Session 3

Question 1

Meninges

Answer 1

Three Membranous Layers that Surround and Protect the Brain and Spinal Cord

Pia mater -microscopically thin, delicate adherent to surface of brain, follows every fold

Arachnoid mater - microscopically thin, delicate adherent to surface of brain, follows every fold Space (subarachnoid) - CSF - Cerebral vessels suppling/draining brain
(Leptomeninges - pia and arachnoid mater)

Dura mater - Potential subdural space

Question 2

Dural Folds and Sinuses

Answer 2

• Dura fuses with the periosteum lining inner table of skull bones
• Dura effectively then has two layers (while within the skull) – Periosteal –part against the inner table of bone – Meningeal = part adjacent to arachnoid
• For most part two layers closely adhered (appearing as a single layer) – but areas where they separate
• Separation of two layers forms – Dural folds – Dural venous sinuses (spaces which are filled with venous blood =venous channels)

Question 3

Venous Sinuses

Answer 3

panopto

Question 4

Dural Folds

Answer 4

Help to Stabilise the Brain and act as Rigid Dividers

A rise in pressure inside the skull e.g. secondary to a bleed can lead to compression and displacement (herniation) of parts of brain under rigid dural folds (1-3) and/or through foramen magnum (4)

use slide 10 lec 1

Question 5

Dural Venous Sinuses

Answer 5

Venous blood filled spaces created by separation of meningeal from periosteal layer of dura
• Found throughout the skull, surrounding the brain within the areas where two layers of dura separate to create a ‘space’
• Dural venous sinuses connected to each other, and receive blood from cerebral veins (draining brain)
• Eventually dural venous sinuses drain into internal jugular vein

Question 6

How does blood drain the brain

Answer 6

slide 12 lec 1

Question 7

sinuses of the brain

Answer 7

slide 13lec 1

Question 8

Cerebral Veins within Subarachnoid Space

Answer 8

Cerebral Veins within Subarachnoid Space Drain into Dural Venous Sinuses

Question 9

Sub dural space

Answer 9

Subdural space: potential space between dura and arachnoid (archoid is pushed up against it by pressure of CSF within subarachnoid space

Question 10

Scalp and emissary Veins

Answer 10

Scalp Veins Also Connect with Dural Venous Sinuses

Emissary veins traverse through the skull

Question 11

Intracranial Haemorrhage

Answer 11

Head trauma can lead to bleeding in ‘spaces’ between meningeal layers
• Blood vessels run along or traverse between the meningeal layers
• Injury and bleeding from these blood vessels will cause accumulation of blood in the ‘space’ between the meningeal layers – Extradural – Subdural – Subarachnoid
• Bleeding can also occur within the brain tissue itself (e.g. contusions, tearing of white matter) – Intracerebral haemorrhage
• Addition of ‘volume’ to an already fixed space (the skull) leads to rise in pressure and damage to brain tissue, brainstem and other important structures e.g. cranial nerves

Question 12

Extradural Haemorrhage

Answer 12

Arterial Bleed

Question 13

Subdural Haemorrhage

Answer 13

Venous bleed usually from bridging veins

Question 14

Subarachnoid Haemorrhage

Answer 14

Arterial bleed
• Secondary to trauma or spontaneous rupture of blood vessel e.g. aneurysm – Usually a branch of ‘Circle of Willis’ (the arterial circuit responsible for supplying brain structures)
• Blood leaks into subarachnoid space, mixing with CSF – Sudden, often fatal
• CT imaging of head – 93% picked up if within 24 hours; 100% if within 6 hours – Lumbar puncture-if CT inconclusive: sample CSF to identify presence of blood (haemoglobin degradation products)

Question 15

Treatment of head intracranial bleed

Answer 15

craniotomy use slide 21

Question 16

Neural networks

Answer 16

The brain works like a vast ‘computer’, with many layers of processing. The strengths of individual synapses within the network determines the behaviour of that network. Learning is the process whereby the strengths of these synapses is changed in order to match up a stimulus with an appropriate behaviour

Question 17

Basic components of the CNS compared to PNS

Answer 17

CNS Cerebral hemispheres Brainstem and cerebellum Spinal cord
PNS Dorsal and ventral roots Spinal nerves Peripheral nerves

Question 18

Anatomical terminology and the CNS

Answer 18

Because the human brain ‘flexes’ at around the level of the midbrain, the superior part of the hemisphere is actually dorsal. The inferior brain is actually ventral. Therefore dorsal/ventral brain structures are not necessarily closest to the back/belly respectively.
Remember that in imaging, right and left are reversed

Question 19

Parts of the brainstem

Answer 19

• Midbrain (mesencephalon) • Eye movements and reflex responses to sound and vision • Pons • Feeding • Sleep • Medulla • Cardiovascular and respiratory centres • Contains a major motor pathway (medullary pyramids, which ultimately decussate)

Question 20

Decussation

Answer 20

The fact that the body is controlled by the contralateral side of the brain has been appreciated since the time of the ancients

Question 21

Sulci, gyri and fissures

Answer 21

Sulcus(pl. sulci): A ‘groove or furrow’ in the brain separating adjacent gyri Gyrus(pl. gyri): A ‘ridge or fold’ in the brain Fissure: A large ‘crack’ or ‘split’ between adjacent large areas of the brain

Question 22

The lateral aspect of the cerebral hemisphere

Answer 22

Frontal lobe: Higher cognition, motor function, speech Parietal lobe: Sensation, spatial awareness
Temporal lobe: Memory, smell, hearing Occipital lobe: Vision Cerebellum: Co-ordination and motor learning

Question 23

The inferior aspect of the cerebral hemisphere

Answer 23

Optic chiasm: A site where fibres in the visual system cross over Uncus: Part of the temporal lobe that can herniate, compressing the midbrain Medullary pyramids: Location of descending motor fibres (each has around 1 million axons!)

Question 24

The medial aspect of the cerebral hemisphere

Answer 24

Corpus callosum: Fibres connecting the two cerebral hemispheres Thalamus: Sensory relay station projecting to sensory cortex
Hypothalamus: Essential centre for homeostasis