The Motor system Flashcards
Motor control involves a dynamically changing mix of c____ and u____ regulation of muscle force, informed by continuous and complex s____ feedback, operating in a framework sculpted by e_____ p______.
conscious
unconscious
sensory
evolutionary
pressures
Types of motor control
Voluntary
Goal-directed
Habit
Involuntary
Which part of CNS responds to pain?
Spinal cord
Which part of CNS responds to loom?
Sensorimotor midbrain
Which part of CNS responds to a learned threat?
Cortex + Limbic system
Sensorimotor system
motor control governed by UMNs and LMNs
LMN begins in spinal cord/ brainstem and projects to muscle
UMN originates in higher centres and project to LMNs
Top down processing
A descending control system but with lots of ascending feedback
Individual muscle fibres act in an ‘a__-o_-n___’ manner, and so control of muscle f___ depends on the way in which l___ motor neurons activate different types of muscle f___.
all-or-none
force
lower
fibre
Muscles
activation of muscle fibres is all or none
Antagonistic arrangement - combined co-ordinated action
Recruitment of muscle fibres - fast /slow twitch, small and large motor units.
Muscle size is about
Cross sectional area of individual fibres and different proportions of the different types of fibre
Tendons
Attach skeletal muscle to bone
Skeletal muscle comprises of
several muscle fasciculi (group of muscle fibres)
A muscle fibre consists of several…
myofibrils
Myofibrils contain the protein filaments…
actin and myosin
(when fibre is depolarised, slide against each other to produce contraction)
What neurotransmitter triggers the biochemical cascade in muscle cells for contraction?
Acetylcholine for the myosin cross-bridge cycle
ATP is needed to break bond between
myosin head and acting filmanent
ATP is produced by
oxidative metabolism
A motor unit consists of
One alpha motor neuron and and the muscle fibres it innervates (all of the same type)
What is the result of more motor unit firing?
More power due to more fibres contracting
Training and exercise lead to changes in the ___ of muscle fibres and the ___ of different muscle fibre types
Thickness
Proportion
The Motor pool
All the LMNs that innervate a single muscle
Contains both alpha and gamma motor neurons
Often arranged in rod like shape within ventral horn of spinal column
Cell bodies in ventral horn activated by
sensory information from muscle
Descending info from brain
2 things the CNS need to know to provide good control of movement
How much tension is on the muscle
What the length (stretch) is of the muscle
What can sense the tension within muscles?
Golgi tendon organs (GTO)
Within the tendon (muscle join to bone) and sends ascending sensory info to brain
Critical for proprioception
What can sense the stretch of muscles?
Muscle spindles
Extrafusal muscle fibres
Provide force
Intrafusal muscle fibres
Sensory device to detect stretch length
Innervated separately by gamma motor neurons. Keep intrafusal fibres set at length which optimises muscle stretch detection
