Nervous System Notes Part 3. EVEN MORE INTERESTING NERVOUS SYSTEM FACTS The human brain alone consists of about 100 billion neurons. If all these neurons.

Nervous System Notes Part 3

EVEN MORE INTERESTING NERVOUS SYSTEM FACTSThe human brain alone consists of about 100 billion neurons. If all these neurons were to be lined up, it would form a 600 mile long line.

At any given point in time, only four percent of the cells in the brain are active, the rest are kept in reserve.

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings

Nervous Tissue: Neurons

Figure 7.4

NOTES – CELLS OF THE NERVOUS SYSTEM

• NEURONS

• 3 basic parts1. Cell Body • 1 nucleus

2. Dendrites • carry information TOWARD the cell body

3. Axon • carries information AWAY from the cell body

• many neurons are surrounded by a MYELIN SHEATH

• fatty tissue that speeds up the nerve impulse


Neuron Classification

Figure 7.6


Figure 7.8a

Structural Classification of Neurons

Multipolar neurons—many extensions from the cell body



Bipolar neurons—one axon and one dendrite

Figure 7.8b



Unipolar neurons—have a short single process leaving the cell body

Figure 7.8c


Nervous Tissue: Support Cells

Support cells in the CNS are grouped together as “neuroglia”

Function: to support, insulate, and protect neurons



Astrocytes

Abundant, star-shaped cells

Brace neurons

Form barrier between capillaries and neurons

Control the chemical environment of the brain



Figure 7.3a



Microglia

Spiderlike phagocytes

Dispose of debris



Figure 7.3b



Ependymal cells

Line cavities of the brain and spinal cord

Circulate cerebrospinal fluid



Figure 7.3c



Oligodendrocytes

Wrap around nerve fibers in the central nervous system

Produce myelin sheaths



Figure 7.3d



Satellite cells

Protect neuron cell bodies

Schwann cells

Form myelin sheath in the peripheral nervous system



Figure 7.3e


Protection of the Central Nervous System

Scalp and skin

Skull and vertebral column

Meninges

Cerebrospinal fluid (CSF)

Blood-brain barrier


Protection of the Central Nervous System

Figure 7.17a


Meninges

Dura mater

Double-layered external covering

Periosteum—attached to inner surface of the skull

Meningeal layer—outer covering of the brain

Folds inward in several areas


Meninges

Arachnoid layer

Middle layer

Web-like

Pia mater

Internal layer

Clings to the surface of the brain


Meninges

Figure 7.17b


Cerebrospinal Fluid (CSF)

Similar to blood plasma composition

Formed by the choroid plexus

Forms a watery cushion to protect the brain

Circulated in arachnoid space, ventricles, and central canal of the spinal cord


Figure 7.18a–b

Ventricles and Location of the Cerebrospinal Fluid


Ventricles and Location of the Cerebrospinal Fluid

Figure 7.18c

Nervous System Notes Part 3. EVEN MORE INTERESTING NERVOUS SYSTEM FACTS The human brain alone consists of about 100 billion neurons. If all these neurons.

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