Lecture 5 Flashcards
What are the five segments of the spinal cord?
•Cervical
•Thoracic
•Lumbar
•Sacral
•Coccygeal
How many nerves in each segment?
•Cervical - 8
•Thoracic - 12
•Lumbar - 5
•Sacral - 5
•Coccygeal - 1
What is the spinal cord continuous with?
The medulla
What is the Foramen Magnum?
The hole where the spinal cord exits the skull
What level does the spinal cord end at?
L1/L2
What is the Spinal cord continuous with?
The medulla
What is the Conus Medullaris?
The sacral part of the spinal cord at L1/L2 where the spinal cord ends
How many cervical vertebrae are there?
7 vertebrae but 8 nerves
Where does the C1 nerve exit?
Between the base of the skull and the C1 vertebrae
How are the cervical nerves named?
The nerve is named for the vertebrae below it
How are the rest of the nerves (not cervical) named?
They are named for the vertebrae above it
What Is the Dural Sac?
The continuation of the spinal cord down to S2 that encapsulates tracts in CSF
What are intervertebral foramen?
Holes that spinal nerves exit between the vertebrae
Where do Ventral roots leave the Spinal Cord?
The anterolateral sulcus
Where do Dorsal roots leave the spinal cord?
At the posterolateral sulcus
What are Dorsal Root Gangla?
Collection of cell bodies of the sensory nerves
Where is the grey matter of the spinal cord found?
In the center
Where does the Posterior Spinal Artery descend?
Down the posterior lateral sulcus
Where does the Anterior Spinal Artery sit?
In the anterior median fissure
Where does the Anterior Spinal Artery come from?
It branches off of the two vertebral arteries and joins together
What is the Denticulate Ligaments?
Areas of the Pia mater that branch out and attach to the dura mater through the arachnoid mater and holds up the spinal cord
What is the Filum Terminale?
An extension of the Pia mater attaches it to the coccygeal bone. It can be cut without consequence because denticulate ligaments hold the spinal cord in place.
What does the Dura Mater become once the nerve leaves the spinal cord?
The epineurium
Where in the spinal cord do Axons enter the spinal cord?
At the dorsal root
Where in the spinal cord do Axons leave the spinal cord?
At the ventral root
What does the Ventral Root contain?
Somatic Motor Axons
What does the Dorsal Root contain?
Axons from the sensory part of the body
What is a spinal nerve?
The collection of all the ventral and dorsal root axons
What occurs in the Grey matter of the spinal cord?
•Sensory neurons can (not always) synapse there
•Cell bodies of motor neurons
What are the six sensory tracts in the spinal cord?
•Fasciculus gracilis (gracile tract)
•Fasciculus cuneatus (cuneate tract)
•Dorsolateral fasciculus (of Lissauer)
•Posterior (dorsal) spinocerebellar tract
•Spinothalamic and spinoreticular tract
•Anterior (ventral) spinocerebellar tract
What does the Fasciculus Gracilis (Gracile Tract) sense?
Light touch
What does the Fasciculus cuneatus (cuneate tract) sense?
Light touch
What does the Posterior (dorsal) spinocerebellar tract sense?
Muscle spindles and joints
What does the Spinothalamic and spinoreticular tract sense?
Pain
What does the Anterior (ventral) spinocerebellar tract sense?
Muscle spindles and joints
What sensory Tracts sense light touch?
•Fasciculus gracilis (gracile tract)
•Fasciculus cuneatus (cuneate tract)
What sensory tracts sense Muscles and Spindle joints?
•Posterior (dorsal) spinocerebellar tract
•Anterior (ventral) spinocerebellar tract
What tract senses pain?
The Spinothalamic and spinoreticular tract
What are the two motor pathways?
•Lateral (crossed) corticospinal (pyramidal) tract
•Anterior (uncrossed) corticospinal tract
What are Cervical and Lumbar Enlargments?
When the cervical and lumbar grey matter areas of the spinal cord enlarge because of motor neurons that extend out to limbs
What is the arterial supply to the spinal cord?
