Ch14NotesSum11

Ch14NotesSum11 - Ch. 14 The Brain & Cranial Nerves The...

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1 Ch. 14 – The Brain & Cranial Nerves • The brain weighs about 3 pounds, and consists of about 100 billion neurons and 1 trillion glial cells Fig. 14-1, p. 461 There are 4 main regions of the brain 1. 2.
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2 Fig. 14-1, p. 461 3. 4. 4a. 4b. 4c. There are 4 main regions of the brain, continued Table 14-1, p. 463 The embryological development of the brain • Initially, the ectoderm layer of the embryo forms a hollow neural tube ; then… FYI
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3 Fig. 14-2, p. 463 The ventricles of the brain • = fluid-filled chambers within the brain • Are lined with ependymal cells • Are filled with cerebrospinal fluid (CSF) Protection and support of the brain • 1. Cranial bones • 2. Cranial meninges • 3. Cerebrospinal fluid • 4. Blood-brain barrier – biochemical protection } mechanical protection
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4 Fig. 14-3, p. 465 The cranial meninges • Are continuous with the spinal meninges (but there are some differences between the two) •1 . Dura mater : Endosteal layer = the thicker part that is fused with the periosteum of the cranium • So there’s no epidural space Meningeal layer = the thinner part that is next to the arachnoid mater – The dura mater forms dural folds and contains large dural (venous) sinuses Fig. 14-3, p. 465 Dural folds = extensions of the meningeal layer of the dura mater into the cranial cavity – They function to stabilize and support the brain – They contain dural (venous) sinuses between the endosteal and meningeal layers, which… • Drain venous blood from the brain (and CSF from the subarachnoid space) ultimately into the internal jugular veins of the neck Include the : –A . Falx cerebri • Is located between the cerebral hemispheres • Contains the superior and inferior sagittal sinuses –B . Tentorium cerebelli • Is located between the cerebrum and cerebellum • Contains the transverse sinus –C
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Fig. 14-3, p. 465 The cranial meninges, continued •2 . Arachnoid mater – Is between the dura mater and pia mater – The subarachnoid space contains CSF •3 . Pia mater – Closely adheres to the surface of the brain Cerebrospinal fluid (CSF) • Functions : – It cushions the brain – It supports the brain (i.e., the brain “floats” in CSF) – It transports nutrients, wastes, and chemicals • Is formed by choroid plexuses in the ventricles (~ 500 mL/day) Choroid plexuses = “leaky” capillaries covered by ependymal cells Ependymal cells : – Are connected to each other by tight junctions – Secrete CSF from the fluid that is filtered by the leaky capillaries • The composition of CSF is quite different from blood : – There are no blood cells – It has significantly different concentrations of ions, nutrients, wastes,
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This note was uploaded on 12/29/2011 for the course BIOLOGY 24011 taught by Professor Pan during the Fall '11 term at HCCS.

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Ch14NotesSum11 - Ch. 14 The Brain & Cranial Nerves The...

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