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anatomy - neuro > motor pathways > Flashcards

motor pathways Flashcards

1
Q

what are descending tracts?

A

-pathways by which motor signals are sent from the brain to lower motor neurones
- the lower motor neurones then directly innervate muscles to produce mvt

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2
Q

what 2 groups are the motor tracts divided into?

A
  • pyramidal tracts
    -extrapyramidal tracts
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2
Q

what are pyramidal tracts?

A

-descending tracts that originate in the cerebral cortex, carrying motor fibres to the spinal cord and brain stem
-they are responsible for the voluntary control of the musculature of the body and face

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3
Q

what are extrapyramidal tracts?

A

-these tracts originate in the brain stem, carrying motor fibres to the spinal cord
-responsible for the involuntary and automatic control of muscles such as muscle tone, balance etc

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4
Q

are there synapses within the descending pathways?

A

no, except at the termination of the descending tracts, the neuron’s synapse with a lower motor neurone

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5
Q

what do ‘pyramidal tracts’ derive their name from?

A

medullary pyramids of the medulla oblongata which they pass through

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6
Q

what can the pyramidal tracts be subdivided into?

A
  • pyramidal system is divided based on cranial nerves and spinal nerves
    corticobulbar tracts
    -corticospinal tracts
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7
Q

what are corticobulbar tracts?

A

group of upper cranial motor nerves that start in the cortex and end in the brainstem

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8
Q

what are the corticospinal tracts?

A

-group of upper motor nerves that start in the cortex and end in the spinal cord

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9
Q

how many neutrons are there in the descending pathways and what are they called?

A
  • 2 neurons
    -upper motor neurons
    -lower motor neurons
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10
Q

what are upper motor neurons?

A

neurons from cerebral cortex too the brainstem (cranial nerve) or the spinal cord (spinal nerve)

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11
Q

what are lower motor neurons ?

A

-neurons going to innervate the muscle from the brainstem cranial nerve motor nucleus or from the anterior horn cell of the spinal cord

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12
Q

where do the corticospinal tracts begin and where do they receive inputs from?

A

-they begin in the cerebral cortex
-they receive inputs from the primary motor cortex, premotor cortex and supplementary motor area

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13
Q

what is the internal capsule?

A

a white matter pathway located between the thalamus and the basal ganglia

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14
Q

in the corticospoinal tract, after the neurons move from the cerebral cortex, where do they travel to?

A
  • they go to the internal capsule
    -after the IC, they pass through the crus cerebra of the midbrain, the pons and into the medulla
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15
Q

what happens to the cortciospinal tract once it reaches the medulla?

A

it divides into 2 - the lateral corticospinal tract and the anterior corticospinal tract

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16
Q

Describe the lateral corticospinal tract

A

-larger of the 2 tracts
-it descends on the lateral part of the spinal cord
-fibres then cross over to the opposite side of the body at the level pf the medulla
-the fibres then synapse with the lower motor neurons of the ventral horn of the cord
-lower motor neurons then innervate the muscles, leading to voluntary control

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17
Q

describe the anterior corticospinal tract

A

-smaller in comparison to the lateral corticospinal tract
-descends on the anterior/ventral side of the spinal cord
-fibres dont cross over like lateral pathway, but they continue to descend ipsilaterally for a distance before crossing over @ level of cord
-fibres eventually synapse with lower motor neurons in the ventral horn of cord

18
Q

what is the function of the corticobulbar tracts?

A

-These tracts are involved in the control of movements of the head, face, and neck, as well as certain functions related to speech, swallowing, and facial expressions.
- Unlike the corticospinal tracts, which primarily control movements of the limbs and trunk, the corticobulbar tracts control movements of the head and face.

19
Q

what is a upper motor neuron lesion?

A

-damage or dysfunction to the upper motor neurons in the brain or spinal cord
-can occur due to trauma, stroke, spinal cord injury

20
Q

Describe an upper motor lesion the cerebral hemisphere

A

-lesions in the cerebral hemisphere (specifically the motor cortex) can lead to motor deficits on the contralateral side of the body
-ie if lesion occurs in the left hemisphere, the deficits will be on the right side of the body

21
Q

describe an upper motor lesion in the spinal cord

A
  • lesion in the spinal cord - then there is ipsilateral deficits
    -lesions in the spinal cord will affect upper motor neurons as they descend from the brain to synapse with lower motor neurons of the cord
22
Q

what are examples of symptoms associated with UMN lesions in the spinal cord?

