Anatomy of the Spinal Cord
The meninges are three protective connective tissue coverings that encircle the spinal cord and brain. What is their order, from superficial to deep?
Dura mater, arachnoid mater, pia mater
At which point does the secondary neuron of the dorsal column pathway decussate?
The medulla (either gracile or cuneate nucleus)
TRUE OR FALSE: Secondary neurons in the spinothalamic pathway decussate significantly earlier than in the dorsal column pathway
TRUE
TRUE OR FALSE: Sensory information takes a journey along 2 neurons, whereas motor information takes a journey across 3
FALSE (other way)
Where does the cervical enlargement extend from/to?
C4-T1
The dorsal column pathway is a pathway of conscious sensation. It is located within the posterior (dorsal) column of the spinal cord. Give three of its functions:
Discriminative touch, pressure, vibration, proprioception
The spinothalamic tract is a collection of neurons that carries information to the brain about what? (3x)
Pain, temperature, itch, general light touch
Descending pathways can be divided into which two broad groups?
Dorsolateral
Ventromedial
Because the spinal cord is shorter than the vertebral column, nerves that arise from the lumbar, sacral, and coccygeal regions of the spinal cord do not leave the vertebral column at the same level they exit the cord. What are these nerves at the end of the nerves that extend beyond the spinal cord?
Corda equina (because it looks like a horse's tail)
The first neuron receives information from a sensory receptor and enters into the spinal cord. What does it do before entering the dorsolateral fasciculus?
Ascend 1-2 spinal segments
Sensory pathways are also known as ascending spinal tracts. Sensory neurons are which types of neurons?
Pseudounipolar afferents
Which group of descending tracts controls fine movement?
Dorsolateral
What is the difference between the white and grey matter in terms of what they consist of?
White matter = bundles of myelinated axons of neurons
Grey matter = cell bodies, unmyelinated axons, and neuroglia
How is T6 used as a marker between the fasciculi of the dorsal column?
Above T6 = fibres enter the cuneate fasciculus
Below T6 = fibres enter the gracile fasciculus
Where is the spinothalamic tract located?
Within the anterior portion of the lateral column of the spinal cord
The corticospinal tract has a variety of functions. Which tract is involved in the voluntary motor control of the limbs?
Lateral corticospinal tract
Triangular-shaped membranous extensions of the pia maters uspend the spinal cord in the middle of its dural sheath. What are these ligaments called?
Denticulate ligaments - project laterally. Protect the spinal cord against sudden displacement that could result in shock
Using information from the foot as an example, describe how sensory information goes on a three neuron journey in the dorsal column pathway:
Information from the foot enters the most medial aspect of the spinal cord. It ascends in the gracile fasciculus and synapses in the gracile nucleus in the medulla. The secondary neuron will decussate to form the medial lemniscus pathway heading towards the thalamus. It then synapses in the thalamus with a third neuron, and this neuron will head towards the aspect of the somatosensory cortex associated with the foot
The secondary neurons of the spinothalamic tract and dorsal column pathway decussate in different patterns. How do they differ?
Dorsal column: lemniscal decussation in medulla (to contralateral side towards thalamus)
Spinothalamic: decussation at every spinal level (around 1-2 segment difference from entry level) (much earlier!)
The corticospinal tract is not fully myelinated until aged 2 years old. Babies show a positive Babinski sign. What does this mean?
When a relatively sharp object is dragged along the lateral aspect of the sole of the foot, you would expect the individual curl their toes. When the individual does not have a normal corticospinal tract (or a baby), extension occurs (splayed back))