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Summary Neuro system anatomy
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Nervous system anatomy notes. completely up to date, extensive and in depth ready for 2nd year neuro anatomy
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By: ms16434 • 6 year ago
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NEURO ANATOMY• Be able to identify the following structures on the DORSAL SURFACE OF MIDBRAIN :
- Medulla
- Gracile tubercle
- Cuneate tubercle
- 4th ventricle
- Superior and inferior colliculi (tectum)
• The superior colliculi holds the nuclei for the visual sensory nerves and the inferior
holds the nuclei for the auditory nerves.
• They can also be seen on a lateral/sagittal section of the brain:
• They make up the tectum which is the most superior part
of the brain stem
4th Ventricle
• The trigone area located just medially to the medial sulcus just below the 4th ventricle contains
nuclei of certain cranial nerves:
- Hypoglossal trigone (which is the most medial trigone)
- Vagal trigone (which lies just laterally to the hypoglossal trigone)
- The Vestibular area (lies ontop of the vagal trigone)
• Trochlea nerve is the only cranial nerve that can be seen on the dorsal surface of the midbrain
, Sensory pathway :
• The dorsal column- medial lemnscus pathway :
- Fine touch, propriception, vibrations from periphery to cerebellar cortex
• The medulla is a continuation of the spinal cord within the skull
• The medulla contains the gracile and cuneate tubercles which are located on respectively on
their gracile and cuneate fasciculi just below the obex on either side of the median sulcus.
These tubercles contain dorsal column nuclei.
• The Fasciculi are ascending sensory tract pathways which run in the white matter of the
dorsal horn in the spinal cord all the way up to the medulla containing sensory information.
At the top of the fasciculi just before the obex and 4th ventricle, are the cuneate and gracile
nuclei/tubercles. These as mentioned above contain the dorsal column nuclei.
• The gracile fasciculus carries sensory information from the
lower limbs
• The cuneate fasciculus carries sensory information from
the upper limbs
• Inferior to the tubercles the sensory information is
ipsilateral. So going up the gracile and cuneate fasciculi
sensory information is ipsilateral
• Once in the tubercles at the superior part of the fasciculi,
the neurones then dessicate and information is then
controlateral
• This sensory pathway is called the dorsal column- medial
lemnscus pathway which can be broken down into 3 orders:
- First order: From dorsal root ganglia to the
medulla via the gracile and cuneate fasciculi up
the spinal cord
- Second order: decussation in the medulla in the
gracile and cuneate tuberculi/nuclei
- Third order: Thalmus to the post central gyrus
,• Spinothalamic tract (anterolateral tract):
- Contains course touch, pain and temperature
• First order: The cell bodies in the dorsal root ganglia (e.g
neurones from the skin) synapse in the dorsal horn of the
spinal cord.
• The neurones which they synapse onto are called tract
cells. dessucate at the spinal level.
• Second order: The tract cells then dessucate at the spinal
level and travel up through the medulla to the thalamus
where they synapse
• Third order: neurones from the thalamus then synapse
onto the cerebral cortex
• Spinocerebella tract:
- Contains unconscious proprioception
• All sensory information from the cranial nerves goes to the thalmus then to the cortex.
EXCEPT OLFACTORY NERVE which is the other way around.
• The IVth ventricle:
- The IVth ventricle is located posteriorly to the medulla and the pons but anteriorly to
the cerebellum.
- The Rhomboid fossa
- The relations of the IVth ventricle are:
- Laterally: Middle cerebellar peduncles
- Anteriorly: Superior Cerebellar peduncle
- Posteriorly: Gracile and cuneate tubercle
- Superiorly: Narrows and is roofed over where central canal forms aqueduct
of midbrain
- Inferiorly: Obex (inferior apex)
- The floor of the ventricle has raised areas with cranial nuclei e.g hypoglossal, vagus
and vestibular nerves.
,• Identify the following on the medical surface of the cerebrum: DIENCEPHALON
- Thalamus
- Hypothalamus
- Pineal and mammillary body
- Lateral ventricle
- Interventricular formen and 3rd ventricle
- Cerebral aqueduct and 4th ventricle
- Corpus callosum
,• The Thalamus:
- The thalamus is symmetrical structure with 2 halves that are approximately 4cm each.
- They have an oval appearance in cross sections
- They are situated either side of the third ventricle
- The interthalmic adhesion is a flattered disc on the medical surface of each thalami
which joins them.
- Each half of the thalamus is divided into 3 parts by sheets of white matter: anterior,
medical and lateral.
• Specific thalamic nuclei groups project and receive fibres from restricted areas of the
cortex
• Non- specific thalamic nuclei project diffusely to large areas of the cortex.
NUCLEI RECEIVES FIBRES FROM PROJECTS FIBRES TO
Anterior nuclear group Mammillary bodies (limbic) Cingulate cortex
Medial nuclear group Hypothalmus, amygdala (limbic) Prefrontal cortex
Ventral anterior nucleus Basal ganglia Premoto cortex
Ventral lateal nucleus Globus pallidus, substantia nigra, cerebellum Primary motor cortex (frontal)
Ventral posterior nucleus Lateral: somatic afferent fibres from the body Somatosensory cortex (parietal)
Medial: somatic afferent fibres from head
Medial geniculate nucleus Inferior colliculus Auditory cortex (temporal)
Lateral geniculate nucleus Optic tract and superior colliculus Visual cortex (occipital)
Pulvinar Extensive connections with association cortices of parietal, temporal and occipital lobes
, • Cingulate cortex is located above the corpus callosum in the limbic region of the brain
• The Epithalamus is a small region above the thalamus containing habenula and pineal
body - the habenula is the stalk of the pineal body
• The Pineal body: Is an endocrine gland which synthesises and secreted melatonin which
has an effect of the circadian (24h) rhythm of bodily functions.
• Melatonin has an inhibitory effect on gonads, hence a lesion may result in an abnormal
sexual development. The pineal body commonly calcifies with age (becoming visible on
radiographs)
• The Internal capsule:
• Contains virtually all cerebral cortical projection fibres including those to and from the
thalamus, corpus striatum, pontine nuclei, tectum of the midbrain (where superior and
inferior colliculi are), reticular formation, cranial nerve nuclei and spinal cord.
• Gross arrangement:
- Frontal projections are most anterior
- Temporal and occipital projections are most posterior
- Parietal fibres in between
- Thalamic radiations: anterior and medial thalamic connections pass through anterior
limb of internal capsule; lateral nuclei of thalamic projections pass through posterior
limb of internal capsule
- Optic radiations from the lateral geniculate to the occipital cortex pass in the
retolenticular part of internal capsule
- Auditory fibres from medial geniculate to the temporal lobe pass in the retro &
sublenticular part of the internal capsule.
- The internal capsule carries both motor and sensory tract fibres closely together
hence lesions in the internal capsule can result in impairments to both motor and
sensory.
BLOOD SUPPLY: The blood supply of the internal capsule
is variable but is commonly from small perforating branches
of the middle cerebral artery and anterior cerebral artery.
In addition, the anterior choroidal artery (AChA) from the
internal carotid artery supplies the posterior limb of the
internal capsule
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