A
  • initial weakness / paralysis
    -hypertonicity - increased muscle tone
    -hyperreflexia (exaggerated response of reflexes)
    -clonus -rhythmic, involuntary contraction & relaxation of muscle
    -babinskis response (extension of the big toe and fanning of other toes)
23
Q

what is a lower motor lesion?

A

-damage of dysfunction of the lower motor neurones which innervate muscles
- can occur at various levels eg in the spinal cord or in the peripheral nerves

24
Q

what are examples of symptoms of a lower motor neuron lesion?

A

-weakness
-wasting of muscles
-fasciculations (spontaneous contractions of muscles)
-hypotonicity
-hyporelfexia

25
Q

what is the mnemonic to distinguish the different characteristics of upper vs lower motor lesions?

A

-STORM
-strength, tone, others, reflexes, muscle mass, babinski sign

26
Q

what do spinal reflexes test?

A

integrity of the sensory, CNS and motor reflex arc

27
Q

what are examples of reflexes?

A

-patella (knee jerk reflex)
-biceps
-triceps
-achilles tendon reflex

28
Q

describe the patellar tendon reflex

A

-patella tendon tapped w/ hammer
-this causes stretching of the tendon which activates sensory receptors within quad muscles
-muscle spindles send a signal to cord
- in response, the cord quickly sends a signal back through motor nerves to quad muscles, causing it to contract
-leads to extension of the leg

29
Q

why is the patellar reflex a monosynaptic reflex?

A

because it involves only one synapse between the sensory neuron (afferent neuron) and the motor neuron (efferent neuron) in the spinal cord

30
Q

describe a UMN lesion vs LMN lesion affecting the facial nerve

A

1- UMN - wrinkling of forehead is spread and face droops below the eye
2- LMN - facial muscles damaged above and below eyes

31
Q

what is the extrapyramidal system?

A

system involving neurons starting in other brain centre nuclei eg basal ganglia
- they dont pass through the pyramids of the medulla, unlike the pyramidal system
-involved in controlling fine tune mvt

32
Q

what are 4 examples of extrapyramidal pathways?

A

-rubrospinal pathway
-tectospinal tract
-vesticulospinal tract
-reticulospinal tract

33
Q

what is the rubrospinal pathway?

A

-pathway originating in a brain structure called the red nucleus located in the midbrain
-recieves inputs from cerebellum, and cerebral cortex

34
Q

what does the rubrospinal pathway control?

A

-tone of flexor muscles in the limbs

35
Q

describe the tectospinal tract

A

-The tectospinal tract is a neural pathway in the central nervous system involved in the control of head and neck movements in response to visual and auditory stimuli, particularly those related to orientation and coordination of the eyes and head.

36
Q

where does the tectospinal tract originate from?

A

neurons in the superior colliculus

37
Q

describe the vestibulospinal tract

A

-The vestibulospinal tract is a neural pathway in the central nervous system involved in the regulation of posture, balance, and head movement

38
Q

describe the vestibulospinal tract pathway

A
  • originates from the vestibular nuclei - medial and lateral nuclei
    -fibres descend ipsilaterally in the spinal cord
    -synpases on anterior horn cells and control posture and tone of extensor muscle s
39
Q

describe the reticulospinal tract

A

-The reticulospinal tract is a neural pathway in the central nervous system involved in the control of posture, balance, and locomotion
- it originates from the reticular formation (pons and medulla)

40
Q

how do medial (pontine) vs lateral *medullary) neurons descend in the reticulospinal tract?

A
  • medial fibres descend ipsilaterally in the cord
    -lateral fibres descend bilaterally in the cord
41
Q

what are examples of extrapyramidal problems?

A

parkinsons - rigidity, shuffling gait, bradykinesia (slowed mvt), resting tremor

42
Q

what is polio?

A

virus that typically affects there anterior horn cells causing LMN injury presentation in spinal nerves

anatomy - neuro (28 decks)

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