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Neuroanatomy > Descending Pathways > Flashcards

Descending Pathways Flashcards

1
Q

two modes of control

A

external and internal control

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2
Q

external control

A

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

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3
Q

which parts of the brain relate to external control

A

parietal cortex, premotor cortex, cerebellum

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4
Q

internal control

A

non-sensory guided - proprioceptors

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5
Q

what parts of the brain relate to internal control

A

prefrontal cortex, supplementary motor area, basal ganglia

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6
Q

what are motor projection fibres

A

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

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7
Q

what are commissural fibres

A

the axons of neurons that join the two cerebral hemispheres

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8
Q

what are association fibres

A

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

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9
Q

upper motor neuron

A
  • cell body originates in the cerebral cortex or brainstem
  • does not transmit impulses directly to muscles
  • glutamatergic
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10
Q

what are upper motor neurons also known as

A

first order neurons

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11
Q

lower motor neuron

A
  • cell body originates in the anterior grey column of spinal cord, brainstem or cranial nerve nuclei
  • transmits impulses directly to muscles
  • uses neurotransmitter acetylcholine
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12
Q

what are lower motor neurons also known as

A

second order neurons

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13
Q

whar is the spinal reflex arc

A

reflexes that occur without spinal input

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14
Q

name two reflexes

A
  • patellar reflex
  • abdominal skin reflex
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15
Q

how do reflexes work

A

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

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16
Q

pyramidal tracts vs extrapyramidal tracts

A

pyramidal tracts pass through the medullary pyramids
extrapyramidal tracts do not

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17
Q

what do the fibres do in pyramidal tracts

A
  • originate in motor cortex
  • most cross to contralateral side
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18
Q

where do fibres of extrapyramidal tracts originate

A

brainstem

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19
Q

name two types of pyramidal tract

A
  • corticospinal
  • corticobulbar
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20
Q

where are cell bodies of pyramidal tracts located

A

precentral gyrus of frontal lobe (primary motor cortex)

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21
Q

where do corticospinal tracts originate

A

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

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22
Q

where do corticospinal tracts recieve input from

A

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

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23
Q

where do corticospinal tracts travel to

A

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

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24
Q

what do anterior corticospinal tracts control

A

central axial and proximal muscles involved in postural control

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25
Q

where do the fibres of anterior corticospinal tracts decussate

A

in spinal cord

26
Q

what do lateral corticospinal tracts control

A

appendicular muscles for fine movement of ipsilateral limbs

27
Q

where do lateral corticospinal tract fibres decussate

A

in the pyramids

28
Q

what are corticobulbar tracts also known as

A

corticonuclear tracts

29
Q

what nerves do the corticobulbar tracts synapse with

A

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

30
Q

do all corticobulbar tract fibres decussate

A

no

31
Q

corticobulbar tracts function

A
  • responsible for voluntary movement of face (CN VIII), head and neck (CN IX)
  • involved in phonation, swallowing and facial expression (CN VII and IX)
32
Q

upper motor neuron lesion

A
  • causes spastic paralysis (muscles become tight, stiff and contracted, hypertonia)
  • in the absence of UMN control the LMN exhibits hyperactivity
33
Q

lower motor neuron lesion

A
  • causes flaccid paralysis (muscles are limp and lack firmness, hypotonia)
  • loss of reflexes
  • muscle atrophy (later symptom)
34
Q

example of LMN lesion

A

bulbar lesion of facial nerve

35
Q

lesion A

bulbar lesion of facial nerve

A

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

36
Q

Lesion B

bulbar lesion of facial nerve

A

entire face is affected on one side

37
Q

causes of other bulbar lesions

A

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

38
Q

what do bulbar lesions cause

A

bulbar palsy

39
Q

bulbar palsy symptoms

A
  • 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
40
Q

what is amyotrophic lateral sclerosis (ALS)

A
  • 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
41
Q

function of extrapyramidal tracts

A

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

42
Q

structures involved in extrapyramidal tracts

A
  • basal ganglia
  • red nucleus
  • substantia nigra
  • reticular formation
  • cerebellum
43
Q

name the four extrapyramidal tracts

A
  • vestibulospinal
  • reticulospinal
  • rubrospinal
  • tectospinal
44
Q

where does the vestibulo spinal tract arise

A

vestibular nuclei

45
Q

vestibulospinal tract function

A

conveys balance information to spinal cord

46
Q

is the vestibulospinal tract contralateral or ipsilateral

A

ipsilateral

47
Q

where does the reticulospinal tract arise

A

in reticular formation of the pons

47
Q

reticulospinal tract function

A

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

48
Q

where does the rubrospinal tract arise

A

red nuclei

49
Q

is the rubrospinal tract contralateral or ispsilateral

A

contralateral

50
Q

rubrospinal tract function

A

plays a role in fine control of the hand

51
Q

where does the tectospinal tract arise

A

in the superior colliculi

52
Q

tectospinal tract function

A

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

53
Q

what are extrapyramidal syndromes

A

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

54
Q

name four extrapyramidal syndromes

A
  • akathisia
  • dystonia
  • parkinsonism
  • tardive dyskinesia
55
Q

what are extrapyramidal diseases

A

impairments of the central nervous system

56
Q

name three extrapyramidal diseases

A
  • parkinsons disease
  • huntingtons chorea
  • tourettes syndrome
57
Q

akathisia

A

motor recklessness

58
Q

dystonia

A

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

59
Q

parkinsonism

A

parkinsons like signs (tremor, rigidity, bradykinesia)

60
Q

tardive dyskinesia

A

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

Neuroanatomy (23 decks)

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