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Nervous Tissue I:Functional Organization, Spinal

Cord and Spinal Nerves

Lecture 12

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Nervous Tissue

• Found in brain, spinal cord and nerves

• Property– Ability to produce action potentials (electric

signals)

• Cells– Nerve cells or neurons– Neuroglia or support cells

– Oligodendrocytes and Schwann cells

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The Nervous System

• Subdivisions– Central nervous system (CNS)– Peripheral nervous system (PNS)

• Sensory receptor– Receptor of sensory information

• Nerve– Made up of a bundle of axons

• Ganglion– Collection of cell bodies of neurons

• Plexus– Network of spinal nerves

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Central Nervous System

• Consists of– Brain

• Located in cranial vault of skull

– Spinal cord• Located in vertebral

canal

• Brain and spinal cord– Continuous with each

other at foramen magnum

• TractFig. 14.1

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Peripheral Nervous System

• Two subcategories– Sensory or afferent

– Motor or efferent• Divisions

– Somatic nervous system

– Autonomic nervous system (ANS)

» Sympathetic

(fight or flight)

» Parasympathetic

(rest and digest)Fig. 14.2

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Spinal Cord• Extends from foramen

magnum to second lumbar vertebra

• Segmented– Cervical

– Thoracic

– Lumbar

– Sacral

• Gives rise to 31 pairs of spinal nerves

• Not uniform in diameter throughout length

Fig. 16.1

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Meninges

• Connective tissue membranes surrounding spinal cord and brain– Dura mater– Arachnoid mater– Pia mater

• Spaces– Epidural: Anesthesia

injected– Subdural: Serous fluid– Subarachnoid:

cerebrospinal fluid (CSF)

Fig. 16.2

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Cross Section of Spinal Cord• White matter

– Myelinated axons forming tracts

– Three funiculi (columns)

• Gray matter– Neuron cell bodies,

dendrites, axons

– Three hornsFig. 16.3

Fig. 16.4

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Spinal NervesCervical Plexus

• C1-C4• Phrenic nerve

– from C3-C5 (cervical and brachial plexus)

– innervates diaphragm

Fig. 16.8

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Brachial Plexus• C5-T1• Major nerves

– Radial– Ulnar– Median

Fig. 16.9

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Lumbar Plexus

Fig. 16.10

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Sacral Plexus

Fig. 16.11

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Review Question

Compression of the ________ nerve against the medial epicondyle of the humerus will produce strong tingling sensations along the forearm and hand.

(a) Radial(b)Median(c) Phrenic(d)Femoral(e) Ulnar

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Points to Remember• Nervous system consists of central nervous system

(brain and spinal cord) and peripheral nervous system (all nervous tissue outside of central nervous system)

• Sensory (afferent) neurons carry sensory information to brain and spinal cord

• Motor (efferent) neurons carry motor away from brain and spinal cord to spinal nerves and cranial nerves

• Spinal nerves have a dorsal root (sensory neurons) and a ventral root (motor neurons)

• Names of nerves in plexuses generally describe the body region they travel

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Questions?