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Nervous System - CNS Protection

Nervous System - CNS Protection. This set of lecture notes is the third in the series on the Nervous system and needs to be considered alongside the other two sets.

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Nervous System - CNS Protection

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  1. Nervous System - CNS Protection • This set of lecture notes is the third in the series on the Nervous system and needs to be considered alongside the other two sets. • The aim of this lecture is for you to develop understanding of the structures and processes involved in the protection of the nervous system.

  2. Learning Outcomes : 1. Outline the role of the cranium and vertebral column in protecting their underlying structure. 2. Outline the blood flow to the brain. 3. Identify the role of the neuroglial cells in forming the blood brain barrier. 4. Identify the structure and function of the meninges. 5. Describe the formation, circulation and functions of cerebrospinal fluid

  3. Nervous System - CNS Protection • In the previous two lectures on the nervous system you have gained understanding of some of the important parts and function of the brain and the spinal cord. • Today’s lecture will focus on the protection and support that the Brain and Spinal Cord get from certain structures in order to function normally.

  4. Bony Protection : • A) Cranium: formed by 8 different bones fused together. E.g. One of them is the Frontal bone! Others are: the Ethmoid bone and the Sphenoid bone etc. • Has a vault and a base

  5. The cranium • Bones are joined together at Sutures, Completely fused in the Adult. • Fontanelles in the infant. • Commonest ones?

  6. Bony Protection B) Vertebral column: • Sturdy shelter for spinal cord. • Foramina of vertebrae are stacked up one on top of another and • the bony ring of vertebral bone surrounds the spinal canal.

  7. Meningeal Covering protection: Meninges: • Three layers of membranes surround and cover the brain and the spinal cord. • The membranes are of different nature from each other . • Collectively serve to offer protection to the underlying soft brain and spinal cord.

  8. Lay out of the Meninges

  9. Meninges (I) outermost - Dura Mater (ii) middle - Arachnoid Mater (iii) innermost - Pia Mater Clinical application: • Brain injury may involve any one of these layers of the meninges and the blood vessels underlying them. posing a threat to health.

  10. Fluid Protection: • Cerebrospinal Fluid (CSF) circulates around the brain and spinal cord to offer nourishment and protection against chemical and physical injury. • How is this fluid formed? • Ventricles of the brain . • Choroid Plexuses. • Formation is continuous.

  11. Cerebrospinal fluid What is the composition of Cerebrospinal Fluid? • It is a clear, colourless fluid, containing many constituents of plasma, such as: • water, electrolytes, gases, some white blood cells etc • But No red blood cells

  12. Cerebrospinal fluid • How does it circulate and get reabsorbed? • Circulates within ventricles and central canal of spinal cord. • Also circulates within Sub Arachnoid Space. • Reabsorption occurs within Arachnoid villi and venous sinuses in cranium. • Continually reabsorbed • Returned to right side of Heart

  13. VENTRICLES

  14. Activity Activity 2: • With a colleague, discuss the contributing factors that may lead to the development of hydrocephalus and the implication of this condition on health.

  15. Blood Flow Protection: • A) Blood supply: Brain is very sensitive and requires adequate blood supply. Why? Activity: Try to answer the above by relating to the need of the brain for glucose and oxygen. • Many major arteries provide this supply and these join to form a circle in the base of the brain from which all parts of brain get their supply (Circle of Willis). See diagram!

  16. The Circle of Willis

  17. Blood Flow Protection B) Blood-Brain Barrier : • Not all substances can pass from the blood into brain cells. Why? • Tight junction of capillary cells. • Presence of Astrocytes and their false feet. • Activity 4 : In the tutorial session discuss the clinical importance of the blood-brain barrier and how this may affect the route of drug administration

  18. Blood Brain Barrier • There are only several small brain regions that lack the blood-brain barrier. • Mostly these serve to monitor the chemical changes in the blood and to co-ordinate homeostatic activities of the nervous and endocrine systems

  19. Conclusion • Thus the central nervous system, despite its soft and delicate structure, is able to function normally even under conditions of great challenge from the external environment, • Without the protective mechanisms explored in the lecture, this normal function would not be possible.

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