Descending Pathways

Question 1

two modes of control

Answer 1

external and internal control

Question 2

external control

Answer 2

sensory guided (visual or auditory system is needed to execute movements)

Question 3

which parts of the brain relate to external control

Answer 3

parietal cortex, premotor cortex, cerebellum

Question 4

internal control

Answer 4

non-sensory guided - proprioceptors

Question 5

what parts of the brain relate to internal control

Answer 5

prefrontal cortex, supplementary motor area, basal ganglia

Question 6

what are motor projection fibres

Answer 6

Neurons in the motor cortex give rise to axons that travel through the corona radiata and the internal capsule

Question 7

what are commissural fibres

Answer 7

the axons of neurons that join the two cerebral hemispheres

Question 8

what are association fibres

Answer 8

axons of neurons that unite different parts of the same cerebral hemisphere

Question 9

upper motor neuron

Answer 9

• cell body originates in the cerebral cortex or brainstem
• does not transmit impulses directly to muscles
• glutamatergic

Question 10

what are upper motor neurons also known as

Answer 10

first order neurons

Question 11

lower motor neuron

Answer 11

• cell body originates in the anterior grey column of spinal cord, brainstem or cranial nerve nuclei
• transmits impulses directly to muscles
• uses neurotransmitter acetylcholine

Question 12

what are lower motor neurons also known as

Answer 12

second order neurons

Question 13

whar is the spinal reflex arc

Answer 13

reflexes that occur without spinal input

Question 14

name two reflexes

Answer 14

• patellar reflex
• abdominal skin reflex

Question 15

how do reflexes work

Answer 15

sensory neuron synapses with interneuron which then synapses with motor neuron - interneuron is the connection not spinal cord

Question 16

pyramidal tracts vs extrapyramidal tracts

Answer 16

pyramidal tracts pass through the medullary pyramids
extrapyramidal tracts do not

Question 17

what do the fibres do in pyramidal tracts

Answer 17

• originate in motor cortex
• most cross to contralateral side

Question 18

where do fibres of extrapyramidal tracts originate

Answer 18

brainstem

Question 19

name two types of pyramidal tract

Answer 19

• corticospinal
• corticobulbar

Question 20

where are cell bodies of pyramidal tracts located

Answer 20

precentral gyrus of frontal lobe (primary motor cortex)

Question 21

where do corticospinal tracts originate

Answer 21

five layers of cortex - internal pyramidal layer, contains large pyramidal neurons

Question 22

where do corticospinal tracts recieve input from

Answer 22

motor and premotor cortical areas: somatosensory cortex, parietal lobe and cingulate gyrus

Question 23

where do corticospinal tracts travel to

Answer 23

through internal capsule to the cerebral peduncles and then tbey come to lie on the ventral surface of the medulla (pyramids)

Question 24

what do anterior corticospinal tracts control

Answer 24

central axial and proximal muscles involved in postural control

Question 25

where do the fibres of anterior corticospinal tracts decussate

Answer 25

in spinal cord

Question 26

what do lateral corticospinal tracts control

Answer 26

appendicular muscles for fine movement of ipsilateral limbs

Question 27

where do lateral corticospinal tract fibres decussate

Answer 27

in the pyramids

Question 28

what are corticobulbar tracts also known as

Answer 28

corticonuclear tracts

Question 29

what nerves do the corticobulbar tracts synapse with

Answer 29

synapse with motor nuclei of cranial nerves beginning at the level of the upper pons

Question 30

do all corticobulbar tract fibres decussate

Answer 30

no

Question 31

corticobulbar tracts function

Answer 31

- responsible for voluntary movement of face (CN VIII), head and neck (CN IX) - involved in phonation, swallowing and facial expression (CN VII and IX)

Question 32

upper motor neuron lesion

Answer 32

- causes spastic paralysis (muscles become tight, stiff and contracted, hypertonia) - in the absence of UMN control the LMN exhibits hyperactivity

