39 - Circulation of the CNS

Question 1

Proportion of cardiac output required by CNS

Answer 1

~10-20%

Question 2

Broad layout of CNS vasculature

Answer 2

Dense network of small vessels.

Densest in the grey matter, less dense in the white matter

Question 3

What form the Circle of Willis?

Answer 3

Formed by vertebro-basilar system and internal carotid system

Question 4

What form the basilar artery?

Answer 4

Vertebral arteries fusing.

Question 5

Vertebral artery

Answer 5

Formed by a branch of subclavian arteries.

Ascends through spine, enters foramen magnum

Question 6

Internal carotid artery

Answer 6

Branch of the common carotid artery.
Ascends through neck.
Enters through foramen lacerum

Question 7

What does the internal carotid form in the Circle of Willis?

Answer 7

Two branches: anterior cerebral artery

Middle cerebral artery

Question 8

What does the basilar artery form in the Circle of Willis?

Answer 8

Posterior cerebral artery

Question 9

What links the anterior, middle and posterior cerebral arteries?

Answer 9

Posterior and anterior communicating arteries

Question 10

Path of anterior cerebral artery

Answer 10

Arches around the corpus callosum.
Projects branches to medial frontal and parietal lobes through longitudinal fissure.
EG motor, somatosensory cortices of lower limb

Question 11

Possible appearances of a blockage of anterior cerebral artery

Answer 11

Contralateral hemianaesthesia of lower limbs.

Contralateral spastic paralysis of lower limbs

Question 12

Origin of middle cerebral artery

Answer 12

Internal carotid

Question 13

Path of middle cerebral artery

Answer 13

Travels through lateral fissure to supply lateral surface of the brain.

Question 14

Parts of brain, functions, supplied by middle cerebral artery

Answer 14

Frontal, parietal, occipital
Superior surface of temporal lobe

Motor, sensory cortices for most of the body.
If person has language lateralised to left hemisphere, language areas.

Question 15

Possible effects of blocking middle cerebral artery

Answer 15

Spastic paralysis to most of the body.

Language problems.

Question 16

Posterior cerebral artery supply

Answer 16

Supplies inferior temporal lobe, all medial occipital lobe

Question 17

Possible functions impaired by blocking posterior cerebral artery

Answer 17

Contralateral visual field affected

Question 18

Small perforating arteries

Answer 18

Branch from Circle of Willis.

Supply deep structures of cerebrum near where they branch.

Question 19

Things supplied by anterior-most perforating arteries

Answer 19

Optic chiasm, anterior hypothalamus

Question 20

Things supplied by lenticulostriate arteries

Answer 20

Basal ganglia, internal capsule

Question 21

Things supplied by ventral perforating arteries

Answer 21

Ventral midbrain, posterior hypothalamus and thalamus

Question 22

Things supplied by pontine perforating arteries

Answer 22

Ventral pons

Question 23

From where does the ophthalmic artery branch?

Answer 23

Internal carotid, before it branches into the anterior and middle cerebral arteries

Question 24

From where does the choroidal artery branch?

Answer 24

Internal carotid, before it branches into the anterior and middle cerebral arteries

Question 25

Things supplied by the ophthalmic artery

Answer 25

Passes into orbit: eye (including retina), top of nasal cavity and frontal scalp

Question 26

Things supplied by the anterior choroidal artery

Answer 26

Structures in deep lateral hemispheres: Optic tract, lateral ventricles, hippocampus

Question 27

Thing that the vertebro-basilar system broadly supplies

Answer 27

Brainstem

Question 28

``` Branches of the basilar artery 1 2 3 4 ```

Answer 28

Posterior cerebral artery Superior cerebellar artery Anterior inferior cerebellar artery Posterior inferior cerebellar artery (variable, about 10% of the time)

Question 29

``` Branches of the vertebral artery 1 2 3 4 5 ```

Answer 29

``` Meningeal branches Posterior spinal Anterior spinal Posterior inferior cerebellar artery (variable. Originates here most of the time) Basilar artery ```

Question 30

Supply of the midbrain

Answer 30

Posterior cerebral arteries (on the way to the occipital lobe) give branches into the midbrain. Superior cerebellar artery gives branches to most-posterior part.

Question 31

Supply of the pons

Answer 31

Basilar artery runs across anterior part, gives off pontine branches

Question 32

Supply of the medulla

Answer 32

Posterior inferior cerebellar artery (most of the postero-lateral) Anterior spinal artery (medial, anterior part) Vertebral artery (anterolateral)

Question 33

Effect of blocking anterior spinal artery 1 2 3

Answer 33

``` Damage to pyramids (corticospinal tract) leads to contralateral hemiparesis. Medial lemniscus (contralateral somatosensory deficit) Hypoglossal nucleus (ipsilateral flaccid paralysis, because affecting lower motor neurons). ``` Called 'medial medullary syndrome'

Question 34

Anterior spinal arteries

Answer 34

Runs in midline fissure through ventral spine. | Formed by branches of vertebral arteries fusing.

Question 35

Posterior spinal arteries

Answer 35

Two, one on each side of dorsal spine. | Each formed by one vertebral artery.

Question 36

Where do spinal arteries anastamose?

Answer 36

In circumferential arteries, which wrap around spine

Question 37

Reinforcement of blood supply to spine

Answer 37

Segmental branches of the aorta feed into spinal blood supply thorough radicular arteries (EG intercostal or lumbar arteries)