• One anterior spinal artery
• Two posterior spinal artery
•Anterior and Posterior radicular arteries
Where does the anterior spinal artery come from?
The two branches branch off of the spinal artery and join together
Where does the Anterior Spinal Artery sit?
The anterior median sulcus
Where do the Posterior Spinal Arteries come from?
Posterior Inferior Cerebellar Arteries (PICA)
What does the two Posterior Spinal Arteries sit in?
The posterolateral sulcus
What do the Anterior and Posterior Radicular Arteries do?
Supply to dorsal and ventral roots and the lateral portions of the spinal cord. Anastomoses with anterior spinal artery and helps blood flow there
Where do the Anterior and Posterior Radicular Arteries originate from?
The Aorta
What vessel supplies the inner portion of the spinal cord?
The Anterior Spinal Artery
What does the Anterior Spinal Artery Supply?
Most of the spinal cord and all of the grey matter even in the dorsal horn
What does the posterior spinal artery supply?
Some of the white matter tract in the spinal cord
What can save some of the white matter tracts if the Anterior Spinal Artery is blocked?
Blood from the Pial branches of the radicular Artery
What is the pathway of a Motor neuron in a typical spinal nerve?
It will exit the ventral root go through the vertebral foramen and branch and become DPR (dorsal primary ramus) or the VPR (Ventral Primary Ramus) along with sensory axons
What is the pathway of a Sensory neuron in a typical spinal nerve?
It will exit the dorsal root go through the vertebral foramen and branch and become DPR (dorsal primary ramus) or the VPR (Ventral Primary Ramus) along with motor axons
What does the Dorsal root contain?
Purely sensory axons
What does the Ventral root contain?
Purely motor axons
What does the Dorsal Primary Ramus contain?
Both sensory and motor axons
What does the Ventral Primary Ramus contain?
Both motor and sensory axons
Why do we use T4 as a typical spinal nerve?
Because they stay segmental
What are Segmental Spinal Nerves?
Spinal nerves that arise from a certain spinal (segmental) level, and innervate somatic structures derived from the somites of that same level. They don’t mix with different level spinal nerves
Where are Segmental Spinal arteries usually found?
At the Dorsal Primary Ramus and the Ventral Primary Ramus of the Thoracic Nerves. And the Dorsal Primary Rami from C1 to the coccyx (except for the thoracic ones)
What are Non-segmental nerves?
When the ventral primary rami of spinal nerves (not the thoracic section) fuse to form nerve plexuses with other levels in the spinal cord
What innervates the Diaphragm?
C3, C4, and C5
What does each sensory nerve supply?
A dermatome
How do Dermatomes work?
Even though the sensory nerves intermix to form a plexus, when they reach the skin they stay true to their dermatome
What are the two important sensory tracts?
•Dorsal Columns-Medial Lemniscal Tract
•Spinothalamic (anterolateral) Tracts
What does the Dorsal Columns-Medial Lemniscal Tract sense?
light touch, mechanosensory, discriminative touch, conscious proprioception
What does the Spinothalamic (anterolateral) Tracts sense?
Pain
What pathway senses light touch, mechanosensory, discriminative touch, conscious proprioception?
Dorsal Columns-Medial Lemniscal Tract
What pathway senses pain?
Spinothalamic (anterolateral) Tracts
What are the two tracts of the Dorsal Columns-Medial Lemniscal Tract?
The Gracile tract and the Cuneate Tract
What is the difference between the Gracile Tract and the Cuneate Tract?
Gracile Tract - Lower limbs
Cuneate Tract - Upper limbs
What is the Pathway of the Gracile Tract?
Sensation at lower limb ➡️ Travels to spinal cord along Gracile Tract ➡️ Synapses and switches sides at the medulla at the Gracile Nucleus ➡️ Travels up the Medial Lemniscus pathway ➡️ Synapses at the Ventral Posterior Nucleus of the Thalamus ➡️ Primary Sensory Cortex
