Question

• What are the tour layers of protection for the CNS? • Where is cerebrospinal fluid (CNS) formed? Where does it circulate? Where does it drain? What happens if the drainage of CSF is blocked?

Answer 1

Ans) The brain is protected by the skull (cranium), cerebrospinal fluid and 3 protective membranes (Meninges).

The spinal cord is protected similarly but with vertebrae instead of the cranium.

Explaination:
- The brain is first protected by the skull (cranium). This offers physical protection and so naturally is one of the hardest bones in the body. The skull acts like a helmet for your brain, and helps to prevent damage from mechanical stress (things like knocks and falls).

- The spinal cord is also surrounded by some very hard bone, but this time it comes in the form of the vertebrae.

- Next, we have the three protective membranes - the meninges. These are made out of connective tissue and provide a cushioning from the hard skull of the brain, jolting against the vertabrael column (in the spinal cord) or from any damaging impacts.

- The three meninges are the Dura Mater (outer), The Arachnoid (middle) and the Pia Mater (inner).
You could remember this order with some sort of mnemonic or story such as - Dur-ing (Dura Mater)the invasion of the Arachn-ids (arachnoid), Pia-nos (Pia Mater) were very rare.

- Finally, there is a special fluid, called cerebrospinal (cerebro for brain, spinal for the spinal cord) that circulates the entire central nervous system. It occupies the space between the Pia Mater and Arachnoid and supplies nutrients (like blood in the rest of the body), disposes of waste and acts as a shock absorber.

The neural stem cells, principally radial glial cells, multiply and generate neurons through the process of neurogenesis, forming the rudiment of the CNS. The neural tube gives rise to both brain and spinal cord.

- Cerebral circulation is the movement of blood through the network of cerebral arteries and veins supplying the brain. The rate of the cerebral blood flow in the adult is typically 750 milliliters per minute, representing 15% of the cardiac output.

- Most of the body's organs remove dead cells and other waste using the lymphatic system. ... Although the human brain has blood vessels, there was no evidence it has a lymphatic system. Recently, studies in mice found evidence of the brain's lymphatic system in the dura, the brain's leathery outer coating.

- Some brain tumours block the normal circulation of this fluid. Because it cannot drain away, the fluid builds up inside the skull and around the spinal cord.This fluid on the brain is called hydrocephalus. It can cause symptoms, such as headaches and sickness.