Central Nervous System part B

Brain Protection

• The brain is safeguarded by bone, meninges, and cerebrospinal fluid (CSF).
• The blood-brain barrier shields the brain from harmful substances.

Meninges

• The CNS is covered in three connective tissue membranes:
  • Dura mater
  • Arachnoid mater
  • Pia mater
• These membranes serve several functions:
  • Cover and protect the CNS
  • Protect blood vessels and enclose venous sinuses
  • Contain cerebrospinal fluid (CSF)
  • Form partitions within the skull

Dura Mater

• Leathery, strong meninx made up of two layers of fibrous connective tissue.
• The layers separate in specific areas to form dural sinuses.

Arachnoid Mater

• The middle meninx, loosely enveloping the brain.
• There is a subdural space between arachnoid mater and dura mater.
• Below the arachnoid is the subarachnoid space, filled with CSF and large blood vessels.
• Arachnoid villi protrude superiorly, allowing CSF absorption into venous blood.

Pia Mater

• The innermost meninx, composed of delicate connective tissue that clings tightly to the brain.

Cerebrospinal Fluid (CSF)

• A watery solution similar to blood plasma, but with less protein and different ion concentrations.
• It acts as a liquid cushion, providing buoyancy for CNS organs.
• This prevents the brain from being crushed under its own weight.
• It offers protection from blows and other traumas.
• It nourishes the brain and carries chemical signals throughout it.

Choroid Plexuses

• Capillary clusters forming tissue fluid filters, hanging from the roof of each ventricle.
• They have ion pumps that regulate CSF ion concentrations.
• They assist in cleansing CSF by removing waste products.

Blood-Brain Barrier Functions

• A protective mechanism maintaining a stable environment for the brain.
• It separates bloodborne substances from neurons.
• This selective barrier allows free passage of nutrients.
• It is ineffective against substances diffusing through plasma membranes
• Stress enhances the ability of chemicals to pass through the blood-brain barrier.

Spinal Cord

• CNS tissue confined within the vertebral column from the foramen magnum to L1.
• Provides bi-directional communication between the brain and the body.
• It is protected by bone, meninges, and CSF.
• The space between the vertebrae and the dural sheath (dura mater) is called the epidural space; it is filled with fat and a network of veins.

Spinal Cord Features

• Conus medullaris: the terminal portion of the spinal cord.
• Filum terminale: a fibrous extension of the pia mater anchoring the spinal cord to the coccyx.
• Denticulate ligaments: delicate shelves of pia mater attaching the spinal cord to the vertebrae.

Spinal Cord Connections

• 31 pairs of spinal nerves connect to the cord via paired roots.
• Cervical and lumbar enlargements: regions where nerves serving upper and lower limbs emerge.
• Cauda equina: a collection of nerve roots at the inferior end of the vertebral canal.

This quiz covers the protective structures surrounding the brain, including the bones, meninges, and cerebrospinal fluid (CSF). Furthermore, it delves into the individual layers of the meninges: dura mater, arachnoid mater, and pia mater, highlighting their roles and characteristics.