Essay 161 - Internal Morphology of Spinal Cord Flashcards
How is the White matter divided?
3 Funiculi on each side:
- Anterior - Lies between the anterior median fissure and point of emergence of the ventral nerve root.
Connected by the anterior white commissure.
2.
Lateral - Lies between the ventral and dorsal nerve roots
- Posterior - Lies between the posterolateral sulcus and posterior median sulcus.
What are nuclei?
These are grouped together neurons which are similar in structure and function.
Based on what does nuclei differ?
- Cellular composition
- Relationship with the peripheral neurons (sensory, motor and parasympathetic)
- Tracts (ascending or descending)
Rexed laminae of Grey matter?
This is made up of a system of 10 layers of grey matter with each corresponding to a specific nucleus.
Posterior grey horn gives which types of neurons?
- Funicular (afferent) neurons - which gives rise to ascending tracts of spinal white matter.
- Interneurons -
The processes of these stay within the grey matter.
They connect either same segments or connect several different segments.
Connections can be either ipsilateral (to the same side) or contralateral (to the opposite sides).
How many types of nerve cell groups are present in the posterior grey horn?
- Zona spongiosa
- Substantia gelatinosa
- Nucleus proprius
Zona spongiosa?
- Otherwise known as the nucleus posteromarginalis
- Found at the very apex of the posterior horn
- Composed of large stellate or fusiform neurons, whose
axons reach other spinal segments.
Substantia gelatinosa?
- Nucleus at Rexed lamina II
- Occupies the apical portion of the posterior grey horn
of all segments - Composed mainly of small Golgi type II neurons, which
receive general somatic afferents from the cells of the
spinal ganglion. - Additionally, they receive input from supraspinal levels
that can modify their primary sensory functions.
Nucleus proprius?
- Contain laminae III - VI
- Situated anterior to the Substantia gelatinosa
- Constitutes the major bulk of the posterior grey horn
throughout the cord. - Receives general somatic efferents for discriminative
touch and proprioception. - They, in turn, give rise to ascending tracts
Lateral grey horn contains how many nuclei?
- 3 nuclei, none of which extend throughout the whole
spinal cord - Is occupied by laminae VII of Rexed
Nucleus dorsalis?
- Thoracicus, Clarke’s column
- Group of neurons that extend from C8 to L4
- Cells are associated with proprioception from tendon
and muscle spindles. - Their axons form an ascending path to the ipsilateral
cerebellum (posterior spinocerebellar tract).
Interomediolateral nucleus?
- Visceral motor nucleus
- Its thoracolumbar part (T1 - T12) gives rise to
preganglionic sympathetic fibres, which travel along
the ventral roots of the spinal nerves to reach the
sympathetic ganglia. - Its sacral part (S2 - S4) gives rise to preganglionic
parasympathetic fibres.
Intermediomedial nucleus?
- Visceral sensory nucleus
- Extends from the T1 - L2 segment
- These neurons are reached by the axons of the
afferent viscerosensory neurons, located in the spinal
ganglia. - The neurons of the intermediomedial nucleus give rise
to visceral ascending pathways.
Anterior Grey Horn?
- Includes laminae VIII and IX
- Its cellular composition and thickness varies along the
spinal cord
What are the two types of efferent motor neurons of the anterior grey horn?
- Large alpha-efferent neurons
Synapse with groups of extrafusal myocytes - Small gamma-efferent neurons
Synapses with groups of intrafusal muscle fibres
Both are:
- Cholinergic
- Multipolar neurons with short branching dendrites and
long axons, which form the ventral roots of the spinal
nerves.
- Lower Motor Neurons (LMN) because they receive
massive input from Upper Motor Neurons (UMN) in
cerebral motor cortex via descending (efferent)
pathways.
