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Human Physiology II - KCUMB > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

Neurons in the spinal cord

A

Upper motor neurons
Lower motor neurons
Renshaw cells

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2
Q

Upper motor neurons

A

Descends the spinal cord to level of the appropriate spinal nerve root
Synapses with lower motor neuron or interneuron

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3
Q

What is the neurotransmitter from the UMN to the LMN?

A

Glutamate via glutamatergic receptors

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4
Q

Lower motor neurons

A

Typically found in anterior gray portion of SC or cranial nuclei of brainstem
Terminate at effector with acetylcholine as nt
Cranial nerves are unique LMNs

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5
Q

Renshaw cells

A

Inhibitory cells in the anterior horns of spinal cord

Receive collateral branches from alpha motor neurons

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6
Q

What happens when renshaw cells transmit signals to surrounding motor neurons?

A

lateral inhibition

fluidity of limb movement is enhanced

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7
Q

What happens when renshaw cells transmit signals to the same motor neuron?

A

Results in recurrent inhibition

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8
Q

Types of sensory fibers

A

A-aplha or A-beta: conduction rate 30-120 m/sec
A-delta: conduction rate 4-30 m/sec
C fibers: conduction rate is less than 2.5 m/sec

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9
Q

What fibers are nociceptors and thermoreceptors are related to?

A

C fibers or A-delta fibers

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10
Q

Muscle spindle

A

Consists of 3-12 intrafusal fibers
With finer movements the number of muscle spindles required increases
Innervated by small gamma motor neurons
Detects changes in muscle length

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11
Q

Intrafusal fibers

A

Innervated by small gamma motor neurons (group II afferents)
Encapsulated within a sheath to form muscle spindle
Run parallel to extrafusal fibers

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12
Q

Central region of the muscle spindle

A

no contractile fibers

functions as a sensory receptor

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13
Q

Extrafusal fibers

A

Make p the “muscle fibers” that are innervated by alpha motor neurons

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14
Q

Nuclear bag fibers

A

Type of intrafusal fiber
Detect change in muscle length
Innervated by group Ia afferents and dynamic gamma efferents
Multiple nuclei located in a central “bag-like” configuration

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15
Q

Nuclear chain fibers

A 
Type of intrafusal fiber
Detect static change in muscle length
Innervated by group II afferents and static gamma efferents
More numerous than bag fibers
Multiple nuclei arranged in a single row
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16
Q

What corrects for increase in muscle length?

A

Muscle spindle

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17
Q

What does stimulation of the central region of intrafusal fiber result from?

A

Lengthening of entire muscle

Contraction of ends of intrafusal fibers

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18
Q

What does stimulation of sensory fibers (Ia and II) result in?

A

Stimulation of alpha motor neurons and contraction and shortening of muscle

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19
Q

Muscle spindle gamma motor neurons

A

Innervate intrafusal fibers
Adjust sensitivity of muscle spindle
Coactivated with alpha-motor neurons

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20
Q

Brain areas controlling gamma neurons

A

Bulboreticular region of brain stem
Cerebellum
Basal nuclei
Cerebral cortex

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21
Q

Types of gamma fibers

A

A-gamma: supply small intrafusal fibers in middle of muscle spindle
Gamma-dynamic: excite nuclear bag intrafusal fibers
Gamma-static: excite nuclear chain intrafusal fibers

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22
Q

Golgi tnedon organ

A

Encapsulated receptor through which muscle tendon fibers pass
Arranged in series with extrafusal fibers
Stimulated by contracting or stretching of muscle
Detects muscle tension
Opposite of stretch relfex

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23
Q

Circuitry of golgi tendon

A

Type Ib afferent stimulates inhibitory interneuron which inhibits the anterior alpha neuron

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24
Q

Reciprocal inhibition

A

Flexor reflex on one side will cause flexion on the same side and extension on the opposite side

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25
Q

Functions of premotor and supplementary motor cortex

A

Generate plan for movement
Cause more complex patterns of movement
Anterior part creates a motor image
Supplementary is responsible for creating a mental rehearsal of a movement

26
Q

UMN classification

A

Classified according to where they synapse in the ventral horn

27
Q

Medial activation system

A

Innervate postural and girdle muscles

28
Q

Lateral activation system

A

Associated with distally located muscles used for fine movements

29
Q

Nonspecific activating system

A

Facilitate local reflex arcs

30
Q

Origin of corticospinal tract

A

Primary motor cortex
Premotor cortex
Somatosensory area

31
Q

Pathway of corticospinal tract

A

Site of origin -> internal capsule -> medullary pyramids -> Crosses in lower medulla -> lateral columns of spinal cord (later corticospinal tract)

Some fibers do not cross but continue down ipsilaterally in ventral corticospinal tract

32
Q

Lateral corticospinal tract

A

Made up of corticospinal fibers that have crossed in the medulla
Supply all levels of spinal cord

33
Q

Anterior corticospinal tract

A

Made up of uncrossed corticospinal fibers that cross near level of synapse with LMNs
Supply neck and upper limbs

34
Q

Functions of corticospinal tract

A

Adds speed and agility to conscious movement (esp hand)

Provides a high degree of motor control

35
Q

Where are giant pyramidal cells located?

