Biology 210 Chapter 13The Central Nervous System

Edited by John McGill

Supplemental Notes by Beth Wyatt

Original PowerPoint By: Jack Bagwell

Last Updated: April 10, 2023

DIVISIONS OF THE NERVOUS SYSTEM

There Are Several Ways That the Nervous System Can Be Organized BASED ON LOCATION

OF ORGANS CENTRAL NERVOUS

SYSTEM (CNS) PERIPHERAL NERVOUS

SYSTEM (PNS)

DIVISIONS OF THE NERVOUS SYSTEM

Organs centrally located

CENTRAL NERVOUS SYSTEM (CNS) BRAIN SPINAL CORD

DIVISIONS: Peripheral Nervous System

Organs (Nerves) Peripherally Located 2 Kinds of Nerves

CRANIAL NERVES (Originate From Brain) SPINAL NERVES (Originate From Spinal Cord)

Classification Based on Pathways

BASED ON DIRECTION IN WHICH PATHWAYS CARRY INFORMATION NEURONS CONDUCT NERVE IMPULSES) AFFERENT (aa ferent)

DIVISION: All Afferent Neurons

EFFERENT (ee ferent) DIVISION: All Efferent Neurons

Classification Based on Effectors

BASED ON EFFECTORS INNERVATED/REGULATED

SOMATIC NERVOUS SYSTEM (SNS)

AUTONOMIC NERVOUS SYSTEM (ANS)

Somatic: Voluntary Effectors SOMATIC NERVOUS SYSTEM

(SNS)Effectors: Skeletal Muscles

Voluntary Somatic Effectors

Autonomic: Involuntary Effectors

BASED AUTONOMIC NERVOUS SYSTEM (ANS) Effectors: Cardiac and Smooth Muscle,Glands

Involuntary Autonomic/Visceral Effectors)

Autonomic: 2 Divisions

SYMPATHETIC DIVISION-Response of Autonomic Effectors During Stress PARASYMPATHETIC DIVISION-Response of Autonomic Effectors During

Nonstress

COVERINGS OF THE BRAIN AND SPINAL CORD

Coverings Provide Protection 2 Kinds

OUTER COVERING - BONE CRANIAL BONES: BRAIN VERTEBRAE: SPINAL CORD

INNER COVERING – MEMBRANES (MENINGES) LAYERS OF MENINGES

DURA MATER ARACHNOID MEMBRANE PIA MATER

BONE COVERS THE BRAIN AND SPINAL CORD

CRANIAL BONES: BRAIN VERTEBRAE: SPINAL CORD

Vertebra & Spinal Cord

INNER COVERING MEMBRANES (MENINGES)

LAYERS OF MENINGES DURA MATER ARACHNOID MEMBRANE PIA MATER

LAYERS OF MENINGES

DURA MATER Outermost Layer of Meninges Tough, White An Extension of Periosteum

Dura Mater of Inferior Sheep BrainDura Mater of Inferior Sheep Brain

Pituitary

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LAYERS OF MENINGES ARACHNOID MEMBRANE

Middle Layer of Meninges Delicate

LAYERS OF MENINGES

PIA MATER Innermost Layer of

Meninges Thin Transparent Adheres to CNS Contains Blood

Vessels

Pia Mater of Superior Sheep BrainPia Mater of Superior Sheep Brain

SPACES BETWEEN MENINGES

EPIDURAL SPACE SUBDURAL SPACE SUBARACHNOID SPACE

EPIDURAL SPACE “Space Above Dura” (Between Bone & Dura Mater) Contains Connective Tissue (Adipose)

Epidural Space

SUBDURAL SPACE “Space Below Dura”

(Between Dura Mater & Arachnoid)

Contains a Serous Fluid That Provides Lubrication

SUBARACHNOID SPACE

SPACES “Space Below the Arachnoid” (Between Arachnoid & Pia Mater)

Contains Cerebrospinal Fluid

CEREBROSPINAL FLUID

The Fluid That Circulates In and Around the CNS FUNCTION

Protection (A Cushion of Fluid)

