Voluntary movement

Question 1

What are the 3 types of movement?

Answer 1

involuntary actions (reflexes), semi-automatic actions, voluntary actions

Question 2

What are semi-automatic actions?

Answer 2

voluntary actions that do not require though (often repeated movement sequences, appear stereotypes but very adaptable)

Question 3

Examples of semi-automatic actions

Answer 3

walking, breathing, chewing (can be voluntarily adjusted)

Question 4

What is the name of the collection of neurons that drive semi-automatic actions?

Answer 4

central pattern generators (CPGs)

Question 5

What are the basic components of a neuron?

Answer 5

Dendrites (cell projections that receive inputs), cell body, axon, axon terminal (contain synaptic vesicles for synaptic release)

Question 6

What are central pattern generators (CPGs)?

Answer 6

collection of neurons with rhythmic output that will influence motor patterns of muscle groups

Question 7

What are the 2 feedback loops involving the CPG?

Answer 7

reflex feedback and central feedback

Question 8

Describe the reflex feedback of the CPG?

Answer 8

CPG output innervate effector organs which feedback to the CPG (repeats)

Question 9

Describe the central feedback involving CPGs?

Answer 9

CPG outputs innervate higher control neurons which reinnervate CPG (ensure output is constantly relevant)

Question 10

How can the environment influence semi-automatic actions?

Answer 10

Environment provides sensory feedback either directly to the CPG or indirectly to higher control neurons that innervate CPG

Question 11

Characteristics of voluntary actions

Answer 11

self-initiated, purposeful, learned, improved with practice, adaptable

Question 12

What section of the brain is involved in voluntary movements?

Answer 12

motor cortex

Question 13

Describe the location of the sensory cortex

Answer 13

posterior to the central sulcus

Question 14

Describe the location of the motor cortex

Answer 14

anterior to the central sulcus

Question 15

Name of the mapping of the brain dedicated to motor processing different regions of the body

Answer 15

motor homunculus

Question 16

Why do the trunk and lower limbs have less representation in the motor homunculus?

Answer 16

muscles are large, just require power not precision. Low density of motor units

Question 17

Why do the hands and face have a great motor homunculus representation?

Answer 17

high density of motor neurons as the muscles are very small (to allow greater movement precision)

Question 18

How many neurons are involved in sensory pathways?

Answer 18

3 neurones

Question 19

What are the 2 motor/descending pathways (voluntary)?

Answer 19

corticospinal and corticobulbar pathways

Question 20

How many neurons are involved in corticospinal/corticobulbar pathways?

Answer 20

2 motor neurons

Question 21

Outline the general corticospinal/corticobulbar pathway

Answer 21

motor cortex innervates the upper motor neuron which projects down to the brainstem/spinal cord where it synapses with a lower motor neuron which innervates the effector muscle

Question 22

Where are the cell bodies of upper neurons located?

Answer 22

motor cortex

Question 23

Where are the cell bodies of lower motor neurons located?

Answer 23

either in brainstem or spinal cord (depending on location of target muscle)

Question 24

What are the 3 sections the white matter of the spinal cord is divided into?

Answer 24

dorsal funiculus, lateral funiculus, ventral funiculus

Question 25

What are the 2 possible areas of white matter in the spinal cord that descending axons can pass through?

Answer 25

dorso-lateral funiculus (lateral corticospinal tract) or ventro-medial funiculus (anterior corticospinal tract)

Question 26

Which motor neurons are innervated by the corticobulbar pathway?

Answer 26

cranial nerve nuclei (bilateral)

Question 27

Where is the term corticobulbar derived from?

Answer 27

cortico - as upper motor neuron nuclei located in cortex bulbar - lower motor neuron nuclei located in brainstem

Question 28

Which motor neurons are innervated by the corticospinal pathway?

Answer 28

motor neurons with their nuclei located in the spinal cord

Question 29

Where is the term corticospinal derived from?