Question 33

lower motor neuron lesion

Answer 33

- causes flaccid paralysis (muscles are limp and lack firmness, hypotonia) - loss of reflexes - muscle atrophy (later symptom)

Question 34

example of LMN lesion

Answer 34

bulbar lesion of facial nerve

Question 35

lesion A | bulbar lesion of facial nerve

Answer 35

upper face is spared because both hemispheres contribute to movements of upper face and unaffected hemisphere can compensate

Question 36

Lesion B | bulbar lesion of facial nerve

Answer 36

entire face is affected on one side

Question 37

causes of other bulbar lesions

Answer 37

injury to cranial nerve nuclei or axons of glossopharyngeal, vagus and/or hypoglossal nerves due to brainstem stroke or tumor

Question 38

what do bulbar lesions cause

Answer 38

bulbar palsy

Question 39

bulbar palsy symptoms

Answer 39

- nucleus of glossopharyngeal/vagus nerve: pharyngeal muscle weakness and posterior 1/3 of tongue - ie. swallowing issues - nucleus of hypoglossal nerve: progressive loss of speech and tongue muscle atrophy ie. dysarthria

Question 40

what is amyotrophic lateral sclerosis (ALS)

Answer 40

- upper and lower motor neuron disease - Leads to muscle weakening, twitching, and an inability to move the arms, legs, and body. * The condition slowly gets worse as more and more muscle groups are affected. * When the muscles in the chest area stop working, it becomes hard or impossible to breath on one's own. * ALS does not affect the senses (sight, smell, taste, hearing, touch). It only rarely affects bladder or bowel function, or a person's ability to think or reason * no known cure

Question 41

function of extrapyramidal tracts

Answer 41

involuntary and automatic control of movements, posture and muscle tone - more control of over muscles in the midline than those in the periphery ie. gross motor more than fine motor

Question 42

structures involved in extrapyramidal tracts

Answer 42

- basal ganglia - red nucleus - substantia nigra - reticular formation - cerebellum

Question 43

name the four extrapyramidal tracts

Answer 43

- vestibulospinal - reticulospinal - rubrospinal - tectospinal

Question 44

where does the vestibulo spinal tract arise

Answer 44

vestibular nuclei

Question 45

vestibulospinal tract function

Answer 45

conveys balance information to spinal cord

Question 46

is the vestibulospinal tract contralateral or ipsilateral

Answer 46

ipsilateral

Question 47

where does the reticulospinal tract arise

Answer 47

in reticular formation of the pons

Question 47

reticulospinal tract function

Answer 47

medial fibres: exites voluntary movements lateral fibres: inhibits voluntary movements

Question 48

where does the rubrospinal tract arise

Answer 48

red nuclei

Question 49

is the rubrospinal tract contralateral or ispsilateral

Answer 49

contralateral

Question 50

rubrospinal tract function

Answer 50

plays a role in fine control of the hand

Question 51

where does the tectospinal tract arise

Answer 51

in the superior colliculi

Question 52

tectospinal tract function

Answer 52

coordinates head movements in relation to visual stimuli (recieves input from optic nerves)

Question 53

what are extrapyramidal syndromes

Answer 53

collections of symptoms that usually occur after long-term use of psychiatric medication

Question 54

name four extrapyramidal syndromes

Answer 54

- akathisia - dystonia - parkinsonism - tardive dyskinesia

Question 55

what are extrapyramidal diseases

Answer 55

impairments of the central nervous system

Question 56

name three extrapyramidal diseases

Answer 56

- parkinsons disease - huntingtons chorea - tourettes syndrome

Question 57

akathisia

Answer 57

motor recklessness

Question 58

dystonia

Answer 58

involuntary contraction of muscles (eye, neck, tongue, limbs)

Question 59

parkinsonism

Answer 59

parkinsons like signs (tremor, rigidity, bradykinesia)

Question 60

tardive dyskinesia

Answer 60

repetitive, involuntary movements (chewing, tongue protrusion, lip puckering)