FLUID SPACES The Spaces Where Cerebrospinal Fluid Circulates

CEREBROSPINAL FLUID: FLUID SPACES WITHIN BRAIN

VENTRICLES 4 Fluid Spaces Within the

Brain LATERAL (FIRST

AND SECOND) VENTRICLES

THIRD VENTRICLE FOURTH

VENTRICLE CEREBRAL AQUEDUCT

WITHIN SPINAL CORD CENTRAL CANAL

CEREBROSPINAL FLUID within the BRAIN

VENTRICLES: 4 Fluid Spaces Within the Brain LATERAL (FIRST AND SECOND) VENTRICLES

2, Located in Each Cerebral Hemisphere The Largest of the Ventricles

CEREBROSPINAL FLUID within the BRAIN

VENTRICLES: 4 Fluid Spaces Within the Brain THIRD VENTRICLE

Lies Inferior and Medial to the Lateral Ventricles

CEREBROSPINAL FLUID within the BRAIN

VENTRICLES: 4 Fluid Spaces Within the Brain FOURTH VENTRICLE

Diamond Shaped Space, Located Between the Brainstem and the Cerebellum

CEREBROSPINAL FLUID within the BRAIN

CEREBRAL AQUEDUCT Canal That Connects the Third and Fourth

Ventricles

CEREBROSPINAL FLUID within the SPINAL CORD

CENTRAL CANAL Passageway Within the Spinal Cord Continuous With the Fourth Ventricle

CEREBROSPINAL FLUID Circulation

AROUND BRAIN AND SPINAL CORD SUBARACHNOID

SPACE

CEREBROSPINAL FLUID Formation

FORMATION FROM BLOOD Choroid Plexuses: Capillary Networks Located in

Each of the Ventricles As Blood Flows Through Choroid Plexuses, Some of the Fluid from Blood Filters Through the

Plexuses and into the, Ventricles, The Fluid is Now Known as CSF

Choroid Plexuses

CEREBROSPINAL FLUID Circulation

FROM LATERAL VENTRICLES

THIRD VENTRICLE CEREBRAL AQUEDUCT FOURTH VENTRICLE* CENTRAL CANAL SUBARACHNOID SPACE BACK TO BLOOD

(ARACHNOID VILLI)

CEREBROSPINAL FLUID Circulation 2nd Pathway

*NOTE: ADDITIONAL PATHWAY:

ONCE IN FOURTH VENTRICLE

SUBARACHNOID SPACE BACK TO BLOOD

(ARACHNOID VILLI) Arachnoid Villi: Fingerlike

Extensions of Arachnoid That Project into Blood Vessels

SPINAL CORD STRUCTURE LOCATION,

EXTENT, SHAPE Spinal Cavity Extends from

Foramen Magnum to Lower Border of the First Lumbar Vertebra (approx. 18 inches)

Oval Cylinder

SPINAL CORD STRUCTURE: Grooves

ANTERIOR MEDIAN FISSURE Deep Groove in the

Anterior Midline

POSTERIOR MEDIAN SULCUS Groove in the Posterior

Midline

Anterior Median Fissure

1.Anterior median fissure 2.Olive 3.Pyramids 4.Cerebellum

Posterior Median Sulcus: 400X+

Posterior Median Sulcus & Others

SPINAL CORD: NERVE ROOTS

NERVE ROOTS/SPINAL NERVES Spinal Nerves Attached to Spinal Cord by

Nerve Roots (example nerves) DORSAL NERVE ROOT: NF OF AFFERENT

NEURONS VENTRAL NERVE ROOT: NF OF EFFERENT

NEURONS

DORSAL NERVE ROOT: NF OF AFFERENT NEURONS

Unipolar Receptors/Dendrites in Sense Organs Axons (Peripheral Portion) in Spinal Nerve Cell Bodies in Dorsal Root Ganglion Axons (Central Portion) in Dorsal

Nerve Root

VENTRAL NERVE ROOT: NF OF EFFERENT NEURONS

Efferent Neurons: Multipolar Dendrites/Cell Bodies in Gray Matter of Spinal Cord Axons in Ventral Nerve Root and S. Nerve

Spinal Cord Cross Section

http://www.uoguelph.ca/zoology/devobio/210labs/ecto2.html

Spinal Cord: Afferent (unipolar) & Efferent (multipolar) Neurons

Spinal Cord: Spinal Cord: Gray and White MatterGray and White Matter

The spinal cord consists of Gray Matter:

Consists of cell bodies of interneurons and motor neurons

White Matter Consists of axons of

neurons originating in the spinal cord and brain.

