MOTOR SYSTEMS

Question 1

Where is the 4th ventricle in the brain?

Answer 1

between the cerebellum and the brain stem

Question 2

describe the anatomical features of the midbrain in ventral view?

Answer 2

there are 2 cerebral peduncles which are like stalks that attach the cerebrum to the brain stem.
In between we have the interpeduncular fossa.
at the top we have the mammillary bodies

Question 3

describe the anatomical features of the medulla in ventral view?

Answer 3

down the middle is an anterior median fissure which is continuous with the spinal cord, either side we have the pyramids and lateral to these we have the olives.

Question 4

describe the anatomical features of the midbrain in dorsal view?

Answer 4

we have 2 superior and 2 inferior colliculi

Question 5

describe the anatomical features of the pons in dorsal view?

Answer 5

a pair of superior, a pair of inferior and a pair of lateral cerebellar peduncles.

Question 6

describe the anatomical features of the medulla in dorsal view?

Answer 6

the cuneate fascicule and gracile fascicule (more medial) are visible

Question 7

what is the function of the 4th ventricle in the brain?

Answer 7

To protect the human brain from trauma (via a cushioning effect) and to help form the central canal, which runs the length of the spinal cord.

Question 8

why is the brain stem so important?

Answer 8

it houses cranial nerves 3-12.
3 and 4 airse from the midbrain
5,6,7 and 8 arise from the pons
9,10,11,12 arise from the medulla

Question 9

what are the functions of the brain stem?

Answer 9

Controls the flow of messages between the brain and the rest of the body
Controls basic body functions such as breathing, swallowing, heart rate, blood pressure, consciousness, and wakefulness

Question 10

what is brain stem death?

Answer 10

Patient unconscious (related to reticular system in the pons which controls wakefulness)
Patient cannot breathe or cough (CNX)
Patient cannot swallow (CNV, VII)
No pupillary reflex (CNII & III)
No gag reflex (CNIX)

Question 11

how are motor pathways different to sensory pathways?

Answer 11

motor information is passed along a 2 neuron pathway rather than 3. an upper motor neurone and a lower motor neurone

Question 12

what are the key features of upper motor neurones?

Answer 12

they’re entirely within the CNS, their origin is either cerebral cortex, cerebellum or brainstem, they form descending tracts

Question 13

where and what do upper motor neurones synapse with?

Answer 13

lower motor neurones in brainstem or spinal cord

Question 14

what are lower motor neurones?

Answer 14

cranial or spinal nerves that project to muscles and produce a response

Question 15

what are the 2 broad groups of descending tracts?

Answer 15

dorsolateral and ventromedial

Question 16

what is the function of dorsolateral descending tracts?

Answer 16

to supply distal muscles and control fine movement

Question 17

what is the function of the ventromedial descending tracts?

Answer 17

to supply proximal limbs and trunk muscles as well as control posture and movement correction

Question 18

what are the 2 dorsolateral descending tracts called?

Answer 18

lateral corticospinal and rubrospinal

Question 19

what are the 4 ventromedial descending tracts called?

Answer 19

anterior corticospinal, reticulospinal, tectospinal and vestibulospinal

Question 20

describe the reticulospinal tract?

Answer 20

1st order neurones arise from the pons and the medullary reticular formation, it remains ipsilateral and runs the entire length of the spinal cord. it then synapses with a lower motor neurone in the medial aspect of the ventral horn. the lower motor neurone supplies the trunk and the proximal upper/lower limbs

Question 21

what is the function of the reticulospinal tract?

Answer 21

posture, gait related movements

has a role in modulating sensation

Question 22

what is sensory modulation?

Answer 22

The ability to respond appropriately to sensory information and remain at an appropriate level of alertness

Question 23

describe the tectospinal tract?

Answer 23

1st order neurone arise from the superior colliculi.
it decussates in the midbrain and receives input from the peripheral retina. it then synapses with a lower motor neurone in the cervical spinal cord and this lower motor neurone innervates the shoulder girdle and neck.

Question 24

what are the functions of the tectospinal tract?

Answer 24

to turn the head in response to visual stimuli and to coordinate head and eye movement

Question 25

Describe the vestibulospinal tract?

Answer 25

1st order neurones arise from the vestibular nuclei. it remains ipsilateral. it synapses with a lower motor neurone in the medial aspect of the ventral horn. the lower motor neurone innervates the shoulder girdle and neck.

Question 26

what is the difference between medial and lateral vestibulospinal tracts?

Answer 26

medial stops in the cervical region whilst lateral travels down through all the spinal segments

Question 27

what are the functions of the vestibulospinal tracts?

Answer 27

to position the head an neck

balance and controlling movements in response to sudden postural changes

Question 28

what does polysegmental mean?

Answer 28

that nerves come out at every spinal level

Question 29

describe what it means to say the ventromedial tracts provide bilateral innervation?
why is this important?

Answer 29

the unilateral axon (one side) innervates both sides of the body
this is important as we need to have control over both sides of out body simultaneously

Question 30

what would happen if we had a unilateral lesion on a ventromedial tract?
what about a bilateral lesion?

Answer 30

unilateral- no obvious defects
bilateral- loss of posture correction reactions, loss of navigational control, loss of trunk mobility and loss of ability to reach out. however you would still be able to flex the elbow and use the digits

Question 31

describe the rubrospinal tract?

Answer 31

1st order neurone originates in the red nucleus of the midbrain and decussates in the midbrain.

Question 32

what is the function of the rubrospinal tract?

Answer 32

to control muscle tone in upper limbs and to coordinate movement

Question 33

what would happen if there was an isolated lesion in the rubrospinal tract?

Answer 33

you would get impaired distal arm and hand movement and intention tremors

Question 34

describe the corticospinal tract pathway?

Answer 34

1st order neurones arise from the primary and motor cotexes and the sensory cortex. they pass through the internal capsule and then through the cerebral peduncles in the midbrain. 85% of fibres decussate below the pyramids in the medulla (lateral corticospinal tract= in dorsolateral region) but 15% remain ipsilateral (anterior corticospinal tract-in ventromedial region).this neurone then synapses with a lower motor neurone in the ventral horn at all spinal segments

Question 35

what are the functions of the corticospinal tract?

Answer 35

voluntary motor control of skeletal muscles, fine movement and sensory modulation

Question 36

which skeletal muscles do a)the lateral corticospinal tract and b)the anterior conticospinal tract supply?

Answer 36

lateral= limbs
anterior= trunk

Question 37

when does the corticospinal tract become fully myelinated?

Answer 37

at 2 years of age

Question 38

what is the Babinski test?

what is a positive sign? what is a negative sign?

Answer 38

running a sharp object up the lateral aspect of the sole of the foot
posititive= toes extend (something wrong)
negative= toes flex

Question 39

what happens if you get a lesion above decussation in the corticospinal tract?

Answer 39

Contralateral spastic paresis (very high muscle tone and severe weakness) & +ve Babinski’s (upgoing toe)

Question 40

what happens if you get a lesion below decussation in the cotricospinal tract?

Answer 40

Ipsilateral spastic paresis & +ve Babinski’s

Question 41

what are the symptoms of lesions in the corticospinal tract?

Answer 41

loss of independent finger flexion. loss of speed and agility. clumsiness. weakness

Question 42

what are the effects of lesions in the dorsolateral pathways?

Answer 42

normal walk and posture correction but arms hang imply and to reach the patient would use shoulder circumduction and fingers would flex together