Module B-07 Flashcards by hasina ashraf

Which are the 3 extracellular fluid compartments and the volume of each?

1) Plasma
2) Interstitial fluid
3) CSF

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Where is majority of fluid of body found ?

Intracellular 60%

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Where is CSF found?

1) Intraventricular (23ml)

2) Subarachnoid space (67-117 ml)

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volume of CSF

90-140ml

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4 functions of CSF

1) Maintains Extracellular environment
2) Removes metabolites from CNS
3) regulated cerebral blood flow and pulomonary ventilation
4) Cushions brain

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How does CSF influence cerebral blood flow and pulmonary ventilation?

Owing to changes in its pH

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What is present in high levels in CSF compared to plasma?

Cl-, Mg++ and Na+ (only slightly higher)

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What is present in low levels in CSF compared to palsma

protein, glucose, K+ ,Ca++

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At what levels is lumbar puncture done

L3/L4 or L4/L5

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What is relevance of a lumbar puncture?

1) analysis of CSF

2) measurement of intracranial pressure

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4 adverse effects of Elevated intracranial pressure (ICP)

1) Nausea
2) Bradycardia
3) Systemic hypertension
4) Papilledema

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What does the Monroe-Kellie Doctrine state?

An increase in volume of one component (e.g., brain, blood, or cerebrospinal fluid) will elevate pressure (ICP) or decrease the volume of one of the other elements.

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What are the 3 components of the Blood Brain Barrier

1) Endothelial cells,
2) Astrocytic endfeet
3) Capillary basement membranes

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What are 2 characteristics of capillaries of the brain

lack fenestrations and have tight junctions to prevent paracellular flow (only Transcellular flow takes place)

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What can pass through the BBB?

Small hydrophobic molecules, blood gases, small uncharged polar molecules,urea and glycerol

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The higher the Oil/water partition coefficient the ____ (less/more) effective the transfer of the solute across the BBB

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What are 2 substances moved by facilitated diffusion across the BBB

L-DOPA and Glucose

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Ratio of solubility in oil versus water predicts

transcellular transfer of solutes into CNS

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What transporter is used in BBB endothelial cells for glucose transport?

GLUT-1

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What transporter is used in BBB endothelial cells for L-DOPA transport?

Neutral amino acid carrier

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How does glycine cross the BBB (brain to blood)

Na+-dependent cotransporter ( secondary active transport)

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What can cause the tight junctions of BBB to become leaky?

1) Hypertension (high blood pressure)
2) Hyperosmolality
3) Trauma, ischemia, inflammation or pressure
4) Infection

How does hyperosmolarity cause leaky endothelium

hypertonic infusions shrink endothelial cells and disable tight junction but this is reversible

Clinical use of hyperosmolarity with BBB

may permit delivery of lipid-insoluble drugs to

the CNS

What differs circumventricular organs from rest of CNS

lack tight junctions in capillaries and thus lack | the BBB

Name the Circumventricular organs

1) Area postrema 2) Median eminence 3) Neurohypophysis 4) Organum vasculosum 5) Pineal body 6) Subcommissural organ 7) Subfornical organ

What cells line the ventricles

Ependymal cells (group1)

What cells form the choroid plexuses?

Secretory Ependymal cells (group 2 )

where does CSF circulate?

the ventricles, the spinal canal and the entire | subarachnoid space

Where does CSF come from?

1) Choroid plexus (70%) | 2) specialized secretory ependymal cells of the subcommisural organ (30%)

How is CSF transported by choroid plexus?

- co-transporters for Na+ , K+ and Cl in the basolateral membrane - co-transporters for K+ and Cl ions in the microvilli of the apical membrane. - The membranes also have ion channels for Na+, K+ and Cl in addition to Na/K pumps. - net transport of Na+, K+ and Cl into ventricles, with water following by local osmosis. - transport of water also involves specific water channels (aquaporins) of which AQP1 is expressed in the choroid plexus.

How much CSF is produced per day?

500ml per day

CSF accumulation leads to________

Hydrocephalus

Where does CSF drain into

Subarachnoid space=> Arachnoid villi(granulations) =>Superior Sagittal SInus => venous system

CSF composition: Increased protein, normal glucose, RBCs present

Subarachnoid hemmorhage

CSF composition: Very high protein, normal glucose, few WBCs present

Guillian-Barre syndrome

CSF composition: increased protein, normal to decreased glucose, Increased number of WBC Tumor cells

Metastatic cancer in the meninges

CSF composition: Increased protein, normal glucose, excessive WBCs (lymphocytes)

Viral meningitis

CSF composition: Increased protein, Decreased glucose, increased WBCs (lymphocytes)

Tubercular meningitis

CSF composition: Increased protein, decreased glucose, increased number of WBCs (polymorphonuclear leukocytes)

Bacterial Meningitis

Where are changes in CSF composition detected in the CNS

CSF osmolality are sensed by mechanosensitive, nonselective cation channels expressed in the supraoptic and paraventricular nuclei. These nuclei also bear osmolarity sensing volume regulated anion channels in glial cells

2 types of hydrocephalus

noncommunicating( obstructive) | communicating

Common feature of both types of hydrocephalus

increased ventricular volume

What causes Obstructive hydrocephalus

obstruction (conegnital or cellular debris)of - interventricular foramina, - cerebral aqueduct - or foramina of fourth ventricle

What causes Communicating hydrocephalus

• Overproduction – Choroid tumor • Insufficient drainage – Malfunction of arachnoid villi • Ex vacuo – Enlargement secondary to tissue loss

What happens in Hydrocephalus ex vacuo

ventricular enlargement arises as spatial compensation for neurodegenerative losses of brain mass without increasing intracranial pressure

what happens in Normal pressure hydorcephalus

Transient increases in ICP ( not seen in older patients)

What forms blood CSF barrier

Choroid plexus

what is brain edema?

localized or generalized excess accumulation of water in the intracellular and/or extracellular spaces of both the grey and white matter

Two types of Brain edema

1) Vasogenic | 2) Cytotoxic

What causes Vasogenic edema?

disruption of the BBB => increase in capillary permeability

What causes cytotoxic edema

- tissue damage or by an inadequate blood supply to neurons and glia. - When the Na/K pump eventually fails in the ATP-starved cells, ionic gradients dissipate, leading to cellular swelling

Treatment fro Brain edema

Osmotherapy

Why arent astrocytes damaged during brain edema

capable of regulating their cellular volume | after the initial swelling