Cerebral Vasculature and Brain Homeostasis Flashcards by Peter Bang

All of the following is true regarding CSF, EXCEPT for what?

A. there is ~150mL of CSF around the brain at any given moment

B. we make ~ 550mL/day of CSF

C. CSF is regularly recycled in the ventricles

D. None of the above are correct

CSF is regularly recycled in the ventricles

CSF is NOT RECEYCLED

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The CSF in the brain flows through 4 ventricles which are each connected by small foramen, apertures, and aquaducts. Which of the following connects the LAteral Ventricles to the 3rd Ventricle?

A. Intraventricular Foramen

B. Cerebral Aquaduct

C. Median Aperture

D. Lateral Apertures

Intraventricular Foramen

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The CSF in the brain flows through 4 ventricles which are each connected by small foramen, apertures, and aquaducts. Which of the following connects the 4th Ventricle to the cisterna magna?

A. Intraventricular Foramen

B. Cerebral Aquaduct

C. Median Aperture

D. Lateral Apertures

Median Aperture

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The CSF in the brain flows through 4 ventricles which are each connected by small foramen, apertures, and aquaducts. Which of the following connects the 3rd ventricle to the 4th ventricle?

A. Intraventricular Foramen

B. Cerebral Aquaduct

C. Median Aperture

D. Lateral Apertures

Cerebral Aquaduct

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The CSF in the brain flows through 4 ventricles which are each connected by small foramen, apertures, and aquaducts. Which of the following connects the 4th ventricle to the arachnoid space?

A. Intraventricular Foramen

B. Cerebral Aquaduct

C. Median Aperture

D. Lateral Apertures

Lateral Apertures

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T/F: The blocking of any of the aquducts, foramen, or apertures that connect the ventricles will absolute stop the flow of fluid to the ventricles they correlate with

True; duh

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The Choroid plexus is generally produces the CSF and is found in all of the ventricles. However, what two ventricles have the most?

A. Lateral and 3rd

B. 3rd and 4th

C. Lateral and 4th

D. None of the above

Lateral and 4th ventricles

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The choroid plexus makes about ___-____% of the CSF, while the rest of the CSF is produced by tissue lining the ______ and blood vessels

The choroid plexus makes up about 50-70% of the CSF, while the rest of the CSF is produced by tissue lining the ventricles and blood vessels

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Producing CSF is a two stage process that involvesfilatration of blood plasma and modifying the ion composition. The filtration of plasma (serum) is passive and involves two main pressures Hydrostatic and Oncotic, both with a tissue and capillary aspect. Which of the following correctly describes capillary Hydrostatic pressure ?

A. Osmotic pressure inside the capillary that pulls fluid in to the vessel

B. Pressure that surrounds the capillary and pulls fluid out of the vessel

C. Small pressure surrounding the capillary that pushes fluid into the capillary

D. Large pressure within the capillary that pushes fluid out of the vessel

Large pressure within the capillary that pushes fluid out of the vessel

Capillary Hydrostatic Pressure is Blood Pressure

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Which of the following is true of passive filatration of serum during the first stage in forming CSF?

A. Blood pressure in the capillary is less than tissue hydrostatic pressure

B. Fluid moves from the ventricles into the blood vessels

C. The capillary and tissue oncotic pressures cancel each other out

D. All the above are correct

The capillary and tissue oncotic pressures cancel each other out

B/C the oncotic pressures cancel one another out, and the capillary hydrostatic pressure is greater than tissue hydrostatic pressure, fluid is pushed out of the blood vessels and into the ventricles

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A. Osmotic pressure inside the capillary that pulls fluid in to the vessel

B. Pressure that surrounds the capillary and pulls fluid out of the vessel

C. Small pressure surrounding the capillary that pushes fluid into the capillary

D. Large pressure within the capillary that pushes fluid out of the vessel

Pressure that surrounds the capillary and pulls fluid out of the vessel

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Production of CSF is constant over a wide range of intracranial pressures. How is this information clinically relevant?

Even if their is a high intercranial pressure, our bodies will continue to make CSF…uh oh boom goes the dynamite

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Although the CSF is filtered blood plasma/serum, the concentration of certain ions are different. What 2 ions are the same for the most part?

HCO₃

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Although the CSF is filtered blood plasma/serum, the concentration of certain ions are different. What 3 ions are greater in concentration in the CSF than the plasma?

