Week 1 - F - Anatomy 3 - Spinal nerves (reflexes, dermatomes, myotomes)

Question 1

When testing the dermatomes and myotomes, which one test the sensory function and which test the motor function of spinal nerves?

Answer 1

testing dermatomes tests the sensory function of the spinal nerves testing myotomes tests the motor function of spinal nerves

Question 2

What is the nerve modality of the anterior and posterior rootlets? What is the modality of the spinal nerve?

Answer 2

Anterior rootlets - motor Posterior rootlets - sensory (just like posterior to the central sulcus, the postcentral gyrus is the primary somatosensory cortex of the brain)

Question 3

Testing the dermatomes of the body - need to learn these What dermatomes are: Back of scalp and adam’s apple? Badge patch? Jugular notch? (What is the other name for jugular notch) Clavicle and shoulder tip? lateral forearm? Thumb and index finger? Middle finger? PinkY?

Answer 3

• Back of scalp and adam’s apple - C2
• spinal root
• Badge patch - C5
• Jugular notch aka suprasternal notch - C3
• Clavicle and shoulder tip - C4
• lateral forearm - C6
• Thumb & index finger - C6
• Middle finger - C7
• PinkY - C8

Question 4

What dermatomes is the medial/lateral forearm? What dermatome is the medial arm/sternal angle? What lies at T4 dermatome? What dermatome is the umbilicus? What dermatome is the xiphoid process? What dermatome is the pubic symphysis?

Answer 4

Medial forearm is T1 Medial arm and sternal angle is T2 T4 dermatome is the male nipple Umbilicus is T10 dermatome Xiphoid process is T8 dermatome Pubic symphysis is T12 dermatome

Question 5

Which deratome is the groin? The anterior thigh? The medial thigh? the anterior knee? The posterior knee? The medial shin / medial malleolus? The lateral shin / dorsum of foot?

Answer 5

Grin is L1 anterior thigh is L2 Medial thigh is L3 Anterior knee is L3 Posterior knee is S2 Medial shin/medial malleolus is L4 Shin/dorsum of foot is L5

Question 6

Which dermatome is the heel / lateral foot? Posterior knee? Perianal skin? Buttock? perineum?

Answer 6

Heel/lateral foot is S1 Posterior knee - S2 Perianal skin - S5 Buttock - S3 Perineum - S4

Question 7

Which named nerve innervates the badpatch? What two muscles does the axillary nerve supply?

Answer 7

The axillary nerve - roots C5 and 6 Axillary nerve supplies the deltid and teres minor

Question 8

If someone were to touch the anterior aspect of the T10 dermatome, how would the actual potentials reach the spinal cord?

Answer 8

Action potnetial would travel along the axons of the T10 anterior rami until reaching the spinal nerve The APs would then travel via the spinal nerve to the posterior root then rootlets before arriving at the posterior horn of the spinal cord

Question 9

When do we tend to give nerves coming from spinal nerves a name?

Answer 9

When the nerves have more than one nerve root

Question 10

Nerves that often (but not always!) have more than one spinal nerve root and therefore overlap more than one ‘true’ dermatome What are the spinal nerve roots of the femoral nerve and how many true dermatomes does it therefore cross? What dermatomes of the leg are supplied by these dermatomes?

Answer 10

The spinal nerve roots are L2,3,4 The femoral nerve crosses 3 true dermatomes L2 dermatome - supplies the anterior thigh L3 dermatome - supplies medial thigh and anterior knee L4 dermatome - supplies medial shin and medial malleolous

Question 11

What does the cervical plexus span from? What are the four named nerves that come from the anterior rami of the cervical plexus?

Answer 11

Spans from anterior rami of C1-4 Lesser occipital (C2,3) Great auricular (C2,3) Transverse auricular (C2,3) Supraclavicular nerves (C3,4)

Question 12

Which of the four cervical plexus supplies the angle of the madible with sensation? Which nerves supplies the face with sensation?

Answer 12

The great auricular nerve (C2,3) The face with sensation is the trigeminal nerve (V1,V2,V3)

Question 13

Where is it that the four nerves of the cervical plexus exit the neck? What is the point known as?

Answer 13

They exit at the midpoint of the posterior border of the sternocleidomastoid muscle This is known as the nerve point of the neck or Erb’s point

Question 14

What other nerve arrives at the nerve point of the neck? What are the 4 nerves of the cervical plexus?

Answer 14

The spinal accessory nerve also arises at the midpoint of the posterior border of the sternocleidomastoid muscle Lesser occipital nerve (C1,2) Greater auricular nerve (C2,3) Transverse auricular nerve (C2,3) Supraclavicular nerves (C3,4)

Question 15

The peripheral cutaneous innervation of the trunk is really straight forward Intercostal nerves go from T2 to T121 What is the peripheral cutaneous nerve that innervates T12 dermatome level? Lies just above the lumbar plexus

Answer 15

This would be the anterior rami of T12 known as the subcostal nerve

Question 16

The bifurcation of the anterior rami of L1 supplies the skin of the anterolateral lower trunk wall What are these nerves known as?

