Transcript Pathways File - Marjon Moodle

PATHWAYS:
MOVEMENT AND SENSATION
Pedro Amarante Andrade, PhD
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BIOSCIENCES
FOR SPEECH AND LANGUAGE THERAPY
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THE MOTOR SPEECH
SYSTEM
Conceptual level
Planning level
Linguistic
Motor
Motor Programming level
Motor Control circuit
The pathways (direct and indirect)
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MOVEMENT OVERVIEW
• Complex and incompletely understood
• Planned in sensorimotor areas of the cortex
• Is effected by pathways of descending neurons,
under the control of the cerebellum and the
basal ganglia
• Control is achieved through sensory feedback
from muscles/joints
• And information from the eyes and ears (vision
and balance) also influences the motor pathways
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MOVEMENT OVERVIEW
http://www.sofiatopia.org/equiaeon/ibrain12.jpg
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MOVEMENT OVERVIEW
http://7e.biopsychology.com/vs11.html
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VOLUNTARY MOVEMENT
• Although skeletal movement is under our
voluntary control, much of it is automatic
• Speech, chewing, swallowing comes under the
heading of automatic movements that can be
altered voluntarily
• Can be affected by developmental
abnormalities, or acquired brain injury
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CONTROL CIRCUITS
• The cerebellum: coordinates motor and
sensory information
• Gets info from the cortex about what muscles
SHOULD be doing, and compares this with
what is ACTUALLY happening
• The basal ganglia: involved in control of
background movement, and initiation of
movement patterns
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CONTROL CIRCUITS
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LOCATION OF THE BASAL GANGLIA
http://antranik.org/cerebral-white-matter-and-gray-matter-and-basal-ganglia/
https://kin450neurophysiology.wikispaces.com/Basal+Gan
glia+II
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THE DIENCEPHALON
THALAMUS
Principles of Anatomy and Physiology 2012. Tortora G.J. and
Derricskon B.pp. 496
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THE DIENCEPHALON
THALAMUS
https://kin450neurophysiology.wikispaces.com/Basal+Gan
glia+II
Principles of Anatomy and Physiology 2012. Tortora G.J. and
Derricskon B.pp. 511
Conditions: Akinetic mutism and Thalamic aphasia
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CORTICAL REPRESENTATION
OF MOVEMENT
Psychology.wikia.com
HOMUNCULI
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HOMUNCULI
Neuroscience, Third Edition. 2004. Purves et al
pp. 205
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CORTICAL REPRESENTATION
OF MOVEMENT
HOMUNCULI
The primary motor cortex is
somatotopically arranged in
the precentral gyrus with the
body represented upside
down and individual areas
represented out of
proportion to their actual
size
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THE PATHWAYS
The motor pathways:
• Direct and indirect activation pathways
The white matter pathways
The sensory pathways
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SENSORY AND MOTOR
TRACTS
Principles of Anatomy and Physiology 2012. Tortora G.J. and
Derricskon B.pp. 509
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FUNCTIONAL DIVISIONS OF THE
MOTOR SYSTEM
Direct activation
• Upper motor neurons: corticobulbar and
pathway
corticospinal tracts
(pyramidal tracts):
Indirect activation
• Upper motor neurons: corticorubral,
pathway
corticoreticular, rubrospinal, reticulospinal,
(extrapyramidal
vestibulospinal and related tracts
tracts):
• Final common pathway (FCP):
• Lower MNs: generates activity in skeletal (voluntary) muscles
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FUNCTIONAL DIVISIONS OF THE
MOTOR SYSTEM
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DIRECT
PATHWAYS
LCS – 90% Decussate at
Medulla
ACS – 10% not decussate
CB – Control CNs III, IV, V,
VI, VII, IX, X, XI and XII
(some decussate some
don’t)
Principles of Anatomy and Physiology 2012. Tortora G.J. and
Derricskon B.pp. 615
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DIRECT
PATHWAYS
LCS – 90% Decussate at
Medulla
ACS – 10% not decussate
CB – Control CNs III, IV, V,
VI, VII, IX, X, XI and XII
(some decussate some
don’t)
Principles of Anatomy and Physiology 2012. Tortora G.J. and
Derricskon B.pp. 615
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DIRECT
PATHWAYS
THE
CORTICOSPINAL
TRACT
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DIRECT
PATHWAYS
THE
CORTICOSPINAL
TRACT
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DIRECT
PATHWAYS
THE
CORTICOBULBAR
TRACT
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DIRECT
PATHWAYS
THE
CORTICOBULBAR
TRACT
www.eyesthetica.com
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DIRECT PATHWAY
Summary
• Originates in the (predominantly) frontal cortex of each
hemisphere
• Directly connects this cortex to the lower motor neurons
• The upper motor neurons synapse on:
– anterior horn cells in the spinal cord (corticospinal tract)
– cranial nerve nuclei (corticobulbar tract)
• The lower motor neurons emerge at the spinal and bulbar
levels, and activate skeletal muscle
• The ‘express’ route
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DIRECT
PATH.
