Motor Control Flashcards
What are 2 thing muscles can only do?
Contract or relax
How many muscles fibres are activated?
All or none
Skeletal muscle is attached to bone by what?
A tendon
What are the parts of muscles, from actin and myosin to skeletal muscle?
Actin and myosin myofilaments contained in Myofibrils, several of these form Muscle fibres, several of these form Muscle fasiculis, several of these form Skeletal muscle
What is a motor unit made up of?
An alpha motor neurone (a type of lower motor neurone) and all the extrafusal skeletal muscle fibres it innervates
What does an AP in the alpha motor neurone caise?
An AP in all extrafusals
If less extrafusals are being innerated by the alpha motor neurone, what happens to the movement?
Greater variation in movement
Increased fine regulation of movement
Eg, fingertips & tongue
Alpha motor neurones controlling distal muscles are found where in the spinal cord?
Laterally in spinal cord
Alpha motor neurones controlling proximal muscles are found where in the spinal cord?
Medially in spinal cord
What happens when there’s damage to a motor unit?
Adjacent motor units get bigger
Decreased co ordination
At a neuromuscular junction, where does the axon divide?
Axon divides into a number of short processes that lie in the grooves on the muscle fibre surface
What is the region that lies directly under the terminal portion of the axon called?
Motor end plate
What is a neuromuscular junction?
The junction of an axon terminal with the motor end plate
What is caused due to the differences in electrochemical gradients across the plasma membrane in a NMJ?
Produces a local depolarization of the motor end plate - the end plate potential (EPP)
What is the end plate potential?
The NMJ version of excitatory postsynaptic potential (EPSP) but is a much stronger depolarization
What is the magnitude of a single EPP compared to that of an EPSP?
End plate potential magnitude is much larger than that of an Excitatory post synaptic potential
Why is the magnitue of a simgle EPP larger than that of an EPSP?
Because the neurotransmitter is released over a larger surface, therefore binding to more receptors and opening more ion channels
Where is the AP then propagated to in one EPP?
More than sufficient to depolarize all adjacent fibres in the alpha motor unit
Over surface of the muscle fibre into the T tubules
Every AP in a motor neurone normally produces…
An AP in each muscle fibre in the motor unit
In contrast to synaptic junctions, where multiple EPSPs must occur in order for threshold to be reached
All neuromuscular junctions are….
Excitatory
What is the definition of muscle tone?
It is the degree of contraction of a muscle (or the proportion of motor units that are active ay any one time)
A muscle with high tone feels….
Firm and rigid
Resists passive stretch
A muscle with low tone feels….
Soft or flaccid
Offers little resistance to passive stretch
When a person becomes increasingly alert, more activation of…. And this causes?
Alpha motor neurones
Muscle tone increases
What is an upper motor neurone?
From motor cortex to spinal cord
What is an lower motor neurone?
Neurones that connect the impulse from the spinal cord to the effector
What are symptoms of upper motor neurone syndromes?
Weakness or paralysis Spasticity Increased muscle tone - hypertonia Over responsive reflexes - hyperreflexia Positive babinski sign
How to test for the positive babinski sign?
Run a sharp instrument along lateral border of sole of foot
Causes extension of big toe (bends up) & fanning of other toes
What are symptoms of lower motor neurone syndromes?
Weakness or paralysis
Decreased or absent muscle tone (hypotonia)
Decreased or absent refleced (hyporeflexia)
Involuntary muscle twitches (fasciculations)
Muscle atrophy