Answer 16

These are the iliohypogastric and ilioinguinal nerves

Question 17

What are all the nerves of the lumbar plexus and their nerve roots? (arising from superior to inferior)

Answer 17

Iliohypogastric - L1 Ilioinguinal - L1 Genitofemoral nerve - L1,2 Lateral cutaneous nerve of the thigh - L2,3 Femoral nerve - L2-4 Obturator nerve - L2-4

Question 18

Are the posteiror parts of the back dermatomes supplied by anterior or posterior rami coming from the spinal nerve?

Answer 18

posterior parts of the back dermatomes are supplied by posterior rami

Question 19

Which anterior rami supplying the arms are important for referred pain in an MI? Which areas are supplied by these nerve roots?

Answer 19

This would be T1 and T2 anterior rami T1 - medial forearm T2 - medial arm and sternal angle

Question 20

Which nerve supplies peripheral cutaneous innervation to the badge patch? What are its nerve roots? What is the deramtomal area over the badge patch?

Answer 20

C5,6 - axillary nerve Dermatomal area - C5

Question 21

What are the nerves of the brachial plexus and their nerve roots?

Answer 21

Musculocutaneous - C5,6,7 Axillary - C5,6 Median - C5,6,7,8 and T1 Radial - C5,6,7,8 and T1 Ulnar - C8 and T1

Question 22

Which nerve supplies the anterior aspect of the thumb and lateral 2.5 fingers?

Answer 22

This is the median nerve (C5, 6,7,8 and T1)

Question 23

What does the median nerve supply with peripheral cutaneous innervation on the posterior aspect of the thumb?

Answer 23

It supplies the tip of the thumb and tips of the lateral 2.5 fingers

Question 24

What does the radial nerve supply with peripheral cutaneous innervation on the anterior and posterior aspect of the hand? What does the ulnar nerve supply? (same areas in question?

Answer 24

Radial nerve supplies the skin at base of thumb + anatomical snuffbox of thumb and the posterior aspect of the lateral 2.5 fingers - not including tips Ulnar nerve supplies the medial 1.5 fingers anterior and posterior

Question 25

What other part of the body is supplied by this dermatome?

Answer 25

thumb and lateral forearm - C6 dermatome Named nerve - radial nerve Roots - C5,6,7,8 and T1 Crosses 5 true dermatomes

Question 26

After supply the muscles of the anterior forearm with motor innervation, what does the musculocutensou nerve become after the elbow joint as it supplies the lateral forearm?

Answer 26

Lateral cutaneous nerve of the forearm

Question 27

For peripheral cutaenous innervation of the leg Which nerve supplies the lateral, medial, psoterior and anterior thigh? State their nerve roots

Answer 27

Lateral thigh - lateral cutaneous nerve of the thigh - L2,3 Medial thigh - Obturator nerve - L2,3,4 Anterior thigh - Femoral nerve - L2,3,4 Posterior thigh - Posterior cutaneous nerve of the thigh - S1,2,3

Question 28

Which nerve supplies the lateral leg and the lateral aspect of the dorsum of the foot?

Answer 28

This is the sural nerve - formed from branches from the tibial and common fibular nerve

Question 29

What is the continuation of the femoral nerve known as? What area does it supply with cutaneous innervation?

Answer 29

Known as the saphenous nerve Supplies the anterior leg with cutaneous innervation

Question 30

What nerve supplies the dorsum of the foot and 1st web space? Which nerve supplies the plantar aspect of the foot?

Answer 30

Majority of dorsum of foot - superficial fibular nerve (L4,5S1) 1st web space - Deep fibular nerve - L5 Plantar apsect f foot is supplied by tibial nerve - L4-S3

Question 31

Say that someone applies deep pressureto the superior aspect of the anterior thigh (say L2), describe how this would be relayed back? (inlcuding the tract)

Answer 31

https://s3.amazonaws.com/classconnection/403/flashcards/11907403/png/pjpg-15E42EFFB186A649E16.png

Question 32

Which dermatome is the star on? Which peripheral named nerve supplies cutaenous innervation? What are the nerve roots? The are of cutaneous innervation passes how many true dermatomes?

Answer 32

The star is in the L2 dermatome Femoral nerve supplies peripheral cutaneous innervation - L2,3,4 Pass though 3 true dermatomes

Question 33

Femoral nerve will contain axons that connect with three spinal cord segments Therefore the area of motor innervation of the femoral nerve will cross how many true myotomes?

Answer 33

Will cross three true myotomes

Question 34

What muscles does the femoral nerve provide with motor innervation?

Answer 34

Quadriceps femoris (vastus lateralis, vastus intermedius, vastus medialis, rectus femoris Also sartorius and pectineus and iliopsoas All the muscles of the anterior aspect of the leg

Question 35

What is a myotome?

