APE 3: The Peripheral Nervous System Flashcards
How many spinal nerve roots supply the upper limb?
5
Which spinal nerve roots supply the upper limb?
C5-T1
How many trunks does the brachial plexus have and what are they?
- three trunks
- superior, middle and inferior
What do the trunks of the brachial plexus cross?
The posterior triangle of the neck
How many divisions does the brachial plexus have and what are they?
- six divisions
- anterior and posterior parts of each trunk
How many cords does the brachial plexus have and what are they?
- three cords
- lateral, posterior and medial
Which nerves make up the 5 main branches of the brachial plexus?
- Musculocutaneous nerve
- Axillary nerve
- Median nerve
- Radial nerve
- Ulnar nerve
Which muscles does the musculocutaneous nerve innervate?
Brachialis, biceps brachii and coracobrachialis
What muscles does the axillary nerve innervate?
Teres minor and deltoid muscles
What muscles does the median nerve innervate?
Most of flexor muscles in arm, thenar muscles, lateral palmar- first 3 and a half digits
What muscles does the radial nerve innervate?
Triceps brachii and muscles in posterior compartment of forearm
What muscles does the ulnar nerve innervate?
Muscles of the hand, flexor carpi ulnaris and medial half of flexor digitorum profundus
Where is the axillary nerve most vulnerable to damage?
Within the axilla
When might the axillary nerve be injured?
By direct trauma to the shoulder, fracture of the humeral surgical neck, shoulder dislocation
What won’t the patient be able to do with a damaged axillary nerve?
Unable to abduct shoulders, shoulder becomes flattened in appearance
Where is the radial nerve most vulnerable to damage?
In the radial groove
What will cause damage to the radial nerve?
Fracture of the humeral shaft
What will be seen in a patient with damage to the radial nerve?
Inability to extend wrist and fingers, causes wrist drop
Where is the ulnar nerve most vulnerable to damage?
As it passes behind the medial epicondyle of the humerus
What can cause damage to the ulnar nerve?
Trauma at the level of the medial epicondyle (at the elbow)
What can be seen in a patient with damage to the ulnar nerve?
Flexion of the wrist is accompanied by abduction, abduction and adduction of the fingers and thumb can’t occur, movement of 4th and 5th digits is impaired
Where is the median nerve most vulnerable to damage?
Deep to the flexor retinaculum in the wrist
What can cause damage to the median nerve?
Lacerations just proximal to the flexor retinaculum, carpal tunnels syndrome
What can be seen in a patient with damage to the median nerve
Paralysed thenar muscles and two lateral lumbricals
How many spinal roots supply the lower limb?
8
Which spinal nerve roots supply the lower limb?
L1-S3
What spinal nerve roots supply just the lumbar plexus?
L1-L4
What does the lumbar plexus branch within?
Psoas major muscle
What is lateral and medial to the psoas major muscle
Lateral is the femoral nerve
Medial is the obturator nerve
Which compartments of the thigh does the lumbar plexus supply?
Anterior and medial compartments
What is the rest of the lower limb supplied by?
The sacral plexus
Which spinal nerve roots supply the sacral plexus?
S1-S3 and the lumbosacral trunk (L4/L5)
Where is the sciatic nerve found?
Inferior to the piriformis muscle and deep to the hamstring muscle
How can the sciatic nerve be commonly injured?
Intramuscular injections
Which compartment of the thigh does the sciatic nerve supply?
Posterior compartment
Which two branches does the sciatic nerve bifurcate into
Tibial nerve and common fibular (peroneal) nerve
What does the tibial branch of the sciatic nerve supply?
The posterior thigh (hamstrings) muscles
Which other muscles does the tibial nerve supply?
Soleus and gastrocnemius
Where does the common fibular nerve wrap around?
The neck of the fibula
What causes damage to the common fibular nerve?
Fracture to the fibula or tight plaster cast
What happens as a result of damage to the common fibular nerve?
Foot drop
Which compartment of the thigh does the femoral nerve supply?
Anterior compartment of the thigh (quadriceps)
What 2 actions is the quadriceps muscle responsible for?
Hip flexion and leg extension
Which compartment of the thigh does the obturator nerve supply?
Medial compartment (adductor)
What type of pathology can cause irritation to the medial compartment of the thigh?
Ovarian pathology
How many roots attach a spinal nerve to the cord?
2
What does the anterior (ventral) root contain?
Motor fibres leaving the spinal cord
What does the posterior (dorsal) root contain?
Sensory fibres entering the spinal cord
Which root contains a ganglion?
The dorsal root
What does the dorsal root ganglia contain?
The cell bodies of primary sensory neurons
How are the nerves numbers with respect to their vertebrae and what is the exception to this?
Number of vertebrae is the same as the number of nerves
Exception= cervical region where there’s 8 nerves but only 7 vertebrae
How do nerves travel with respect to their vertebrae and what is the exception to this?
A nerve always travels inferiorly to its vertebrae
Exception= in cervical vertebrae, 7 nerve are all superior to its vertebrae and the 8th nerve is inferior to the 7th vertebra
What do the nerves divide into?
Anterior and posterior primary rami
Where does the posterior rami pass to and what does it supply?
Passes dorsally to supply the extensor muscles of the spine and overlying skin
Where does the anterior rami pass to and what does it supply?
Passes ventral to supply the limbs and the body wall
Which common viral infection can affect the skin of an individual dermatome?
Shingles, herpes virus
What are the intercostal nerves?
Spinal nerves emerging from the vertebral column and running with the ribs
How many intercostal and subcostal nerves are there and where does the subcostal nerve run?
11 intercostal and 1 subcostal
The subcostal nerve runs under rib 12
What are the two ‘beads on string’ that run on either side of the vertebral column?
The sympathetic chains
What supplies the sympathetic chains?
The thoraco-lumbar regions of the spinal cord
Which nerve innervates the thorax and the abdomen?
The vagus nerve
Which nerve supplies the diaphragm and which vertebral level is it at?
The phrenic nerve- C3,4,5
What is the phrenic nerve important for?
Breathing
What innervates the limbs?
The cervical and lumbar enlargements
What is the conus medullaris
Where the spinal cord ends at a tapering point
What is the cauda equina composed of?
Many dull, yellow-coloured roots
What is the filum terminale?
A single white fibrous cord
At which vertebral level and anatomical landmark is lumbar puncture done?
L4, where there is the line connecting both iliac crests
What is the denticulate ligament?
What the pia mater forms on either side of the spinal cord between the dorsal and ventral roots
Where is the needle placed to perform an epidural?
Outside the dural sac
