Exam 3 (weeks 5-8) Flashcards
What are the components of the peripheral nervous system?
- 31 spinal nerve pairs
- 12 cranial nerve pairs
- Ganglia
What is a dermatome?
An area of skin that sensation is innervated by 1 (or 2) spinal nerve(s).
What is a nerve plexus?
A cluster of spinal nerves that form new terminal branches.
What is the primary dorsal rami?
Smaller (less neurons)
Can’t form a nerve plexus
What are the spinal nerve rami that contribute to the lateral cord?
Musculocutaneous nerve
Median nerve
C5-C7
What are the spinal nerve rami that contribute to the posterior cord?
Axillary nerve
Radial nerve
C5-T1
What are the spinal nerve rami that contribute to the medial cord?
Median nerve
Ulnar nerve
C8-T1
Musculocutaneous Nerve
Anterior brachial plexus nerve branch
Lateral cord
Travels in the middle of the arm to the lateral forearm
Motor innervation: muscles in the anterior comp of the arm.
Sensory innervation: skin on the lateral forearm
Median nerve
Anterior brachial plexus nerve branch
Lateral and medial cord
Travels in the middle of the forearm, through the carpal tunnel to the lateral palm and fingers
Motor innervation: muscles in the anterior forearm, thenar muscles
Sensory innervation: skin on the lateral palm (thumb/thenar) and lateral digits
Ulnar nerve
Anterior brachial plexus nerve branch.
Medial cord
Travels in the medial arm, behind medial epicondyle, in the medial forearm, and hand.
Motor innervation: hypothenar muscles and other intrinsic hand muscles
Sensory innervation: skin on medial hand (palm)
Axillary nerve
Posterior brachial plexus nerve branch
Posterior cord
Wraps around surgical neck of humerus
Motor innervation: deltoid muscle
Sensory innervation: skin over shoulder
Radial nerve
Posterior brachial plexus nerve branch
Posterior cord
Travels posterior in the radial groove in the arm, continues to the posterior forearm and hand.
Motor innervation: muscles in the posterior comp of arm and forearm
Sensory innervation: skin over posterior arm, forearm, and posterior/ dorsal hand.
Somatic sensory impairment
Pain
numbness/anesthesia
Tingling
Somatic motor impairment
Muscle weakness
Paralysis
What nerve does a surgical neck fracture damage?
A fracture of the surgical neck of the humerus can damage the axillary nerve
Somatic symptoms of impairment: weak abduction of arm, numbness over shoulder
Also can be caused by glenohumeral joint dislocation
What nerve is damaged with mid-shaft fracture of humerus?
The radial nerve
Somatic symptoms of impairment:
Weak wrist extension
Wrist drop
Numbness of posterior forearm and hand
What nerve is damaged during medial epicondyle fracture?
Ulnar nerve
Somatic symptoms of impairment
Weak grip
Numbness of medial digits
(Hitting your funny bone)
What is carpal tunnel syndrome?
Compression of median nerve
Inflammation of structures in carpal tunnel can lead to medial nerve compression
Somatic symptoms of impairment
Weak handgrip
Loss of thumb opposition
Loss of sensation in lateral digits
Femoral nerve
Lumbar plexus branch
Passes deep to inguinal ligament to the anterior thigh to the medial foot
Motor innervation: anterior thigh compartment
Sensory innervation: skin on the anterior thigh, medial surface of leg and foot
What nerve is being tested in the patellar reflex test?
The femoral nerve
Tap to structure below patella and ends with knee extension
After that message travels to CNS to produce an efferent message
How does the patellar reflex work?
Afferent (to CNS)
1. Femoral nerve activated by stretch of QF muscle
2. Ventral primary rami
3. Spinal nerve
4. Dorsal root ganglion (cell body of sensory neuron).
5. Dorsal root
6. Dorsal horn (CNS)
Efferent
7. Anterior horn (motor neuron cell body, CNS)
8. Ventral root
9. Spinal nerve
10. Ventral primary rami
11. Femoral nerve innervated quadriceps (QF contracts producing knee extension)
Obturator nerve
Lumbar plexus branch
Travels through obturator foremen to the medial thigh
Motor innervation: medial thigh compartment muscles
Sensory innervation: skin of medial thigh
Sciatic nerve
Sacral plexus branch
Passes through greater sciatic notch emerges below piriformis
Descends posterior thigh comprised of 2 nerves:
- Tibial nerve (medial branch)
- Common fibular nerve (lateral branch)
These innervate posterior thigh and all leg and foot muscles.
Tibial nerve
Sacral plexus branch
Travels from the post thigh to the medial leg near tibia to the plantar foot surface
Motor innervation: posterior thigh compartment, posterior leg compartment and most foot muscles
Sensory innervation: skin on plantar foot surface