6- CNS anatomy

Question 1

What components make up the diencephalon

Answer 1

Thalamus - higher area of the diencephalon - this is a relay station
for information going between the cerebral cortex and other parts
of the CNS in both directions
• Hypothalamus - found inferior to the thalamus and is important in
coordinating homeostasis

Question 2

What are the 4 primary cortical areas and what do they do

Answer 2

 Primary motor cortex – involved in effector/motor functions
 Primary somatosensory cortex – receives sensory input from the body
 Primary visual cortex – first location to receive input from the retina
 Primary auditory cortex – first location to receive input from the inner ear

Question 3

What are the 2 cortical associated areas

Answer 3

Broca’s area – involved in producing intelligible speech
 Wernicke’s area – involved in comprehension of language
 These areas are much better represented in the LEFT hemisphere

Question 4

What are the 4 cortical lobes

Answer 4

Frontal Lobe – most anterior lobe
 ParietalLobe
 Occipital Lobe – most posterior
lobe
 TemporalLobe

Question 5

Describe the 3 groves dividing the cerebral hemispheres

Answer 5

 Central sulcus – can be thought to run medially through the
lateral aspect of the hemisphere, with the frontal lobe just anterior and the parietal lobe just posterior to the sulcus
Lateral fissure – anterior to and below the central sulcus, the lateral fissure separates the frontal and temporal lobe (the frontal lobe being anterior, and the temporal lobe posterior)
 Parietal-occipital sulcus – posterior to the central sulcus, the parietal-occipital sulcus runs posterior to the parietal lobe and anterior to the occipital lobe, separating the two lobes.

Question 6

What is the basal ganglia and what are it’s components

Answer 6

BASAL GANGLIA – groups of neurones referred to as nuclei within each hemisphere that are responsible for the control of movement, as well nerve signalling within the brain

Caudate + Putamen = Corpus Striatum - connected to cortex, thalamus, nigra
•Putamen + Globus Pallidus = Lentiform nucleus

Question 7

Describe the components of the meninges

Answer 7

o DURA MATER – touch membrane attached to bone or forming partitions between the hemispheres (dural folds) with venous sinuses in their margins
o ARACHNOID MEMBRANE – thin membrane attached to the underside of the dura
o PIA MATER – delicate membrane closely adherent to the surface of the brain and spinal cord
Clinical significance – CSF flows in the subarachnoid space

Question 8

Describe the components of the ventricular system

Answer 8

 LATERAL VENTRICLE – 2 C-shaped spaces (with posterior protruding “spurs”) lie on either side of the corpus callosum. The structure of the ventricle consists of: Anterior horn and main body
 THIRD VENTRICLE – single ventricle which bisects the diencephalon along the mid-saggital line between the two hemispheres.
 AQUEDUCT – narrow channel goes through the midbrain, and then forms the fourth ventricle
 FOURTH VENTRICLE – forms posterior to the brain stem anterior to the cerebellum
 CENTRAL CANAL – narrow channel goes down into the spinal cord

Question 9

How is CSF produced and what is its function

Answer 9

 CSF continuously secreted by CHOROID PLEXUS (glands) within each ventricle
o Formed by the filtration and modification of blood, and differs both cellularly and in its ionic concentrations
 FUNCTION – important in the protection of the soft-tissue of the brain from both gravity and trauma
o Also has metabolic functions, as important in removing waste and delivery of substrates to the brain tissue
 Circulates through the ventricular system and the SUB-ARACHNOID SPACE within the meninges

Question 10

How many vertebrae and nerves are there

Answer 10

31, 30 nerves

Question 11

What are the 5 types of vertebrae and their associated nerves

Answer 11

 Consists of 5 types of vertebrae:
o CERVICAL – 7 vertebrae, 8 nerves which lie above and below each vertebra
o THORACIC – 12 vertebrae, 12 nerves which lie below each vertebra o LUMBAR – 5 vertebrae, 5 nerves which lie below each vertebra
o SACRAL – 5 vertebrae, 5 nerves which lie below each vertebra
o COCCYX – 2 vertebrae (but this is variable, may be fused to form one bone), with 1 COCCYGEAL nerve associated