SPINAL CORD: Gray Matter

GRAY MATTER In Spinal Cord, Gray Matter Primarily Consists of Cell

Bodies of Interneurons and Motor Neurons

SPINAL CORD: Gray Matter

LOCATION: Central Portion of Spinal Cord, Resembles Letter “H” DIVISIONS: GRAY HORNS (COLUMNS), ANTERIOR, POSTERIOR,

& LATERAL

SPINAL CORD: White MatterSPINAL CORD: White Matter

White MatterWhite Matter Consists of axons of neurons originating in the spinal cord Consists of axons of neurons originating in the spinal cord

and brain.and brain.

SPINAL CORD: White Matter

LOCATION: Peripheral to Gray Matter DIVISIONS

WHITE COLUMNS: ANTERIOR, POSTERIOR, LATERAL

TRACTS White Columns Further Subdivided into Tracts

Names of Tracts Often Indicate 2 Things About Tract: Where Tract Begins/Ends White Column in Which Tract Located

SPINAL CORD: White Matter

WHITE COLUMNS ANTERIOR POSTERIOR LATERAL

Gray and White Matter

SPINAL CORD: White Matter

FUNCTIONS PROVIDES CONDUCTION ROUTES (2

WAY) FOR NERVE IMPULSES TRAVELING TO AND FROM THE BRAIN (WHITE MATTER)

White Matter of the Spinal Cord (Tracts) Conducts Impulses Toward and Away from the Brain Ascending tracts conduct impulses up the SC

toward the brain Descending tracts conduct impulses down the SC

away from the brain

SPINAL CORD: ASCENDING TRACTS

Conduct Impulses Up the SC Toward the Brain

FUNCTION Ascending Tracts Have a Sensory Function (Carry

Impulses Related To General Sensations: Hot, Cold, Pain, Pressure, Touch & Kinesthesia)

IMPORTANT ASCENDING TRACTS SPINOTHALAMIC TRACTS FASCICULI GRACILIS AND CUNEATUS SPINOCEREBELLAR TRACTS

SPINAL CORD: DESCENDING TRACTS

DESCENDING TRACTS Elaboration Conduct Impulses Down the SC Away from the

Brain FUNCTION Descending Tracts Have a Motor Function

(Carry Impulses that Will Result in Voluntary Movement of Skeletal Muscles)

IMPORTANT DESCENDING TRACTS CORTICOSPINAL TRACTS RETICULOSPINAL TRACTS RUBROSPINAL TRACTS

Spinal Cord TractsSpinal Cord Tracts

Ascending TractsAscending Tracts Spinocerebellar tracts

Impulses from stretch receptors are carried to the spinal cord. These tracts originate in the spinal cord and transmit signals to

the cerebellum Involved in regulation of muscle tone without reaching

consciousness. Spinothalamic tracts

Fibers concerned with pain, thermal sense, and light touch Originate in the spinal cord. Convey sensory impulses to the thalamus.

Dorsal column: Fasciculi Gracilis and Cuneatus Tracts Arise from spinal ganglion cells The fasciculi terminate upon large nuclear masses (the nuclei

gracilis and cuneatus) in the medulla. Conveys signals associated with tactile, pressure, and

kinesthetic (or positional) sense to sensory areas of the cerebral cortex.

Descending TractsDescending Tracts Corticospinal tract

Concerned with skilled voluntary activity, the corticospinal tract originates from premotor, primary motor, and primary sensory cortex.

Synapse with interneurons and motor neurons. Rubrospinal tract

Arises from cells in the midbrain. Fibers of this tract descend the spinal cord and terminate on

interneurons. Cells of the midbrain receive input from the motor cortex and from

the cerebellum (via the superior cerebellar peduncle). The rubrospinal tract brings flexor muscle tone under the control of

these two regions of the brain. Reticulospinal tract

Arises from the reticular formation of the pons and medulla Fibers of this tract influence voluntary movements, muscle tone, and

a variety of spinal reflexes. Fibers terminate at all spinal levels. Receive input from regions of the motor cortex.

