Nervous 3RG
Cerebrospinal Fulid ( CSF)
- - Formed primarily by choroid plexuses . Richly vascularized masses of pia matter tissue that dip into pockets formed by ependymal cells - - forms as a result of selective transport mechanisms across membranes of choroid plexuses
Blood-brain barrier ( BBB)
- Brain capillaries have tight junctions that prevent passage of materials. Capillary walls are different • Fewer pores • Tight junctions • Special carriers - Water soluble substances do not cross easily.
cerebrospinal fluid ( CSF)
- Brain floats in cushioning fluid
Cerebrospinal Fulid ( CSF)
- Constant production and flow out of CNS and into venous system. - Produced in brain ventricles
Meninges
- Dura mater - Arachnoid mater - Pia mater
Connective tissue Membranes- 3 meninges:
- Dura mater (outer): superficial - Arachnoid mater (middle): a delicate and richly vascularized layer - Pia mater (inner): bound tightly to brain
CSF
- MADE in Choroid Plexus - DRAINED through arachnoid villus
Blood-brain barrier ( BBB)
- Only small lipid soluble substances (O2, CO2, alcohol, steroid hormones) can diffuse through capillary membrane. - All other molecules must be transported into brain by carrier proteins
Blood-brain barrier ( BBB)
- Protects brain from chemical fluctuations in blood . Strictly limits exchange between blood and brain - Minimizes possibility that harmful blood-borne substances might reach central nervous tissue
Subarachnoid space
- Space between arachnoid mater and pia mater - Filled with Cerebrospinal Fulid ( CSF)
Cerebrospinal Fulid ( CSF)
- Supports (buoys) mass - Cushions CNS - Nourishes brain tissue - Contains proper electrolytes for CNS - Filtered from blood plasma in choroid plexuses
Cerebrospinal Fulid ( CSF)
- Surrounds and cushions brain and spinal cord - Serves as a shock-absorbing fluid to prevent brain from brain from hitting skull. - Exchange of materials between neural cells and interstitial fluid surrounding brain
Dura mater
- Tough and leathery - Most superficial
Pia mater
- gentle mother - innermost layer - highly vascularized
CSF function
- shock absorption - support - nourishment
Arachnoid mater
- spider-like mother - a delicate and rickly vascularized layer - Subarachnoid space is filled with cerebrospinal fluid
Dura mater
- tough mother - outermost - thickest
A choird plexus
..........consists of a combination of specialized ependymal cells and permeable capillaries for the production of CSF
In several locations, the inner dura mater extends in to the..........., forming a sheet that dips.........and then returns
...In several locations, the inner dura mater extends in to the cranial cavity, forming a sheet that dips inward and then returns
Cerebrospinal Fluid (CSF)
1. Intervertebral disc 2. Vertebral body 3. Dura mater 4. Extradural or epidural space 5. Spinal cord 6. Subarachnoid space
LP (lumbar puncture)
= spinal tap (needle introduced into subdural space to collect CSF)
2 extensive folds originate in the roof of the 3rd ventricle (located between the lateral walls of the diencephalon) and extend to the interventricular foramina and cover the floors of the lateral ventricles.
A region of choroid plexus is also found in the 4th ventricle between the cerebellum and pons....
Blood-brain barrier ( BBB)
Allows careful selection of what substances can cross to neurons. It is also a diffusion barrier that allows only water and small lipophilic molecules to freely access the brain in accordance with their concentration gradients.
Anesthesia caused by local anesthetic injection into epidural or sacral caudal space. The caudal epidural space is the lowest portion of the epidural system and is entered through the sacral hiatus...
Anesthesia caused by local anesthetic injection into epidural or sacral caudal space. The caudal epidural space is the lowest portion of the epidural system and is entered through the .........
Spinal anesthesia
Anesthesia following local anesthetic injection into lumbar subarachnoid space.
Epidural
Anesthesia injected
Cerebrospinal fluid is produced by modified ependymal cells of the choroid plexus found in all components of the ventricular system except for the cerebral aqueduct and the posterior and anterior horns of the lateral ventricles
Cerebrospinal fluid is produced by modified ependymal cells of the choroid plexus found in all components of the ventricular system except for the cerebral aqueduct and the posterior and anterior horns of the lateral ventricles
Blood-brain barrier ( BBB)
Discovery of blood-brain barrier. The discovery of the BBB dates back more than 100 years when, in the 1880s, Paul Ehrlich observed that intravenous administration of certain dyes (e.g. trypan blue) stained all organs except the brain and the spinal cord. He concluded that the dyes had a lower affinity for binding to the nervous system as compared to other tissues. In 1913, Edwin Goldman, an associate of Ehrlich, demonstrated the very same dyes, when directly injected into the cerebrospinal fluid (CSF), readily stained nervous tissue but not other tissues. The term "blood-brain barrier" was coined, however, by Lewandowsky in 1898, after he and his colleagues had performed experiments to demonstrate that neurotoxic agents affected brain function only when directly injected into the brain but not when injected into the vascular system. It took an additional 70 years until Reese and colleagues localized the barrier to the capillary endothelial cells within the brain by electron-microscopic studies.
