Upper limb nerve injuries Flashcards
(108 cards)
What is the corticospinal tract (CST), also known as the pyramidal tract?
- a collection of axons that carry movement-related information from the cerebral cortex to the spinal cord
- relate to voluntary movement
The corticospinal tract (CST), also known as the pyramidal tract is a collection of axons that carry movement-related information from the cerebral cortex to the spinal cord. Is this an ascending or descending tract?
- descending tract
- carries instructions from motor cortex to spinal cord
What is the definition of an upper and lower motor neuron?
- UMN = begin in the cerebral cortex and end in brain stem or spinal cord
- LMN = begin in spinal cord or brain stem and end at target tissue
The corticospinal tract (CST), also known as the pyramidal tract is a descending tract of a collection of axons that carry movement-related information from the cerebral cortex to the spinal cord. Where do these synapse in the spinal cord and is this efferent or afferent?
- synapse at ventral/anterior horn
- efferent as they are effector neurons
The upper motor neurons of all cranial nerve of the brain (except CN I and CN II) synapse where?
- brain stem
The upper motor neurons of all cranial nerve of the brain (except CN I and CN II) synapse at the brainstem. Where do CN I (olfactory) and II (optic nerve) come from?
- cerebrum
The brainstem is composed of 3 major parts, the midbrain, the pons and the medulla. Using football formation of 4-4-2, working inferior to superior, which upper motor neurons of which cranial nerves synapse at the medulla of the brainstem?
- 4 in total
- CN IX (9) glossopharyngeal
- CN X (10) vagus nerve
- CN XI (11) accessory nerve
- CN XII (12) hypoglossal nerve
The brainstem is composed of 3 major parts, the midbrain, the pins and the medulla. Using football formation of 4-4-2, working inferior to superior, which upper motor neurons of which cranial nerves synapse at the pons of the brainstem?
- 4 in total
- CN V (5) trigeminal nerve
- CN VI (6) abducens nerve
- CN VII (7) facial nerve
- CN VIII (8) vestibulocochlear nerve
The brainstem is composed of 3 major parts, the midbrain, the pins and the medulla. Using football formation of 4-4-2, working inferior to superior, which upper motor neurons of which cranial nerves synapse at the midbrain of the brainstem?
- 2 in total
- CN III (3) oculomotor nerve
- CN IV (4) trochlear nerve
Once an upper motor neuron (UMN) travels down the corticospinal tract (pyramidal, voluntary movement tract) it synapses at the ventral/anterior horn of the spinal cord or brain stem. What lower motor neuron will the UMN synapse with to elicit voluntary movement?
1 - gamma motor neuron
2 - beta motor neuron
3 - beta 1a motor neuron
4 - alpha motor neuron
4- alpha motor neurons
- allow us to contract skeletal muscle
Once an UMN synapses with the alpha motor neuron, a LMN in the spinal cord or brainstem receives information to initiate an action. What modulates this to ensure we don’t over contract?
- proprioceptors through gamma motor neurons
- feedback through muscle spindles and golgi tendon organs
- ensure the muscle is not damaged
How do UMN and LMN lesions affect the reflexes ?
- UMN = brisk reflexes
- LMN = reduced reflexes
How do UMN and LMN lesions affect the muscle strength?
- UMN = reduced strength (no message getting to muscles)
- LMN = proximal weakness
How do UMN and LMN lesions affect muscle tone ?
- UMN = increased tone
- LMN = reduced tone
In an UMN lesions there is pyramidal weakness. What is this?
1 - unaffected
2 - flexors become stronger than extensors
3 - extensors become stronger than flexors
4 - complete loss of flexion and extension
2 - flexors become stronger than extensors
- rubrospinal tract facilitates flexion and inhibits extension
- reticulospinal tract can inhibit alpha and gamma motor neurons, thus fine tuning the movements, including balancing between flexion and extension
- in UMN the reticulospinal tract is lost so rubrospinal tract takes over, hence weaker in extension compared to flexion
How do UMN and LMN lesions affect the sensations?
- UMN = cortical sensations are lost
- LMN = peripheral sensations are lost
In addition to the corticospinal tract (pyramidal) there is another tract that also synapses with at the ventral (anterior) horn of the spinal cord. This is really important for doing what with the alpha and gamma motor neurons?
1 - inhibit gamma neurons only
2 - inhibit alpha neurons only
3 - fine tuning alpha and gamma neurons to fine tune them
4 - inhibiting alpha and gamma neurons altogether
3 - fine tuning alpha and gamma neurons to fine tune them
- this inhibition is fine tuning to ensure control and balance, NOT stopping alpha and gamma motor units altogether
The Reticulospinal Tract works closely with the corticospinal tract (pyramidal), synapsing with the ventral (anterior) horn of the spinal cord. The reticulospinal tract inhibit alpha and gamma motor neurons, thus fine tuning movements and balance. If there is a UMN lesion this inhibition is lost. What can this do to muscle tone and reflexes?
1 - increased reflexes with loss of tone
2 - increased reflexes with increased tone
3 - loss of reflexes and tone
4 - loss of reflexes with increased muscle tone
2 - increased reflexes with increased tone
- increased muscle tone as no inhibition of alpha motor units
- increased reflexes as no inhibition of gamma motor units
What is the difference between spasticity and rigidity?
- spasticity = velocity dependent (increased speed = increased tone) and only in one direction (flexor)
- rigidity = not velocity dependent and the same in both directions (flexion and extension for example)
Which nerve roots innervate the upper limbs?
- C5-T1
In terms of nerves, what does a dermatome relate to?
- a specific nerve root supplying a region of the skin and its senses
In terms of nerves, what does a myotome relate to?
- 1 nerve root supplying motor function to a muscle
If a nerve root is damaged, is this classed as peripheral nerve damage?
- no
- the peripheral nerve has not formed yet
Match the nerve roots with the muscle group and movement:
- C5, C6, C7, C8, T1
- Deltoid, Biceps, Triceps, Forearm extensors, Deep forearm flexors, Intrinsic muscles of the hand
- Shoulder abduction, Elbow flexion, Elbow extension, Wrist extension, Wrist flexion
Finger extension, Finger flexion, Finger abduction
- C5 = deltoid muscles and shoulder abduction
- C6 = biceps, elbow flexion
- C7 = triceps, superficial forearm flexors and extensors, elbow extension
- C8 = forearm extensors and deep forearm flexors, finger extension and flexion
- T1 = intrinsic muscles of the hand, finger abduction