L2 and L3 Questions

Question 1

Describe the anatomy of a mixed spinal nerve

Answer 1

all spinal nerves are mixed they come from dorsal (sensory) roots and ventral (motor) roots that combine into spinal nerves after they mix they also split into ventral and dorsal rami (for innervation of anterior and posterior tissues, respectively)

Question 2

How many pairs of spinal nerves are there?

Answer 2

31 pairs: C1-C8, T1-T12, L1-L5, S1-5, 1x coccygeal

Question 3

What is the relationship between a spinal nerve and a nerve plexus?

Answer 3

spinal nerves that innervate important muscles braid together into a nerve plexus that branches off, this ensures some innervation to key muscles (especially in the cervical and lumbar regions) when damage occurs at a spinal nerve

Question 4

List the cranial nerves and identify their target innervation

Answer 4

I. Olfactory: sensory nose

II. Optic: sensory eye

III. Oculomotor: motor eye

IV: Trochlear: motor eye

V. Trigeminal: sensory face

VI: Abducens: motor eye

VII: Facial: motor eye

VIII: Vestibulocochlear: sensory hearing and balance

IX: Glossopharyngeal: sensory tongue and pharynx

X: Vagus: motor parasympathetic (many visceral organs)

XI: Accessory: motor sterno-cleidomastoid and trapezius muscles

XII: Hypoglossal: motor tongue

Question 5

Explain the concept of dermatomes and myotomes

Answer 5

dermatomes and myotomes are regions of skin and groups of muscles that are primarily innervated by a single spinal nerve

Question 6

Draw a typical spinal segment showing the organisation of a spinal nerve with its sensory, motor and autonomic fibres

Answer 6

Question 7

Name the two main descending pyramindal tracts. How are they anatomically different?

Answer 7

lateral and anterior (ventral) corticospinal tracts, lateral crosses midline at the decussation of the pyramids and runs laterally in the spinal cord, anterior runs anteriorly in the spinal cord and the signal crosses the midline when it passes on to the lower motor neuron

Question 8

List cortical brain regions important for movement and indicate which lobe of the brain they can be located

Answer 8

primary motor cortex: frontal lobe

supplementary motor cortex: frontal lobe

premotor cortex: frontal lobe

prefrontal cortex: frontal lobe

Question 9

Differentiate between the basic funcitons of the anterior and posterior horns of the spinal cord

Answer 9

anterior horns: movement of muscles (both distal and proximal)

posterior horns: sensory information

Question 10

Describe the anatomical path of an upper motor neuron that controls the foot as it projects to the spinal cord

Answer 10

muscles of the foot are distal, therefore lateral corticospinal tract. UMNs originates from primary motor cortex and via the internal capsule (as the corticospinal tract), crosses at decussation of the pyramids, travels down to lumbar (?) spinal sections and connects to LMNs which goes to the foot

Question 11

What percentage of upper motor nuerons cross to the contralateral side of the nervous system? Where does this occur?

Answer 11

80% at the decussation of the pyramids