Lecture 5.1 Flashcards
(126 cards)
1
Q
decussate definition
A
cross over from one side of the CNS to the opposite side
2
Q
ipsilateral definition
A
the same side
3
Q
contralateral definition
A
the opposite side
4
Q
afferent definition
A
ascending, input (sensory)
5
Q
efferent definition
A
descending, output (motor)
6
Q
spinal somatic sensory systems function
A
mediate touch, limb position senses, pain, itch, and temp senses
7
Q
spinal somatic sensory system first stage
A
sensory neurons or specialized sensory receptor cells of the body detect changes in the body and environment
8
Q
spinal somatic sensory systems stage two
A
sensory information is sent to the central nervous system through the spinal cord and brainstem
9
Q
spinal somatic sensory system stage 3
A
sensory info is relayed through the thalamus to the primary sensory cortex in the parietal lobe or cerebellum
10
Q
what do stimuli characteristics do receptors encode?
A
nature (modality), location, intensity, and duration of stimuli
11
Q
what sensations are encoded from sensory receptors?
A
5 senses, balance, position, pain, sensory info from internal organs
12
Q
kinds of sensory receptors
A
chemoreceptors, photoreceptors, mechanoreceptors, nociceptors
13
Q
chemoreceptors
A
“chemical sensory”, smell, taste, internal stimuli like pH
14
Q
photoreceptors
A
“light sensors,” visual receptors of the retina
15
Q
mechanoreceptors
A
most varied type, respond to physical deformation, cutaneous receptors for touch, muscle length and tension, auditory and vestibular
16
Q
nociceptors
A
pain receptors, noxious or obnoxious
17
Q
what general categories can the sensory receptors be in?
A
- a neuron that has a free nerve ending (dendrites) embedded in a tissue (fine touch/pain/temp)
- a neuron that has dendrites encapsulated in connective tissue (crude touch/pressure)
- specialized receptor cell w/ distinct structural components that interpret a specific type of stimulus (specialized for light)
18
Q
accumulation of axons
A
- greater distribution of white matter ascending the spinal cord
- more sensory axons added from periphery; fully intact motor tracts that have not branched off yet
19
Q
descending white matter tracts
A
pyramidal tracts, extrapyramidal tracts
20
Q
ascending white matter tracts
A
dorsal column medial lemniscus system, spinocerebellar tracts, spinothalamic tract
21
Q
two pyramidal tracts
A
lateral corticospinal tract, anterior corticospinal tract
22
Q
four extrapyramidal tracts
A
rubrospinal tract, reticulospinal tract, vestibulospinal tract, tectospinal tract
23
Q
two dorsal column medial lemniscus system tracts
A
gracile fasciculus, cuneate fasciculus
24
Q
three spinocerebellar tracts
A
posterior spinocerebellar tract, anterior spinocerebellar tract, cuneocerebellar tract
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two spinothalamic system tracts
lateral spinothalamic tract, anterior spinothalamic tract
26
what three anatomical principles are neurons in the sensory tract arranged according to
1. sensory modality
2. somatotropic
3. medial-lateral rule
27
sensory modality
different types of sensory info travel through distinct sensory pathways
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sensory modality DELETE
different types of sensory info travel through distinct sensory pathways
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somatotropic anatomical principle
ascending tracts are organized according to site of origin (body map)
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medial-lateral rule
sensory neurons that enter a low level of the spinal cord are more medial within the spinal cord/ sensory neurons that enter at a higher level of the spinal cord are more lateral within the spinal cord
31
which three neurons do ascending sensory signals travel through
1. first order
2. second order
3. third order
32
where do spinocerebellar tracts terminate
in the cerebellum rather than traveling to the thalamus and cortex
33
where do dorsal column medial lemniscus and spinothalamic tracts travel
thalamus and cortex
34
where does the gracile fasciculus transmit info from
lower body, all spinal levels
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where does cuneate fasciculus transmit info from
upper body, only cervical
36
what kind of information does the dorsal (posterior) column medial lemniscus (DCML) pathway transmit
- conscious proprioception (joint position)
- vibration
- discriminative (fine) touch
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where does DCML pathway terminate
somatosensory cortex
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what does the DCML third order neuron synapse with
the ventral posterolateral thalamus (VPL)
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where do 2nd order DCML neurons synapse in
dorsal column nuclei (gracile or cuneate nucleus) in the medulla (brainstem), and decussates to contralateral side
40
where does decussation occur for DCML pathway, if it occurs
medulla
41
characteristics of DCML tracts
only two separate tracts within the spinal cord; they decussate in the brainstem and travel as one pathway (the medial lemniscus) up to the thalamus and to the cortex
- carry the same kind of info in the spinal cord
42
what distinguishes the two DCML tracts
the origin of their input from the PNS
43
what are the spinothalamic tracts (anterolateral system) responsible for
transmitting crude touch, pressure, temp, pain
44
where do the anterior spinothalamic and lateral spinothalamic tracts decussate
in the spinal, cord, but at different locations
45
what kind of info does the anterior spinothalamic tract carry
pressure, light/crude touch
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what kind of info does the lateral spinothalamic tract carry
pain, temp
47
what is the path the anterolateral system takes
brainstem --> thalamus in the same column --> somatosensory cortex
48
where is the 2nd order anterolateral system neuron found
spinal cord
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where do the 2nd and 3rd order neurons synapse FOR WHAT????
