SUPPORTING STRUCTURES
Overview of Topics
Types of Supporting Cells
Circulation in the CNS
Meninges
CerePospinal Fluid
Lesson Objectives
- Describe the basic functions performed by supporting cells in the CNS and explain how each is accomplished.
- Discuss the difference between microglia and other supporting cells.
- Discuss the importance of maintaining adequate circulation of blood to the brain.
- Describe the meninges and explain their function.
- Discuss the production, flow, absorption, and function of the cerebrospinal fluid.
- Explain how myelin is formed in the CNS and how this differs from the formation of myelin in the PNS.
Supporting structures function in the CNS by:
- Providing physical support
- Removing degenerating neural tissue
- Forming myelin
- Forming cerebrospinal fluid
- Forming "blood-brain barrier"
Types of supporting cells: Glia ("Glia" means glue)
Protoplasmic astrocytes (star-shaped)
- Surround cell bodies & vessels in CNS
Fibrous astrocytes
- Offer structural support to tracts in CNS
Oligodendroglia (glia cells) - supporting functions:
- Important in nourishment of neurons
- Form myelin in CNS
Microglia - arise from mesoderm
- Mobile & phagocytic
- Most frequently found with degenerative diseases such as chorea and encephalitis
Ependymal cells - inner walls of ventricles
- Filtering blood to form CSF (choroid plexus)
Schwann sheath cells - form myelin sheath in PNS
- Cytoplasm makes up neurilemma
Circulation
Arteries--supply blood to body from heart
- Route blood to small capillaries
Capillaries have single cell walls which allow materials in blood plasma to pass out into surrounding tissue & allow waste to enter vascular system
Veins-- return blood to heart
- 15% of the blood passes to the brain
- Glucose is the principle material delivered in neural tissue
- When circulation is blocked, neural tissue is rapidly destroyed (2-3 min)
Meninges
Cerebrospinal fluid (CSF)
Terms to Know
| Cerebrospinal fluid |
Microglia |
Glia cells |
| Ependymal cells |
Schwann sheath cells |
Pia |
| Lateral ventricles |
Fourth ventricle |
Foramen of Magendie |
| Blood-brain barrier |
Fibrous astrocytes |
Foramen of Luschka |
| Choroid plexus |
Cerebral aqueduct |
Subarachnoid space |
| Third ventricle |
Dura |
Phagocytic |
| Protoplasmic astrocytes |
Terminal feet |
Arachnoid (villi) |
| Neurilemma |
Capillaries |
Venous sinuses |
Links to Associated Areas