Protection of CNS
Enclosed by hard, bony structures - Cranium (skull) encases brain - Vertebral column surrounds spinal cord Wrapped by 3 protective and nourishing membranes
Circulation cerebrospinal fluid
Entire volume (125-150 mL) is replaced about 3.7 times a day
CSF
Fills the space between the arachnoid and pia mater, as well as the internal cavities of the brain ( ventricles) and spinal cord
Circulation cerebrospinal fluid
Finally moves through the subarachnoid space to the arachnoid villi, which allow it to flow into the dural sinuses
In circumventricular organs (CVOs, not shown), which contain neurons specialized for neurosecretion and/or chemosensitivity, the endothelium is leaky
In circumventricular organs (CVOs, not shown), which contain neurons specialized for neurosecretion and/or chemosensitivity, the endothelium is leaky
In humans the choroid plexuses weigh about 2 g in total so that the rate of CSF secretion is approximately 0.2 ml min-1 per g of tissue
In humans the choroid plexuses weigh about 2 g in total so that the rate of CSF secretion is approximately 0.2 ml min-1 per g of tissue
Circulation cerebrospinal fluid
It circulates from the lateral ventricles to the foramen of Monro (Interventricular foramen), third ventricle, aqueduct of Sylvius (Cerebral aqueduct), fourth ventricle, foramen of Magendie (Median aperture) and foramina of Luschka (Lateral apertures), subarachnoid space over brain and spinal cord.
Epidural
It is the space within the canal (formed by the surrounding vertebrae) lying outside the dura mater (which encloses the arachnoid mater, subarachnoid space, the cerebrospinal fluid, and the spinal cord).
Ventricular system
Lateral ventricles -> 3rd ventricle -> cerebral aqueduct -> 4th ventricle -> central canal
Blood-brain barrier ( BBB)
Limits use of drugs for treatment of brain and spinal cord disorders - Many drugs cannot penetrate BBB
Circulation cerebrospinal fluid
Much of the fluid is reabsorbed at the arachnoid granulations, into the venous system, as well as into the capillaries of the CNS and pia mater. 1 cmH2O= 0.73554 mmHg
Circulation cerebrospinal fluid
Normal CSF pressure as measured by lumbar punctur
Blood-brain barrier ( BBB)
Prevents certain circulating hormones that could also act as neurotransmitters from reaching brain
Circulation cerebrospinal fluid
Produced by the modified ependymal cells in the choroid plexus (approx. 50-70%) and the remainder is formed around blood vessels and along ventricular walls.
Subdural
Serous fluid
Major function of CSF
Serves as a shock-absoring fluid to prevent brain from bumping against hard skull
Meninges
Skin -> galea aponeurotica -> connective tissue -> bone -> dura mater -> Arachnoid mater
Cerebrospinal fluid ( CSF)
Surrounds and cushions brain and spinal cord
The ventricles are filled with cerebrospinal fluid (CSF) which bathes and cushions the brain and spinal cord within their bony confines
The ......... are filled with cerebrospinal fluid (CSF) which bathes and cushions the brain and spinal cord within their bony confines
The Cerebrospinal fluid (CSF) fills the ventricles of the brain, the spinal canal and the subarachnoid space (and in humans has a total volume of approximately 140 m
The Cerebrospinal fluid (CSF) fills the ventricles of the brain, the spinal canal and the subarachnoid space (and in humans has a total volume of approximately 140 m
This is a common cause of hydrocephalus (known colloquially as "water on the brain"),
The aqueduct between the third and fourth ventricles is very small, as are the foramina, which means that they can be easily blocked, causing high pressure in the lateral ventricles
This allows tissue-blood exchange, but as these sites are separated from the rest of the brain by an external glial barrier, and from CSF by a barrier at the ependyma, CVOs do not form a leak across the BBB. Modified, with permission, from Ref.163 © (1990) Kluwer Academic
This allows tissue-blood exchange, but as these sites are separated from the rest of the brain by an external glial barrier, and from CSF by a barrier at the ependyma, CVOs do not form a leak across the BBB. Modified, with permission, from Ref.163 © (1990) Kluwer Academic
Circulation cerebrospinal fluid
Total production of CSF is about 400-500 ml/day (about .36 ml/min
Anesthestics
are often injected into epidural space Injection into correct space is vital; mistakes can be lethal
Periosteal
attached to the skull
Dural sinuses may be found
between the 2 layes of a dural fold
Subarachnoid
cerebrospinal fluid ( CSF) and blood vessels
Dura mater
have two layers: - Periosteal - Meningeal
Originally thought to be a narrow fluid-filled interval between the dural and arachnoid; now known to be an artificial space created by the separation of the arachnoid from the dura as the result of trauma or some ongoing pathologic process;
in the healthy state, the arachnoid is attached to the dura and a naturally occurring subdural space is not present
Epidural
is external to dura
Circulation cerebrospinal fluid
is reabsorbed into venous sinus blood via arachnoid granulations. It had been thought that CSF returns to the vascular system by entering the dural venous sinuses via the arachnoid granulations (or villi)
The spinal cord
lies within the spinal cavity, consisting of the vertebral column, the meninges, spinal nerves, spinal fluid, blood vessels, and a cushion of adipose/fat tissue.
Blood-brain barrier
limits access of blood-borne materials into brain tissue
Cerebrospinal Fluid (CSF)
manufactured in choroid plexus 135 ml- 150 ml, t1/2 (half-life) = 3 hrs Hydrocephalus- blockage of CSF flow
LP lumbar spine
needs to be flexed so can go between spinous processes
These dural folds
provide additional support for the brain
Male
smooth curv
Female
straight line
Barriers are present at three main sites:
the brain endothelium forming the blood-brain barrier (BBB) (1), the arachnoid epithelium (2) forming the middle layer of the meninges, and the choroid plexus epithelium (3), which secretes cerebrospinal fluid (CSF)
Meningeal
true external covering, extends downward and suppronds spinal cord
This is a common cause of hydrocephalus (known colloquially as "water on the brain"),
which is an extremely serious condition due to both the damage caused by the pressure as well as nature of whatever caused the block (e.g. a tumor or inflammatory swelling).
