clinical neurophysiology

Question 1

what body area is supplied by nerve roots C1-C8?

Answer 1

neck and arms

Question 2

what body area is supplied by nerve roots T1-T12?

Answer 2

intercostals/chest

Question 3

what body area is supplied by nerve roots L1-L5?

Answer 3

legs

Question 4

what body area is supplied by nerve roots S1-5?

Answer 4

pelvic floor and organs

Question 5

what is the function of the intervertebral disc?

Answer 5

cushioning for vertebrate and act as shock absorbers for the spine

Question 6

what is an intervertebral disc prolapse and what type of pain does it cause?

Answer 6

intervertebral disc prolapse = when the nucleus pulposus bulges out due to trauma or congenital weakness and presses on spinal nerve roots –> radicular pain

Question 7

what is sciatica and what nerve root is affected?

Answer 7

Sciatica is pain that radiates down the back of the leg on one side (along path of sciatic nerve but not related to it)
Caused by nerve root issue at L5

Question 8

what is epidural space in SC, is it potential or true in the SC and what is found in it?

Answer 8

space between the dura and and vertebral periosteum
True space in SC
Filled with fat and venous plexuses

Question 9

what is the denticulate ligament and where are lateral denticulate ligaments found?

Answer 9

extensions of Pia mater that anchor the spinal cord to the dura (run in subarachnoid space)

lateral denticulate ligaments separate the anterior and poster roots

Question 10

Form the anterior and posterior roots, which is motor and which is sensory?

Answer 10

Anterior/ventral = motor
Posterior/dorsal = sensory

Question 11

if there was an arterial problem in the spinal cord what part would it usually affect?

Answer 11

affects anterior part of spinal cord

Question 12

what part of the body does the fasciculus gracilis sense fine touch, vibrations and proprioception from?

Answer 12

from ipsilateral lower limb

Question 13

what part of the body does the fasciculus cuneatus sense fine touch, vibrations and proprioception from?

Answer 13

ipsilateral upper limb

Question 14

what does the spinocerebellar tract detect?

Answer 14

proprioception from limbs to cerebellum

Question 15

what does the Spinothalamic tract detect?

Answer 15

pain and temperature from the contralateral side of the body

Question 16

how do the anterior and lateral corticospinal tracts differ ?

Answer 16

Anterior (15%)= motor to ipsi- and contralateral anterior horn
Lateral (85%)= motor to ipsilateral horn

Question 17

where are motor and sensory cell bodies found?

Answer 17

Motor cell body found in ventral/anterior horn

Sensory cell body found in dorsal root ganglion

Question 18

what is one muscle fibre supplied by?

Answer 18

one motor neuron

Question 19

what is the difference between extrafusal and intrafusal muscle fibres?

Answer 19

extrafusal muscle fibres are normal skeletal muscles fibres which are found outside muscle spindles.
intrafusal muscle fibres are muscle fibres found within muscle spindles.

Question 20

what do gamma motor neurons control and innervate?

Answer 20

innervates intrafusal muscle fibres

controls fine motor movements

Question 21

what do alpha motor neurons control and innervate?

Answer 21

innervate extrafusal muscle fibres

they cause muscle contraction

Question 22

what are muscle spindles and what do they do?

Answer 22

collections of 6-8 specialised muscle fibers that are located within the muscle mass
They act as specialised receptors that signal the length and rate of change of length (velocity) of the muscle

Question 23

what are 1a sensory afferents and what is their role?

Answer 23

these are sensory fibres which are found in the central portion of intrafusal fibres
They provide information about length and velocity of the muscle

Question 24

describe the relay of information to and from a muscle spindle fibre in alpha-gamma coactivation

Answer 24

The muscle starts off at rest at a certain length and has a constant firing rate of 1a afferent nerves.

The muscle is stretched which also causes the muscle spindle to stretches and the Ia afferent fires more strongly.

When the muscle is released from the stretch and contracts (shortens), the muscle spindle becomes slack, causing the Ia afferent to fall silent (as no tautness to signal about).

The muscle spindle is rendered insensitive to further stretches of muscle.

To restore sensitivity, gamma motor neurons fire and cause the spindle to contract, thereby becoming taut and able to signal the muscle length again.

Question 25

describe the knee jerk reflex

Answer 25

if you hit patellar tendon, muscle belly stretches and muscle spindle also stretches. This stretch is detected by muscle spindles in quadriceps muscle and increases signal frequency via sensory afferent fibres. the sensory neurons synapse with motor neurons in spinal cord which cause contraction of quadriceps muscle and relaxation of hamstring muscle.

Question 26

what do Golgi tendon organs signal about?

Answer 26

Golgi tendon organs signal information about the load or force applied to a muscle

Question 27

what are golgi tendon organs? What do they consist of and how do they function as part of the golgi tendon reflex?

Answer 27

Golgi tendon organs are specialised receptors that are located between the muscle and the tendon. They consist of numerous collagen fibres. The organ is innervated by primary afferents called Group Ib fibers, which have specialized endings that weave in between the collagen fibres. When force is applied to a muscle, the Golgi tendon organ is stretched, causing the collagen fibers to squeeze and distort the membranes of the primary afferent sensory endings. As a result, the afferent is depolarised, and it fires action potentials to signal the amount of force.

Question 28

list the 3 main modalities used to assess CNS function?

Answer 28

EEG (electroencephalography) - record electrical activity in the cortex Nerve conduction studies and EMG (electromyography) - assess function of PNS, NM junction and nerve roots. EP (evoked potentials) - response to sensory stimulation

Question 29

list the components of the peripheral nervous system

Answer 29

``` Nerve roots which form a: plexus which run into: peripheral nerves nueromuscular junction muscle body ```

Question 30

describe how the speed of nerve conduction would be assessed peripherally ?

Answer 30

Stimulate the median nerve and record electrical activity in muscle. Time between electrical stimulus and activity in muscle = latency stimulate further up the arm e.g. lateral to biceps tendon and record the latency. measure the distance between the 2 points of stimulus and use v = d/t to calculate speed of nerve conduction

Question 31

what would reduced amplitude of nerve conduction speed suggest?

Answer 31

axonal damage

Question 32

what would reduced speed of nerve conduction suggest?

Answer 32

demyelination

Question 33

what nerve is compressed in carpal tunnel syndrome?

Answer 33

median nerve

Question 34

what causes foot drop

Answer 34

``` problem with tibialis anterior either due to: trauma or compression of common peroneal nerve at fibular head or damage to sacral plexus or damage to sciatic nerve or L4/5 nerve root lesion ```

Question 35

what is Guillain barre syndrome and what are its clinical features?

Answer 35

immune reaction to an initial infection, destroy myelin sheaths. Clinical features: weakness in all limbs (progresses over DAYS), previous infection, areflexia, no ocular involvement, speech and swallowing are normal

Question 36

what is myasthenia gravis and what are its clinical features?

Answer 36

autoimmune reaction again the ACh receptor Clinical features: fatiguable weakness (progresses over WEEKS/MONTHS), head drop, difficulty swallowing, double vision in evening, ptosis, voice becomes quieter when speaking

Question 37

what are 2 conditions that cause chronic generalised weakness?

Answer 37

motor neuron disease | neuropathy

Question 38

what are 2 conditions that cause acute weakness?

Answer 38

Guillain barre syndrome | myasthenia gravis

Question 39

what is the neurophysiological test for epilepsy? what else is this tests useful for?

Answer 39

electroencephalography | used for deteriorating cortical function

Question 40

what are evoked potentials useful for?

Answer 40

useful in intraoperative monitoring