Download SPHS 4050, Neurological Bases, PP 08b

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project

Document related concepts

Neurocomputational speech processing wikipedia , lookup

Biological neuron model wikipedia , lookup

Allochiria wikipedia , lookup

Optogenetics wikipedia , lookup

Neuroregeneration wikipedia , lookup

Mirror neuron wikipedia , lookup

Neuroeconomics wikipedia , lookup

Apical dendrite wikipedia , lookup

Axon wikipedia , lookup

Neuropsychopharmacology wikipedia , lookup

Synaptogenesis wikipedia , lookup

Environmental enrichment wikipedia , lookup

Neuroanatomy wikipedia , lookup

Axon guidance wikipedia , lookup

Neuromuscular junction wikipedia , lookup

Caridoid escape reaction wikipedia , lookup

Nervous system network models wikipedia , lookup

Central pattern generator wikipedia , lookup

Development of the nervous system wikipedia , lookup

Eyeblink conditioning wikipedia , lookup

Evoked potential wikipedia , lookup

Cognitive neuroscience of music wikipedia , lookup

Basal ganglia wikipedia , lookup

Microneurography wikipedia , lookup

Feature detection (nervous system) wikipedia , lookup

Rheobase wikipedia , lookup

Synaptic gating wikipedia , lookup

Cerebral cortex wikipedia , lookup

Embodied language processing wikipedia , lookup

Premovement neuronal activity wikipedia , lookup

Motor cortex wikipedia , lookup

Transcript
08b
Direct (Pyramidal) Motor
Systems
(Associated with material in Chapter 16)
Overview of the motor systems
• Extrapyramidal systems
– Brainstem to spinal cord (indirect activation)
– Feedback loop to direct system via basal ganglia
• Cerebellar system
– Feedback loop to direct system via cerebellum
• Pyramidal systems (direct activation)
– corticospinal
– corticonuclear (corticobulbar)
Structural components of motor system
• Cerebral cortex
• Subcortical nuclei of the cerebrum: Basal
ganglia
– putamen, caudate, globus pallidus,
subthalamic nucleus and substantia nigra
• Brainstem ( PNS)
• Cerebellum
• Spinal cord ( PNS)
• PNS  Peripheral mechanism
• Pre-frontal association cortex (“executive
•
•
•
•
function”= planning, reasoning, problem
solving) Responsible for deciding when to
move/act, and when not to.
Limbic association cortex (emotion)
provides input to pre-frontal cortex
Posterior parietal cortex synthesizes two
inputs, to make sense of where body is
relative to other objects. Input from
– Primary somato-sensory cortex
– Visual cortex of occipital lobe
Output of posterior parietal cortex and prefrontal cortex sent to pre-motor cortex, so
details of the desired movement can be
programmed there.
Output of pre-motor cortex goes to primary
motor cortex, where the direct motor
pathway starts (cell bodies of start of
efferent pathway are here)
Component of
motor system:
Cortex
Component of motor system: Brainstem
and associated cranial nerves
Cranial nerves (PNS) have
associated nuclei in the brainstem
(CNS), which are organized in
columns/clusters in the brainstem.
Nuclei are groups/clusters of
_____________ in the
______________. This is where
_____________ occur. Cranial
nerves are made of axons. In the
motor system, the cell bodies
associated with these axons are
found in the _________________
of the brainstem. The motor
neuron is the final common
pathway for motor impulses to the
muscles (effectors) of the
face/head.
Components of the motor
system: Spinal cord and
associated spinal nerves
The central gray matter of the
spinal cord is made up of
_____________. This is where
_____________ occur. Spinal
nerves are made of axons. In the
motor system, the cell bodies
associated with these motor
neurons are found in the
_________________ of the spinal
cord, ____________ horns. The
motor neuron (alpha motor
neuron) is the final common
pathway for motor impulses to the
muscles (effectors).
Now that we’ve looked at (revisited) the structural components
that make up the direct, pyramidal
motor systems, let’s look more
closely at these systems.
Remember: Contrast the direct system with
the indirect pathways and basal ganglia
feedback look (which are extra pyramidal)
and the cerebellar feedback loop, which
were covered in the previous lecture.
Pyramidal systems (direct)
• Corticospinal
• Corticonuclear (corticobulbar)
Do you see the
locations of synapses?
Where is the efferent
(motor) pathway?
Example of pathways
Whole bundles of axons course
together in pathways, like those you
see in the illustration above.
How many synapses
are there in this
pathway? How many
bundles/groupings of
neurons make up the
pathway?
In pyramidal (direct activation) pathways , the pathway
is generally made up of two sets of neurons that
convey the efferent impulses caudally
• Upper motor neurons (1st order neurons of the motor
pathway)
– multipolar neuron which functions as interneuron
– cell bodies are in primary motor cortex (pre-central gyrus)
– axons descend
• ….synapse to lower motor neurons (2nd order neurons of the
motor pathway): Multipolar neurons which function as motor
neuron (alpha motor neuron)
– In efferent pathways to head, pharynx, larynx, and muscles
of shoulder shrugging and head turning, cell bodies are in
nuclei of the brainstem, and axons are in the cranial nerves
– In efferent pathways to body, cell bodies are in the central
gray matter, and axons are in the spinal nerves
Major motor system/group: Pyramidal
system
• Pyramidal systems
– Primary, direct activation pathway from cortex to
muscles, under voluntary control
• Corticospinal system
• Corticonuclear system (formerly corticobulbar
system)
– Precise control for small groups of muscles *,
primarily contralateral (some ipsilateral)
– Rapid and precise movement (direct innervation)
* Small group of muscles does not necessarily
mean that the muscles in that group are small!
Cortical origins of
pyramidal system
• Majority of fibers begin in
•
primary motor cortex (precentral gyrus)
Location in the primary
motor cortex depends on
which structure they
control (see homunculus),
e.g.
– legs/feet
– hands
– face and tongue
Pyramidal tracts originate in cortex and consist of
upper motor neurons (1st order) and
lower motor neurons (2nd order)
Do you see how fibers
of upper motor
neuron descend in
corona radiata, then
through internal
capsule?
Example of
corticospinal
Example of
Corticonuclear
(cranial nerve VII=facial nerve)
The facial nerve
(cranial nerve VII)
contains the fibers of
the lower motor
neuron of the
corticonuclear
(cortical bulbar)
pathway for facial
movement
Pyramidal tracts originate in cortex and consist of
upper motor neurons (1st order) and
lower motor neurons (2nd order)
During the descent, the axons of the
upper motor neuron send off collaterals
to the cerebellum (via the pons), as
input for coordination of movement.
In medulla, corticospinal UMN courses
through the pyramids (in medulla),
crossing at pyramidal (motor)
decussation
(to cerebellum)
Example of
corticospinal
Example of
Corticonuclear
(cranial nerve VII
=facial nerve)
Pyramidal innervation
primarily contralateral,
with some ipsilateral
innervation
Fibers
cross
Fibers
don’t
cross
Upper face:
Mostly
contralateral,
some ipsilateral
Contralateral
Ipsilateral
Lower face:
Contralateral
only