Answer 29

cortico - upper motor neurons have their nuclei in the motor cortex spinal - lower motor neurons have their nuclei in the spinal cord (ventral horn)

Question 30

Function of the corticobulbar pathway

Answer 30

carries motor information from the primary motor cortex to the muscles of the head and neck by synapsing with motor cranial nerves in the brainstem

Question 31

Function of the corticospinal pathway

Answer 31

Carries motor innervation from the primary motor cortex to the muscles of the trunk and limbs

Question 32

Examples of nerves innervated by the corticobulbar pathway

Answer 32

trigeminal (V), facial (VII), vagus (X), hypoglossal (XII)

Question 33

Motor function of trigeminal nerve (V)

Answer 33

muscles of mastication

Question 34

Motor function of the facial nerve (VII)

Answer 34

muscles of facial expression

Question 35

Motor control of the vagus nerve

Answer 35

soft palate, pharynx, larynx

Question 36

Motor control of the hypoglossal nerve (XII)

Answer 36

extrinsic muscles of tongue

Question 37

Describe the route of the upper motor neurons in the corticobulbar pathway

Answer 37

cell bodies located in motor cortex. Axon descends through basis pedunculi (part of midbrain) towards either the pons (trigeminal or facial motor nuclei) or to the medulla (nucleus ambiguus) where the upper neuron bifurcates for bilateral innervation

Question 38

Which part of the midbrain do the upper motor neurons for both the corticobulbar and corticospinal pathways descend through?

Answer 38

basis pedunculi

Question 39

Where is the trigeminal motor nucleus located?

Answer 39

pons

Question 40

Where is the facial motor nucleus located?

Answer 40

pons

Question 41

Where are the vagus and hypoglossal motor nuclei located?

Answer 41

nucleus ambiguus in the medulla

Question 42

What is the main difference between the corticobulbar and corticospinal pathways?

Answer 42

axons in the corticospinal pathway project further as they descend into the spinal cord whereas corticobulbar upper motor neurons only descend into the brainstem (pons or medulla)

Question 43

What percentage of corticospinal projections cross to the contralateral side at the medulla?

Answer 43

85% of corticospinal projections

Question 44

Where in the medulla do 85% of corticospinal projections cross over?

Answer 44

pyramidal decussation

Question 45

Where do the remaining 15% of corticospinal projections cross over?

Answer 45

at the level of the target lower motor neuron

Question 46

What region of the white matter do the 85% of the corticospinal projections that cross over at the pyramidal decussation descend?

Answer 46

lateral corticospinal tract in the dorso-lateral funiculus

Question 47

How far along the spinal cord does the lateral corticospinal tract (in dorso-lateral funiculus) descend?

Answer 47

entire length of the spinal cord

Question 48

What region of the white matter do 15% of the corticospinal projections that remain on the same side descend in?

Answer 48

anterior corticospinal tract in the ventro-medial funiculus

Question 49

How far along the spinal cord does the anterior corticospinal tract (in ventro-medial funiculus) descend?

Answer 49

to mid thoracic region only

Question 50

Which side of the brain does the motor pathway controlling distal muscles (hands, feet, tongue, lower face) originate?

Answer 50

opposite side of the brain

Question 51

Which muscles can receive bilateral descending cortical motor commands?

Answer 51

e.g. some muscles of the upper face. E.g. gag reflex involves bilateral innervation of nucleus ambiguus

Question 52

Which 2 neurons can innervate the lower motor neuron causing muscle contraction?

Answer 52

upper motor neuron (voluntary from motor cortex) or muscle afferent (reflex from stretched muscle spindles)

Question 53

What is the effect of an upper motor neuron lesion?

Answer 53

voluntary movement cannot occur, but reflex responses are still possible

Question 54

Causes of upper motor neuron lesion

Answer 54

stroke, trauma

Question 55

What is the effect of a lower motor neuron lesion?

Answer 55

loss of voluntary and reflex response - no movement can occur

Question 56

Cause of lower motor neuron lesion

Answer 56

peripheral nerve injury

Question 57

Name of the condition that involves temporary (unilateral) paralysis of the muscles of facial expression

Answer 57

Bell's palsy

Question 58

Which nerve is affected in Bell's palsy?