ventral posterolateral thalamus (VPL)
50
where does the anterolateral system terminate
the contralateral somatosensory cortex
51
somatotopic organization
where the secondary neuron in the thalamus project to in the somatosensory cortex depends on where the corresponding sensory neuron in the body originated
52
what are the spinocerebellar tracts responsible for
transmitting unconscious proprioception from muscles, tendons, joints; muscle tone; balance
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posterior spinocerebellar tract origination
lower body
54
posterior spinocerebellar tract decussation characteristics
stays ipsilateral to the side of the body that it enters
- uncrossed tracts enter the cerebellum via the inferior cerebellar peduncles (medulla)
55
cuneocerebellar tract origination
upper bod
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cuneocerebellar tract decussation characteristics
stays ipsilateral; uncrossed tracts enter cerebellum via inferior cerebellar peduncles (medulla)
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anterior spinocerebellar tract origination
lower body
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anterior spinocerebellar tract decussation characteristics
decussates in the spinal cord at the level of entry but decussates again in the brainstem to return to the ipsilateral side of the brain
- enters cerebellum via superior cerebellar peduncles
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posterior spinocerebellar tract neuron locations
1st order: enters spinal cord (lower body), 2nd order: within spinal cord (Clarke's nucleus); no 3rd order neuron
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cuneocerebellar tract neuron locations
1st order neuron: enters spinal cord (upper body), 2nd order neuron: medulla
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anterior spinocerebellar tract neuron locations
1st order neuron: enters spinal cord (lower body), 2nd order neuron: within spinal cord, no 3rd order neuron
62
why do the spinocerebellar tracts not have 3rd order neurons
all tracts terminate in the ipsilateral cerebellum (not the cortex), so no 3rd order neurons
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characteristics of descending tracts
- the pathways by which motor signals are sent from upper motor neurons in the cortex to lower motor neurons
- lower motor neurons then directly innervate muscles to produce movement
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descending pathway synapses
no synapses within the descending pathways
- at the termination of the descending tracts, the first order upper motor neurons synapse with a lower motor neuron within the brainstem or spinal cord
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where are the lower motor neuron cell bodies
within the CNS
- send fibers out into the PNS to make direct connections with muscles, glands, etc
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where do the pyramidal tracts originate
cerebral cortex
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pyramidal tracts function
- carrying motor fibers to the brain stem and spinal cord
- responsible for the voluntary control of muscles
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extrapyramidal tract origination
brain stem
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extrapyramidal tract function
- carrying motor fibers to the spinal cord
- responsible for the involuntary and automatic control of muscles (muscle tone, balance, posture, and locomotion)
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what are the pyramidal tracts
corticospinal tracts, corticobulbar tracts
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corticospinal tracts
lateral corticospinal tract, anterior corticospinal tract
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what are the extrapyramidal tracts
vestibulospinal, reticulospinal, rubrospinal, tectospinal
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vestibulospinal tracts
medial and lateral
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reticulospinal tracts
medial/pontine and lateral/medullary
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why are the pyramidal tracts named that way
they pass through the pyramids in the medulla
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what are the pyramidal tracts responsible for
voluntary control of the muscles of the face and body
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corticospinal tracts function
supply muscles of the body
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corticobulbar tracts function
supply muscles of the head, neck, and face
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corticospinal tracts path
cerebral cortex --> internal capsule --> brainstem
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where does the corticospinal tract divide into two
most caudal part of the medulla
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lateral corticospinal tract path after dividing from the corticospinal tract
decussates in the pyramids --> spinal cord --> terminates in ventral horn --> lower motor neurons of the spinal cord supply distal muscles (limbs)
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medial corticospinal tract path after dividing from the corticospinal tract
spinal cord --> decussates in the cord --> terminates in ventral horn --> supply proximal muscles (trunk)
