Anatomy 3: Anatomy of Spinal Nerves Flashcards
What type of receptors exist in all body wall structures for somatic general sensory spinal nerves. List some examples
Sensation specific receptors
Pain, touch, temperature, proprioception, vibration
What type of fibres do somatic motor axons on spinal nerves synapse onto on the body wall?
Skeletal muscle
What type of fibres do sympathetic axons on spinal nerves synapse onto?
Smooth muscle
What fibres does the spinal cord segmental synapse between for spinal reflexes?
Somatic sensory and somatic motor axons
Describe the types of general sensory somatic symptoms that the body wall percieves
Pain (neuralgia) Pins and needles (paraesthesia) Numbness (anaesthesia) Sensitivity (hyperanaesthesia) Hot or cold Loss of coordination/ balance/ clumsiness (ataxia)
Describe the types of somatic motor symptoms that the body wall percieves
Muscle stiffness, tightness or spasm (cramp)
Muscle flappiness or looseness (hypotonia)
Muscular weakness (reduced power)
Loss of coordination/ balance/ clumsiness (ataxia)
What are the neural components of the body wall?
Somatic general sensory fibres
Somatic motor fibres
Sympathetic fibres (motor to organs)
Spinal reflexes
What is used to test sensory function of spinal nerves?
Dermatomes
What is used to test motor function of spinal nerves?
Myotomes
In what situation, would we test both motor and sensory function of spinal nerves?
Spinal reflexes
What area of the brain is common for CVA?
Internal capsule
Identify the dermatomal locations of the cervical roots in the upper limb
C1: SN has no sensory axons
C2: Back of scalp and Adams apple (area that looks like a helmet with a strap tied below the chin)
C4: Clavicle and shoulder tip (neck lace)
C3: Back of neck and jugular notch (area between C2 and 4)
C5: ‘Badge patch’ (anterior chest and continues to wrist) WE DIVE TO T1 (most of arm)
C6: Thumb (+ index finger, if you join together they make 6) and lateral posterior arm
C7: Index and middle finger (continuation) and middle posterior forearm
C8: Ring and little finger (continuation) and medial posterior forearm
Identify the dermatomal locations of the thoracic roots in the upper limb and trunk
Entire area makes the letter T
T1: Medial forearm (limbs are topmost )
T2: Medial arm and sternal angle
T4: Male nipple ('boob')
T8: Xiphoid process
T10: Umbilicus (bell butTEN)
T12: Pubic symphysisIdentify the dermatomal locations of the lumbar roots in the pelvis and lower limb
Supplies legs and loin
L1: Groin ‘hands in pockets’ (1nguinaL area)
L2: Anterior thigh
L3: Anterior thigh
L4: KNEE (to medial malleolus) (down on L4s) )
L5: Dorsum of foot (middle part of sole is triangle like an inverted V (roman for 5) and big toe (biggest number = biggest toe)
Identify the dermatomal locations of the sacral roots in the lower limb
Concentric fashion (out to in)
S1: Heel (POSTERIOR LEG) and last two toes (smallest no. = smallest toe)
S2: Posterior knee (lateral leg and foot inc. little toe) (FREE INC, GENITAL AREA)
(BULLSEYE OF ANUS)
S3: Buttock (FREE INC. GENITAL AREA)
S4: Perineum
S5: Perianal skin (anus)
What is the sensory area supplied by the posterior ramii, allowing us to test these ramii?
Supply a strip of skin centrally down back and posterior neck (C2 - C8 spinal nerves)
How would we test the sensory component of the anterior ramii?
Forms plexuses - cervical, brachial, lumbar, sacral which can be tested
Which spinal cord levels do not contribute to anterior ramii?
T2 - T12
Which nerves are formed from the bifurcation of L1?
Ilioinguinal and iliohypogastric
Which nerves are formed from the anterior ramii of T2 - T11?
Intercostal nerves
Which nerve is formed from the anterior ramii of T12?
Subcostal nerve
What is the difference between a spinal nerve and a named nerve?
