Motor Systems

Question 1

What is the fundamental loop in all movements?

Answer 1

Sensing -> decision making -> muscle activation -> force production -> motion -> sensing

Question 2

What is another name for muscle cells?

Answer 2

Fibres

Question 3

What is the plasma membrane of a muscle cell called?

Answer 3

Sarcolemma

Question 4

What are myofibrils?

Answer 4

Organelles of muscle fibres

Question 5

What structure contains many muscle fibres?

Answer 5

Fascicle

Question 6

What connects a skeletal muscle to bone?

Answer 6

Tendon

Question 7

Where in a muscle cell are myofilaments found?

Answer 7

Myofibril

Question 8

What are the myofilaments?

Answer 8

Thin actin and thick myosin

Question 9

What structural change happens when a muscle contracts?

Answer 9

Z-discs are brought closer together

Question 10

What is the sarcoplasmic reticulum?

Answer 10

Endoplasmic reticulum of muscle fibres

Question 11

What is between the T tubule and sarcoplasmic reticulum?

Answer 11

Voltage-gated Ca2+ channel

Question 12

What are the three key mechanisms for modulating muscle dynamics?

Answer 12

Adjust calcium release/uptake, change ATP production, change how effectively myosin hydrolyses/binds to ATP

Question 13

What is an isometric muscle contraction?

Answer 13

Force = load (no movement)

Question 14

What is a concentric muscle contraction?

Answer 14

Force > load (muscle shortening)

Question 15

What is an eccentric muscle contraction?

Answer 15

Force < load (muscle lengthening)

Question 16

What are the upper motor inputs?

Answer 16

Basal ganglia and cerebellum

Question 17

What are the descending systems?

Answer 17

Motor cortex, brain stem

Question 18

What are local circuit neurones responsible for?

Answer 18

Reflex coordination

Question 19

What are motor neurone pools responsible for?

Answer 19

Lower motor neurones -> skeletal muscles

Question 20

What are alpha motor neurones?

Answer 20

Lower motor neurones

Question 21

Where is the soma of alpha motor neurones?

Answer 21

Ventral horn

Question 22

What do alpha motor neurones innervate?

Answer 22

Muscle, with intermediate synapses

Question 23

What is a motor unit?

Answer 23

One alpha motor neurone and all the muscle fibres innervated by it

Question 24

What is interesting about fibres within one motor unit?

Answer 24

They are all the same fibre type

Question 25

What are the properties of a fast-twitch muscle fibre?

Answer 25

High force and fast fatiguing

Question 26

What are the properties of slow-twitch muscle fibres?

Answer 26

Low force, slow fatiguing

Question 27

What are type 1 muscle fibres?

Answer 27

Slow oxidative

Question 28

Which muscle fibre type is oxidative and has high myoglobin?

Answer 28

Type 1

Question 29

What are type 2A muscle fibres?

Answer 29

Fast oxidative glycolytic (intermediate)

Question 30

What are type 2X muscle fibres?

Answer 30

Fast glycolytic

Question 31

Which muscle fibre type is glycolytic and has low myoglobin?

Answer 31

Type 2X

Question 32

How does stimulation rate affect contraction force?

Answer 32

Increased force with increased stimulation rate

Question 33

What are the two types of summation?

Answer 33

Temporal and spatial

Question 34

How are muscles inhbited?

Answer 34

Glycinergic inhibition of innervating motor neurones in spine

Question 35

What neurones are involved in spinal reflexes?

Answer 35

Alpha motor and local circuit neurones

Question 36

What are intrafusal fibres?

Answer 36

Fibres within the muscle spindle

Question 37

What are the two types of intrafusal fibres?

Answer 37

Nuclear bag and nuclear chain

Question 38

hat are the two ending types of intrafusal fibres?

Answer 38

Annulospiral and flower spray

Question 39

What are gamma moor neurones?

Answer 39

Afferent neurones attached to muscle spindles

Question 40

What are the sensory organs of muscles?

Answer 40

Muscle spindles

Question 41

Which fibres do alpha motor neurones synapse with?

Answer 41

Extrafusal fibres

Question 42

Where are the cell bodies of sensory neurones?

Answer 42

Dorsal root ganglia

Question 43

Where are the cell bodies of motor neurones?

Answer 43

Ventral horn

Question 44

What are Ia fibres sensitive to?

Answer 44

Phasic rate of change in length

Question 45

What are II fibres sensitive to?

Answer 45

Change in length

Question 46

Which afferents are primarily nuclear bag fibres?

Answer 46

Ia afferents

Question 47

Which afferents are primarily nuclear chain fibres?

Answer 47

II afferents

Question 48

What is controlled by gamma efferents?

Answer 48

Sensitivity via stimulation of intrafusal fibres

Question 49

How fast is the myotatic reflex?

Answer 49

~30ms

Question 50

What happens in the myotatic reflex?

Answer 50

Monosynaptic activation of extensor, interneurone-mediated inhibition of flexor

Question 51

Where are Ib afferents located?

Answer 51

Within tendons

Question 52

What happens in the clasp knife reflex?

Answer 52

Activation of tricep Golgi tendon organs, inhibition of bicep

Question 53

Where are Golgi tendon organs located?

Answer 53

In tendons at the end of the muscle

Question 54

What is the sensory input of the crossed extensor reflex?

Answer 54

Delta sensory fibres via DRG

Question 55

What action is caused by the crossed extensor reflex?

Answer 55

Stepping away from something causing the foot pain

Question 56

What type of reflexes can be produced with interneurones?

Answer 56

Complex stereotyped

Question 57

How do leeches swim?

Answer 57

Sequential contraction and relaxation of body wall muscles

Question 58

What is the step cycle?

Answer 58

Leg flexion/extension, swing/stance

Question 59

What was observed when connection between brain and legs was prevented in a cat?

Answer 59

Hind legs could walk on a treadmill through reflexes alone

Question 60

Why does restoring movement in paraplegic patients rely entirely on monosynaptic contacts?

Answer 60

There is no surgical access to the ventral root where motor neurones can be stimulated

Question 61

What does the basal ganglia control?

Answer 61

Initiation of movement

Question 62

What disease is associated with hyper-inhibition of basal ganglia?

Answer 62

Parkinson's

Question 63

What disease is associated with hypo-inhibition of basal ganglia?

Answer 63

Huntington's

Question 64

What part of the brain controls movement?

Answer 64

Cerebral cortex

Question 65

What is the cerebellum responsible for?

Answer 65

Sensory-motor coordination and integration

Question 66

What information is compared in the cerebellum?

Answer 66

Intentional cortex actions, actual peripheral actions

Question 67

What does cerebellar hypoplasia cause?

Answer 67

Difficulty in controlling movements and posture, no feedback (only feedforward)

Question 68

What do the basal ganglia and cerebellum modulate?

Answer 68

Locomotor commands

Question 69

How is locomotion brought about?

Answer 69

Central pattern generators, no brain input