Brain stem and spinal cord Flashcards
Describe the gross anatomy of the spinal cord.
(brain stem) –> cervical enlargement –> lumbosacral enlargement –> cauda equina –> filum terminale
Describe the internal anatomy of the spinal cord.
White matter (outer): dorsal column, lateral column and ventral column
Gray matter (inner, “butterfly”): dorsal- and ventral horn
What are the four segments of the spinal cord called?
Cervical-, thoracic-, lumbar- and sacral segments
How many of the different segments are there?
C8, T12, L5, S5
How does the white:gray matter ratio differ thorughout the segments?
More gray the further down the spinal cord
What is Rexed’s ten laminae, and what does it reflect?
A division of the gray matter of the spinal cord, reflecting the functional aspects, e.g., VII = autonomic NS, VIII + IX = motor system
What is the dorsal root vs the ventral root (sensory/motor)?
Dorsal: sensory (afferent)
Ventral: motor (efferent)
What lies in the very middle of the spinal cord?
The central canal, which is the caudal part of the ventricular system
How does the motor neurons differ from the sensory neurons?
They are bigger
How many of the cranial nerves originate or terminate in the brain stem?
10: NIII-NXII
Describe the cranial nerve I (NI).
Name: olfactory nerve
S/M: sensory
Major function: sense of smell
Connection to the brain: telencephalon
Describe the cranial nerve II (NII).
Name: optic nerve
S/M: sensory
Major function: vision
Connection to the brain: diencephalon
Describe the cranial nerve III (NIII).
Name: Oculomotor nerve
S/M: motor
Major function: eye movements, pupilary constriction
Connection to the brain: mesencephalon
Describe the cranial nerve IV (NIV).
Name: trochlear nerve
S/M: motor
Major function: eye movements
Connection to the brain: mesencephalon
Describe the cranial nerve V (NV).
Name: trigmental nerve
S/M: motor and sensory
Major function: somatic sensation from face, mouth, muscles of mastication
Connection to the brain: pons
Describe the cranial nerve VI (NVI).
Name: abducens nerve
S/M: motor
Major function: eye movenments
Connection to the brain: pons
Describe the cranial nerve VII (NVII).
Name: facial nerve
S/M: motor and sensory
Major function: controls muscles of facial expression, taste, lacrimal and salivary glands
Connection to the brain: pons
Describe the cranial nerve VIII (NVIII).
Name: auditory nerve
S/M: sensory
Major function: hearing, sense of balance
Connection to the brain: pons and medulla oblongata
Describe the cranial nerve IX (NIX).
Name: glossopharyngeal nerve
S/M: motor and sensory
Major function: taste
Connection to the brain: medulla oblongata
Describe the cranial nerve X (NX).
Name: vagus nerve
S/M: motor and sensory
Major function: autonomic
Connection to the brain: medulla oblongata
Describe the cranial nerve XI (NXI).
Name: spinal accessory nerve
S/M: motor
Major function: neck movements
Connection to the brain: medulla oblongata and spinal cord
Describe the cranial nerve 12 (NXII).
Name: hypoglossal nerve
S/M: motor
Major function: tounge movements
Connection to the brain: medulla oblongata
Where does the cranial nerves of the brain stem originate or terminate?
In cranial nerve nuclei
How does the ventral vs. dorsal surface of the brain stem differ in structure?
Ventral: Mesencepahlon with cerebral peduncle, pons, medulla oblongata with pyramid and olives
Dorsal: Mesencepahlon with superior and inferior colliculus, pons with rhomboid fassa, medulla oblongata (open superior, closed inferior)
What is the rhomboid fossa?
The connection between the brainstem and the cerebellum
Where is the 4th ventricle located?
On the dorsal side of the brainstem, between the brainstem and the cerebellum
Describe the internal structure of the brainstem.
Complex.
Gray matter: cranial nerve nuclei + other nuclei
Whiter matter: ascending and descending tracts + tracts within the brainstem
Reticular formation
How are the motor nuclei generally located compared to the sensory nuclei?
Medial
What does the internal structure of the closed part of the medulla oblongata resemble?
The internal structure of the spinal cord
What nuclei are located in the closed part of the medulla oblongata?
Dorsal column and trigmental sensory
What tracts are located in both the closed and open part of the medulla oblongata?
Medial lemniscus (sensory) and corticospinal (motor)
What nuclei are located in the open part of the medulla oblongata?
Inferior olivary, sensory cranial (nucleus of the solitary tract, trigmenial sensory nucleus) and motor cranial (dorsal motor nucleus of vagus, hypoglossal nucleus, nucleus ambiguus)
How does the hypoglossal nerve and the vagus nerve differ from each other?
Hypoglossal: one nucleus, one function
Vagus: several nuclei (trigmenial sensory, ambigus, solitary tract, dorsal motor), several functions
Describe the structure of the ventral surface of pons.
Crossing fibers (to cerebellum)
What nuclei and tracts are located in the caudal part of the pons?
Nuclei: facial
Tracts: medial lemniscus + corticospinal
What nuclei and tracts are located in the upper part of the pons?
Nuclei: trigminal nerve (head)
Tracts: medial lemniscus + corticospinal
What structure lies dorsal to the mesencephalon?
The cerebral aqueduct
What are the superior colliculus function?
Visual system
What structure is also found in the upper part of the mesencephalon, and what function?
Substansia nigra, motor system
What nuclei are located in the mesencephalon?
Oculomotor, trochlear and abducens
What are the difference between descending and ascending tracts?
De: down
A: up
Which tracts are found in the white matter of the spinal cord?
De: corticospinal tract (for voluntary movements)
A: spinothalamic tract (for pain and temp.), dorsal column (for touch and proprioception)
Describe the pyramidal tract system.
Main motor tracts controlling voluntary movements
Cortex –> brain stem: corticobulbar tract
Brain stem –> spinal cord: corticospinal tract
How many neurons are there in the pyramidal tract system?
2:
- upper motor: cellbody in cortex, axon decends in the pyramidal system and crosses the midline
- lower motor: cellbody in the ventral horn or motor cranial nerve nuclei, axon reaches skeletal muscle via a peripheral nerve
Where does the fibers of the corticospinal tract cross, and where does these crossing fibers end?
On the ventral surface of medulla oblongata, ends in the lateral corticospinal tract. The non-crossing fibers end in the ventral
What are the two main sensory pathways?
1) Dorsal column-medial lemniscal pathway: touch and proprioception
2) Spinothalamic tract: temp and pain
How many neurons are there in the sensory systems?
3:
- 1st neuron: cellbody in spinal ganglion
- 2nd neuron: cellbody in the spinal cord or brain stem –> axon crossed midline
- 3rd neuron: cellbody in thalamus –> axon projects to the cerebral cortex
Describe the dorsal-medial lemniscus pathway.
1st neuron: spinal ganglion –> posterior collumn (spinal cord) –> 2nd neuron: dorsal column nuclei –> medial lemniscus (brain stem) –> 3rd neuron: thalamus –> cerebral cortex
Describe the spinothalamic tract pathway.
1st neuron: spinal ganglion –> 2nd neuron: dorsal horn (spinal cord) –> spinothalamic tract (spinal cord and brain stem)–> 3rd neuron: thalamus –> cerebral cortex
