Chapter 16: Spinal Cord and Spinal Nerves Flashcards
Describe the spinal cord and be able to label it’s features on a diagram.
(Diagram Pg. 486 & 488)
- Link between body and brain
- Spinal cord and spinal nerves serve 2 important functions
- Pathway for sensory and motor impulses
- Reflexes
- External surface has 2 longitudinal depressions:
- Posterior median sulcus
- Anterior median fissure
List the (5) regions of the spinal cord and how many pairs of spinal nerves are in each region.
Cervical Region (8 pairs) Thoracic Region (12 pairs) Lumbar Region (5 pairs) Sacral Region (5 pairs) Coccygeal region (1 pair)
(Total: 31 pairs of nerves)
What is the conus medullaris and why is it significant?
It’s the tapering end of the spinal cord.
It marks the official end of the spinal cord proper (approx. L1).
What is the caudal equina and what does it mean?
Cauda equina means “horses tail.”
Inferior to the conus medullaris, is the caudal equina which is nerve roots that protect inferiorly from the spinal cord.
What is the filum terminale?
- thin strand of pia mater that anchors the conus medullaris to coccyx
- within caudal equina
White Matter vs Gray Matter
(in the spinal cord)
Be able to identify the structures in the diagram.
(Diagram Pg. 490)
Gray matter
- In the middle of spinal cord
- Cell bodies of motor neurons
- Horns (anterior, posterior, and lateral)
- Gray Commisure
White Matter
- Outside of gray matter
- Funiculus (anterior, posterior, and lateral)
- White Commisure
Describe the arrangement and function of the meninges in the spinal cord.
(Outermost to innermost)
Be able to identify these layers on the diagram.
(Diagram Pg. 488)
Vertebra
Epidural Space
- between outermost meninge (dura mater) and periosteum covering the inner walls of vertebra
DURA MATER
- fuses the connective layers that surround the spinal nerves
Subdural space
- potential space between dura mater and arachnoid mater
ARACHNOID MATER
Subarachnoid space
- Real space filled with CSF
PIA MATER
- Innermost layer adheres directly to the spinal cord
Describe the components contributing to a spinal nerve.
Be able to identify the structures in the diagram on Pg. 492.
Anterior rootlets - from spinal cord come together to form anterior roots
Anterior roots - contain motor axons only (voluntary movement, efferent)
Cell bodies of the motor axons are in the anterior and lateral horn (gray matter in spinal cord)
Posterior rootlets
Posterior roots - contain sensory axons only (sensory, afferent)
Cell bodies of the sensory axons are in the posterior root ganglion
Anterior and posterior roots combine in the intervertebral foramen to form a spinal nerve (obviously containing both motor and sensory axons)
Define dermatome. Be able to label and describe them.
(Diagram Pg. 493)
A specific segment of skin supplied by a single spinal nerve.
- The skin of the body is may be divided into sensory segments that collectively make up a “dermatome map”
(Pg. 493)
Define myotomes.
Why do you think they are significant to our field?
A group of muscles primarily innervated by the motor fibers of a single nerve root.
My guess:
Based on muscle function tests, we can tell where an injury is located (what nerve is not functioning properly). ie. If a patient has weakness while performing dorsiflexion, it can be an indication that something is wrong with spinal nerve L4.
ie. This is why on intake forms it asks if you have trouble controlling bladder/bowel. It can be a red flag for injury to S3-5.
Myotomes!
List what muscle groups are innervated by these nerves: C3-5: C5: C6: C7: C8, T1: T1-T12: L1, 2: L3: L4: L5: S1: S3-5:
C3-5: Diaphragm/breathing"C3-5 keep the diaphragm alive!" C5: Shoulders, bicep C6: Elbow flexors, wrist extensors C7: Elbow extensors, wrist flexors C8, T1: Finger flexors/abductors T1-T12: Chest wall and back mm L1, 2: Hip flexor L3: Knee extensor L4: Ankle dorsiflexor L5: Great toe extensor, hamstrings S1: Ankle plantar flexors, hamstrings S3-5: Bowel, bladder
What do intercostal nerves innervate?
Travel in the intercostal space between two adjacent ribs.
Innervate
Define a nerve plexus and list the primary nerve plexuses in the body (4).
Nerve plexus: network of interweaving anterior rami of spinal nerves; occurs on both sides of the body;
Nerve plexuses split into multiple named nerves which innervate various body structures.
Primary Plexuses:
- Cervical Plexus
- Brachial Plexus
- Lumbar Plexus
- Sacral Plexus
Describe the structure of the brachial plexus.
Brachial plexuses - (right and left - one on each side) network of nerves that innervates the pectoral girdle and entire upper limb
Formed by anterior rami of C5-T1
List the peripheral nerves that come off of the brachial plexus (5) with their sensory (S) and motor (M) innervations.
- Axillary Nerve
M: Deltoid Muscles
S: Skin over deltoid - Musculocutaneous Nerve
M: Anterior upper arm muscles
S: Lateral forearm - Median Nerve
M: Forearm flexors, thenar group muscles
S: Palm and thumb through half of 4th finger; dorsal tips of fingers - Radial Nerve
M: Extensors upper and lower arm
S: Posterior arm, posterior forearm, dorsal aspect of lateral 3 digits (but not tips) - Ulnar Nerve
M: Anterior forearm muscles and intrinsic hand muscles
S: Lateral half of of 4th finger and the pinky
