copyright © 2006 by allyn and bacon chapter 3 the anatomy of the nervous system the systems,...

Copyright © 2006 by Allyn and Bacon

Chapter 3The Anatomy of the

Nervous System

The Systems, Structures, and Cells that Make Up Your Nervous System

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General Layout of the Nervous System

Central Nervous System (CNS)• Brain (in the skull)

• Spinal Cord (in the spine)

Peripheral Nervous System (PNS)• Located outside of the skull and spine

• Serves to bring information into the CNS and carry signals out of the CNS


General Layout of the Nervous System

Peripheral Nervous System• Somatic Nervous System

Afferent nerves (sensory)

Efferent nerves (motor)

• Autonomic Nervous SystemSympathetic and parasympathetic nerves

Both are efferent


Autonomic Nervous System

All nerves are efferent Sympathetic and parasympathetic

nerves generally have opposite effects Two-stage neural paths, neuron exiting

the CNS synapses on a second-stage neuron before the target organ


Autonomic Nervous System

Sympathetic Thoracolumbar “fight or flight” Second stage

neurons are far from the target organ

Parasympathetic Craniosacral “rest and restore” Second stage

neurons are near the target organ


Meninges, Ventricles, and CSF

CNS - encased in bone and covered by three meninges• Dura mater - tough outer membrane

• Arachnoid membrane - weblike• Pia mater - adheres to CNS surface

Cerebrospinal fluid (CSF)• Fluid serves as cushion


Protecting the Brain

Chemical protection• The blood-brain barrier – tightly-packed cells

of blood vessel walls prevent entry of many molecules

Physical protection• Skull

• Meninges

• Cerebrospinal fluid (CSF)


Cells of the Nervous System

Neurons – structural classes• Multipolar

• Unipolar

• Bipolar

• Interneurons Glial cells – various types, provide a

wide variety of supportive functions


Glial Cells

Myelin producers• Oligodendrocytes (CNS)

• Schwann cells (PNS) Astrocytes – largest glia, many functions Microglia – involved in response to injury

or disease


Terminology Note

CNS PNSMyelin-providing glia

Oligodendrocytes Schwann Cells

Clusters of cell bodies

Nuclei (singular nucleus)

Ganglia(singular ganglion)

Bundles of axons

Tracts Nerves


Neuroanatomical Techniques

Golgi stain – allows for visualization of individual neurons

Nissl stain – selectively stains cell bodies

Electron microscopy – provides information about the details of neuronal structure


Neuroanatomical Tracing Techniques

Anterograde (forward)

• tracing where axons project to Retrograde (backward)

• tracing where axons are projecting from


Neuroanatomical Directions

In humans, the spinal cord is bent. Top of the head = dorsal or superior Back = dorsal Medial – towards the middle Lateral – towards the side Proximal – close Distal - far


Sections of the Brain

Horizontal – a slice parallel to the ground Frontal (coronal) – slicing bread or

salami Sagittal – a midsagittal section separates

the left and right halves


The Spinal Cord

Gray matter – inner component – primarily cell bodies

White matter – outer – mainly myelinated axons

Dorsal – afferent, sensory Ventral – efferent, motor


The Five Major Divisions of the Brain


Major Structures of the Brain

Myelencephalon = medulla• Composed largely of tracts

• Origin of the reticular formation

Metencephalon• Many tracts

• Pons – ventral surface

• Cerebellum - coordination


Major Structures of the Brain

Mesencephalon • Tectum (dorsal surface)

• Inferior colliculi – audition

• Superior colliculi - vision

• Tegmentum (ventral) – 3 ‘colorful’ structures

• Periaqueductal gray – analgesia

• Substantia nigra – sensorimotor

• Red nucleus– sensorimotor


Major Structures of the Brain Diencephalon

• Thalamus – sensory relay nuclei• Hypothalamus

Regulation of motivated behaviors Controls hormone release by the pituitary

Telencephalon• Cerebral cortex• Limbic system• Basal ganglia


Telencephalon – Cerebral Cortex

Convolutions serve to increase surface area.

Longitudinal fissure – a groove that separates right and left hemispheres

Corpus callosum – largest hemisphere-connecting tract


Telencephalon – Subcortical structures

Limbic system – regulation of motivated behaviors• Mammillary bodies, hippocampus, amygdala,

fornix, cingulate, septum Basal ganglia motor system

• Amygdala, striatum (caudate nucleus + putamen), globus pallidus

copyright © 2006 by allyn and bacon chapter 3 the anatomy of the nervous system the systems,...

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cns slide

bacon cells

efferent slide

cushion slide

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target organ slide