CO₂: the brain uses so much oxygen, that a lot of CO₂ is present

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What 4 substances are found in lesser concentration in CSF compared to the blood plasma?

Protein

Glucose

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We know that [K+] is less in the CSF as compared to serum. Why is this the case?

Our bodies make CSF with low potassium concentration, in order to compensate for the natural efflux of potassium out of the blood

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Which of the following correctly explains why its important for CSF to have enough protein?

A. Protein is a good hydrogen ion buffer and this helps regulate the pH

B. Without protein, hydrogen ion levels would decrease causing the blood to be basic

C. Protein helps transport potassium out of the blood

D. None of the above are correct

Protein is a good hydrogen ion buffer and this helps regulate the pH

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How does the body get rid of CSF?

CSF is reabsorbed by the arachnoid villi in the end

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When removing CSF, the arachnoid villi projects from the pia mater into the sinuses to reabsorb fluid that’s found between what two layers?

A. Pia and arachnoid mater

B. Arachnoid and meningeal dura layer

C. periosteal dura and meningeal dura layer

D. Skull and dura layer

Arachnoid and meningeal dura layer

The bulk flow of CSF into the sinuses for reabsorption is the primary way we get rid of CSF, however, what other process is utilized?

A. Dehydration

B. recycling of CSF back into blood

C. pinocytosis

D. None of the above

pinocytosis

Which of the following correctly expresses how the reabsorption of CSF is related to intracranial pressure?

A. The more pressure in the subarachnoid space, the less I filter out

B. The more pressure in the subarachnoid space, the more I filter out

C. Pressure greater than 68 mm CSF leads to no more reabsorption

D. Pressure less than 68 mm CSF leads to no more reabsorption

E. B and D

D. A and D

The more pressure in the subarachnoid space, the more I filter out

Pressure less than 68 mm CSF leads to no more reabsorption

What stage in the CSF’s life cycle is the most controlled, why?

Reabsorption stage

the reabsorption stage is dependent on intracranial pressure

Which of the following is the normal mm CSF where reabsorption is optimal?

A. Less than 68

B. 98

C. 112

D. greater than 112

112

NOTE: neurons are also VERY sensitive to pressure (think of foot falling asleep)

The Blood Brain Barrier are specialized capillaries in the brain that have 2 components that limit exchange. What are these 2 components?

Tight junctions between endothelial cells

Glial end feet that surround the blood vessel

The BBB doesn't let a lot of materials through, however what 4 things can move readily via passive diffusion? Explain how.

H2O: aquaporin 4 CO2: highly lipid soluble O2 Free steroid hormones

Glucose is the MAJOR energy source of neurons and the brain, but sadly it does not readily cross the BBB without a transporter. Depending on where the glucose is entering and its destination influences what transporter is used. Which of the following transporters would glucose use to get across the endothelial cells on capillaries and reach the brain? A. Insulin independent GLUT 1 55K B. Insulin dependent GLUT 3 C. Insulin independent GLUT 1 45K D. Any of the above

Insulin independent GLUT 1 55K

Glucose is the MAJOR energy source of neurons and the brain, but sadly it does not readily cross the BBB without a transporter. Depending on where the glucose is entering and its destination influences what transporter is used. Which of the following transporters would glucose use to get across the endfoot processes of astroglia and reach the brain? A. Insulin independent GLUT 1 55K B. Insulin dependent GLUT 3 C. Insulin independent GLUT 1 45K D. Any of the above

Insulin independent GLUT 1 45K

What transporter does glucose use to get to the neurons? A. GLUT 1 B. GLUT 2 C. GLUT 3 D. GLUT 4

GLUT 3

The Na/K/2Cl transporter is responsible for moving ions from the CSF to the brain through the BBB. Expression of this transporter is controlled by the release of what 2 factors released from endothelial cells of blood vessels? The transporter is mostly related to the concentration of what ion, why?

Endothelin 1 Endothelin 3 Potassium: elevated levels of K seem to lead to the removal of all of the ions of the transporter (Na/K/2Cl)

T/F: The Na/K/2Cl transporter makes the ions neutral in order to cross the BBB

True

As it turns out, many drugs are able to cross the BBB, but are moved back into the blood by what protein? A. Endothelin 1 and 3 B. P-glycoprotein C. G-glycoprotein D. E-glycoprotein

P-glycoprotein *this binds to many substances which is not typical of most transporters*

Which of the following correctly articulates the function of the BBB? A. Maintain electrolyte composition of CSF as it relates to K concentration B. Maintain electrolyte comonsition of CSF by maintaing Vm C. Protect the brain from toxins D. All of the above E. Some of the above F. None of the above

All of the above

There are 4 regions in the brain called Circumventricular organs, where it is necessary that these places are exposed to blood borne substances in order to do their jobs effectively. Because of this need, the BBB is "NERF'd" in these areas. What is missing in these regions that allows them to be exposed more?

