Properties of the Motor Unit Flashcards
define motor unit
The minimal functional unit of the motor system. It consists of a somatic efferent (alpha-motoneuron) and all the extrafusal muscle fibres it supplies e.g.
extra-ocular muscles (1 neurone :10 fibres)
quadriceps (1 neurone:1000 fibres)
what are the 4 components of the motor system?
- Motoneurons (Neuronal tissue)
- Skeletal Muscles (Muscular tissue)
- The Neuromuscular Junction (where the neurone and muscle connect – specialised synapse).
- Connective tissue
what do the motor systems of the body work together to do?
Set muscle tone of the body – a small amount of sustained muscle contraction responsible for body posture
Bring about voluntary movement via antagonistic muscle pairs
define innervation ratio
The number of muscle fibres innervated by a single motor neurone.
Generally, the smaller the innervation ratio the more precise the movement.
where do the motor neurones originate from in the NS?
NS –> PNS –> efferent system –> somatic motor efferents (for upper motor neurones) –> alpha motor neurone (for lower motor neurone)
what are the 2 types of muscle?
striated
non- striated
what are the 2 muscles that are striated?
skeletal
cardiac
what is the muscle that is non- striated?
smooth
what are both striated and non-striated muscles made of?
Striated and non-striated muscles are both made of muscle tubulars.
In striated, however the tubulars are arranged in a PARALLEL formation.
In non-striated they run in EVERY direction.
define myogenic
what muscles are myogenic
generate their own electrical activity - ANS only controls rate & strength of contraction
Both cardiac and smooth muscle are myogenic
what are the 4 important functions of the skeletal muscle?
Set muscle tone of the body – a small amount of sustained muscle contraction responsible for body posture
Allow for voluntary movement via antagonistic muscle pairs
Stabilises joints
Generate heat – mechanical efficiency of skeletal muscle is 20% so 80% is lost by heat.
describe the general anatomy of skeletal muscles
The single cell of muscle is known as a myocyte - muscle fibre
Myofibrils are the most abundant organelle within them
Myocytes collect together form a fascicle
The neurovascular bundle (blood vessels) of any muscle runs in between and in parallel with muscle fascicles
Fascicles collect to form a muscle
what is the order in the organisation of the muscle starting from the most superficial layer first?
muscle –> fascicles –> muscle fibres –> myofibrils –> myofilaments
what are the 3 tissues that envelope the skeletal fibres?
Epimysium – CT enveloping all fascicles
Perimysium – CT enveloping a fascicle
Endomysium – CT enveloping each muscle fibre
what is the importance of tendons?
A tendon is a tough band of fibrous connective tissue
Attaches muscle to bone
It forms a point of confluence, bringing together the individual contractions of the myocytes to produce a combined action at a usually a joint.
Skeletal muscle can be classified according to the assemblies of their fascicles… what are these 5 classifications?
convergent/triangular
circular/sphincteric
parallel/strap
fusiform
Pennated Muscles