Answer 35

A myotome is a single spinal nerve and all the muscles it innervates

Question 36

Clinical Testing of Upper Limb Myotomes What myotome brings about abduction and adduction of the arm? What muscles also?

Answer 36

Abduction of arm - C5 - Deltoid Adduction - pectoralis major and lattismus dorsi - C7 (C7 back down from heaven)

Question 37

What muscle is it and what myotome causes flexion of the arm? Which muscle and myotome causes extension? Which nerves supply these muscles?

Answer 37

Flexion of arm - C5,6 myotome - biceps brachii (supplied by the musculocutaneous nerve) Extension of the arm - C7,8 myotome - trcipes brachii (supplied by the radial nerve)

Question 38

What is the function of the palmar and dorsal interossie of the arms? What myotome is this?

Answer 38

Palmar interossie - adduction Dorsal interossie - abduction Both T1 spinal nerve

Question 39

Which spinal nerve brings about flexion and extension of the fingers?

Answer 39

Flexion of finger - C8 Extension of fingers - C7

Question 40

What are the myotomes for the extension of the muscles at the hip joint and flexion of the muscles at the knee joint? (REMEMBER THE RHYME THAT ENDS WITH KICK MY BUM)

Answer 40

L5,S1 myotomes

Question 41

Which muscle group brings about extension at the knee joint? Which myotome?

Answer 41

These are the quadriceps femoris L3,4 myotomes

Question 42

Which myotomes are plantar and dorsi flexion of the foot?

Answer 42

Plantar felxion - L4,5 Dorsiflexion - S1,2 - gastrocneumius and soleus (and plantaris) -

Question 43

STATE THE DIFFERENT MYOTOMES INVOLVED IN * Hip flexion * Hip extension * Knee flexion * Knee extension * Ankle forsiflexion * Ankle plantarflexion Useful to remember the rhymes

Answer 43

Hip flexion (psoas major) - L2,3 lift the knee Hip extension (hamstrings/glut max) and knee flexion (hamstrings) - L5,S1 kick the bum Knee extension (quadriceps) - L3,4 kick the door Ankle dorsiflexion (tibialis anterior) - L4,5 touch the sky Ankle plantarflexion (gastronceumius and soleus) - S1,2 stamp the shoe

Question 44

What do the gastrocnemius, soleus and plantaris form? What is the triceps surae?

Answer 44

Form the calcaneal tendon Triceps surae - gastrocnemius 2 heads and soleus

Question 45

Testing a Spinal Nerve Myotome for Motor Function Describe how the action of the muscle is acheieved ie for a muscle supplied by the L3 myotome? (quadriceps femoris) When do action potentials leave via a posterior rami for supply to a muscle?

Answer 45

APs generated in the primary somatomotor cortex (precentreal gyrus) The APs are connected to the spinal cord via the axons of the corticospinal tract APs travel down the axons and 85% decussate at the medulla and reach the L3 spinal cord segement in th anterior horn Aps then leave via the anterior ramus and weave passed a plexus into a named nerve - femoral in this case Only posterior rami if postural neck or back muscles

Question 46

What is the difference between upper and lower motor neurones?

Answer 46

Upper motor neurones originate in the motor cortex of the brain and descend to the spinal cord where the synapse on the lower motor nuerones of the spinal cord in the anterior horns of grey matter Lower motor neurones then travel to the peripheral nerves which give the motor supply to the muscles

Question 47

What is an involuntary response to stimulus known as?

Answer 47

This is known as a reflex

Question 48

In the patellar reflex How does this reflex occur once the patellar ligament is tapped?

Answer 48

Patellar ligament is tapped Strecthes quadriceps fibres this stimulates strecth receptors in the quadrcieps and action potentials in the anterior rami axons of the femoral nerve travel back to the dorsal horn of the grey matter and synapse onto lower motor neurones these lower motor neurones then travel via anterior roots and rami to reach the quadrcieps NMJ and quadriceps contract

Question 49

Does upper or lower motor neuone lesions result in these symptoms Flaccidity? Atrophy? Spasticity? Absence of atrophy?

Answer 49

UMN lesion - spasticity and no atrophy LMN lesion - flaccidity and atrophy

Question 50

What are the spinal nerve reflex arc roots for the biceps, knee jerk and ankle jerk reflex? What are the muscles and their nerve roots during flexion of the arm, extension? and dorsiflexion of the foot and extension of the knee?

Answer 50

* Biceps reflex - C5/6 * Triceps -C7,8 * Brachiocardialis - C5,6 * Knee jerk - L3,4 * Ankle jerk - S1,2 * Flexion of arm - biceps brachii - C5,6 * extension of arm - triceps brachii - C7,8 * Dorsiflexion of foot - Triceps surae - S1,2 * Extension of the knee - Quadriceps femoris - L3,4