Spinal Cord TractsSpinal Cord Tracts

SPINAL CORD : Reflexes

REFLEX CENTER FOR ALL SPINAL REFLEXES (GRAY MATTER) Gray Matter of the Spinal Cord Functions as Reflex Centers for

Spinal Reflexes Reflex Center: Center of a Reflex Arc Spinal Reflexes: Reflexes Whose Arcs Pass Through the SC

SPINAL CORD : Reflexes

SPINAL CORD : Reflexes

THE BRAIN

DIVISIONS BRAINSTEM

MEDULLA OBLONGATA PONS MIDBRAIN

CEREBELLUM DIENCEPHALON CEREBRUM

SIZE In Adults, Weighs Approx.

3 Pounds

THE BRAIN: Brainstem

BRAINSTEM Extension of SC into

the Cranial Cavity STRUCTURE

MEDULLA OBLONGATA Lowermost Division

PONS Middle, Swollen

Division MIDBRAIN

Uppermost Division

THE BRAIN: Brainstem

MIDBRAIN: Uppermost Division; Has 2 Important External Landmarks

CEREBRAL PEDUNCLES: Form Floor of Midbrain CORPORA QUADRIGEMINIA

Cerebral Peduncles

Midbrain: Copora Quadrigemina

CORPORA QUADRIGEMINIA Forms Roof of Midbrain CQ Consists of 4 Rounded Structures

SUPERIOR COLLICULI (2): Visual Centers INFERIOR COLLICULI (2): Auditory Centers

CORPORA QUADRIGEMINIA

THE BRAIN: Reticular Formation

LOCATIONS OF GRAY AND WHITE MATTER IN BRAINSTEM WHITE MATTER –outside RETICULAR FORMATION – inside

Reticular Formation = Mixture of Gray and White Matter Located in the Core of the Brainstem

Reticular Formation http://www.medinfo.ufl.edu/year2/neuro/neuroexam/nems5000.html

Reticular Formation http://www.medinfo.ufl.edu/year2/neuro/neuroexam/nems5000.html

THE BRAIN: Brainstem Tracts (white matter)

FUNCTIONS The Functions of the Brainstem are

Similar to the Functions of the SC PROVIDES CONDUCTION

ROUTES (2 WAY) FOR NERVE IMPULSES TRAVELING BETWEEN SPINAL CORD AND BRAIN (WHITE MATTER)

The White Matter of the Brainstem is Organized into Tracts (Ascending & Descending Which are an Extension of The Tracts of the Spinal Cord

http://brainimaging.waisman.wisc.edu/~mlazar/TRAVIS_2.html

THE BRAIN: Reticular Formation

REFLEX CENTER FOR BRAIN REFLEXES (GRAY MATTER) Portions of Gray Matter Located Within the

Reticular Formation Functions as Reflex Centers for Brain Reflexes

(Brain Reflexes: Reflexes Whose Arcs Pass Through the Brainstem)

THE BRAIN: Brain Reflexes 2 Kinds of Reflex Centers in Brainstem

VITAL REFLEX CENTERS (MEDULLA) Reflex Centers for Vital Reflexes Vital Reflexes: Reflexes that are Essential for

Survival; Examples: Breathing, Heart rate, BP

Names of Vital Reflex Centers: Respiratory Centers, Cardiac Control Centers,

Vasomotor Center

All of the Vital Reflex Centers are Located in the Medulla (Medulla Associated with Basic Survival)

THE BRAIN: Brain Reflexes

NONVITAL REFLEX CENTERS (MEDULLA, PONS, MIDBRAIN) Reflex Centers for Nonvital Reflexes (Not

Essential for Basic Survival: Vomiting, Coughing, Hiccuping, Swallowing,

Sneezing, etc.); Centers Have Same Names as Reflexes

Nonvital Reflex Centers Located in All Parts of the Brainstem

Brain Illusions and Information

http://www.exploratorium.edu/exhibits/changingill/

http://www.wnet.org/archive/closetohome/animation/neuron-main.html

http://videocast.av.com/default.cfm?FeatureID=105640