Global Brain Activity

Question 1

How does CSF differ from serum?

Answer 1

Less protein & less K

Similar Na & HCO3 & osmolality

Question 2

What is homeostasis?

Answer 2

Maintenance of the environment to optimise conditions for the brain to work.

Question 3

Which is the most important ion in terms of osmosis?

Answer 3

Na - H2O follows Na.

Question 4

Where does K+ levels have significant influence?

Answer 4

In the peripheral system - important in maintaining the heart beating at the right pace.

Question 5

How is acid-base balance affected by ventilation?

Answer 5

Hypoventilation - acidosis
Hyperventilation - alkalosis

Question 6

What is the normal values of Na in the blood?

Answer 6

135-145

Question 7

What is hyponatremia?

Answer 7

Low levels of Na outside the cell - means the intracellular content of Na is higher - so water floods into cells causing cerebral oedema

Question 8

How does the brain try to compensate for hyponatremia?

Answer 8

Shifts out the CSF & pushes K+ & osmoloytes out of the cells trying to draw the water out.

Question 9

How does cerebral oedema affect the blood flow to the brain?

Answer 9

It causes decreased blood flow.

Question 10

What is the difference between acute and chronic hyponatremia?

Answer 10

Acute - no time to adapt - cerebral oedema & compression can occur.

Chronic - body is able to adapt if the hyponatremia is gradual.

Question 11

How does carbamazepine affect Na levels?

Answer 11

Causes hyponatremia.

Question 12

How does compression of the brainstem affect breathing regulation?

Answer 12

It can depress breathing

Question 13

What is central pontine myelinolysis?

Answer 13

Hyponatremia = swollen cells - if you treat (with Na) and overcorrect - can cause shrunken cells - this damages the cytoskeleton of the cell & demyelinates neurons –> problems.

Question 14

What are the symptoms of Central Pontine Myelinosis?

Answer 14

Quadriplegia
Emotional incontinence
Seizures
Coma
Death
Pseudobulbar Palsy

Question 15

What is Central Pontine Myelinosis caused by?

Answer 15

Rapid overcorrection of low Na levels.

Question 16

What is hypernatremia?

Answer 16

Lots of Na in the interstitium - water leaves cells and moves to the extracellular space = shrinkage of cells.

Question 17

How can hypernatremia affect veins and arteries?

Answer 17

It can cause them to tear & haemorrhage

Question 18

What does the brain do to try and compensate for hypernatremia?

Answer 18

Uptakes K+ into cells
Uptakes osmolytes into the cells

Question 19

What can overcorrection of hypernatremia cause?

Answer 19

Cerebral oedema

Question 20

What is the ideal pH range for the brain?

Answer 20

7.35 - 7.45

Question 21

What does the Henderson Hasselbach equation demonstrate?

Answer 21

That there is an inverse relationship between HCO3 and CO2.

Question 22

Can CO2 cross the BBB?

Answer 22

Yes - easily

Question 23

What regulates cerebral blood flow?

Answer 23

CO2 levels in the brain (more CO2 - inc BF & vice versa)

Question 24

How does hyperventilation affect Ca?

Answer 24

Causes hypocalcemia.

Question 25

What are the symptoms of hyperventilation?

Answer 25

Lightheadedness, syncope, seizures & hypocalcaemia

Question 26

What are the symptoms of hypoventilation?

Answer 26

Morning headaches, visual disturbances, confusion

Question 27

How does hypoventilation affect the brain?

Answer 27

Increased CO2 = inc blood flow to the brain - causing increase pressure - - headaches, disturbances and confusion.

Question 28

Apart from Na, K, HCO3 - which other ions have impacts on the brain?

Answer 28

Ca, Mg & P Ca & Mg - help stabilise neuronal signalling pathways - so low levels = abnormal firing.

Question 29

What is it called when the brain is affected by an external agent or condition.

Answer 29

Encephalopathy

Question 30

Hypocalcaemia is associated with low/high levels of which ions?

Answer 30

Low K & Mg High P

Question 31

What does a CT scan with contrast show?

Answer 31

If there is breakdown of the BBB

Question 32

What are CT scans based on?

Answer 32

Density of different materials

Question 33

What does windowing and levelling do?

Answer 33

Allows you get change the pictures you get - and therefore see different materials with different densities - e.g. brain window, bone window, blood window.

Question 34

What are the pros of CT?

Answer 34

Quick Metal compatible Cheap

Question 35

What are the disadvantages of CT?

Answer 35

Low resolution - esp brainstem / cerebellum Radiation dose

Question 36

What does CT use to image?

Answer 36

Lots of X-rays

Question 37

What does MRI use to image?

Answer 37

The magnetism of proton molecules

Question 38

Why is MRI preferable over CT?

Answer 38

You get more detailed pictures with MRI than CT

Question 39

How can dye show if the BBB is leaky?

Answer 39

Dye should remain in the arterial / vascular systems - if there is an injury to the BBB you will get leakiness of the dye into other areas.

Question 40

What are the pros of MRI?

Answer 40

Detailed Wide range of imagining possibilities No ionising radiation

Question 41

What are the cons of MRI?

Answer 41

Metal = issue Claustrophobia Time consuming Loud Can heat up the body

Question 42

What is an fMRI?

Answer 42

Uses characteristics of oxy & deoxy - measures local neuronal activity based on vascular response to glucose - shows which areas of the brain are metabolising glucose.

Question 43

How does transport of glucose affect vessels?

Answer 43

Causes the BVs to dilate

Question 44

What are default areas on an fMRI?

Answer 44

Areas where the brain is always metabolising - is the background system running when no specific task is assigned.

Question 45

How does PET-CT work?

Answer 45

Injection with radioactive substance - uses CT to outline where in the body this is.

Question 46

What are the cons of PET-CT?

Answer 46

Radioactive isotopes Very expensive - used sparingly

Question 47

What is used to determine whether a tremor is Parkinsons?

Answer 47

SPECT (single photon emission computed tomography)