subcortical control of movement Flashcards
what is the Basic layout of the subcortical motor
system
- spinal cord
- medulla
- pons
- cerebellum
- midbrain
- thalamus
- basal ganglia
how do muscles contract
Stretching a muscle is detected in the muscle and
leads to increased activity in sensory neurones that in
turn leads to an increase in the activity of motor
neurons that innervate the same muscle, while
inhibiting the motor neurons that innervate
antagonists
features of a reflex
rapid automatic control of movement.
* little or no voluntary control.
* some are very simple:
* stretch reflex.
* some are more complex:
* swallowing, breathing.
* these mainly happen in the spinal cord and low in the brain
stem.
3 parts of the brain stem + location
the brainstem sits at the top
of the spinal cord and is
made of three parts:
1. medulla
2. pons
3. midbrain
what are the 2 important brain stem nuclei groups
reticular formation
vestibular nuclei (VN)
what is the vestibular nuclei (VN)
The vestibular nuclei (VN) are the
nuclei for the vestibular system
and are located in the brainstem.
what is the reticular formation
The reticular formation is a set of
interconnected nuclei that are
located throughout the brainstem.
what is the Vestibulospinal tract
The vestibulospinal tract originates
in the vestibular nuclei. They send
most of their output to the spinal
cord and to the muscles that move
the eyes.
what is the vestibular system?
The vestibular system is the
sensory system that provides the
sense of balance and spatial
orientation for the purpose of
coordinating movement with
balance.
what is the Vestibulospinal tract function
the function is to alter posture
what is the reticular formation?
he reticular formation is a set of
interconnected nuclei that are
located throughout the brainstem.
* It is a very old part of the brain
what is the reticulospinal tract
The reticulospinal tract originates in
reticular formation.
* These tracts function in maintaining
tone, balance, and posture
functions of the Reticulospinal Tract
the reticulospinal tract functions to maintain
our posture. Before we lift a weight with our
arm, muscles of the leg are excited to
support our body posture. This postural
control is via the fast-acting excitatory
action of the reticulospinal tract
features of the cerebellum
the cerebellum has a very
conserved, highly folded
structure in all animals
* 10% volume of the brain.
* More than neurones than
the cortex.
* 69B v 16B
* input:output connections
ratio.
* 40:1
the 3 parts of the cerebellum
superior cerebellar peduncle
middle cerebellar peduncle
inferior cerebellar peduncle
features of the superior cerebellar peduncle
- efferent (out) pathway to the red
nucleus and the cortex (via the
thalamus) & sup colliculus.
functions of the middle cerebellar peduncle
- most fibres originate in the pons
- input from sensory, visual, vestibular
and motor systems. - but its largest input is from the cortex.
features of the inferior cerebellar peduncle
carries information to and from the the
spinal cord (and the body) and
vestibular nuclei.
The red nueclues
The red nucleus is a roughly spherical
collection of cell bodies in the midbrain.
It is called the red nucleus because it is
extremely vascular. In fresh tissue the
red nucleus is distinctly pinker than the
surrounding tissue.
The red nucleus receives a very large
input from the cerebellum and from the
primary motor cortex.
location of the rubrospinal fibers
rubrospinal fibers that originate in the red
nucleus cross the midline immediately after
exiting the nucleus. Then they course in the
ventrolateral part of the brainstem to the cord.
In the cord rubrospinal fibers occupy the same
part of the white matter as the corticospinal
tract.
where do the rubrospinal fibers terminate
Rubrospinal fibers terminate primarily in the
cervical and lumbar enlargements of the
cord, which contain motor neurones for
muscles in the fore- and hindlimbs,
respectively.
functions of the basal ganglai
movement regulation
* skill learning
* habit formation
* reward systems
* selection of appropriate
behaviours
* self-initiation of
behaviours
describe the 2 pathways of the BG
he DIRECT pathway
that runs DIRECTLY
through the basal
ganglia
- the INDIRECT
pathway takes a
longer loop through
the basal ganglia
features of the direct loop
short loop though the basal
ganglia.
* has excitatory effect on
cortex.
* Net effect is pro-movement.
features of the indirect loop
long loop through the basal
ganglia.
* has inhibitory effect on
cortex.
* Net effect is anti-movement.
what would happen if the basal ganglia got damaged
damage to the BG produces
states where there is too
much, or too little movement
what would damage to the cerebellum do
damage to the cerebellum
produces states where
movements can still be made,
but they are uncoordinated.
brain maps
Because of the close
relationship with the body
surface & muscles, both the
primary sensory and motor
cortex have detailed
somatotopic maps of the body in
them.
* Areas of the body with many
highly innervated muscles and
densely packed sensory
receptors have expanded
representations in the brain.
3 main cortical motor regions
1) neurones increase their firing rates before
movements and specific features of this activity are often closely related to specific movement features,
2) neurons
send their axons to terminate in motor centres in the brainstem and spinal cord,
3) electrical stimulation in these
areas elicits movements,
4) neurones send their axons to connect most densely with other motor areas.
features of the primary motor cortex
Neurones in the primary motor cortex
have a simple relationship to movement.
They fire around 5 to 100 ms before
movement onset and can code for the
basic parameters of movement, i.e.:
* Force.
* Direction.
* Extent.
* Speed.
features of the pre-motor cortex
a more complex relationship to
movement. They code for the more complex
aspects of movement, for example:
* planning movement.
* spatial guidance of movement.
* sensory guidance of
movement.
features of the Supplementary motor cortex
more complex aspects of
movement. They code for the more
complex aspects of movement, for
example:
* coordinating temporal sequences of
actions.
* bimanual coordination.
* initiation of internally generated as
opposed to stimulus driven
movement *NB – the SMA is well
connected to the basal ganglia.
features of the primary sensory
cortex
touch: vibration, heat, pain, pressure.
* Proprioception: Afferent information, including
joint position sense, kinesthesia, and sensation
of resistance:
* Joint position sense: The ability to
recognize joint position in space.
* Kinesthesia: The ability to appreciate and
recognize joint movement or motion.
* Sensation of resistance: The ability to
appreciate and recognize force generated
within a joint.
features of the posterior parietal
cortex
integration of sensory, visual
information to execute complex
movement in the environment.
* representations for different motor
effectors (e.g. arm vs. eye)
* a command apparatus for operation
of the limbs, hands and eyes within
immediate extrapersonal space
features of the corticospinal tract
The most important tract in the
human for precise control of the
limbs.
* Origin:
* primary motor cortex (30%)
* Premotor, supplementary (30%)
* Somatosensory, parietal,
cingulate (40%)
* About 1 million fibers in humans.
* 90% cross at lower medulla
* All are excitatory
hierarchy of movement
the complexity of the movements the
nervous system controls increases as you
move toward (and through the brain):
spinal cord – simple reflexes.
medulla – complex reflexes.
cerebellum – coordinated movement.
basal ganglia – programmed movements.
cortex – complex conscious movements.
