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Human Physiology II - KCUMB > Exam 2 > Flashcards

Exam 2 Flashcards

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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
Functions of premotor and supplementary motor cortex
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
UMN classification
Classified according to where they synapse in the ventral horn
27
Medial activation system
Innervate postural and girdle muscles
28
Lateral activation system
Associated with distally located muscles used for fine movements
29
Nonspecific activating system
Facilitate local reflex arcs
30
Origin of corticospinal tract
Primary motor cortex Premotor cortex Somatosensory area
31
Pathway of corticospinal tract
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
Lateral corticospinal tract
Made up of corticospinal fibers that have crossed in the medulla Supply all levels of spinal cord
33
Anterior corticospinal tract
Made up of uncrossed corticospinal fibers that cross near level of synapse with LMNs Supply neck and upper limbs
34
Functions of corticospinal tract
Adds speed and agility to conscious movement (esp hand) | Provides a high degree of motor control
35
Where are giant pyramidal cells located?
Motor cortex
36
What results from lesions of the corticospinal tract?
Reduced muscle tone Clumsiness Weakness Not complete paralysis (unless both pyramidal and extrapyramidal systems are involved)
37
Corticobulbar tract
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
Association neurons of the corticobulbar tract
Leave reticular formation and synapse in cranial nerve nuclei Synapse with LMN
39
Red nucleus
Evolutionary primitive portion of the brain | Fibers from the primary motor cortex and branches from the corticospinal tract synapse in the magnocellular portion
40
Magnocellular portion of red nucleus
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
What does stimulation of the red nucleus result in?
Stimulation of flexors | Inhibition of extensors
42
Vestibulospinal tract
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
Utricle
Macula on horizontal plane | Determine orientation of head when it is upright
44
Saccule
Macula on vertical plane | Orientation when lying down
45
Macula
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
Functions of cerebellum
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
Vermis of cerebellum
Location for control functions for muscle movements of the axial body, neck, shoulders and hips
48
Intermediate zone of cerebellum
Concerned with controlling muscle contractions in the distal portions of the upper and lower limbs
49
Lateral zone of cerebellum
Associated with cerebral cortex with planning of sequential motor movements
50
Dentate nuclei, emboliform nuclei and globose nuclei
Lesions in these nuclei lead to extremity ataxia Project to red nucleus Related to limb musculature and fine manipulative movement
51
Fastigial nuclei
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
Granular cell layer
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
Purkinje cell lyer
Middle layer | Made of purkinje cells
54
Molecular layer
Outermost layer | Contains stellate cells, basket cells, purkinje dendrites, golgi type II and axons of granule cells
55
Granular cells
Axons form parallel fibers in cortex (+)
56
Golgi cells
Project from parallel fibers to granular cell bodies (-)
57
Basket cells
Project from parallel fibers to Purkinje axon hillock (-)
58
Stellate cells
Project from parallel fibers to purkinje dendrites (-)
59
Basket cells and stellate cells do what to purkinje cells?
Provide lateral inhibition to provide dampening
60
Purkinje cells
``` Extensive dendritic branching Receive input from parallel fibers Project to intracerebellar nuclei (-) ONLY output from cortex ** Output is always inhibitory ```
61
Climbing fibers
``` 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
Mossy fibers
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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