Cerebral Blood flow

Question 1

what are the 2 main categories of circulation and the arteries involved in the cerebral blood flow circulation?

Answer 1

Anterior circulation: brings blood flow to the brain
1. carotids
2. anterior cerebral artery
3. middle cerebral artery

Posterior circulation: arteries surrounding the brain
1. Vertebrals/ basilar
2. posterior cerebral artery- posterior is an artery surrounding the brain

Question 2

which artery supplies 80% of blood flow to the brain?

Answer 2

Internal carotid artery

Question 3

how much does the vertebral arteries contribute to the flow of brain?

Answer 3

20%

Question 4

what 2 arteries provide most of the blood flow to the brain?

Answer 4

Carotids: the internal carotid and external carotid because they branch from arteries coming from the heart

Question 5

Where is the physical location that the carotids bifurcate to on the human head?

Answer 5

Internal carotid- go to the base of the skill- meets with the basilar artery
External carotid- goes to the base of the ear

Question 6

do veins or arteries bring deoxygenated blood flow back down to heart from brain and body?

Answer 6

veins

Question 7

which artery arises from the vertebral arteries and delivers blood flow to the brain traveling through the mibrain, pons and medulla?

Answer 7

basilar artery

Question 8

posterior auricular artery function and location

Answer 8

vestibular function (maintain your balance and sense of orientation)- supplies blood to posterior scalp and ear

shallow artery behind ear, easily damaged
originates from external carotid artery

Question 9

what areas of the brain does the anterior cerebral artery supply?

Answer 9

Frontal lobe
- parietal and corpus callosum

Question 10

what areas of the brain does the posterior cerebral artery supply?

Answer 10

occipital lobe
- thalamus and midbrain

Question 11

what areas of the brain does the middle cerebral artery supply?

Answer 11

insula (deep), parietal and temporal
(lateral frontal, parietal and temporal)

Question 12

which artery is largest of the cerebral arteries and is often affected in strokes?

Answer 12

MCA (middle)

Question 13

which structure supplies blood to opposite sides of the brain / in many directions so if there is a stroke or blockage, it acts as a safeguard for occlusions?

Answer 13

the circle of willis

Question 14

posterior circulation includes ______ and ________ cerebral artery

Answer 14

superior: which goes to the pons (superior cerebral artery goes to the pons because it is above/on top of the medulla)

posterior: which goes to the cerebellum (remember cerebellum is structure behind pons)

Question 15

non-invasive ultrasound that uses sound waves to examine blood flow in the brain and creates images of vascularity in the brain (like hemorrhage, intracranial pressure, vasospasms etc.)- is that a TCD (transcranial) ultrasound or extracranial ultrasound?

Answer 15

CD (transcranial) ultrasound

uses a headband to measure middle cerebral artery pulse wave in temporal region (no bone to obstruct). Non invasive - bc it used the headband that measure from outside (trans-cranial)

Question 16

does the extracranial or TCD ultrasound measure the external carotid?

Answer 16

the extracranial measures the external carotid

TCD- measure middle cerebral artery

Question 17

what are the 3 measurements of oxygen consumption?

Answer 17

1. BOLD (blood oxygen level dependent imaging) fMRI- functional magnetic resonance imaging (MRI) measuring the replacement of hemoglobin/oxygen use in brain using magnetic fields; studies cognitive function because when brain is active, blood flow and oxygen inc in surrounding area. Can take a lot of analysis and is expensive. Can be used in dementia.
2. NIRS - near infrared spectroscopy
   put headband on head and look at oxygenation in frontal lobe using light (non invasive)
3. In ear pulse wave analysis- looks inside ear at external carotid. Looks at peripheral pressure waveforms and generates central waveforms. Estimates cardiac output by analyzing arterial blood pressure.

Question 18

what is the myogenic mechanism in relation to cerebral autoregulation?

Answer 18

ability of arteries and arterioles to automatically adjust blood flow in response to changes in blood pressure- reflex from muscle, brain does not consciously do it.

Brain stays perfused despite fluctuations in blood pressure at the heart. Even if there is a lack of blood flow in the body, the brain can still focus.

This mechanism is important because the brain can’t control/change extraction of oxygen from blood, so this mechanism keeps blood flow stable bc brain needs 20% of energy for entire body. Keeps blood flow perfused to brain.

Question 19

________ occurs more commonly in men, who are older than 65, and more so in black and LatinX communities

Answer 19

Stroke

Question 20

blood flow to the brain is blocked by a blood clot or plaque buildup. This prevents oxygen and nutrients from reaching brain cells, which can lead to brain damage, disability, or death is what type of stroke: ischemic or hemorrhagic

Answer 20

ischemic

Question 21

which stroke type is more common?

Answer 21

ischemic

Question 22

what is a hemorrhagic stroke?

Answer 22

blood vessel in or on the brain ruptures and bleeds –> brain cell and tissue damage, swelling, and pressure

Can be caused by: high blood pressure, aneurysm, arteriovenous malformation, head injury, and bleeding disorder

Question 23

what are 3 risk factors that increase your chances of a stroke that contribute to atherosclerosis?

Answer 23

HTN (140/90)
hypercholesterolemia
smoking

other things not related to ATH but can inc risk of stroke is can be:
- DM
- alc more than 2x per day
- oral contraceptive WITH smoking

Question 24

which artery is the most common to have a stroke in?

Answer 24

Middle cerebral artery, feeds most of the brain

Question 25

Which artery is more likely to get a TIA (temporary ischemia/occlusion of blood)? symptoms less than 24 hrs with no lasting damage

Answer 25

internal carotid. 2nd leading artery affected for stroke after middle cerebral

Question 26

what parts of the body does the MCA artery in stroke affect?

