The Motor System Flashcards
Areas of importance for Motor System
Basal Ganglia
Cerebellum
Motor Cortex
Brainstem Centres
Spinal Cord and Brainstem Circuits
Basal Ganglia and movement
Gating proper initiation of movement
A regulatory system
Cerebellum in motor system
Sensory motor coordination
A regulatory system
Motor Cortex in Motor system
Planning initiating and directing voluntary movements
Receives input from regulatory systems
Brainstem centres in the motor system
Basic movements and postural control
Where are action potentials initiated in the motor system?
Corticospinal tract
Upper Motor Neurons
CNS and PNS
Where are muscular contractions initiated in the motor system?
Neuromuscular junction
Lower Motor Neurons
PNS
Where is movement execution initiated in the motor system?
Basal ganglia
Muscles
Cerebellum
Spinal cord
CNS and PNS
Where is sensory feedback initiated in the motor system?
Dorsal column pathways
Sensory neurons
Spinocerebellar pathways
CNS and PNS
Where is neuronal activity initiated in the motor system?
Supplementary motor area
Motor cortex
Premotor cortex
CNS
Role of the motor cortex
Its functions are voluntary movements, skill acquisition and motor learning.
Neural encoding for direction control and movement speed
Main pathways in the motor system
The corticospinal and the pyramidal tracts.
Motor Maps
Motor maps are necessary for body part representation and somatotopic
Role of the Basal Ganglia
Comprise 4 interconnected nuclei that influence behaviour by regulating the activities of the upper motor neurons
Receives input from the motor cortex, sensory feedback and other brain areas. It sends signals to the thalamus and the motor cortex.
Nuclei of the basal ganglia
Striatum
Globus Pallidus
Subthalamic nucleus
Substantia nigra
Striatum
Composed of the caudate nucleus and the putamen nucleus.
Where the information comes to, then is processed by the other nuclei
Globus Pallidus (GP)
Divided into an internal (GPi) and external (GPe) segments
Main output nuclei of the BG
Subthalamic Nucleus (STN)
Only excitatory nucleus in the basal ganglia
Part of the indirect pathway
Substantia Nigra (SN)
Divided into a pars compacta (SNc) and a pars reticulata (SNr)
Dopamine
Direct vs indirect basal ganglia pathways
The direct pathway facilitates movement, and the indirect pathway inhibits unwanted movements.
Primary Motor Cortex (M1)
Executes voluntary movements , Somatotopic organisation.
Generates action potential,
Sends signals via the corticospinal tract
Premotor Cortex
Plans and prepares movements,
Integrates sensory information.
Interacts with the basal ganglia and cerebellum and coordination
Supplementary Motor Area (SMA)
Plans and coordinates complex movements
Sequential and bimanual actions
Receives sensory feedbacks
Adjusts movements in real-time
Relationship between basal ganglia and motor cortex is crucial for the _ and _ of voluntary movements
Initiation and regulation
The basal ganglia act as a gate keeper, facilitating the selection of appropriate motor plans while inhibiting unwanted actions through a complex feedback loop.
Optimised motor output for smooth and coordinated actions
Input to BG from prefrontal cortex
Sends signals to the basal ganglia for processing
* Cognitive function
* Decision making
* Attention
* Working memory
Basal Ganglia Processing Loop
Cognitive loop
Limbic loop
Modulates emotional responses and reward-based learning
Cognitive loop of BG
Direct pathway: Facilitates cognitive actions and decisions
Indirect pathway: Inhibits irrelevant thoughts and actions
Limbic loop of BG
Receives input from the Limbic System
Emotions, motivation etc
How does the BG modulate emotional responses and reward-based learning?
Dopamine modulation
Regulates emotional and cognitive processing
Output of the BG
Refines cognitive decisions and sends signals back to the prefrontal cortex for goal-oriented behaviour
Influences emotional responses and modulates motivation to feed to the limbic system for reward-based behaviours.
Structure of the cerebellum
Made of:
* Spinocerebellum
* Cerebrocerebellum
* Vestibulocerebellum
Spinocerebellum
Muscle Tone Regulation and Limb Movement Coordination
Feedback Processing
Important for real-time adjustments
Facilitates adaptive control
Cerebrocerebellum
Movement Planning and Fine Motor Control
Motor Learning
Sensory integration for Refinement
Crucial for planning and initiation
Vestibulocerebellum
Balance Maintenance
Regulates postural stability
Coordinates eye and hand movements
Afferent Neuron
Sensory
Efferent neuron
Motor
Reflexes
Rapid, predictable, and involuntary responses to stimuli, serving as the building blocks of the motor system’s functionality.
Reflex arcs
The neural pathways involved in reflex actions,
Facilitate rapid communication between sensory receptors and motor neurons, allowing for instantaneous responses that bypass higher brain centres
Role of reflexes
Maintaining posture, balance, and protective responses, contributing to the body’s homeostasis and survival.
Muscle stretch reflex
- Stretching stimulates sensory receptor
- Sensory neuron excited
- Within integrated centre (spinal cord) sensory neuron activates motor neuron
- Motor neuron excited
- Effector (same muscle) contracts and relieves the stretching