Spinal nerves are axons originating from one spinal cord level e.g. L5 spinal nerve, whereas named nerve are axons originating from 1 or more spinal cord levels supplying an area e.g. musculocutaneous nerve (C5, 6, 7)
Identify the plexus and list the nerve roots giving rise to the named nerve cutaneous innervation of the neck
CERVICAL PLEXUS
Anterior ramii of C1, 2, 3, 4
Identify the specific sensory nerves and roots which form the named nerve cutaneous innervation of the neck
CERVICAL PLEXUS
LITTLE GOATS TRED SOFTLY:
Starting from -
11 o’clock: Lesser occipital nerve (C2) - posterior to external ear
1 o’clock: Great auricular nerve (C2, 3) - angle of mandible and external ear
3 o’clock: Trasverse cervical nerve (C2, 3) - anterior neck
6 o’clock: Supraclavicular (C3, 4) - clavicle, shoulder pain
What is the nerve point?
Point at which sensory nerves of cervical plexus converge
Which sensory nerve is involved in referral of pain from the diaphragm?
Supraclavicular nerve (C3, 4)
Which nerve roots are important in referred pain from the myocardium?
T1, T2
What supplies the anatomical snuffbox?
Cutaneous branches of the radial nerve
Identify the specific sensory PERIPHERAL nerves and roots that form the named nerve cutaneous innervation of the upper limb
BRACHIAL PLEXUS
Shoulder - middle finger (lateral) and back up (medial)
Supraclavicular (C3,4) - Shoulder
Axillary nerve (C5, 6) - Badge patch area
Radial nerve (C5, 6, 7, 8, T1) - Lateral arm (and most of posterior)
Cutaneous branch of musculocutaneous (C5, 6, 7) - Lateral half of anterior forearm (and a bit posterior)
Radial nerve (Lateral hand - snuffbox)
Median nerve (C5, 6, 7, 8, T1) - Lateral 3 1/2 digits (and posterior fingertips of these fingers)
Ulnar nerve (C7, C8, T1) - Medial 1 1/2 fingers (and these fingers posteriorly)
Median antebrachial cutaneous nerve
Identify the sensory PERIPHERAL nerves of the lumbosacral plexus that form the named nerve cutaneous innervation of the ANTERIOR lower limb
1ST LAYER: lateral to medial Subcostal nerve (T12) - corner Genitofemoral nerve (L1, L2) - 1 or 2 balls Ilioinguinal nerve (L1) - 1lioinguinaL
2ND LAYER: lateral to medial
Lateral cutaneous nerve of the thigh (L3, L4)
Femoral nerve (L2, L3, L4) - FRONT
Obturator nerve (L2, L3, L4) - OPEN YOUR LEGS
3RD LAYER: lateral to medial
Deep fibular nerve (L2, L3) - TELLING A FIB - HIDING SOMETHING
Superficial fibular nerve
Saphenous nerve (L3, L4) - from femoral - SECRET
4TH LAYER: lateral to medial
Sural nerve (S1, S2) - ‘sweet’ little toe
Superficial fibular nerve (L4, L5, S1) - shoe (most of foot)
Deep fibular nerve (L5) - ‘fin’ - toe web
Identify the sensory PERIPHERAL nerves of the lumbosacral plexus that form the named nerve cutaneous innervation of the POSTERIOR lower limb
1ST LAYER: lateral to medial
Iliohypogastric nerve (L1) - ‘1Lio’
Posterior ramii (cluneal nerves) (S1, S2, S3) - ‘No clue = hiding at back)
Ilioinguinal nerve
2ND LAYER: lateral to medial
Lateral cutaneous nerve of thigh
Posterior cutaneous nerve of thigh (S1, S2, S3)
Obturator and femoral nerves
3RD LAYER: lateral to medial
Common fibular nerve
Sural nerve (from tibial and common fibular: S1, S2 - SECRET (in middle)
Saphenous nerve
4TH LAYER: lateral to medial
Tibial nerve (L4, L5, S1, S2, S3)
Calcaneal nerve (HEEL)
Medial and lateral plantar nerves (SOLE)
Describe the route of a somato-sensory action potential from the skin to the somatosensory cortex
Stimulated nerve
AP generated by receptors in L2 dermatome
AP enters lumbar plexus and reaches L2 anterior ramii
AP continues to L2 spinal nerve, then posterior root and rootlets
AP reaches posterior horn of spinal cord
Identify the myotomes supplied by the cervical plexus
C1 - C4 motor axons - neck and strap muscles, diaphragm
Identify the myotomes supplied by the brachial plexus
C5 - T1 motor axons - muscles of upper limb, extrinsic back muscles (control upper limb and scapula)
Identify the myotomes supplied by the lumbosacral plexus
L1 - S4 motor axons - muscles of lower limb, perineal skeletal muscle
Identify the myotomes supplied by T12 - L3 motor axons
Postural back muscles (posterior ramii) Intercostal muscles (anterior ramii) AL abdominal wall muscles (via thoracoabdominal, subcostal, iliohypogastric, ilioinguinal)
How do you clinically test the C5 motor axons, supplying a myotome? What muscle are you testing?
