Biology 210 Chapter 13 The Central Nervous System Edited by John McGill Supplemental Notes by Beth Wyatt Original PowerPoint By: Jack Bagwell Last Updated: March 28, 2017

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 Brain Pituitary Optic Chiasma

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 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 Olive Pyramids 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: Gray 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 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 Matter Consists of axons of neurons originating in the spinal cord 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 Tracts

Ascending Tracts Spinocerebellar tracts Spinothalamic 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 Tracts Corticospinal tract Rubrospinal 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 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 SIZE BRAINSTEM CEREBELLUM DIENCEPHALON CEREBRUM MEDULLA OBLONGATA PONS MIDBRAIN CEREBELLUM DIENCEPHALON CEREBRUM SIZE In Adults, Weighs Approx. 3 Pounds

THE BRAIN: Brainstem BRAINSTEM STRUCTURE 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

Reticular Formation http://www. medinfo. ufl

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