Answer 58

facial nerve (CN VII)

Question 59

What are the functions of additional descending motor projections?

Answer 59

coordinate movements, help maintain posture/balance, integrates actions of several muscles

Question 60

Where do additional descending motor projections arise from?

Answer 60

basal ganglia, cerebellum, brainstem

Question 61

What is the basal ganglia comprised of?

Answer 61

several interconnected sub-cortical nuclei

Question 62

How is the basal ganglia linked to the cerebral cortex?

Answer 62

via feedback loops

Question 63

Function of the basal ganglia

Answer 63

influence motor activity and motor control (influence/regulate output from motor cortex and initiate actions and switch from one action to another)

Question 64

What structure connects the 2 cerebral hemispheres?

Answer 64

corpus callosum

Question 65

What is the name of the bundles of white matter that relay information up to the sensory cortex / down from the motor cortex?

Answer 65

internal capsule

Question 66

What are the names of the large holes in the central portion of the cerebral hemispheres?

Answer 66

2 lateral ventricles and third ventricle (become continuous in midline)

Question 67

What are the components of the basal ganglia?

Answer 67

body of caudate nucleus, putamen, globus pallidus, thalamus, substantia nigra

Question 68

Location of body of caudate nucleus

Answer 68

lateral protrusion into the lateral aspect of the lateral ventricles

Question 69

What is the putamen?

Answer 69

collection of cells that form a cluster of grey matter within the basal ganglia

Question 70

Location of putamen

Answer 70

lateral to internal capsule

Question 71

What is the globus pallidus?

Answer 71

subnucleus of the basal ganglia

Question 72

Location of globus pallidus

Answer 72

medial to putamen, lateral to internal capsule

Question 73

Location of thalamus

Answer 73

medial to internal capsule, protruding into the lateral aspects of the third ventricle

Question 74

How does the substantia nigra appear in a coronal section?

Answer 74

dark, speckled appearance

Question 75

What are the 3 'action selection' centres of the basal ganglia?

Answer 75

1) corpus striatum 2) sub-thalamic nuclei 3) substantia nigra

Question 76

What is the corpus striatum composed of?

Answer 76

body of caudate nucleus, putamen, globus pallidus

Question 77

What is the thalamus composed of?

Answer 77

7 principle subthalamic nuclei

Question 78

2 examples of basal ganglia disorders

Answer 78

Parkinson's disease and Huntington's disease

Question 79

Which part of the basal ganglia is affected in Parkinson's disease?

Answer 79

Substantia nigra

Question 80

What is the cause of Parkinson's disease?

Answer 80

loss of dopamine expressing cells in substantia nigra (dopamine deficiency)

Question 81

What are the effects of Parkinson's disease?

Answer 81

hypokinetic disorder (reduce movements), resting tremor, poverty of movement, mask-like face, difficulty initiating movements

Question 82

What is the resting tremor associated with Parkinson's called?

Answer 82

Paralysis agitans

Question 83

Which aspect of the basal ganglia is affected in Huntington's disease?

Answer 83

Corpus striatum

Question 84

What effects does Huntington's disease cause?

Answer 84

hyperkinetic disorder (increase movements), excessive, uncontrolled movements

Question 85

Cause of Huntington's disease

Answer 85

imbalanced neurotransmitters in Corpus striatum - decreased GABA levels

Question 86

Function of cerebellum

Answer 86

coordinates movements, regulates actions of antagonistic muscle groups, maintains balance, compares actual performance with what is intended

Question 87

Which receptors transmit information to the cerebellum to maintain balance?

Answer 87

proprioceptors

Question 88

Which reflex is important for maintaining posture?

Answer 88

stretch reflexes (mediated by muscle spindles)

Question 89

What happens to maintain posture when you sway forwards?

Answer 89

muscles on the back of the leg are stretched which evokes the stretch reflex, pulling you back to the vertical position

Question 90

What actions help maintain an upright posture?

Answer 90

correcting actions (slight rocking)

Question 91

What structure connects the sensory and motor cortexes?

Answer 91

association cortex