Answer 26

Face and upper extremity

Question 27

what parts of the body does the PCA artery in stroke affect? think about what parts of the body the PCA supplies

Answer 27

occipital lobe- vision thalamus- homeostatic temporal lobe- auditory and temp

Question 28

What is the process of an atherosclerosis forming?

Answer 28

1. endothelial damage to cells 2. fatty stage where cholesterol/LDL (bad cholesterol) accumulate in artery: LDL migrates to intima and is oxidized. 3. macrophages bind to the oxidized LDL to form foam cells (big inflammatory cells) 4. foam cells interact with T-cells to produce cytokines that interact with the vessel wall 5. Smooth cells migrate to the intima 6. smooth cells secrete extracellular matrix proteins that form a fibrous cap over the foam cells 7. Capped foam cells form plaques that protrude into arterial lumen- obstructing blood flow 8. plaques can rupture= platelet aggregation to heal rupture and form a thrombus (blood clot) thrombosis causes an acute or chronic ischemia

Question 29

The vertebral artery supplies blood to which areas and parts of the body?

Answer 29

upper spinal cord, brainstem, cerebellum, posterior brain

Question 29

The internal carotid artery has many branches that supply the eyes and face: 1. Ophthalmic artery- supplies what organs of the face? 2. Middle cerebral artery- supplies motor and sensory to face and UE/LE? 3. Anterior cerebral artery- supplies motor and sensory to UE or LE?

Answer 29

1. ophthalmic artery - lacrimal glands (crying), eye, extraocular muscles, parts of forehead, upper nose 2. Middle cerebral artery- supplies face and UE 3. anterior cerebral artery- LE

Question 30

how is cerebral blood flow measured?

Answer 30

ultrasound (doppler) in conscious humans cerebral blood flow is a dynamic measurement- depends on position you are in, what the outcomes will be. DIFFERENT positions cause fluctuations.

Question 31

what is a drawaback of a TCD?

Answer 31

you can only measure velocity with TCD. To get blood flow measurement- need velocity and area/diameter of vessel

Question 32

what is an extracranial ultrasound?

Answer 32

measures external carotid- much bigger vessel and easy to access through the neck/ Can measure velocity and diameter . This extracranial ultrasound is done a lot clinically to see is there is atherosclerosis (blockage of blood) compared to TCD which is mainly used for research. Disadvantage- ultrasound is expensive.

Question 33

what is cerebral hypoperfusion?

Answer 33

too little blood flow to the brain

Question 34

describe how gravity affects blood flow

Answer 34

syncope (fainting when standing or changing positions). When you stand up, there is decreased blood flow to the brain bc gravity pulls blood flow to the legs. In healthy people it vasoconstricts (vessels get smaller) so it pushes blood flow back up to heart, but it does not always work- some people struggle and develop POTS

Question 35

is blood flow static or dynamic?

Answer 35

dynamic- changes with positioning of body

Question 36

how does cerebral autoregulation differ in healthy population vs POTS population in the head tilt test and why does this happen?

Answer 36

blood flow normally drops 10% in healthy pop, in POTS pts it drops 20% (2x). In POTS, their body has adapted to bad circulation. When bloody flow drops, chemoreceptors make the pressure increase and ventilation goes up (to get more blood flow). . HR is the last thing that goes up. In POTS, MAP keeps dropping despite blood pressure being in normal range. MAP= average blood pressure in an individual during a single cardiac cycle. MAP is the pressure that drives blood throughout the circulatory system. ChatGPT: Normally, when you stand up, gravity pulls blood down towards your legs. To keep your brain well-supplied with blood, your heart rate increases slightly, and your blood vessels tighten (constrict) to push blood back up. In POTS, this system doesn’t work properly. Your heart rate speeds up too much (tachycardia), but your blood vessels don’t constrict effectively. This leads to less blood returning to the heart and brain. If enough blood doesn’t reach the brain, it can result in symptoms like dizziness, lightheadedness, brain fog, and sometimes fainting

Question 37

how does the body account for autoregulation of blood pressure in pregnant people?

Answer 37

During pregnancy, blood volume increases by 30–50% to meet the metabolic demands of the growing fetus and placenta. Cardiac output (the amount of blood the heart pumps per minute) also increases, peaking at about 40–50% above pre-pregnancy levels by the second trimester. Despite the increased blood volume and cardiac output, blood pressure generally remains normal or slightly lower in early and mid-pregnancy due to vascular changes. There is a wider range of buffering in arterial pressure to account for blood pressure changes which protects the brain from postpartum hemorrhage and eclampsia.

Question 38

How fast does an ischemic stroke happen?

Answer 38

fast- 3.5 hours

Question 39

what is a hematoma?

Answer 39

Collection of blood that forms outside the the blood vessels in an organ tissue or body space Types of intracranial hemorrhage: - epidural hematoma - subdural hematoma - subarachnoid hemorrhage - intracranial bleeding

Question 40

what is a subdural hematoma?

Answer 40

below dura mater, b/w dura mater and brain= does not touch skull. Think below the skull but between the brain. SLOW expansion of VENOUS blood SLOW BLEED- damage is greater bc it can be missed Vein is more tough than artery- so fall has to be worse to damage vein SDH are more common than epidural Death rate is higher for SDH- 50%- delayed symptom's, sneak up on you concave/crescent shaped

Question 40

what is an epidural hematoma?

Answer 40

above dura mater= between skull and dura matter (outermost layer covering brain) think b/w outside of brain and skull. FAST bleed of ARTERIAL blood easier to dx bc they are sudden and obvious typically lens/convex/lemon shaped shaped bc they cannot cross the sutures (located in one specific lobe)