Download Neuroscience 5 – Organisation of the CNS

Neuro 5 – Organisation of the CNS
Anil Chopra
1. Draw a diagram to explain the
relationship between the following major
divisions of the CNS spinal cord,
brainstem, cerebellum, diencephalon,
cerebral hemisphere.
2. Define the functions of the dorsal and
ventral horns of the spinal cord and
explain how the dorsal and ventral roots
and spinal nerves relate to them.
The dorsal horns contain the attachments for the
dorsal roots which are on the posterior side of the
spinal cord. They contain autonomic sensory
nuclei. Flow of info toward spinal cord.
cerebral
hemisphere
diencephalon
midbrain
brainstem
pons
medulla
The ventral horns contain the attachments for the
ventral roots, which are on the anterior side of the
spinal cord and contain motorneurone cell bodies.
Flow of information is away from the spinal cord.
3. Define 3 components of the brainstem and
state the main functions of the brainstem
The Brainstem consists of:
Medulla: contains sensory and motor neurones and
mainly nuclei. It forms the cardiovascular centre
and part of the respiratory centre. 5 out of the 12
cranial nerves attach here.
Puns: a bridge between the midbrain and the medulla. Contains sensory and motor
neurone tracts. It also forms part of the respiratory centre.
Midbrain: contain some of the tract and some nuclei as well as some neurons for
some muscle activity.
Generally the brainstem controls autonomic functions such as respiration,
consciousness, cardiovascular function.
4. Describe the functions of the 2 main structures of the diencephalon.
Diencephalon split into:
Thalamus: relay between lower structures and cerebral hemisphere. All information
as it enters the brain (apart from smell) goes via the thalamus.
Hypothalamus: controls homeostasis. Contains centres for the control of thirst, water
balance, temperature. Links nervous and endocrine systems.
cerebellum
spinal cord
5. State the functions of the basal ganglia and cerebellum.
Basal ganglia: they receive information from the cerebral cortex and feed information
back to the motor parts of the cortex. They are involved with the initiation and
termination of some movement and are also involved with memory, learning attention
and some emotions.
Cerebellum: forms part of the hindbrain. It is involved with the maintenance of
posture, muscular tone and coordinating voluntary movement.
6. Draw a diagram of the cerebral hemisphere the cortical lobes and primary
cortical areas.
parietal
frontal
occipital
temporal
Cerebral hemispheres: split into…
Cerebral cortex: has primary areas and association areas which are involved in all
functions but especially with language, memory, emotion.
Corpus Callosum: connects 2 hemispheres across midline. (& basal ganglia)
8. Describe the 3 layers of meninges and their role in protecting the brain.
Dura Mater: tough membrane attaché to bone. Folds over margins to form venous
sinus.
Arachnoid membrane: thin membrane beneath Dura mater
Pia mater: delicate transport membrane attached to surface of brain and spinal cord.
Meninges: synthesis CSF (cerebrospinal fluid) which lies in the subarachnoid space.
It acts as a shock absorber (as well as providing nutrient to brain tissue)
7. Recognise the main structures in an MRI or Diagram
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Lateral ventricle [may be cut through twice in
horizontal or coronal plane]
Third ventricle [may look like a hole or a slit in
coronal and horizontal plane, depending on angle
of section]
Fourth ventricle
Aqueduct
Corpus callosum [may be cut through twice in
horizontal plane]
Frontal lobe
Occipital lobe
Parietal lobe
Temporal lobe
Basal ganglia [may be more than one part]
Thalamus
Internal capsule [both anterior and posterior limbs
seen in horizontal plane]
Optic chiasma
Midbrain
Pons
Medulla
Cerebellum
9. Explain how the major divisions of the brain relate to the crainae fossa at the
base of the skull.
Anterior cranial fossa holds  frontal lobe of cerebral hemisphere.
Middle cranial fossa holds  temporal lobe of cerebral hemisphere.
Posterior cranial fossa holds  cerebellum
Above sphenoid bone is  hypothalamus
Passing through foramen magnum  medulla.
10. Explain the relationships between the spinal segments, spinal nerves and
vertebrae and state at what level a lumbar puncture can be performed safely.
7 cervical vertebrae
8 cervical nerves (above
corresponding vertebra except V8)
12 thoracic vertebrae
12 thoracic nerves (below
corresponding vertebra)
SPINAL CORD STOPS AT L2
5 lumbar vertebrae
5 lumbar nerves (below
corresponding vertebra)
Lumbar puncture is taken
between L4 and L5
5 sacral vertebrae
5 sacral nerves (below
corresponding vertebra)
11. Identify the components of the
ventricular system and relate them
to the divisions of the CNS.
lateral ventricle –
relates to cerebral
hemispheres
Aqueduct –
relates to
midbrain
third ventricle –
realtes to
diencephalon
central canal
fourth ventricle –
relates to pons
and medulla
12. Explain to compensation,
circulation and functions of CSF
– cerebrospinal fluid.
CSF Composition: similar to blood and
has
- glucose
- oxygen
- dissolved ions
Different to blood in that
- CSF has few cells
- CSF has much less protein
- CSF has fewer calcium and potassium ions
- CSF has more magnesium and chloride ions.
CSF Circulation
Choroid plexus  Lateral ventricle  third ventricle  aqueduct

Dural venous sinus  Subarachnoid space  fourth ventricle

Arachnoid villi
Central canal of spinal cord
CSF Functions
 Carries O2 glucose and other nutrients essential for brain tissue function.
 Removes waste products of CNS tissue.
 Provides optimal chemical environment for accurate neuronal signalling. Changes
in ionic compensation can greatly affect neuronal function
 Acts as a shock absorber.
 Buoys the brain – brain “floats” in CSF.
13. State the average total volume and flow rate of CSF.
Total CSF volume = 150ml
Flow rate of CSF = 500ml/day
14. Define hydrocephalus and outline how it may be treated.
Hydrocephalus
Essentially, hydrocephalus is a block in the flow of CSF which results in pressure
being built up around the brain.
2 types:
Communicating:
 All 4 ventricles are affected.
 Blockage outside ventricular system
 Due to meningitis, head injury, congenital, sub-arachnoid haemorrhage, or a
congenital disorder.
Non-communicating:
 Only certain ventricles are affected
 Blockage within the ventricular system
 Due to aqueduct stenosis (narrowing of aqueduct) ventricular or paraventricular
tumours.
Symptoms include headache, drowsiness, blackouts, high intracranial pressure and
increased head circumference in children, loss of upward gaze.
Treatment includes:
 Removal of block e.g. tumour removal
 Diverting CSF to other route i.e. shunt.
 Draining CSF
 Open (create) an alternative pathway – ventriculostomy.
15. Distinguish between an epidural (extradural) and subdural haemorrhage.
Epidural haemorrhage – damage to a meningeal artery between the skill and the dura
after head trauma. Onset of symptoms should be almost instant (headache,
drowsiness, vomiting and seizure)
Subdural Haemorrhage – damage to a meningeal vein between dura and arachnoid
membrane. Onset of symptoms can take hours
Differentiation can be confirmed with imaging.