Summary
www.studyblue.com
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INDIRECT
PATHWAYS
• UMNs synapse
• Helps regulate reflexes & mediates
subconscious automatic muscle activities e.g.
posture and tone
• Many of its activities are inhibitory (i.e.
prevent too much tone/movement)
• The ‘local’ route
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INDIRECT
PATHWAYS
Sometimes called extrapyramidal pathway
• Complex and incompletely understood (esp with
regard to speech pathways)
• Originates in motor, premotor and sensory cortex,
and brainstem
• Composed of numerous short pathways and
interconnected structures (so are polysynaptic)
involving the motor cortex, the basal ganglia, the
limbic system, the thalamus, the cerebellum, the
reticular formation AND nuclei in the brainstem
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INDIRECT
PATHWAYS
Originate in the Cortex:
• Corticoreticular – Cortex to reticular
formation
• Corticorubral – Cortex to red nucleus
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INDIRECT
PATHWAYS
Principles of Anatomy and Physiology 2012. Tortora G.J. and
Derricskon B.pp. 506
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INDIRECT
PATHWAYS
• Rubrospinal - large muscle movement as well as fine motor
control. Terminates cervical spinal cord. Facilitates flexion in
the upper extremities
• Tectospinal - coordinates head and eye movements.
Connects midbrain tectum and spinal cord. Mediates reflex
postural movements of head in response to visual and
auditory stimuli
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INDIRECT
PATHWAYS
Neuroscience, Third Edition. 2004. Purves et al
pp. 395
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INDIRECT
PATHWAYS
• Reticulospinal - descends from reticular formation to
act on the trunk and proximal limb muscles. Involved
mainly in locomotion and postural control but also
connects to CN nuclei responsible for swallowing
• Vestibulospinal – Vestibular nuclei receive
information through vestibulocochlear nerve about
changes in orientation of head. Alter muscle tone,
extend, and change the position of the limbs and
head with the goal of supporting posture and
maintaining balance of the body and head.
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INDIRECT
PATHWAYS
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DIRECT vs
INDIRECT
PATHWAYS
Neuroscience, Third Edition. 2004. Purves et al
pp. 396
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SUMMARY OF DIRECT AND
INDIRECT ACTIVATION PATHWAYS
• Both pathways end on LMNs
• These LMNs receive both excitatory and inhibitory
stimulation from both pathways
• The sum of this input determines the final response of
an individual neuron in the pathway
• The indirect pathway provides the framework (muscle
tone, posture, regulation of reflex activity)
• The direct pathway accomplishes the skilled, discrete
muscle actions
• The LMNs are referred to as the final common
pathways or FCP
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HIND BRAIN +
BRAINSTEM
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NUCLEI
http://what-when-how.com/neuroscience/
the-cranial-nerves-organization-of-the-central
-nervous-system-part-1/
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NUCLEI
http://www.nature.com/gimo/contents/pt1/fig
_tab/gimo2_F2.html
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NUCLEI
CN nuclei lie
at the same
level that
the nerve
enters or
leaves the
brainstem
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WHITE MATTER PATHWAYS
There are three types of white matter pathway:
• Commissural
• Association
• Projection
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WHITE AND GREY MATTER
• White matter = highways for information flow
in the NS
• Grey matter = receives and integrates
incoming and outgoing information
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...COMMISSURAL WHITE MATTER
PATHWAYS
• Commissural white matter pathways connect the 2
hemispheres. The largest is the corpus callosum,
with its posterior splenium, central body or trunk,
anterior genu, and ventrally directed rostrum.
• Besides the corpus callosum, commisural white
matter pathways include the anterior commisure
which connects the olfactory &
temporal regions,
and the posterior commisure
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...PROJECTION WHITE MATTER
PATHWAYS
• White matter projections consist of long tracts
which connect the cortex with the brainstem and
spinal cord
• These long tracts both ascend and descend.
• The corona radiata consists of projection tracts
running to and from the cortex
• The projections converge at the internal capsule
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www.leonidzhukov.ru
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ASSOCIATION WHITE MATTER
PATHWAYS
• Connect cerebral areas within each hemisphere.
• Association pathways are generally bidirectional.
