Control of Body Movement

Question 1

state what it is meant by the key term ‘motor program’

Answer 1

a motor program is the pattern of neural activity required to properly perform a desired movement

Question 2

state what it is meant by the key term ‘proprioception’

Answer 2

proprioception is afferenti information about the position of the body and it’s parts in space

Question 3

state the function of higher control centres

Answer 3

higher control centres form complex plans according to an individual’s intentions and communicates with the middle layer of control via command neurons

Question 4

state the structures of the higher control centres

Answer 4

areas involved with memory, emotions and motivation, and the sensorimotor complex. all these structures receive and coordinate input from many other brain structures

Question 5

state the function of middle layer control centres

Answer 5

convert plans received from higher centres to a number of smaller motor programmes that determine the patters of neural activation required to perform movements

Question 6

state the structures of the middle control centres

Answer 6

sensorimotor complex, cerebellum, parts of the Basel nuclei, some brainstem nuclei

Question 7

state the function of the local level control centres

Answer 7

specific tension on particular muscles and angle of specific joints at specific times necessary to carry out programs and sub-programs transmitted from the middle control level

Question 8

state the structures of the local control centres

Answer 8

brainstem or spinal chord, interneurons, efferent neurons as well as motor neurones

Question 9

state what it is meant by the key term ‘voluntary actions’

Answer 9

voluntary actions are those where movement is accompanied by conscious awareness of what you are doing and why you are doing it. your attention is directed towards the action and it’s purpose

Question 10

state what it is meant by the key term ‘involuntary movemnts’

Answer 10

involuntary movements are unconscious, automatic, reflex movements

Question 11

what percentage off neurones in the spinal chord are interneurones

Answer 11

90% of all neurones in the spinal chord are interneurones

Question 12

what are the two types of interneurones in the spinal chord

Answer 12

1. local interneurones - never the motor neurone they synapse upon
2. others have processes extending up/down short distances in the brainstem or spinal chord, or throughput most of the length of the CNS

Question 13

why are interneurons with longer processes important

Answer 13

interneurons with longer processes are important for integrating complex movements. for example, stepping forward with your left foot as you through a baseball with your right arm

Question 14

state 3 importances of interneurons

Answer 14

1. integrate input form higher processes, peripheral receptors and other interneurons
2. crucial for determining which muscle fibres are activated and when
3. act as ‘switches’ to enable movement to be turned off at command from higher motor centres

Question 15

afferent neurones carry information from sensory neurones from three different places. these different places are:

Answer 15

1. skeletal muscles controlled by motor neurones
2. other nearby muscles, such as those with antagonistic and synergistic actions
3. in the tendon, joints and skin effected by the actions of the muscles

Question 16

state the function of stretch receptors

Answer 16

stretch receptors are embedded within the muscles measure muscle length and the rate of change in muscle length

Question 17

explain the breakdown of stretch receptors (2 things)

Answer 17

1. consist of peripheral endings of afferent nerve fibres wrapped around modified nerve fibres
2. entire apparatus collectively termed muscle spindle

Question 18

state what it is meant by the key term ‘intrafusal fibres’

Answer 18

intrafusal fibres are the modified muscle fibres within the muscle spindles

Question 19

state what it is meant by the key term extrafusal fibres

Answer 19

extrafusal fibres are skeletal muscle fibres that form the bulk of the muscle and generate force and movement

Question 20

within a muscle spindle, there are two types of cells. state and explain what these two types of cells are

Answer 20

1. nuclear chain fibres - responds best to how much the muscle is being stretched
2. nuclear bag fibres - responds to both the magnitude of a stretch and the speed at which a stretch occurs

Question 21

both nuclear chain fibres, and nuclear bag fibres, can be collectively termed as being…

Answer 21

muscle-spindle strength receptors

Question 22

how are muscle spindles attached, and explain the consequential effect of this (4 things)

Answer 22

1. attached by connective tissue in parallel to the extrafusal fibres
2. thus, an external force stretching the muscle also pulls on the intrafusal fibres, stretching them and activating their receptor endings
3. the more or faster a muscle is stretched, the greater the rate of receptor firing
4. in contrast, shortening of the muscle removes tension on the spindle and slows the rate of firing in the stretch receptor

Question 23

explain the concept of the ‘Alpha Gamma Co-activation Mechanism’ (3 things)

Answer 23

1. alpha and gamma motor neurones lie close together in spinal chord or brainstem
2. co-activating both alpha and gamma motor neurones prevents muscle spindle from going slack during shortening
3. ensures info about muscle length is continuously available to provide for adjustment of ongoing actions and to plan and program future actions

Question 24

during a strength reflex, afferent neurones from the muscle spindle enters the CNS, they then divide into branches and take how many different paths

Answer 24

3 different paths

Question 25

explain the first out of the three paths in the stretch reflex (3 points)

Answer 25

1. one path makes excitatory synapses directly onto motor neurones to the muscles that were stretched
2. patella stretch reflex is monosynaptic
3. all other stretch reflexes are polysynaptic

Question 26

explain the second out of the three paths in the stretch reflex

Answer 26

one path makes inhibitory synapses inhibiting antagonist muscles who’s contractions would interfere with the reflex response

Question 27

state what it is meant by the key term ‘Reciprocal Innervation’

Answer 27

reciprocal innervation refers to the activation of neurons to one muscle with the simultaneous inhibition of neurons to it’s antagonistic muscle

Question 28

explain he third out of three paths in the stretch reflex

Answer 28

one path activates synergistic muscles - muscles who’s contraction assist the intended action

Question 29

explain the concept of the ‘Withdrawal Reflex’

Answer 29

1. painful stimuli on skin activates flexor and inhibits extensor muscles of the ipsilateral limb
2. resulting limb moves away in withdrawal reflex
3. same stimuli causes response in collateral limb activating extensors and inhibiting flexors
4. cross extensor reflex allows collateral leg to support BW

Question 30

state what three things muscle tension depends on

Answer 30

muscle tension depends on:

1. muscle length
2. load on the muscle
3. degree off muscle fatigue

Question 31

state what it is meant by the key term ‘Golgi Tendon Organs’

Answer 31

golgi tendon organs are endings of afferent neurones that wrap around collagen bundles in their tendon near their functional muscle

Question 32

explain the ‘Tension Monitoring System’ concept: part 1

3 things

Answer 32

1. when muscle stretched, or extrafusal fibres contract, tension is put on tendon
2. tension straightens collagen bands and disports receptor endings, activating them
3. golgi tendon organs discharge in response to generated tension by contracting muscles and initiate AP’s to the CNS

Question 33

explain the ‘Tension Monitoring System’ concept: part 2

2 things

Answer 33

1. branches of afferent neurons from the golgi tendon organ cause widespread inhibition of the contracting muscle and it’s synergists via interneurones
2. also stimulates the neurons of it’s antagonists