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SFII Test 2 > Descending Spinal Cord Pathways > Flashcards

Descending Spinal Cord Pathways Flashcards

1
Q

Where does the parasympathetic nervous system originate?

A

Brain stem - CN III, VII, IX, X

Sacral cord - sacral nerves

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2
Q

Where does the sympathetic nervous system originate?

A

Thoracic and lumbar segments

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3
Q

Where do autonomic nerves terminate in the spinal cord?

A

Intermediolateral nucleus

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4
Q

What is referred pain?

A

Visceral pain that is referred to an area of the body surface that corresponds to the dermatome innervated by the spinal segment to which the visceral afferents project

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5
Q

What is the basis of referred pain?

A

Convergence of visceral and somatic pain fibers on the same spinothalamic tract cells reached by somatic pain fibers

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6
Q

What is the major voluntary motor pathway and where do most of its fibers come from?

A

Corticospinal tract

40% of its fibers take origin from the primary motor cortex in the precentral gyrus

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7
Q

What is the site of origin, decussation, termination, and function of the lateral corticospinal tract?

A

Origin: Primary motor cortext and other frontal and parietal areas

Pyramidal decussation

Terminates in the entire cored

Function: Movement of contralateral limbs

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8
Q

What is the site of origin, decussation, termination, and function of the rubrospinal tract?

A

Origin: Red nuclues, magnocellular division

Ventral tegmental decussation in the midbrain

Terminates in the cervical cord

Function: Movement of contralateral limbs (uncertain in humans)

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9
Q

What is the origin, termination, and function of the anterior corticospinal tract?

A

Origin: Primary motor cortex and supplementary motor area

Termination: Cervical and upper thoracic cord

Function: Control of bilateral axial and girdle muscles

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10
Q

What are upper motor neurons and lower motor neurons

A

Upper motor neurons project from the cortex to the spinal cord or brainstem, synapse onto LMNs

Lower motor neurons project from anterior spinal roots (or cranial nerves) to various muscles

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11
Q

Where does the corticospinal tract split into lateral and anterior?

A

Pyramidal Decussation

85% of the fibers decussate to form the lateral CS tract, the rest form the anterior CS tract

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12
Q

Where do fibers from the anterior CS tract decussate?

A

Most cross the midline via the anterior white commissure before terminating in the contralateral medial anterior horn

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13
Q

What is the general function of the indirect corticospinal pathways?

A

Primarily regulate the background tone and activity in muscle without which a normal movement could not be made

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14
Q

What part of the anterior gray horn supplies axial muscles?

A

Medially placed motor neuron columns

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15
Q

What part of the anterior gray horn supplies proximal limb segment muscles?

A

Mid region motor neuron columns

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16
Q

What part of the anterior gray horn supplies distal limb segment muscles?

A

Lateral motor neuron columns

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17
Q

How are flexor and extensor motor neuron columns oriented in the anterior horn?

A

Columns supplying extensors lie anterior to those that supply flexors

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18
Q

What motor nucleus supplies the intrinsic muscles of the hand and foot?

A

Retrodorsolateral nucleus

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19
Q

What motor nucleus supplies the diaphragm?

A

Central Nucleus

20
Q

What is fractionation?

A

Small groups of corticomotoneuronal fibers can be selectively activated to execute skilled movements

E.g. moving the index finger independently

21
Q

What are alpha motor neurons?

A

Supply the extrafusal fibers of skeletal muscles

main force generation for muscles

22
Q

What are gamma motor neurons?

A

Supply the intrafusal fibers of neuromuscular spindles

regulate the sensitivity of muscle

23
Q

What are Renshaw cells and their function?

A

Interneurons located within the spinal cord that synapse on Ia inhibitory internuncials and other Renshaw cells

Co-contraction of prime movers and their antagonists in order to fix one or more joints

Attenuate alpha motor neuron activity limiting contraction

24
Q

What is the function of excitatory internuncials?

A

To recruit motor neurons supplying axial and proximal limb muscles indirectly for the LCST

25
Q

What is the function of Ia inhibitory internuncials?

