Topic 14-Stroke

Question 1

Which part of the brain has low/high oxygen consumption?

Answer 1

The brainstem has low oxygen consumption, while the cortex has the highest oxygen consumption and is more vulnerable to hypoxia (low oxygen).

Question 2

Why is the regulation of artery diameter important for brain tissue?

Answer 2

Regulating artery diameter is crucial to maintain a constant blood supply to brain tissues.

Question 3

What are the primary factors that control autoregulation of artery diameter for brain blood supply?

Answer 3

Depends on two factors: blood pressure and metabolites.

Question 4

How does the autoregulation of artery diameter depend on blood pressure?

Answer 4

When blood pressure increases, the arteries can constrict (get narrower) to help regulate the flow of blood and maintain stable pressure. When blood pressure decreases, arteries can dilate (widen) to ensure that enough blood reaches tissues and organs.

Question 5

How does the autoregulation of artery diameter depend on metabolites?

Answer 5

Metabolites can signal arteries to either dilate or constrict depending on the specific needs of the tissue to maintain blood flow

Question 6

What processes in the brain require energy?

Answer 6

Energy is needed for maintaining resting potential, synthesizing, removing, and recycling neurotransmitters (NTs), among other functions.

Question 7

Where does most of the energy for brain functions come from?

Answer 7

Most of the brain’s energy is obtained from the oxidation of glucose.

Question 8

What does the brain require for its energy needs?

Answer 8

The brain requires a constant flow of blood rich in glucose and oxygen to meet its energy demands.

Question 9

Which artery supplies the brainstem and what can damage to this artery affect?

Answer 9

Basilar artery supplies the brainstem, including the pons and cerebellum. Damage to this artery can lead to cerebellar dysfunction and affect pontine nuclei functions.

Question 10

What is the Circle of Willis and its significance?

Answer 10

An interconnected ring of arteries at the base of the brain that provides collateral circulation to ensure a continuous blood supply to the cerebral hemispheres.

Question 11

What is the function of the posterior communicating artery?

Answer 11

The posterior communicating artery branches connects the internal carotid artery (part of the anterior circulation) to the posterior cerebral artery (part of the posterior circulation) in the circle of Willis

Question 12

Into which arteries does the internal carotid artery divide, and what brain areas do they supply?

Answer 12

The internal carotid artery divides into the anterior cerebral artery and the middle cerebral artery, supplying the frontal and temporal lobes of the brain.

Question 13

Which artery is not the primary supplier for the entire midbrain but does provide some blood supply?

Answer 13

The posterior cerebral artery supplies blood to the midbrain but is not its primary supplier

Question 14

Where does the posterior cerebral artery originate from and supply which areas?

Answer 14

Originates from the neck and supplies the occipital lobe and parts of the temporal lobe, impacting vision and perception.​

Question 15

What arteries supply blood to the cerebrum?

Answer 15

The cerebrum receives its blood supply from the internal carotid artery and the posterior cerebral artery,vertebral cerebral artery

Question 16

Which brain regions does the anterior cerebral artery supply blood to?

Answer 16

The anterior cerebral artery supplies blood to the medial surface of the frontal and parietal lobes, including the anterior part of the caudate.

Question 17

What areas does the middle cerebral artery cover, and what does it supply?

Answer 17

The middle cerebral artery fans out over most of the lateral hemisphere and has deep branches that supply subcortical structures including the basal ganglia and thalamus.

Question 18

What are the three main categories in the used to describe the progression of strokes? Their Functions

Answer 18

1)Transient Ischemic Attack (TIA): : Brief loss of brain function with full recovery within 24 hours, caused by reduced blood flow.
2) Completed Stroke: Deficits persist for more than 24 hours but remain stable; the person is not getting worse but is not the same as before.​
3) Progressive Stroke: Deficits increase intermittently over time, often due to repeated issues like embolism (a blockage in a blood vessel).​

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Question 19

Two major causes of Stroke:

Answer 19

1) Ishcemic: Blockage of a blood vessel caused by a blood clot ​
2) Hemorrhagic: Rupture of a blood vessel

Question 20

What is a brain infraction?

Answer 20

A stroke (blockage of blood full) blockage caused by a blood clot, with two types: embolus (occurs from somewhere else in the body and travles till it lodges an artery) and thrombus (formed within one of the arteries

Question 21

What can a thrombus result from?

Answer 21

A thrombus can result from conditions like atherosclerosis, where plaque builds up inside an artery, eventually blocking the vessel.​

Question 22

What is am embolous?

Answer 22

A clot that breaks off from another location and travels through smaller vessels until it becomes stuck, blocking blood flow.​

Question 23

Embolic Stroke

Answer 23

Sudden and occurs when a clot, known as an embolus, travels from another part of the body and gets lodged in the brain’s smaller vessels, abruptly blocking blood flow.

Question 24

What characterizes a thrombotic stroke?

Answer 24

May occur abruptly or worse over several days as plaque builds up and eventually closes an artery

Question 25

What are the consequences of both embolic and thrombotic strokes in the brain?

Answer 25

Both embolic and thrombotic strokes lead to infarcts, causing ischemia (lack of blood flow) and hypoxia (lack of oxygen) in the brain tissue.

Question 26

What is a lakuna? What does it result from?

Answer 26

A hole or pit and refers to small, localized area of damage or tissue death (infarction) in the brain, typically caused by obstructions in small, deep arteries.

Question 27

Where do lakunar infarcts commonly occur and what is their prognosis?

Answer 27

Lakunar infarcts often occur in deep structures such as the basal ganglia, internal capsules, thalamus, and brainstem. Patients with lakunar infarcts tend to have slow development of symptoms and generally experience good recovery due to the small size of the lesions.​

Question 28

What are two potential causes of hemorrhagic strokes in the brain?