Shoulder ABD (also elbow flexion) Deltoid
How do you clinically test the C6 motor axons, supplying a myotome? What muscle are you testing?
Wrist EXT
Biceps brachii
How do you clinically test the C7 motor axons, supplying a myotome? What muscle are you testing?
Elbow EXT
Triceps brachii`
How do you clinically test the C8 motor axons, supplying a myotome? What muscle are you testing?
Finger FLEX
Flexor digitorium superficialis
How do you clinically test the T1 motor axons, supplying a myotome? What muscle are you testing?
Finger ABD
Dorsal interossei
How do you clinically test the L3 motor axons, supplying a myotome? What muscle are you testing?
Knee EXT
Quadriceps femoris
How do you clinically test the L4 motor axons, supplying a myotome? What muscle are you testing?
Ankle DF
Tibialis anterior
How do you clinically test the L5 motor axons, supplying a myotome? What muscle are you testing?
Great toe EXT
Extensor hallucis longis
How do you clinically test the S1 motor axons, supplying a myotome? What muscle are you testing?
Ankle PF
Gastrocneumius
How do you clinically test the S2 motor axons, supplying a myotome? What muscle are you testing?
Knee FLEX
Biceps femoris
Describe the route of a somato-motor action potential from the primary somatomotor cortex (UMN) to skeletal muscle.
Primary somatosensory cortex
AP continues onto UMN axons of CST
AP continues onto anterior horn of L3 spinal cord
UMN synapse with L3 LMN
AP continues to L3 spinal nerve
AP continues onto L3 posterior or anterior ramus
AP enters the lumbar plexus of named nerve and reaches NMJ of supplied nerve
What is a reflex? Describe the patellar reflex
Involuntary response to stimulus
Patella senses stretch, activates APs in femoral nerves and sensory APs to dorsal horn of L3 axons
Axons synapse on LMNs in femoral nerve
Reach quadriceps NMJ and extension occurs
What is a monosynaptic reflex? What does it indicated?
Occurs each time a skeletal muscle is stretched
Normal muscle tone
Reflex muscle contractions are controlled by…
Descending pathways
What sign would suggest an UMN lesions versus a LMN lesion?
Spasticity
Flaccidity
Which axons are activated when testing the tendon jerk of biceps brachii?
C5, C6
Which axons are activated when testing the tendon jerk of brachioradialis?
C6
Which axons are activated when testing the tendon jerk of triceps brachii?
C7, C8
Which axons are activated when testing the knee jerk reflex?
L3, L4
Which axons are activated when testing the ankle jerk reflex?
S1, S2
Anterior roots contain only sensory/motor axons, whilst posterior roots contain only sensory/ motor axons?
Motor
Sensory
The space in the middle of the grey matter in the spinal cord is known as the?
Spinal canal
How do you clinically test the L2 motor axons, supplying a myotome? What muscle are you testing?
Hip FLEX
Iliopsoas
What is different about cervical spinal nerves compared to other spinal nerves?
Cervical spinal nerves exit above the vertebrae but all others exit below
A peripheral distribution of pathology e.g. affecting femoral nerve, rather than dermatomal/myotomal distribution would make you think of what?
Distal site of pathology rather than spinal cord
Which peripheral nerve is damaged in winging of the scapula?
Long thoracic nerve