A

Cause the antagonist muscles to relax before the prime movers contract

Renders antagonists’ motor neurons refractory to stimulation by spindle afferents passively stretched by the movement

first neurons to be activated by the LCST during voluntary movements

26
Q

Describe muscle strength, tone, stretch reflexes, and atrophy in a Lower motor neuron lesion.

A

Strength: Decreased

Muscle tone: Decreased

Stretch reflexes: Decreased

Atrophy: Severe

27
Q

Describe muscle strength, tone, stretch reflexes, and atrophy in a Upper motor neuron lesion.

A

Strength: Decreased

Muscle tone: Increased

Stretch reflexes: Increased

Atrophy: Mild

28
Q

What does flaccid paralysis indicate?

A

Lower motor neuron lesion

Results from denervation of muscle

29
Q

What are pathological reflexes of upper motor neuron lesions?

A

Spasticity

Hyperreflexia

Clasp-knife

Clonus

Abnormal superficial flexor (Babinski)

30
Q

Why does an upper motor neuron lesion cause hyperreflexia?

A

Loss of supraspinal inhibition of LMN’s

31
Q

What spinal roots are involved in abdominal cutaneous reflexes above the umbilicus? Below?

A

Above - T8-T10

Below - T10-T12

32
Q

What spinal roots are involved in the cremasteric reflex?

A

L1-L2

33
Q

What spinal roots are involved in the bulbocavernous reflex?

A

S2-S4

34
Q

What spinal roots are involved in the anal wink?

A

S2-S4

35
Q

What locations are likely affected by a lesion with pure motor hemiparesis or hemiplegia?

A

Coricospinal fibers between the cortex and medulla, internal capsule, basilar pons, cerebral peduncle

Lesion is contralateral to weakness

36
Q

What locations are likely affected by a lesion with hemiparesis and associated somatosensory (or other higher cortical) deficits?

A

Entire primary cortex (body part correlated)

Lesion is contralateral to weakness

37
Q

What locations are possibly affected by a lesion with unilateral arm and leg weakness or paralysis?

A

Arm and leg area of the motor cortex, cortical spinal cord below the medulla and above C5

Side of lesion/weakness depends on if lesion is above (cortical or medulla) the decussation or below

Medullary lesion may also be associated with loss of vibration and joint sense

38
Q

What locations are possible affected by a lesion with faciobrachial paresis or plegia?

A

Face an arm areas of the motor cortex

Lesion is contralateral to weakness

39
Q

What locations are possibly affected by a lesion with brachial monoparesis or monoplegia?

A

Arm areas of the motor cortex or peripheral nerves supplying the arms

If UMN, then UMN signs

If LMN, then LMN signs

40
Q

What locations are possibly affected by a lesion with crural monoparesis or monoplegia?

A

Leg area of the motor cortex, LCST below T1, peripheral nerves supplying legs

Lesion is contralateral to weakness if motor cortex, ipislateral if spinal cord or peripheral nerve

41
Q

What locations are possibly affected by a lesion with unilateral face weakness or paralysis (Bell’s Palsy)?

A

Facial Nerve, Face area, facial nucleus in pons and rostral medulla

Lesion is ipsilateral if facial nerve or nucleus; contralateral if motor cortex or internal capsule

42
Q

What locations are possibly affected by a lesion with brachial diplegia?

A

Medial fibers of both lateral corticospinal tracts and bilateral cervical spine ventral horn cells

Common causes: Anterior and central cord syndrome

43
Q

What locations are possibly affected by a lesion with paraparesis or paraplegia?

A

Bilateral leg areas of the PMC, LCST below T1, Cauda equina syndrome

44
Q

What locations are possibly affected by a lesion with quadraparesis or quadraplegia?

A

Bilateral arm and leg areas of PMC, Bilateral lesions of CSTs between medulla and C5, peripheral nerve or muscle disorders that affect all four limbs

45
Q

What locations are possibly affected by generalized weakness and paralysis?

A

Bilateral lesions of the motor cortex, bilateral lesions of CSTs between corona radiata and pons, diffuse disorders involving all LMNs.

Bilateral pontine ischemia due to basilar artery stenosis

SFII Test 2 (20 decks)

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