subcortical control of movement

Question 1

what is the Basic layout of the subcortical motor
system

Answer 1

1. spinal cord
2. medulla
3. pons
4. cerebellum
5. midbrain
6. thalamus
7. basal ganglia

Question 2

how do muscles contract

Answer 2

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

Question 3

features of a reflex

Answer 3

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.

Question 4

3 parts of the brain stem + location

Answer 4

the brainstem sits at the top
of the spinal cord and is
made of three parts:
1. medulla
2. pons
3. midbrain

Question 5

what are the 2 important brain stem nuclei groups

Answer 5

reticular formation

vestibular nuclei (VN)

Question 6

what is the vestibular nuclei (VN)

Answer 6

The vestibular nuclei (VN) are the
nuclei for the vestibular system
and are located in the brainstem.

Question 7

what is the reticular formation

Answer 7

The reticular formation is a set of
interconnected nuclei that are
located throughout the brainstem.

Question 8

what is the Vestibulospinal tract

Answer 8

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.

Question 9

what is the vestibular system?

Answer 9

The vestibular system is the
sensory system that provides the
sense of balance and spatial
orientation for the purpose of
coordinating movement with
balance.

Question 10

what is the Vestibulospinal tract function

Answer 10

the function is to alter posture

Question 11

what is the reticular formation?

Answer 11

he reticular formation is a set of
interconnected nuclei that are
located throughout the brainstem.
* It is a very old part of the brain

Question 12

what is the reticulospinal tract

Answer 12

The reticulospinal tract originates in
reticular formation.
* These tracts function in maintaining
tone, balance, and posture

Question 13

functions of the Reticulospinal Tract

Answer 13

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

Question 14

features of the cerebellum

Answer 14

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

Question 15

the 3 parts of the cerebellum

Answer 15

superior cerebellar peduncle

middle cerebellar peduncle

inferior cerebellar peduncle

Question 16

features of the superior cerebellar peduncle

Answer 16

• efferent (out) pathway to the red
  nucleus and the cortex (via the
  thalamus) & sup colliculus.

Question 17

functions of the middle cerebellar peduncle

Answer 17

• most fibres originate in the pons
• input from sensory, visual, vestibular
  and motor systems.
• but its largest input is from the cortex.

Question 18

features of the inferior cerebellar peduncle

Answer 18

carries information to and from the the
spinal cord (and the body) and
vestibular nuclei.

Question 19

The red nueclues

Answer 19

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.

Question 20

location of the rubrospinal fibers

Answer 20

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.

Question 21

where do the rubrospinal fibers terminate

Answer 21

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.

Question 22

functions of the basal ganglai

Answer 22

movement regulation
* skill learning
* habit formation
* reward systems
* selection of appropriate
behaviours
* self-initiation of
behaviours

Question 23

describe the 2 pathways of the BG

Answer 23

he DIRECT pathway
that runs DIRECTLY
through the basal
ganglia

• the INDIRECT
  pathway takes a
  longer loop through
  the basal ganglia

Question 24

features of the direct loop

Answer 24

short loop though the basal
ganglia.
* has excitatory effect on
cortex.
* Net effect is pro-movement.

Question 25

features of the indirect loop

Answer 25

long loop through the basal
ganglia.
* has inhibitory effect on
cortex.
* Net effect is anti-movement.

Question 26

what would happen if the basal ganglia got damaged

Answer 26

damage to the BG produces
states where there is too
much, or too little movement

Question 27

what would damage to the cerebellum do

Answer 27

damage to the cerebellum
produces states where
movements can still be made,
but they are uncoordinated.

Question 28

brain maps

Answer 28

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.

Question 29

3 main cortical motor regions

Answer 29

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.

Question 30

features of the primary motor cortex

Answer 30

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.

Question 31

features of the pre-motor cortex

Answer 31

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.

Question 32

features of the Supplementary motor cortex

Answer 32

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.

Question 33

features of the primary sensory
cortex

Answer 33

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.

Question 34

features of the posterior parietal
cortex

Answer 34

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

Question 35

features of the corticospinal tract

Answer 35

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

Question 36

hierarchy of movement

Answer 36

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.