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where do the lateral corticospinal tract neurons project to
distal muscles (limbs)
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where do the medial corticospinal tract neurons project to
proximal muscles (trunk)
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where do corticobulbar tracts arise from
the lateral primary motor cortex
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where do corticobulbar tract fibers converge
internal capsule --> brainstem
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where do corticobulbar neurons terminate
bilaterally on the motor nuclei of the cranial nerves in the brainstem
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where do corticobulbar tract neurons synapse
with lower motor neurons that transmit to muscles of the head, face, and neck
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where do the extrapyramidal tracts originate
brainstem
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where do the extrapyramidal tracts carry motor fibers to
spinal cord
90
what are the extrapyramidal tracts responsible for
involuntary and automatic control of muscles (muscle tone, balance, posture, and locomotion)
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which extrapyramidal tracts do not decussate and have ipsilateral innervation
vestibulospinal, reticulospinal
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which extrapyramidal tracts decussate and have contralateral innervation
rubrospinal, tectospinal
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where do the vestibulospinal pathways arise from
the vestibular nuclei
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vestibular nuclei
receives inputs from the organs of balance in the inner ear and CN8
95
what is the vestibulospinal tract responsible for
upright posture and head stabilization
- detects small movements of the body, motor signals are sent via the vestibulospinal tract to specific muscles to counteract these movements to stabilize the body
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medial vestibulospinal pathway projection
from medial vestibular nucleus to the cervical spinal cord
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medial vestibulospinal pathway function
stabilizing head position by innervating the neck muscles
- bilateral
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lateral vestibulospinal pathway projection
lateral vestibular nucleus to motor signals to extensor muscles in the legs
99
lateral vestibulospinal pathway function
helps maintain upright and balanced posture
- stays ipsilateral
100
what do the reticulospinal tracts do
coordinate automatic/involuntary movements of locomotion and posture control
101
where do the reticulospinal tracts originate
different parts of the reticular formation of the brainstem
102
medial reticulospinal tract (MRST) origination
reticular formation in the pons
103
lateral reticulospinal tract (LRST) origination
reticular formation in the medulla
104
characteristics of both reticulospinal and vestibulospinal tract decussation
both remain ipsilateral and terminate at different levels in the spinal cord
105
what kind of information does the MRST carry
info for controlling extensor motor neurons, enabling the extension of the legs to maintain postural support and contributes to patterned movements (eg stepping)
106
what kind of information does LRST carry
info for controlling flexor motor neurons, inhibiting the MRST extensor muscles and enabling modulating of the stretch reflex
107
where does the tectospinal tract originate
the superior colliculus in the midbrain
108
what composes the tectum
superior and inferior colliculi
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what kind of information does the superior colliculus receive
input from optic nerves
110
where do the tectospinal tract neurons decussate
at the level of the midbrain
111
where does the tectospinal tract terminate
cervical levels of the spinal cord
112
what is the function of the tectospinal tract
coordinates movements of the head in relation to visual stimuli
113
where does the rubrospinal tract originate
red nucleus in the midbrain
114
where do the rubrospinal tract fibers decussate
level of the midbrain and descend into the cervical spinal cord with a contralateral innervation
115
what function does the rubrospinal tract fibers have
fine control of hand movements
116
which descending tracts originate in the cortex?
pyramidal tracts: corticospinal tract (lateral corticospinal tract, anterior corticospinal tract), corticobulbar tracts
117
other name for primary motor cortex
precentral gyrus
118
other name for primary sensory cortex
post-central gyrus
119
which important areas of motor association cortex lie anterior to the primary motor cortex
supplemental motor area and the premotor cortex
120
what are the supplemental motor area and the premotor cortex involved in
higher order motor planning and they project to the primary motor cortex
121
where are the primary sensory and motor areas located
on either side of the central sulcus
122
primary motor cortex function
execution of movement
123
supplemental motor cortex function
execution of sequences of movement (attainment of motor skills - in coordination with the cerebellum)
124
premotor cortex function
planning of movement
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