CNS, Blood Brain Barrier And Neurovascular Unit Flashcards
What other anatomical sites have a barrier similar to the blood brain barrier?
Eye, inner ear and possibly testes
What is a physical anatomic barrier to protect the brain from circulating toxins found in blood?
Blood brain barrier
What structure mediates selective transport in and out of brain, maintains proper CSF and brain environmental concentration of glucose, ions, amino acids, neurotransmitters, hormones and vitamins and regulates interface for metabolism or modification of blood or brain borne substances?
Blood brain barrier
What structure expresses enzymes that degrade many peptides preventing entry to CSF?
Choroid plexus
The neurovascular unit is surrounded by what?
Astrocyte foot pads
What structure in the neurovascular unit has contractile function, participates in vascular development, contributes to the BBB properties, are multipotent cells, have roles in hemostasis and have immune and phagocytic functions?
Pericyte
What is the junction that occurs in epithelial cells that prevents entry of blood born substances?
Tight junction
The neurovascular unit has a high number of what organelle that is needed for energy to move particles back and fourth
Mitochondria
What structures mediate water transport into brain across blood vessels and choroid plexus and remove excess water, electrolytes, and amino acids into ventricles, brain and subarachnoid space?
Aquaporins
What maintain optimal water and it’s contents via astrocytes and are pores that allow water to be transported in and out?
Aquaporin
4 aquaporin is found where?
Astrocytes
1 aquaporin is found where?
Choroid plexus
What types of molecules are able to by pass the BBB?
High lipid soluble, small molecular weight, less molecular ionic charge, specific for transport receptors in choroid plexus or endothelium
Transporting molecules across the blood brain barrier is known as what?
Transcytosis
What are the three mechanisms of transcytosis?
Facilitated transport, active transport and efflux transport
What type of transport requires specific receptor, transports molecules from high concentration to low concentration, found in endothelium or choroid plexus but does not require energy? Ex: D-glucose transporter, large neutral amino acid transporter, actinic amino acid transporter
Facilitated transport
What type of transport requires energy, requires a specific receptor, transports molecules from low concentration to high concentration and is found within the capillary lumen, brain or CSF? Ex: insulin receptor, transferrin receptor
Active transport
What type of transport pumps out unwanted substances out of brain tissues and cells, requires specific receptors and requires energy? Ex: potassium, neurotransmitters, glutamate acid, glycine,
Efflux transporter
In what form is glucose found in the brain?
Glucose-6 phosphate
What areas of the brain lack the blood brain barrier?
Pituitary and pineal glands, area postrema, paraventricular nuclei, capillary endothelium in choroid plexus
What allows release of hormones into blood and CSF?
Pituitary and pineal glands
What detects circulating toxins to trigger vomiting?
Area postrema
What is located inside the 3rd ventricle and releases neurotransmitters and hormones into the CSF?
Paraventricular nuclei
What allows circulating molecules to reach choroid plexus epithelium? Tight junctions are now at the ependyma cells
Capillary endothelium in choroid plexus
What processes open the blood brain barrier?
Ischemia - stroke, vessel exposure to inflammatory cytokines or factors produced by tumors, marked hypertension, hyperosmolar solution arterial injections
What are a few consequences of opening the blood brain barrier?
Vasogenic cerebral edema - plasma leaving capillaries and veins into brain interstitial space, WBC entering brain or CSF, toxic molecules entering the brain - neuronal deaths, seizures, infectious organisms entering brain/CSF
What is a clear colorless fluid that fills the ventricular system and subarachnoid space and is primarily made by the choroid plexuses?
Cerebral Spinal Fluid
What are 3 CSF functions?
Mechanical support for the brain, removes brain metabolic and synaptic products, carries neurotransmitters between brain areas
Reduction of brain weight from 1500 to 50 gm and protection of brain via a water jacket from trauma describes what?
CNS mechanical support for brain
Active transport by efflux moving molecules from CSF across blood brain barrier to choroid plexus veins and CSF exiting into superior Sagittal sinus describes what?
CSF removal of brain metabolic and synaptic products
Molecules being carried from 3rd ventricle to periaquaductal gray matter ( important for sleep) and molecules being carried from choroid plexus to hypothalamus (important for energy balance) describes what?
