Answer 25

gamma mn control feedback gain of spinal loops via feedforward mechanisms from higher motor centres

Question 26

Where to reflexes go through?

Answer 26

ventral horns for the motor bit, the ascending tract pat won’t bother with this as its’ job is to stimulate somatic sensation

Question 27

What effect do golgi tendon organs have on alpha motor neurones?

Answer 27

inhibit them (glycinergic)

Question 28

What will the golgi tendon organ do in an overload situation?

Answer 28

the tension will increase massively, and the golgi tendon will inhibit contraction to save the muscle