Tight junctions are NOT here

Which of the following Circumventricular organs of the brain is derived from neural tissue and needs to knwo what's going on in the environemtn in order to release hormones in the blood? A. Area Postrema B. Organum Vasculosum of the Lamina Terminalis C. Subfornical organ D. Posterior Pituitary

Posterior Pituitary

Which of the following Circumventricular organs is found in the back of the brain near the medulla, and has a chemostatic trigger zone that detects toxins in the blood and triggers vomiting? A. Area Postrema B. Organum Vasculosum of the Lamina Terminalis C. Subfornical organ D. Posterior Pituitary

Area Postrema

Which of the following Circumventricular organs is involved in control of body water/thirst/blood volume control? (select all that apply) A. Area Postrema B. Organum Vasculosum of the Lamina Terminalis C. Subfornical organ D. Posterior Pituitary

Organum Vasculosum of the Lamina Terminalis Subfornical organ

T/F: The Brain gets about 15% of the blood that's produced every minute (750ml/min)

True

The sympathetic innervation of the brain causes contriction when systemic cardiac output or blood pressure increases. This process utilizes which of the following neurotransmitter and receptor pairs? A. Norepinephrine and alpha-adrenergics B. Neuropeptide Y and norepinephrine and alpha-adrenergics C. Ach, Vasoactive intestinal peptide, PHM-27 (derived from pre-pro VIP) and Muscarinic D. All of the above

Neuropeptide Y and norepinephrine and alpha-adrenergics

Parasympathetics related to cerebral circulation utilize NTs: Ach, VIP, PHM-27 to cause vasodilation on which of the following structures? A. Smaller blood vessels B. Venous sinuses C. Larger blood vessels D. All of the above

Larger blood vessels

Which of the following is responsible for releasing neurotransmitter directly back onto the vasculature? A. Sensory neurons on distal blood vessels B. Sensory neurons on proximal blood vessels C. Sympathetics D. Parasympathetics on large blood vessels

Sensory neurons on distal blood vessels

What are the 3 neurotransmitters that sensory neurons release directly back on to distal blood vessels to cause dilation?

Substance P Neurokinin A CGRP

Describe the sequence that involves sensory afferent neurons dilating blood vessels of the brain when their are low amounts of CSF?

Decreased levels of CSF cause the brain to be heavier and be more susceptible to torsion. This torsion is detected by the sensory neurons, which then release NTs to dilate the blood vessels and bring more blood into the system

Cerebral blood flow is under local control, as _______ consumption dictates where in the brain blood will go.

**oxygen consumption**

Cerebral blood flow is strongly regulated so that the systemic (mean arterial) blood flow can change, but cerebral circulation stays the same. Autoregulation is optimal between what ranges of mean arterial blood pressure? *What helps maintain autoregulation?* A. 0 to 60 mmHg B. 60 to 100 mmHg C. 60 to 140 mmHg D. greater than 100

60 to 140 mmHg **sympathetic stimulation causing vasoconstriction** that protects the capillaries of the brain despite increasing systemic vascular resistance

Cerebral blood flow is influenced by intracranial pressure, as intracranial pressure goes ______ venous outflow is __________ which leads to ______ areterial flow

Cerebral blood flow is influenced by intracranial pressure, as intracranial pressure goes **up** venous outflow is \_**obstructed** which leads to **decreased** areterial flow

A decrease in brain perfusion can occur when intracranial pressure goes up. This decrease is detected by the cardiovascular control centers in the \_\_\_\_\_\_, and ______ systemic blood pressure.

A decrease in brain perfusion can occur when intracranial pressure goes up. This decrease is detected by the cardiovascular control centers in the **medulla**, and **increase** systemic blood pressure. *in this case we don't care about the capillaries*

What 3 things might increase the intracranial pressure which can lead to a decrease in brain perfusion?

Hydrocephalus Cerebral Edema Intracranial bleeding