Download Neural Basis of Motor Control

Neural Basis of Motor Control
Chapter 4
Neurological Perspective
“A basic understanding of the physiology
underlying the control of voluntary
movement establishes a more
comprehensive appreciation and
awareness of capabilities and limitations of
the people with whom a practitioner
works.” (Magill, pg 65)
Nervous System
Nerves (Neurons) inside or outside the:
–  Central Nervous System (Nerves inside)
•  Brain and
•  Spinal cord
–  Peripheral Nervous System (Nerves outside
CNS)
•  Efferent nerves (motor)
•  Afferent nerves (sensory)
Neural Activity
The focus of this chapter will be how the
nervous system controls voluntary,
coordinated movement.
Concept 1: The Neuron
•  Neuron are similar to other cells
It has a cell membrane, a nucleus that contains genes, contains
cytoplasm, mitochrondria, and organelles. It carries out basic cellar
processes such as protein synthesis and energy production
Neuron: Basic Unit of CNS
•  Neuron is a nerve
Axon takes information away
from the cell body (soma)
- the neuron has only one
Dendrites bring information to
the cell body (soma)
-neuron may have none
to as many as 1000
dendrites
Summary of Differences
Axons
Dendrites
•  Take information away
from the soma
•  Generally only 1 axon per
cell
•  No ribosomes
•  Can have myelin
•  Branches further from the
soma
•  Bring information to the
soma
•  Rough surfaces (dendritic
spines)
•  Many dendrites per cell
•  Has ribosomes
•  No myelin insulation
•  Branches are near the
soma
Concept 2: Types of Neurons
Neurons are classified by direction that
they send information:
1.  Sensory (afferent) neurons sends information from
sensory receptors (e.g. skin, eyes, ears)
2.  Motor (efferent) neurons sends information AWAY
from the CNS to muscles or organs.
3.  Inter-neurons: send information between sensory and
motor neuron; most are located in CNS.
Sensory Neurons
•  They are unipolar, that is, they have no
dentrites and only one axon.
•  Most sensory neuron are in the peripheral
nervous system
Motor Neuron
•  Two types
–  Alpha motor neurons (predominately in spinal
cord and referred to as the motor horn cells).
Has many dendrites and long branch axons
that connects directly to skeletal muscle
fibers.
–  Gamma motor neurons supplies a portion of
skeletal muscle called intrafusal fibers.
Interneurons
•  Originate and terminate in the brain or
spinal cord
•  They function as connections between
axons descending from the brain.
•  They synapse on motor neurons and
axons from sensory nerves and spinal
nerves ascending to the brain.
Concept 3: Central Nervous
System
•  Functions as the command center
•  Comprises the the brain and spinal cord
•  Integrates and organizes sensory and
motor information to control movement
CNS Components most
involved in Motor Control
•  Cerebrum
•  Diencephalon
•  Cerebellum
•  Brainstem
Cerebrum
• 
• 
• 
• 
Divided into two the right and left cerebral hemispheres
Each hemisphere is covering with gray matter of 2-5 mm thick, folded tissue
of nerve cell bodies called the cerebral cortex
The gray matter contains neurons that send signals from the cortex to other
parts of the CNS (pyramidal cells) or non pyramidal cells.
Each hemisphere of the cortex consist of four lobes
Parietal
Occipital
Frontal
Temporal
Sensory-Specific Areas (Figure 4.4 below)
Proximity of primary sensory and motor cortex areas and their
association areas allows interaction between perceptual and higherorder cognitive functions.
Diencephalon
• 
Diencephalon (contains the thalamus
& Hypothalamus) lies between
cerebrum and the brainstem
–  Hypothalamus lies under the Thalamus
controls the endocrine and the body
homeostasis including temperature, hunger,
thirst, and regulation of carbohydrate energy
use.
–  Thalamus is a relay station for sensory and
motor information that transmits pulses from
one cerebral hemisphere to another and
interconnects the other areas of the brain,
plays important roll in controlling attention,
mood, & perception of pain.
Thalamus
Hypothalamus
Cerebellum
1.  Attaches to the brain stem & Located behind the cerebral hemispheres
2.  Regulates the accuracy & smoothness of movement.
3.  Controls eye-hand movements
4.  Movement timing
5.  Posture Control
6.  It detects errors and corrects errors in movement*
cerebellum
Important Subcortical Component
• 
Basal ganglia plays critical role in
planning and initiating movement,
control of antagonist muscles during
movement, and the control of force.
