BIOMED 1

Question 1

What 2 things does blood carry to the brain?

Answer 1

Oxygen
Glucose

Question 2

What is oxygen in the brain crucial for?

Answer 2

Cellular respiration in neurons (mainly aerobic in mitochondria)

Question 3

What is low oxygen in tissues called?

Answer 3

Hypoxia

Question 4

What is complete loss of oxygen in tissues called?

Answer 4

Anoxia

Question 5

What happens if the brain is deprived of oxygen?

Answer 5

ATP depletion in cells
-> loss of function (eg: ATPase pump)

Question 6

How long does it take for irreversible brain damage to occur in hypoxia vs anoxia?

Answer 6

Hypoxia= 4-6min
Anoxia= 2-3min

Question 7

What is glucose in the brain crucial for?

Answer 7

Making ATP

but… brain can use other substances (eg: ketones, a breakdown product of fat) in ST

Question 8

What are the arteries supplying the brain with blood?

Answer 8

Cerebral arteries

Question 9

In relation to SLT, what happens if blood supply to the brain is disrupted?

Answer 9

Can starve important areas of blood…
- Broca’s area
- Wernicke’s area
- motor/sensory regions (articulation/oral motor control)

Question 10

What are the 5 main upper body arteries?

Answer 10

Question 11

What are the 4 main blood vessels to head and neck?

Answer 11

Common carotid arteries
- external carotid arteries
- internal carotid arteries
Vertebral arteries

Question 12

Where do the common carotid arteries branch into external/internal carotid arteries?

Answer 12

Carotid bifurcation

Question 13

What do the external carotid arteries do?

Answer 13

Several branches deliver oxygenated blood to external tissues of the head

Question 14

What do the internal carotid arteries do?

Answer 14

Delivers oxygenated blood to anterior brain

Question 15

In the brain, what do the internal carotid arteries branch into?

Answer 15

The cerebral arteries
- Middle cerebral arteries (MCA), biggest
- Anterior cerebral arteries (ACA), smaller

Question 16

What do the middle cerebral arteries do?

Answer 16

Provide blood mainly to lateral regions of brain

Question 17

Which specific areas of the brain do the middle cerebral arteries bring blood to?

Answer 17

Most of motor and somatosensory cortex (not lower limbs, as at top of homunculus)
Auditory cortex
Broca + Wernicke’s areas

Question 18

What do the anterior cerebral arteries do?

Answer 18

Provide blood mainly to medial regions of brain

Question 19

Which specific areas of the brain do the anterior cerebral arteries bring blood to?

Answer 19

1cm strip of most medial regions at edge of each hemisphere (frontal + parietal lobes’ medial surface)

Question 20

What do the vertebral arteries do?

Answer 20

Deliver oxygenated blood to posterior brain + cerebellum + brainstem

Question 21

Where do the vertebral arteries pass through to form?

Answer 21

Foramen magnum (either side of medulla)
Merges to form basilar artery (vertebral-basilar arterial system)
Then divides to form L/R posterior cerebral arteries

Question 22

Which specific areas of the brain do the vertebral arteries bring blood to?

Answer 22

Entire occipital lobe (incl. visual cortex)
Inferior + medial surfaces of temporal lobe

Question 23

What are the 2 communicating arteries?

Answer 23

Posterior communicating artery
Anterior communicating artery

Question 24

What does the posterior communicating artery connect?

Answer 24

Connects posterior cerebral artery (PCA) with main internal carotid as it enters the brain

note: red arrow

Question 25

What does the anterior communicating artery connect?

Answer 25

Connects the 2 anterior cerebral arteries (ACA) note: blue arrow

Question 26

What is the Circle of Willis?

Answer 26

The communicating arteries connect blood flow between anterior blood supply and posterior blood supply

Question 27

What are 2 disadvantages of the Circle of Willis?

Answer 27

May not be able to provide enough blood to compensate for large artery blockage eg: basilar artery, carotid artery (communicating arteries are very narrow) May be incomplete in 50-90% of people

Question 28

What are the perforating arteries?