• Association pathways contain short association fibres known
as "U" or arcuate fibres that link adjacent cortical gyri.
• Long association fibres, all of which terminate in the frontal
lobe, include these 5 types: the cingulate, the arcuate
fasciculus, the superior occipitofrontal fasciculus, the inferior
occipitofrontal fasciculus, and the uncinate fasciculus.
• The degree and integrity of neural myelination significantly
influences the speed and efficiency of action potential
propagation.
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PARALYSED MAN WALKS AGAIN
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CORTICAL ANATOMY OF THE MOTOR
SYSTEM
Right
UMN
Right
LMN
Left
UMN
Left
LMN
http://www.sofiatopia.org/equiaeon/ibrain12.jpg
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CORTICAL ANATOMY OF THE MOTOR
SYSTEM
Blood flow
to this region
increases
prior to
movement
actually
occurring
suggesting a
role in
planning the
movement
flow
http://www.sofiatopia.org/equiaeon/ibrain12.jpg
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CASE STUDIES
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CASE 1:
JANE, 17, SUFFERED A C7 SPINAL
CORD INJURY AFTER FALLING FROM
HER HORSE
• Will she exhibit a knee jerk reflex when the
patellar tendon is stretched?
• What will she feel?
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SOME CLUES
• You will need to refer to the pathway in this
particular stretch reflex, and consider the spinal level
involved
• You will need to research the main sensory
pathways which run from the periphery
to the cortex
• Then consider how spinal injury might
affect these pathways
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The diagram illustrates the position of the major
ascending (sensory) and descending (motor) tracts in the
upper spinal cord
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Case 2: Joyce, 74, has had a stroke.
The CT scan shows an infarct in the posterior
limb of the left internal capsule
• What will be the likely effects of this stroke?
• Will her signs and symptoms be of upper
motor neuron or lower motor neuron
damage?
• Will they be contralateral or ipsilateral to the
lesion side?
• List the common signs of both upper and
lower motor neuron damage
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THE CLUE
• Lies in the direct pathway..study this closely
and identify the internal capsule….you may
need to magnify (hint!)
“Elementary, my dear Watson!”
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AN EXAMPLE OF SOMATOTOPIC
ORGANISATION
www.stanfordmedicine25.stanford.edu
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GEORGE, 11, BELL’S PALSY
Or he could be any one
of a number of young
people
with this condition
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BELL’S PALSY
•
•
•
•
Why is it called Bell’s palsy?
What causes it?
Where is the lesion?
Use the ppt slides supplied, your texts and
watch the You Tube materials on the following
slides to help you
• Can it be treated?
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HERE IS YOU CLUE
www.nature.com
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AND MORE CLUES…..
Unilateral UMN v Bells’ palsy
http://www.youtube.com/watch?v=L8hIWPYm6
VE
• http://www.youtube.com/watch?v=UpoOhRO1N0
An explanation of the origin of bulbar v
pseudobulbar palsy
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LATERAL MEDULLARY SYNDROME
• What part of the medulla is affected?
• Why does the patient lose pain and temperature
sensation on the opposite side of the body to the
lesion, but on the same side of the face as the
lesion?
• What are some possible causes?
• What are the other symptoms?
SLTs can be involved in the care of
people with lateral medullary
syndrome
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QUIZ
The three broad classes of movement are
– Reflexes, rhythmic movement and voluntary
movement
• Can you give an example of each class?
• All movement is monitored and controlled via
our senses
• What are the main external and internal
sources of sensory information?
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STUDY THE STRETCH REFLEX
• Revise the structure and function of the
muscle spindle (see lecture 3, Nerves, Muscles
and How They Work)
• Watch the video or review the pathways
involved in the stretch reflex:
• http://www.youtube.com/watch?v=HfuhVWK
8C0U
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NOTE THE TERMS:
• Agonist/antagonist
• Interneuron
• Reciprocal innervation
• If you are unfamiliar with these terms through
your reading, then look them up and write
some definitions now
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PARTICULAR RELEVANCE TO SLT:
• To perform accurate movements, information re
the range, rate and force of contraction, and
position of the muscles, is essential.
• Muscle spindle actions are involved in controlling
the rapid and fine muscle movements required
for speech.
• Sensory nerves from muscle spindles send out a
continuous stream of impulses to the CNS
• Muscle tone is maintained via these feedback
mechanisms
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Why does this reflex involve contralateral pathways?
www.bio.davidson.edu
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THE CORTICAL AREAS RESPONSIBLE
FOR MOVEMENT AND SENSATION
• What is meant by a motor/sensory
homunculus?
– What areas have the most representation?
– What are the main differences you notice between
the two homunculi?
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