CSF carrying neurotransmitters between brain areas
What arises from adipose tissue and regulates energy balance via the hypothalamus via specific receptors in the choroid plexus and walls of the 3rd ventricles?
Leptin
What molecule is synthesized in the liver and is transmitted to the blood, then choroid plexus, then CSF and regulates hibernation?
Hibernation protein complex
What are bipolar ependymal cells that line the sides of the 3rd ventricle and are possibly responsible for the secretion of molecules into the CSF?
Tanycytes
What substance produced by the choroid plexus is critical for brain T4 by binding T4 and preventing removal from the CSF?
Transthyretin
What molecule produced by the choroid plexus produces prostaglandin D2, most potent sleep inducer?
Lipocalin-type prostaglandin D synthase ( L-PGDS)
What substance transmitted by the brain to other brain areas via CSF regulates sexual receptivity around time of ovulation?
Gonadotropin-releasing hormone
What substance transmitted from pineal glands to CSF regulates seasonal control of LH release?
Melatonin
What is the amount of CSF found in the ventricles?
25ml
What is the amount of CSF found in the brain subarachnoid space?
85ml
What is the amount of CSF found in the spinal chord subarachnoid space?
30ml
What is the total amount of CSF in the CNS?
140ml
What comes from blood, enters ventricles via choroid plexus, and returns to blood via superior Sagittal sinus
CSF
What begins as plasma ultrafiltrate across permeable choroidal capillaries, picks up water and ions by transporters at the basolateral side of the choroid epithelium, convected through cytoplasm and actively released or secreted into ventricle CSF on apical side?
CSF
In the choroid plexus what type of junction produces the ultrafiltration?
Gap junction
What are the 2 mechanisms of CSF production by the choroid plexus?
Bulk flow and secretion
Active transport of sodium via Na+-K+ ATPase which pulls water from blood to CSF thru an aquaporin 1 channel describes what?
Bulk flow
Active transport of Na+, amino acids, vitamin C and B6, facilitated transport of glucose and vesicular transport of most macromolecules describes what?
Secretion
Special receptors and energy are required to absorb what type of molecules into the CSF?
Organic bases, amino acids and K+
How much CSF is produced per hour?
23ml
How much CSF is produced per day?
600ml
The choroid plexus produces what percentage of CSF?
2/3
Extrachoroidal produces what percentage of CSF via Virchow Robins spaces and ependyma lining ventricles?
1/3
How many times a day does the total CSF volume turn over?
5 times
What is the space between the Cerebri cortex and pia mater covered blood vessels called?
Virchow-Robin spaces
What areas do brain metabolic products leak into?
Virchow-Robin spaces
CSF flow is mediated by what?
Pulsatile cerebral blood flow
CSF outflow is proportional to what?
CSF pressure
CSF formation is almost independent of what?
CSF pressure (at very high pressures it varies)
CSF absorption is dependent upon what?
CSF pressure
CSF is absorbed from what structure that is supplied by arachnoid villi and granulations which are extensions of the subarachnoid space?
Superior Sagittal sinus
What are the 2 leading theories for CSF flow into the superior Sagittal sinus?
Vacuolar transport across arachnoid villus
One way channel bulk flow through arachnoid villus (leading theory)
What percentage of CSF drains into the superior Sagittal sinus?
80%
What percentage of the CSF drains into lymphatic drainage via cranial nerves and spinal cord roots?
10-25%
A lumbar puncture is important in diagnosing what pathologies?
Infectious meningitis, neoplastic meningitis, small subarachnoid bleed
A lumbar puncture is useful in what pathologies?
MS, acute motor polyneuropathy, benign intracranial hypertension, Guillain-Barré syndrome, narcolepsy with cataplexy
A lumbar puncture is performed at what spinal cord level?
Between L3 and L4
In a LB opening pressure is indicative of what?
Increased cranial pressure
In an LB a cell count (WBC or RBC) is indicative of what?
Infection or hemorrhage
In a LB decreased glucose is indicative of what?
Infection
In a LB bacterial culture and gram stain is indicative of what?
Infection
What are a few contraindications for doing a LB?
Mass in CNS with increased intracranial pressure
Obstructive hydrocephalus
Overlying lumbar skin infection
Bleeding disorder or thrombocytopenia
The BBB is maintained by what?
Tight junctions between endothelial cells