A

Motor cortex

36
Q

What results from lesions of the corticospinal tract?

A

Reduced muscle tone
Clumsiness
Weakness
Not complete paralysis (unless both pyramidal and extrapyramidal systems are involved)

37
Q

Corticobulbar tract

A

UMNs of the cranial nerves - innervating the face, head and neck
Innervates the head
Most fibers terminate in the reticular formation near cranial nerve nuclei

38
Q

Association neurons of the corticobulbar tract

A

Leave reticular formation and synapse in cranial nerve nuclei
Synapse with LMN

39
Q

Red nucleus

A

Evolutionary primitive portion of the brain

Fibers from the primary motor cortex and branches from the corticospinal tract synapse in the magnocellular portion

40
Q

Magnocellular portion of red nucleus

A

Large neurons here give rise to rubrospinal tract which decussates in lower brain stem
Has somatotopic representation of all the muscles of the body

41
Q

What does stimulation of the red nucleus result in?

A

Stimulation of flexors

Inhibition of extensors

42
Q

Vestibulospinal tract

A

Originates in vestibular nuclei and receives major input from vestibular nerve about changes in head position
Goal to maintain balance
Descends in anterior funiculus
Synapses in LMNs to extensor muscles - primarily involved in maintenance of upright posture
Components: Utricle, saccule, semicircular canals

43
Q

Utricle

A

Macula on horizontal plane

Determine orientation of head when it is upright

44
Q

Saccule

A

Macula on vertical plane

Orientation when lying down

45
Q

Macula

A

covered by a gelatinous layer that contains a large number of embedded small calcium carbonate crystals and thousands of hair cells that project cilia in to the gelatinous layer. Cilia bend with direction of gravitational pull. Depolarization d/t change in head position is sent through vestibular nerve

46
Q

Functions of cerebellum

A

Not essential for locomotion
Helps sequence motor activites
Makes corrections to movements while they are being executed
Role in timing and creating smooth, rapid movements

47
Q

Vermis of cerebellum

A

Location for control functions for muscle movements of the axial body, neck, shoulders and hips

48
Q

Intermediate zone of cerebellum

A

Concerned with controlling muscle contractions in the distal portions of the upper and lower limbs

49
Q

Lateral zone of cerebellum

A

Associated with cerebral cortex with planning of sequential motor movements

50
Q

Dentate nuclei, emboliform nuclei and globose nuclei

A

Lesions in these nuclei lead to extremity ataxia
Project to red nucleus
Related to limb musculature and fine manipulative movement

51
Q

Fastigial nuclei

A

Lesions in this nucleus leads to trunk ataxia
Fibers project to reticular formation and vestibular nuclei
Related to postural activity and limb movements via reticulospinal and vestibulospinal tracts

52
Q

Granular cell layer

A

Innermost cell layer
Made up of granular cells, golgi type II cells and glomeruli
Axons of mossy fibers synapse with granular cells and golgi type IIs in the glomeruli

53
Q

Purkinje cell lyer

A

Middle layer

Made of purkinje cells

54
Q

Molecular layer

A

Outermost layer

Contains stellate cells, basket cells, purkinje dendrites, golgi type II and axons of granule cells

55
Q

Granular cells

A

Axons form parallel fibers in cortex (+)

56
Q

Golgi cells

A

Project from parallel fibers to granular cell bodies (-)

57
Q

Basket cells

A

Project from parallel fibers to Purkinje axon hillock (-)

58
Q

Stellate cells

A

Project from parallel fibers to purkinje dendrites (-)

59
Q

Basket cells and stellate cells do what to purkinje cells?

A

Provide lateral inhibition to provide dampening

60
Q

Purkinje cells

A 
Extensive dendritic branching
Receive input from parallel fibers 
Project to intracerebellar nuclei (-)
ONLY output from cortex
** Output is always inhibitory
61
Q

Climbing fibers

A 
Afferent of cerebellar cortex
Originate from medullary olives
Make multiple synapses with purkinje cells
Provide high frequency bursts
"condition" purkinje cells
Play a role in motor learning
62
Q

Mossy fibers

A

Afferent of cerebellar cortex
Originate from multiple centers in the brainstem and spinal cord including vestibulocerebelar, spinocerebelar and pontocerebellar tracts
Make multiple synapses on purkinje cells and result i simple spikes
Synapse on granule cells in glomeruli

Human Physiology II - KCUMB (1 decks)

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