Motor pathways Flashcards
What do motor nerves do?
Voluntary control of movement via skeletal muscle - efferent
What does the motor pathway do?
- Synapses with LMN to take signal from spinal cord to muscle
- UMN is from motor cortex to spinal cord
Motor cortex blood supply
Anterior/medial posterior cerebral arteries
What is the motor cortex formed from?
Grey matter
Where does the motor neuron cross to the contralateral side?
Medulla pyramids
When are mixed nerved formed?
From the horizontal articular surface, where afferent nerves from the dorsal horn and efferent nerves from the ventral horn combine
Where does the right corticospinal tract decussate?
Anterior corticospinal tract
Which side of the body does the right motor cortex innervate?
LHS
Where does the anterior corticospinal tract decussate?
At exit level in spinal cord
Where does the lateral corticospinal tract decussate?
Pyramids
What does the anterior CST supply?
Neck and upper limbs
Fine movements
What is a motor unit?
A motor neuron and all the muscle fibres it innervates
Myotome for shoulder abduction
C5
Myotome for elbow flexion
C5-C6
Myotome for wrist extension
C6-C7
Myotome for finger flexion/extension
C7, C8
Myotome for finger abduction/adduction
T1
Myotome for hip flexion
L2-L3
Myotome for hip extension
L4-L5
Myotome for knee flexion
L2-L3
Myotome for knee extension
L3-L4
Myotome for ankle dorsiflexion
L4-L5
Myotome for ankle plantar flexion
S1-S2
How does the stretch reflex work?
- Muscle groups generally work in pairs - flexors/extensors, abductors/adductors etc
- Contraction of one stretches the other passively - a reflex arc that tenses the stretched muscle
- Provides muscle tone and stability
- 2 nerves and 1 synapse - very fast (monosynaptic stretch reflex)
What are muscle spindles?
Sensory organs in muscles that respond to stretch and position of muscle
How is the sensitivity of a muscle spindle controlled?
Intrafusal muscle fibres innervated by A-gamma efferents
What is the Jendrassik manoeuvre?
Clench teeth and fingers and interlock hands
Test knee jerk reflex
Distraction for patient to test reflexes
How do you examine tone?
Take the weight of a limb and move it around
Are fasciculations found in LMN or UMN?
LMN
Symptoms of neuron damage
Weakness, sensory loss, loss of reflexes, respiratory failure
Causes of neuron damage
MS
Guillon-Barre
How do you diagnose Guillou-Barre?
Lumbar puncture
Characteristic symptom of myasthenia gravis
Drooping eyelids
What is diplopia?
Double vision
Examples of UMN injuries
Stroke, MS, brain injury, cerebral palsy
Examples of LMN injuries
Guillon-Barre, trauma, viruses, polio
What happens if you have a C4 injury?
Quadriplegia / tetraplegia, complete paralysis below neck
What happens id you have a C6 injury?
Partial paralysis of hands and arms as well as lower body
What happens if you have a T6 injury?
Paraplegia, paralysis below chest
What happens if you have an L1 injury?
Paraplegia, paralysis below waist
What type of lesion is a brachial plexus injury from a stab wound?
Lower
What kind of lesion is a stroke from middle cerebral artery thrombosis?
Upper
Affects opposite side of body
What kind of lesion results from compression of median nerve in the right wrist?
Lower
Affects right hand
What kind of lesion results from C5 root irritation from spondylosis of cervical spine?
Lower
What kind of lesion results from transection of spinal cord at C6 after cycle accident?
Upper
Affects both sides of body
Characteristics of UMN injury
Increased tone
Increased reflexes
Upgoing Babinski reflex
No fasciculations
Characteristics of LMN injury
Decreased muscle tone Reduced muscle bulk Decreased reflexes Downgoing (normal) babinski Fasciculations present
