Eye movements are controlled by cranial nerves (CN) 3,4, and 6 (oculomotor, trochlear, and abducens). Helpful Hint** - A nice and easy way to remember this is the following: (LR6SO4)3 = which means that Abducens CN 6 innervates the lateral rectus muscle, Trochlear CN 4 innervates the superior oblique muscle, and Oculomotor CN 3 innervates the rest of the eye muscles.

Trigeminal CN 5 is responsible for the muscles that control mastication (chewing). It is a common error to suspect facial CN 7 due to its innervation of the facial muscles involved with expressions. However, the trigeminal nerve is unique because although it provides sensory to the face, it is also responsible for motor function involved with chewing.

These findings suggest that the patient is experiencing Bell's palsy. This is a common finding with the lower motor neuron lesion of facial CN 7. We ask the patient to raise their eye brows to distinguish Bell's palsy from a stroke. If a patient has half sided facial paralysis and can raise both eyebrows this is usually a red flag.

Compression of the S1 nerve root can lead to weakness in gastrocnemius, peroneus longus, and peroneus brevis muscles causing difficulty with foot push off during walking. The S1 nerve root is also responsible for sensation along the lateral foot, and compression could cause numbness and/or tingling. The achilles reflex (ankle jerk reflex) tests the S1 nerve root. 

When giving an epidural injection the order of structures the needle passes through goes as follows: skin, fascia and subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum, epidural space 

When giving an lumbar puncture the order of structures the needle passes through goes as follows: skin, fascia and subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum, epidural space, dura mater, arachnoid mater, subarachnoid space. Note that the pia mater is not pierced during a lumbar puncture. 

"Saturday night" palsy is a nickname for radial nerve paralysis. Because the wrist extensors are innervated by the radial nerve, this type of paralysis would prevent a person from being able to perform wrist extension. While the supinator is innervated by the radial nerve, the biceps brachii is also a supinator, so although supination may be weaker with radial nerve paralysis, it would not be absent. 

The "soup" method involves collecting a tissue sample from the specific CNS are that one is interested in, isolating it and grinding it to form a homogenate which can be analyzed. This is useful for quantifying binding or molecule levels, through the application of radiolabels to specific neurotransmitters and receptors of interest. The radiolabels let you see how much those neurotransmitters and receptors interact, and what their relative levels are.

When performing a spinal tap the layers that the needle passes through (from superficial to deep)are as follows: epidermis, muscle, ligamentum flavum, epidural space, dura-mater, arachnoid mater, subarachnoid space. The CSF, which you collect in a spinal tap, is located in the subarachnoid space. 

When performing a spinal tap you enter the intervertebral space at the L3/L4 or L4/L5 level. This is because the spinal cord ends around L1/L2. Nerves continue past this point as part of the cauda equina, however they are not in danger of being pierced as they move out of the way of the needle. The needle will pass through various layers until the subarachnoid space where CSF is located.