Question 12

Why is the spinal column longer that the spinal cord

Answer 12

o This is because the spinal cord develops early during embryonic development, but its development stops much earlier than the end of the vertebral column growth

Question 13

Which nerves should a lumbar puncture be taken from

Answer 13

o Therefore when performing a lumbar puncture (for CSF analysis), to protect the spinal cord you would complete the cistern below L2 (preferably between L3 and L4)

Question 14

What are the holes in the spinal column called

Answer 14

INTERVERTEBRAL FORAMINA

Question 15

How is CSF different from plasma

Answer 15

Lower glucose (2/3)
−Much lower protein (200x)
−Lower Ca2+
−Higher Cl-
−Slightly lower pH (7.33)

Question 16

What are the components and functions of the lambic system

Answer 16

Hippocampus,
Amygdala
Olfactory bulbs
Cingulate gyrus
…

motivation,
instinctive behaviour,
emotion,
memory

Question 17

Describe the structure of the cerebellum

Answer 17

Grey cortex (with deep parallel folds, folia), deeper white matter, with nuclei. Two hemispheres divided in lobes, central vermis

Question 18

What bones make up the cranium

Answer 18

Anterior cranial fossa
Middle cranial fossa
Poster is cranial fossa
Sella turnica
Jugular formen
Formen magnum
Carotid canal

Question 19

Where are some of the main structures located in the brain

Answer 19

 Frontal lobe – lies in the anterior cranial fossa
 Temporal lobe – lies in the middle cranial fossa
 Cerebellum – lies in the posterior cranial fossa
 Midbrain – lies at junction between middle and posterior cranial fossa
 Hypothalamus (part of diencephalon) – lies directly above the body of the sphenoid bone
 Optic nerve/chiasma (related structure to the diencephalon) – passes through the optic canal
 Medulla (part of the brain stem) – passes through the foramen magnum

Question 20

What causes communicating hydrocephalus

Answer 20

 COMMUNICATING (all 4 ventricles affected)
o Causes: Block in CSF absorption or CSF flow over brain surface caused by:  Meningitis
 Head injury
 Congenital
 Haemorrhage (sub-arachnoid)

Question 21

What causes non communicating hydrocephalus

Answer 21

NON-COMMUNICATING (not all ventricles enlarged) o Causes: Block in ventricular system caused by:  Aqueduct stenosis
 Ventricular tumours
 Paraventricular tumours

Question 22

What are signs and symptoms of hydrocephalus and how can it be treated

Answer 22

Headache, drowsiness, blackouts, raised intercranial pressure, increased head circumference in child

 Remove cause, e.g. papilloma
Divert CSF with a shunt
 Open alternate pathway, e.g. ventriculostomy

Question 23

Describe the 2 types of haemorrhage and how are they distinguished

Answer 23

 Epidural/ extradural haemorrhage – usually due to a damaged meningeal artery between the skull and the dura after head trauma.
Subdural haemorrhage – usually due to a damaged vein between the dura and arachnoid membrane.
 Both can cause a space-occupying lesion in the confined space of the cranium and hence neurological
deficits.
 Distinguishing between haemorrhages - The first symptoms (which may be headache, drowsiness,
vomiting or seizure) are likely to arise promptly after arterial bleeding in an epidural haemorrhage whereas symptoms may be delayed by hours or days after venous bleeding in a subdural haemorrhage

Question 24

Which structures are effected in meningitis

Answer 24

 Structures infected - Pia mater and subarachnoid space, with some spread to the upper layers of the cortex in severe cases

Question 25

Hoe can bacterial and viral meningitis be distinguished

Answer 25

 CSF Analysis – used to distinguish between bacterial and viral meninigitis
o With bacterial infection there will be a high white cell count, with neutrophils predominating.
Bacteria may be identifiable – cloudy CSF
Protein conc increased and glucose decreased
o With viral infection any increase in white cells is predominantly lymphocytes.
 Protein and glucose level of the CSF are usually normal  Viral identification is unlikely