Motor control Flashcards
Is activation of muscle fibres gradual?
No; all or none
how is skeletal muscle attached to bone
tendon
describe the structure of skeletal muscle
potein filaments make up myofibrils that make up muscle fibres that make up muscle fasiculus which make up muscle
what is a motor unit
an alpha motor unit (LMN) and all the extrafusal skeletal muscle fibres it innervates
what is the effect of less fibres innervated by a motor neurone
greater variation of movement
what happens when an alpha motor neurone depolarises
causes contraction of all fibres in that unit
where are alpha MN that control distal muscles located
laterally in spinal cord
where are alpha MN that control proximal muscles located
medially in spinal cord
what is the motor plate
region of muscle fibre plasma membrane that lies directly under terminal portion of axon
what is a neuromuscular junction
junction of an axon terminal with motor end plate
what do stretch receptors do
monitor muscle length and rate of change of muscle length
describe the structure of stretch receptors
peripheral endings of afferent nerve fibres wrapped around modified muscle fibres - whole apparatus = muscle spindle
what do muscle spindles detect
change in muscle resistance to stretch (contraction AND relaxation) regardless of current muscle length
describe the structure of intrafusal fibres;
middle 1/3; non, contractile, supplied by fast type 1a afferent sensory nerve
end 2/3s; contractile, gamma MN attached, supplied by slow conducting type 2 afferent
how are muscle spindles attached to extrafusal muscle fibres
by connective tissue, in parallel
where are extrafusal fibres found, what do they do and what innervates them
skeletal muscle, muscle contraction, alpha MN
where are intrafusal fibres found, what do they do and what innervates them
muscle spindle, proprioception, gamma MN
what happens if alpha MN alone is activated
increased sensitivity of muscle to stretch
what happens if an alpha AND gamma MN activated
prevents central 1/3 of spindle going slack during muscle contraction
- so info about muscle length will be continuously available so can adjust accoridngly
what happens when an external force is applied to an intrafusal fibre
pulls on intrafusal, receptor ends activated; the more/ faster muscle is stretched the more receptors fire
what happens when an AP arrives at a MN
extrafusal contraction so muscle shortens so tension removed from spindle so slows rate of firing of stretch receptor so reduction in sensory information
what does tension depend on
muscle length
load on muscle
degree of muscle fatigue
what do GTO do
detect changes in muscle tension
where are GTO found
junction of skeletal muscle/ tendon
