Somatomotor System Flashcards
Where are UMN located?
Within the brain and spinal cord
Function of UMN
To initiate or modulate a voluntary movement
- sends signal to LMN whether to start or stop contracting
Where are a large proportion of LMN cell bodies located?
Ventral horn of spinal cord
What is the function of LMN ?
Messenger to muscle to tell it to contract
LMNs innervating flexors are distal/medial to those supplying extensors ?
Flexors - distal
Extensors - proximal
What forms the final point of communication to initiate a muscle contraction?
LMN
Name 2 types of LMN
Alpha MN
Gamma MN
Alpha MN/Gamma MN innervates the bulk of skeletal muscle fibres that generate force.
Alpha MN
Alpha MN/Gamma MN - innervates a sensory organ within the muscle.
Gamma MN
Axons of LMNs exit the spinal cord in the dorsal/ventral roots?
Ventral
Motor neurones are distributed equally within the spinal cord. True or false?
False
- greater number in the cervical and lumbar enlargement as these are supplying the limbs
Muscle contraction results from the individual and combined actions of ____ ?
Motor units
Small motor units are for fine movements. True or false? q
True
Type 1 motor unit fibres
Slow oxidating
Type IIa motor unit fibres
Fast
- ATP derived from oxidative phosphorylation
Type IIb motor unit fibres
Fast
- ATP derived from glycolysis
Fast fatiguing motor units are which type?
Type IIb
Fatigue resistant motor units are which type?
Type IIa
Slow motor units are which type
Type I
The myotatic reflex is a monosynaptic reflex arc. True of false?
True
The knee jerk is underpinned by which type of reflex?
Myotatic
Name 2 types of intrafusal muscle fibres
Nuclear bag fibres
- bag 1 and 2
Chain fibres
what are Intrafusal muscle fibres innervated by?
Gamma-MNs
Where are golgi tendon organs located?
At the junction of muscle and tendon
Function of golgi tendon organs ?
Monitor changes in muscle tension
Where are proprioceptive axons located?
In connective tissue of joints
Function of proprioceptive axons?
Respond to changes in angle, direction and velocity of movement of a joint.
What are the function of Renshaw cells?
Stop motor neurones from firing
Interneurones can be excitatory or inhibitory. True or false?
True