Answer 28

Small arteries that branch off cerebral arteries Supplies deep tissues: thalamus, internal capsule, basal ganglia

Question 29

What is a problem with the perforating arteries?

Answer 29

Narrow- prone to cerebrovascular accident (CVA), can become blocked/damage, can cause stroke

Question 30

Is the brain in direct contact with the skull bones (cranium)?

Answer 30

No- is covered by 3 layers of membrane: meninges

Question 31

What do the meninges do?

Answer 31

Cover and protect the brain + spinal cord

Question 32

What are the 3 main layers of the meninges?

Answer 32

Dura mater (orange) Arachnoid mater (white) Pia mater (red)

Question 33

Describe the dura mater

Answer 33

Very thick, fibrous, protective layer lining the cranial bones 2 layers closely adherent to each other

Question 34

Why does the dura mater have 2 layers?

Answer 34

To tightly wrap around brain so no gaps for it to move around

Question 35

What is the space directly beneath the arachnoid mater called?

Answer 35

Subarachnoid space CSF circulates between the arachnoid mater and pia mater in this space

Question 36

What are the fibrous structures that attach the arachnoid mater to the pia mater?

Answer 36

Mainly strong, flexible collagen fibres

Question 37

Describe the pia mater

Answer 37

Thin layer in close contact with brain Connective tissue, tough, but thin Closely follows contours of most sulci and gyri Vascularised- blood vessels branch and go deep into brain tissue to supply brain with blood

Question 38

On which layer of the meninges do the cerebral arteries start?

Answer 38

Starts by running on top of pia mater in subarachnoid space

Question 39

What are 2 functions of the dural folds?

Answer 39

Provides space for drainage of venous blood (venous sinuses) Creates folds that separate and encase regions of the brain

Question 40

What are the names of the 2 main dural folds that separate and encase brain regions?

Answer 40

Falx cerebri Tentorium cerebelli

Question 41

What does the falx cerebri do (dural fold)?

Answer 41

Vertical Between the cerebral hemispheres Stabilises brain during sudden movement L/R

Question 42

What does the tentorium cerebelli do?

Answer 42

Horizontal Forms roof over cerebellum, separating it from occipital + temporal lobes Stabilises brain when head moved forward/backward

Question 43

Where does the cerebrospinal fluid (CSF) move?

Answer 43

Continually moves around the brain + spinal cord

Question 44

What are the 4 functions of the cerebrospinal fluid (CSF)?

Answer 44

Cushions brain + spinal cord (shock absorber) Gives buoyancy to brain (lowers force brain exerts on tissue during mechanical injury) Nutrient exchange + removal of waste products from the brain Contains dissolved CO2- high CO2 detected by medulla (will increase ventilation rate to clear CO2)

Question 45

Where is CSF made?

Answer 45

Ventricles of the brain (spaces/chambers) by tissue called choroid plexus, by ependymal cells in CNS

Question 46

How many ventricles are there in the brain?

Answer 46

4 Right + left lateral ventricles Third ventricle Fourth ventricle

Question 47

What is the volume of CSF humans have?

Answer 47

120-150ml

Question 48

How fast is CSF produced and replaced?

Answer 48

Produced slowly Replaced approx 6 times/day

Question 49

What does the blood-brain barrier do?

Answer 49

Very tightly regulates molecule transport in/out of CNS Prevents blood cells + plasma components + pathogens from entering brain

Question 50

How are capillaries in the blood-brain barrier specially adapted?

Answer 50

Tight junctions prevent water-soluble agents from crossing into cerebral tissues - small molecules (eg: glucose, amino acids, ions) cross with special transporter protein Surrounded by astrocytes as partly effective barrier (second line of defence, alongside tunica intima with endothelial cells)

Question 51

Which drugs can pass through the blood brain barrier, and which can't?

Answer 51

Lipophilic drugs can dissolve through phospholipid bilayer of endothelial cells and into brain Water soluble drugs can't pass into brain as no receptor transport proteins