(2) CAS anatomy Of The Upper Limb Flashcards
What are 3 myotatic reflexes on the upper limb?
What spinal segment/nerve roots do each of the reflexes consist of?
1) biceps tendon reflex - spinal segment/nerve roots C5 & C6
2) Triceps tendon reflex - spinal segment/nerve roots C7 & C8
3) Brachioradialis (supinator) reflex - spinal segment/nerve roots C5 & C6
What is a reflex?
What does a reflex pathway typically consist of?
Reflex - involuntary response to a stimulus. Can be monosynaptic or multi synaptic
Typical reflex pathway:
1) afferent (sensory) neurones - coveys impulses from sensory receptors in muscle spindle to spinal cord
2) efferent (motor) neurones - running from anterior grey columns of spinal cord to effector organ which is the limb muscle
Most myotatic reflex arcs are monosynaptic
Reflexes should always be compared on? Why?
The reflex arc in the spinal cord plays an important role in maintaining muscle tone
W/O muscle tone —> we won’t be able to maintain normal body posture
Law of reciprocal innervation on reflex skeletal muscle activity?
Reflexes should always be compared on both sides (left and right), as a difference comparatively may increase the relevance of the finding
In the same limb the flexor and extensor muscles cannot contract simultaneously.
Afferent nerves responsible for flexor reflex muscle action must have branches to synapse w the extensor motor neurones of the same limb to inhibit the extensor muscle contraction.
What do abnormally exaggerated myotatic reflexes lead to?
Disorder in any of the components of the reflex arc (muscle spindles, afferent sensory neurones, efferent motor neurones and the effector organs - muscle itself) results in?
Abnormally exaggerated myotatic reflexes lead to an upper motor neurone lesion
Disorder in any of the components of the reflex arc (muscle spindles, afferent sensory neurones, efferent motor neurones and the effector organs - muscle itself) results in: complete absence (areflexia) of reflexes —> suggestive of lower motor neurone lesion
Grading system for documenting the character of reflexes examined
Absent - 0
Decreased but still present (hypo-reflexic) - 1+
Normal - 2+
Hyper-reflexic - 3+
Clonus: repetitive shortening of the muscle after a single stimulation - 4+
Assessment of cutaneous sensation: Light touch segmental innervation of the upper limb
Demonstrate light touch w a wisp of cotton wool to your colleague by touching normal area of skin, just above the clavicle or over sternum
Then ask your colleague to close the eyes while you examine individual dermatomal areas and find out whether they can feel the touch sensation as normal, dull or none at all.
Repeat test on opposite limb and compare
Dermatomal regions of upper limb
Dematome:
C4 - shoulder C5 - lateral side of arm C6 - lateral side of forearm and thumb C7 - middle and ring finger C8 - medial side of hand, forearm and little finger T1 - medial side of forearm and arm T2 - axilla
Peripheral nerve and what dermatomal segment they correlate with
Musculocutaneous- C5, 6 & 7
Median - C6-8, T1
Radial - C5-8, T1
Ulnar - C(7)8, T1
What is a dermatome?
What forms peripheral nerves?
What is a plexus?
Dermatome: area of skin supplied by a single spinal nerve (but possibly by multiple peripheral nerves)
Spinal nerves split off and combine to form peripheral nerves
Plexus - where intersection of nerves takes place. There are both afferent and efferent fibres.
What can an upper limb mononeuropathy result from? What can this lead to?
What can testing of the nerve reveal?
Damage to a single peripheral nerve distal to the brachial plexus can lead to an upper limb mononeuropathy.
An upper limb mononeuropathy can lead to signs of deformity, weakness and sensory loss that are characteristic to the function of the particular nerve.
The location where the lesion/injury has occurred along the nerve can be determined by testing of the nerve.
What is the most prevalent cause of the mononeuropathies? What are some other causes?
Mechanical injury (resulting from compression or trauma); the median nerve at the wrist (carpal tunnel syndrome), ulnar nerve at the elbow or radial nerve compression at the spiral groove.
Malignancy and inflammation can also cause mononeuropathies
What is Mono-neuritis multiplex?
When multiple peripheral nerves are involved and these don’t relate to compression sites; a vasculitis or an antibody mediated response against the peripheral nerves should be suspected.
Where are the following veins located?
Basilic
Cephalic
Median cubital
Cephalic vein - located in the anterior, lateral side of the arm, originating on the lateral dorsal venous arch
Basilic vein - located in the anterior, medial side of the arm, originating from the medial dorsal venous arch
Median cubital vein - located in the superficial network at the cubital fossa. Clinically relevant site for phlebotomy (taking a blood sample)
Superficial veins may be visible in the subcutaneous fat and fascia, superficial to the muscles but if not you still need to be able to point out where they’re likely to be
