Theme 2 Flashcards
What is motor control
A dynamically changing mix of conscious and unconscious regulation of muscle force, informed by continuous and complex sensory feedback operating in a framework sculpted by evolutionary pressures
What are the different types of motor control?
- Voluntary (running, talking)
- Goal-directed (conscious, explicit, controlled)
- Habit (unconscious, implicit, automatic)
- Involuntary (eye movements, cardiac, intercostals)
Describe briefly how we escape pain?
- Pain
- Spinal cord
- Escape
- Motor, autonomic, endocrine defense related ouput
Describe briefly how we avoid looming threat?
- Loom
- Sensorimotor midbrain
- Avoidance
- Motor, autonomic, endocrine defense related ouput
Describe briefly how we avoid a learned threat?
- Threat
- Cortex and limbic system
- Avoidance / Solution
- Motor, autonomic, endocrine defense related ouput
What does more complex, sophisticated threat detection and avoidance require?
Additional or more complex neural processing
What is the overview of the basal ganglia and cerebellum
- Basal ganglia (WHAT to do)
- Cerebellum (HOW to do it)
Where do upper motor neurons have their cell bodies?
Higher centres (cortex and brain stem), project down to lower motor neurons
Where do lower motor neuron have their cell bodies?
Brainstem or grey matter of spinal cord, projecting to muscle
Describe the descending control system
- Association cortex
- Motor cortex
- Brainstem circuits
- Spinal circuits
- Motor units
- Affect on the world
Feedback on all levels
How do individual muscle fibres act
All or none, contracted or not
So control relays on how lower motor neurons activate different fibres
What are the three types of muscle
- Skeletal
- Smooth
- Cardiac
How do we achieve a wide range of movements with all or none muscle contractility?
- Antagonistic arrangement
- Recruitment of a range of muscle fibres (fast / slow twitch, small and large motor units)
What is antagonistic arrangement?
Combined co-ordinated action between opposing muscles
How does training affect muscle fibres
Number of muscle fibres remains unchanged
They change type (fast / slow twitch), and diameter
Describe the structure of muscle fibres in skeletal muscle
- Attached to bone by tendon
- Muscle fasciculi (groups of muscle fibres)
- Muscle fibres (groups of muscle cells)
- Made of myofibrils (actin and myosin)
- When depolarised, actin and myosin slide against each other - contraction
Describe the cellular mechanism of muscle movement
- ACh causes cascade resulting in release of calcium from inside muscle cell
- Myosin head changes shape and binds with actin
- ATP required to break bond between actin and myosin
(rigor mortis, no more ATP, stiff muscles)
What is a motor unit?
Single alpha motor neuron + all the muscle fibres it innervates
How does motor unit size affect movement
Fewer fibres per neuron means greater movement resolution (eg, fingers and tongue)
What is the size principle?
Motor units are recruited in order of size (smallest first)
Fine control typically required at lower forces
What are slow muscle fibres for?
Type 1
Stuff you can do all day eg. maintaining posture
What are fast fatigue resistant muscle fibres for?
Type 2a
Bursts of force, they will fatigue but not for a while (running, swimming)
What are fast fatigueable muscles?
Type 2b
Very quick and powerful contractions, but tire easily
Where do all the alpha motor neurons from the motor units go to?
The motor pool for each muscle in the spinal cord (ventral horn)