Ch 3

1. the cranium - made up of 8 skull gones fused together along zig-zag joints called sutures

2. the meninges - three layes of protective tissue that provide tough out protection to the brain and spinal cord

3. cerebrospinal fluid - clear fluid that buffers the brain and spinal cord from shock

4. blood and oxygen supply - delivered through the bloodstream

5. the blood-brain barrier - flial cells form a protective covering around blood vessels to prevent toxic substances from entering the brain

Dura Mater ("hard mother"); tough, leather-like outer layer

Long channels ("sinuses") serve as veins that drain used blood and cerebrospinal fluid

Pain sensitive

Arachnoid

Separated from Dura mater by tiny fluid-filled space called the sub-dural space

Looks similar to a spider web

Pia Mater ("soft mother")

Separated from arachnoid by the sub-arachnoid space; barely visible, close to brain/spinal cord

Blood vessels carry oxygen/nutrients to CNS; plays key role in removal of waste products

Proper functions of pia mater is essential to brain function

Clear, colorless fluid that nourishes and protects brain and spinal cord

Circulates constantly between subarachoid and large briain cavities called ventricles

Glial cells that cover the choroid plexus (network of capilaries formed by the ventricle walls) produce 3/4 liter of CSF per day

1. Provides soft fluid protective cushion

2. Protects against injury

3. Diffusing waste material

4. Maintains "special environment" for brain (glucose, protien, sodium, chloride, magnesium, neurotransmitters, proper water and acid-base balances)

Brain requires at least 20% of body's energy daily

Neurons cannot store energy and are very particular about the type of fuel they can use - only glucose

Glucose is delivered by blood to the brain; if the brain is deprived of blood for as little as 3 minutes, neurons begin to die and permanent damage can be done

1. Protecting the Brain: works as a filter by tightly sealing capillaries, overlapping the cells that form the capillaries, and by special glial cells ("astrocytes") that surround walls

2. Neurotransmitters: unable to pass through BBB, so must rely on substances that can

3. Neurotoxins: many harmful substances can pass through BBB; some cause damage to ner cells, others cause seizures, coma, or death

Most common; occurs when blood supply to part of the brain is blocked

• a) cerebral thrombosis: blood clot forms in a cerebral blood vessel and blocks blood flow
• b) cerebral embolism: an embolus ("wandering" blood clot) travels from the heart to the small vessels of the brain and creates a sudden blockage
• c) transient ishcemic attack: "mini-stroke", causes a temporary blockage of blood flow to part of the brain

Most common type of hemorrhagic stroke = aneurysm; occurs when an artery in the brain leaks or ruptures; can be caused when a weakened or diseased spot in the wall of an artery/blood vessel bursts