• 
People with Parkinson’s disease and
cerebral palsy affect the basal
ganglia’s functions
• 
People with basal ganglia limitations
experience:
– 
– 
– 
– 
Bradykinesia (slow movements)
Akinesia (reduced amount of movements)
Tremor
Muscular rigidity
Basal ganglia
Concept 4: The Brain Stem
•  Consists of the pons, medulla or medulla
oblongata, and reticular formation
Pons
1.  Pons considered to be part of the brainstem.
2.  Top of the brain stem
3.  Bridge between cerebral cortex and cerebellum
4.  Connects the two hemispheres of the cerebellum
5.  Acts as a relay for the auditory system and movement
6.  Involved in controlling chewing, swallowing, salivating, and respiration
7.  Plays a role in balance
Pons
Medulla or Medulla Oblongata
1.  Considered to be part of the brainstem
2.  Serves as regulatory agent for various internal physiologic processes such as heart
beat, respiration, and gastrointestinal functions.
3.  Site where sensory (ascending) and motor neural (descending) pathways cross over
the body midline and merge on their way to the cerebellum and cerebral cortex.
medulla
Reticular Formation
Located just above pons and
contains the reticular formation
which is considered to be part of
the brainstem)
Plays a major role in arousal,
consciousness, states of sleep,
and relaxation
Primary role is as an integrator
of sensory and motor neural
impulses, that is, inhibits or
increases neural impluses which
in turn influences skeletal
muscle activity.
Reticular
Concept 5: Limbic system
Limbic system controls
behaviors including emotions,
motivation, and learning which
provides impetus for goal
directed movement in
environmental contexts.
Pleasure center of the brain.
Consists of the frontal and
temporal lobes of cerebral
cortex, thalamus,
hypothalamus, and
interconnections nerves of
CNS
Hummm! How does this all
relate to learning a motor skill?
•  http://med.stanford.edu/alumni/media/
video/jennifer-raymond.html
Two major portions of the spinal
cord are the gray and white
matter.
Gray matter is butterfly shape,
central part of spinal cord,
containing 2 pairs of horns.
Dorsal horn involve cells are
involved in transmitting sensory
information.
Ventral horns contain Alpha Motor
Neuron whose axons terminate
on skeletal muscles.
Spinal cord contains interneurons
call Renshaw cells. Nerve fibers
descend from the brain terminate
on interneurons which influence
Alpha Motor Neuron activity.
Concept 6: Spinal Cord
Concept 7: Transportation of sensory information to
the brain
•  Sensory neural pathway (ascending track)
–  Passes through the spinal cord to brain stem to
thalamus to the sensory areas of cerebral cortex and
to the cerebellum
–  There are different specific ascending tracks:
•  Vision has it’s own track to the cerebral cortex
•  Audition has it own track to the cerebral cortex
•  Sensory information has it own tracks to the cerebral cortex.
–  Ascending tracks cross at the brain stem from one
side of the body to another which means information
from one side of the body is received in the opposite
side of the brain.
Next Slide
Concept 8: Transportation of Movement
information from the Brain to the Muscles
•  Motor neural pathway. Transport of movement
information (descending track) that will execute
the movements:
–  Two distinct pathways that function together
•  Pyramidal (corticospinal tract)
–  Transmits neural information that arises from the cerebral
cortex with axons projecting into the spinal cord that cross over
to the opposite side of the body.
–  Primarily associated with fine motor skills (mostly discrete in
nature or what neural scientists call – fractionated movements).
•  Extrapyramidal (brainstem pathways)
–  Transmits neural information that arises in the brainstem with
axons descending into the spinal cord with many of fibers not
crossing over to the opposite side of the body
–  Chiefly found in the reticular formation of the pons and medulla.
–  Primarily associated with postural control and muscle control of
flexion and extension of hands and fingers.
Concept 9: Motor Unit
The end of transmission of motor
neural information is the motor unit.
Commonly defined as the Alpha
motor neuron and muscle fibers it
innervates (motor unit)
Connection between an Alpha motor
neuron and skeletal muscle occurs at
the neuromuscular junction located
at the middle of the muscle.
This synapse allows nerve impulses
to be transmitted so he muscle
contracts and movement occurs.
Alpha Motor Neuron
Concept 10: Performing a Voluntary Motor
Skills
Neural system is hierarchical
organized.
1.  One needs to have cognitive
intent to move.
2.  Various structures work both
hierarchically (top-down or
down-up) and in parallel
(same time).
3.  Different neural activity occurs
when we perform different
skills.
THE END