3. Motor systems

Question 1

Which regions of the cortex are involved in motor control?

Answer 1

All of the frontal lobe

The more anatomically anterior the cortical region, the more abstract or complex it’s role in movement

Question 2

What is the primary motor cortex and where is it located?

Answer 2

Aka. area 4 Primary region of the motor system which works in association with other motor areas

The primary motor cortex is the lowest level of motor hierarchy Located immediately anterior to the central sulcus GO TO LAST FLASHCARDS

Question 3

What is neuronal plasticity? Why is this advantages?

Answer 3

Reorganisation of neural pathways in the brain

Also known as remapping of the motor map In instances of neuronal lesions, neuronal plasticity limits the level of damage that occurs

Question 4

How can a stroke impact motor movement?

Answer 4

If a stroke results in the occlusion of the middle cerebral artery then this can affect almost all of one side of the frontal lobe - produces severe motor disability in all parts of the contralateral body (apart from the lower limb)

This occlusion will also affect the blood supply to the basal ganglia via lenticulostriate arteries

Question 5

What is apraxia?

Answer 5

Motor disorder - an inability to perform complex motor tasks due to neuronal damage e.g. tying your shoelaces, writing, playing the piano - can still move but complex tasks cannot be performed

These patients will have normal reflexes and no muscle weakness but will have difficultly performing motor tasks

Question 6

How can apraxia occur?

Answer 6

Due to damage i.e. lesions to the premotor cortex (anterior to the motor cortex) or damage to the supplementary motor cortex

Question 7

Will apraxia occur if there is damage to only one side of the premotor/supplementary motor cortex?

Answer 7

There may be only a very minimal level of apraxia in this instance

Only minimal symptoms will occur as the contralateral area may be able to take over some functions of the damaged tissue

Question 8

What is the relevance of the frontal eye fields (FEF) and Broca’s area and where are these located?

Answer 8

FEF and Broca’s area - are both specialised cortical areas dedicated to motor control of specific systems

FEF - motor control of the extraocular eye muscles

Broca’s - motor control of the muscles regulating speech These are both located adjacent to the premotor cortex

Question 9

What is the specific function of the FEF and Broca’s area?

Answer 9

Broca’s - enables people to put words together into a sentence i.e. the programming of the sequence of words

FEF - the programming of specific eye movements - of looking from one thing to another

Question 10

How would damage to Broca’s area present in a patient?

Answer 10

This is known as motor aphasia: These patients will have difficulty putting words together in a sentence - so will use very simple or one-word sentences

Patients will have no problem understanding but will have a problem in replying to someone complexly

Question 11

How would damage to the FEFs present in a patient?

Answer 11

This is known as oculomotor apraxia (OMA)

Patients will have a difficulty in moving their eyes horizontally and in moving them quickly to follow a moving object

Patients will have to turn their head in order to compensate for a lack of eye movement initiation to follow an oject

Question 12

What is the role of the parietal lobe in motor control?

Answer 12

This is where the somatosensory cortex lies

From here, 40% of the corticobulbospinal tracts arise

These axons transmit commands to the spinal cord for sensory input and modulation of reflexes

Question 13

Which regions in the frontal lobe are associated with motor control?

Answer 13

Prefrontal cortex - areas 9 and 10 Orbitofrontal cortex - area 11

Question 14

Where is the prefrontal cortex and what is it’s role in movement?

Answer 14

This is located in the frontal lobe - areas 9 and 10

Has the most complex relationship with movement - involved in the planning of movement - where you are generating different potential movements depending on what happens next

Also involved in executive functions

Question 15

What are the executive functions of the brain?

Answer 15

These are problem solving, judgment

Question 16

What is the orbitofrontal cortex and what is it’s role in motor control?

Answer 16

Located in the frontal lobe - area 11

Concerned with the control/inhibition of the limbic system i.e. emotion/emotive behaviour e.g. hunger, thirst, sexual drives

Question 17

How would damage to the orbitofrontal cortex present in a patient?

Answer 17

These patients would have a ‘pseudopsychopathic’ behaviour i.e. impulsive, jocular attitude, sexual disinhibition, complete lack of concern for others

Question 18

How does the basal ganglia have an effect on the motor cortex?

Answer 18

Has an effect via the motor thalamus

SO basal ganglia –> motor thalamus –> motor cortex NB. the cerebellum also projects to the motor thalamus to to the motor cortex

Question 19

How will damage to the motor thalamus present?