Answer 28

1) Bursting of an aneurysm which is a dilation/bulging of an arterial wall
2) Arteriovenous malformations (AVMs)

Question 29

What is an arteriovenous malformation (AVM) and how can it lead to a stroke?

Answer 29

A developmental abnormality in the connections between arteries and veins, which can lead to a stroke if the abnormal vessels rupture.

Question 30

How does high blood pressure affect the risk of hemorrhagic stroke?

Answer 30

High blood pressure can weaken blood vessel walls in the brain, making them more likely to burst and cause a hemorrhagic stroke.

Question 31

What is the immediate consequence of a hemorrhagic stroke within the brain?

Answer 31

Hemorrhagic strokes result in the release of blood into the brain, which deprives downstream vessels of blood flow and exerts pressure on the surrounding brain tissue.

Question 32

How do the symptoms of a hemorrhagic stroke typically progress?

Answer 32

The deficits caused by a hemorrhagic stroke generally worsen within hours of onset due to the increasing pressure from the blood released into the brain.

Question 33

What do brain scans look for after a hemorrhagic stroke?

Answer 33

After a hemorrhagic stroke, brain scans check for asymmetric displacement of structures within the brain to identify the extent and location of bleeding.

Question 34

What is a watershed leison?

Answer 34

An area of the brain that is particularly vulnerable to reduced blood flow because it lies between the territories of two major arteries,

Question 35

What can cause watershed lesions?

Answer 35

Results from emboli that affect affect the brain’s vulnerable border areas between blood supply territories.

Question 36

Where is a common site for watershed lesions and what function can it affect?

Answer 36

A common site for watershed lesions is in the frontal lobe, affecting upper limb function

Question 37

Symptoms that a watershed leison can cause

Answer 37

Decrease in blood pressure causing symptoms like upper limb paresis (weakness) or paresthesia (abnormal sensations).

Question 38

What does the term “umbra” refer to in the context of an ischemic stroke?

Answer 38

Refers to the ischemic core where tissue is irreversibly damaged or dead and does not recover.

Question 39

What is the “penumbra” in stroke pathology?

Answer 39

The “penumbra” is the region surrounding the ischemic core (umbra) that is initially larger and consists of potentially salvageable tissue, but this area reduces over time as the damage progresses.

Question 40

Neural Effects of a Stroke (2)

Answer 40

1) Energy Failure: Ischemia during a stroke leads to hypoxia (oxygen deficiency) and decreased glucose availability, resulting in energy failure and glucose deprivation.
2) Excitotoxicity - excessive exposure to glutamate may kill neurons​

Question 41

How does a stroke-induced lack of oxygen affect the brain’s capillaries?

Answer 41

A lack of oxygen during a stroke increases capillary permeability, leading to fluid leakage into the surrounding brain tissue.

Question 42

Why is the Na+/K+ pump important in neurons and how is it affected during a stroke?

Answer 42

The Na+/K+ pump requires ATP to maintain the resting potential in neurons. During a stroke, the lack of oxygen disrupts ATP production, impairing the function of this pump and thus affecting the resting potential.

Question 43

What happens to glutamate levels in brain tissue during a stroke?

Answer 43

During a stroke, oxygen-deprived neurons release excess glutamate. This leads to increased levels of extracellular glutamate in the brain tissue, which can have harmful effects on neural cells like cell death

Question 44

What are the effects of glutamate excitotoxicity?

Answer 44

Glutamate excitotoxicity leads to an increase in Na+ levels and draws water into the cell. This can result in changes in cell volume and, particularly in the umbra region, can lead to osmotic lysis.

Question 45

How does glutamate excitotoxicity affect intracellular calcium levels?

Answer 45

Glutamate excitotoxicity causes an increase in intracellular Ca++ levels. This increase in calcium activates proteases and lipases, which degrade components of the cell. It may also initiate apoptosis, a programmed cell death process.

Question 46

How can edema (fluid buildup) be managed?

Answer 46

Managed by using a tube (shunt) to redirect excess fluid from the brain and by administering medications like Mannitol and Dexamethasone to reduce fluid and inflammation.

Question 47

How to deal with secondary reactions of a stroke

Answer 47

Reduce inflammation and edema to limit the harmful effects of secondary reactions.​

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Question 48

What is an Acute Treatment for Ischemic Stroke​?

Answer 48

Thrombolytic therapy involves the use of medications such as tissue Plasminogenactivator (TPA) to dissolve blood clots responsible for causing a blockage in the brain’s blood vessels during a stroke.​

Question 49

What is the risk associatd with thrombolytic therapy?

Answer 49

When the clot is dissolved, it can expose delicate and vulnerable blood vessels downstream, potentially leading to a hemorrhagic stroke, where bleeding occurs within the brain. ​

Question 50

How can brain tissue be saved during a stroke?

Answer 50

Brain tissue can be saved during a stroke by protecting neurons from damage and using strategies
1) Use glutamate antagonists to counteract harmful effects.​
2) Apply calcium and sodium blockers to safeguard brain tissue.​
3) Consider antioxidants to combat free radical damage. -Free radicals can damage our cells, so antioxidants help protect our cells from this damage by neutralizing these harmful molecules​

Question 51

Why is the use of neuroprotective treatments important in stroke management?

Answer 51

1) They can extend the effectiveness of clot-busting treatments. 2)Neuroprotective treatments before clot-busting therapies can lead to better outcomes in stroke patients.

Question 52

How is hypothermia a neuroprotective strategy?

Answer 52

It lowers the body’s temperature, which slows down metabolic processes and reduces the brain’s oxygen and energy demands, helping to protect brain tissue from damage during conditions like cardiac arrest or stroke.