Neurological Basis of Movement

Question 0

Do efferent (motor neurones) leave the spinal cord dorsally or ventrally?

Answer 0

Ventrally

Question 1

Do afferent (sensory) neurones enter the spinal cord doorsally or ventrally?

Answer 1

Dorsally

Question 2

What aspect of a muscle detects stretch at the beginning of a reflex arc?

Answer 2

Muscle spindle

Question 3

What does stretch of the muscle spindle produce?

Answer 3

An action potential

Question 4

What are the steps that follow stretch detection after a tendon is struck with a hammer?

Answer 4

1) stretch of spindle
2) 1a afferent neurone activated
3) enters the spinal cord
4) excitatory synapse with alpha motor neurone occurs in cord (homonymous muscle contracts)
= 4) simultaneously, excitatory synapse with inhibitory interneurone - inhibits alpha motor neurone that projects to heteronymous muscle (antagonist relaxes)

Question 5

What is the role of the Golgi tendon organ in reflexes?

Answer 5

It produces an inverse myotatic reflex. Unlike the muscle spindle it is activated by prolonged muscle contraction and via a 1b afferent pathway inhibits contraction as a protective measure (e.g. Makes you drop heavy things)

Question 6

Activation of alpha motor neurones causes what?

Answer 6

Muscle contraction

Question 7

What is the role of the gamma motor fibre (neurone)?

Answer 7

It keeps the muscle spindle under tension (taut) so that it can always detect stretch even when muscle contracted (allowing alpha motor neurones to continue firing and continue contraction)

Question 8

Without gamma motor neurones what would happen to the muscle spindle during muscle contraction?

Answer 8

It would become flaccid and unable to mediate movement / detect stretch

Question 9

Where are the cell bodies of both alpha and gamma motor neurones located?

Answer 9

The anterior horn if the spinal cord

Question 10

What do alpha motor neurones do that gamma motor neurones do not?

Answer 10

Directly adjust the length of the muscle

Question 11

When does the brain become involved in movement?

Answer 11

During voluntary movement

Question 12

In which lobe of the brain is the motor cortex located?

Answer 12

The posterior part of the Frontal Lobe

Question 13

What is the corticospinal tract?

Answer 13

The tract which conveys axial and limb MOTOR CONTROL

It is a DESCENDING tract

Question 14

Where does the corticospinal tract begin?

Answer 14

In the (pre-central gyrus) primary motor CORTEX of the brain

Question 15

Where do the fibres that will ultimately innervated the limbs decks sate in the corticospinal tract?

Answer 15

In the medulla (these fibres comprise 75-90% of all fibres in this tract)

Question 16

What does the terms ‘Pyramids’ refer to the corticospinal tract?

Answer 16

The pyramids are the corticospinal tracts as they go through the medulla

Question 17

What lobe of the brain is the somatosensory cortex located in?

Answer 17

The parietal

Question 18

Briefly, what does the somatosensory cortex do?

Answer 18

Receives sensory info via ascending pathways and filters irrelevant sensory signal via descending fibres
(Damage can result in many symptoms including Agraphesthesia - problems processing complex sensory info)

Question 19

What does the premotor area of the brain do?

Answer 19

Plans intended movements requiring visual guidance

Question 20

What does the supplementary motor area do?

Answer 20

Co-ordinates voluntary movements

Question 21

What does the posterior parietal cortex do?

Answer 21

Integrates other sensory info - damage may result in agnosia (failure to know)

Question 22

What is Apraxia?

Answer 22

An inability to perform certain motor movements despite sensory and motor pathways remaining intact

Question 23

What is the most important ascending (sensory) tract feeding back to the CNS?

Answer 23

The Spinothalamic

Question 24

What sensations does the Spinothalamic tract send up to the CNS?

Answer 24

Pain
Temperature
Touch
Pressure

Question 25

Through what does the Spinothalamic tract project to the cortex?

Answer 25

The thalamus

Question 26

What is the role of the thalamus in the Spinothalamic tract and dorsal columns?

Answer 26

It processes sensory information before it sends it on to the cortex

Question 27

What sensory information does the Spinocerebellar tract relay and to where?

Answer 27

It relays proprioceptive information to the cerebellum

Question 28

What do the dorsal ascending tracts deal with?

Answer 28

Joint position and fine discriminatory touch

Question 29

What effect does tetanus toxin have and how?

Answer 29

Tetanus toxin inhibits both inhibitory neurotransmitters Glycine and GABA resulting in dangerous over-activity of muscle “tetanic spasm” which can even result in long bone fractures

Question 30

What does a lower motor neurone innervate?

Answer 30

Skeletal muscle

Question 31

What neurotransmitter do LMNs release at the neuromuscular junction?

Answer 31

Acetylcholine

Question 32

What two types of nerve fibre are found in LMNs?

Answer 32

Alpha and gamma

Question 33

Where do LMNs arise?

Answer 33

Brainstem (muscles of head and neck)
Spinal cord (muscles of rest of body)

Question 34

What do upper motor neurones innervate?

Answer 34

Lower Motor Neurones

Question 35

Where do UMNs arise?

Answer 35

In the brain

Question 36

What neurotransmitter do UMNs release?

Answer 36

Glutamate (excitatory)

Question 37

What principle explains how the left side of the brain controls the motor function of the right and vice versa?

Answer 37

Decussation of the pyramids

Question 38

Where does decks satin occur in the Spinothalamic tract?

Answer 38

As it ascends, crosses over in the white ventral commissure in the spinal cord

Question 39

Axial motor control is associated with which division of the corticospinal tract?

Answer 39

The VENTRAL corticospinal tract

Question 40

Limb motor control is associated with which division of the corticospinal tract?

Answer 40

The LATERAL corticospinal tract