Answer 19

Damage to the motor thalamus can result in severe paralysis

Question 20

What is the corticobulbospinal tract composed of?

Answer 20

Composed of two motor tracts - the corticobulbar tract and the corticospinal tract

Question 21

Through which structure does the corticobulbospinal tract pass?

Answer 21

Passes through the internal capsule - this is a fibre bundle passing between the caudate and the putamen nuclei

Question 22

Through which part of the brainstem does the corticobulbospinal tract pass?

Answer 22

These two motor tracts pass through the midbrain and then through the medulla

SO motor cortex –> internal capsule –> midbrain –> medulla –> spinal cord

Question 23

Give the path and function of the corticobulbar tract

Answer 23

Motor functions of the non-oculomotor cranial nerves (muscles of the head, face and neck)

Motor cortex to the medullary pyramids

Terminates on the cells of the relevant cranial nerve nuclei

Terminates on cells of the pontine nuclei, reticular formation and the red nucleus

Question 24

What is the red nucleus?

Answer 24

Aka. nucleus ruber

This is a large, round nucleus in the midbrain next to the subtantia nigra Involved in motor coordination

Question 25

Give the path of the corticospinal tract

Answer 25

This follows the corticibulbar tract and then splits at the medulla - continues onto the lower medulla

Here, it decussates to form the large lateral corticospinal tract and the small medial corticospinal tract

Question 26

Where is the motor deficit if there is a lesion above/below the spinal cord? Why is this?

Answer 26

Lesion above spinal cord - motor deficit on the OPPOSITE side Lesion of spinal cord - motor deficit on the SAME side

This is because decussation of motor tracts occurs in the upper portion/just above the spinal cord

Question 27

What is located at the region of the primary motor cortex?

Answer 27

The motor homonculus is located along this region

Question 28

What is the layout of the motor homonculus?

Answer 28

The feet and legs are in the central region where a sagittal section would be

Then to the hip, trunk, shoulder, elbow

Then to the hands and fingers

Finally the face

Question 29

What is the result of lesions in the primary motor cortex?

Answer 29

This results in paralysis or paresis of specific muscle groups depending on the region of the homonoculus

Question 31

Define spasticity

Answer 31

Abnormally increased muscle tone

Often have incresed tendon reflexes

Question 32

What is the cause of spasticity?

Answer 32

Upper motor neurone lesion

Question 33

Define clonus

Answer 33

Series of jery contractions of a particular muscle

Question 34

What is the cause of clonus?

Answer 34

Sudden stretching of the muscle

Question 35

What is meant by hyperreflexia?

Answer 35

Where abnormally brisk tendon reflexes are seen in one or more muscles

Overactive/overresspinsive reflexes

Due to damage to the spinal cord at the level of T5 or above

Question 36

What do spasticity, clonus and hyperreflexia signifty damage to?

Answer 36

Corticospinal tract

Question 37

What is decorticate posturing and what does this signify damage to?

Answer 37

Lying supine and arms are adducted and flexed

Wrists are also flexed and legs are internally rotated/extended

Planter flexion of the feet

Damage to the corticospinal tract in the medulla

Question 38

What is decerebrate posturing and what does this indicated damage to?

Answer 38

Arms adducted and extended and wrists pronated and fingers flexed

Planter flextion of the feet

Indicated severe injury to the brain at the level of the brainstem, including damage to corticospinal and rubrospinal tracts

Question 39

Out of decerebrate and decrotical posturing, which is the more serious?

Answer 39

Decerebrate

Question 40

How will someone with an acute lesion in the motor cortex present and why?

Answer 40

Initial paralysis - followed by a variable degree of recovery (motor weakness and fatigue will not recovery)

This is due to plasticity in the cortex

Question 41

What is meant by ‘hemiplegic dystonia’?

Answer 41

Persistant spasticity and a profound motor weakness - persistant flexion of the arms and persistant extension of the legs

Question 42

What is the ‘clasp knife reflex’?

Answer 42

Hyperactivity of the flexor muscles

Question 43

What does the clasp knife reflex indicated damage to?

Answer 43

Chronic cerebral motor lesion

Question 44

What is spinal shock?

Answer 44

Clincal condition occuring after acute damage to the spinal cord - to any of the descending tracts

Question 45

Chronic signs of spinal shock

Answer 45

Clonus

Hyepractive and exaggerated reflexes

Babinski