The Central Nervous System PART 1

The Central Nervous System Central nervous system – the brain and spinal cord Directional terms unique to the CNS Rostral – toward the nose Caudal – toward the tail Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Embryonic Development of the Brain Brain arises from the rostral part of the neural tube Three primary brain vesicles in 4-week embryo Prosencephalon – the forebrain Mesencephalon – the midbrain Rhombencephalon – the hindbrain Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Embryonic Development of the Brain Secondary brain vesicles Prosencephalon Divides into telencephalon and diencephalon Mesencephalon – remains undivided Rhombencephalon Divides into metencephalon and myelencephalon Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Embryonic Development of the Brain Structures of the adult brain Develop from secondary brain vesicles Telencephalon the cerebral hemispheres Diencephalon thalamus, hypothalamus, and epithalamus Metencephalon pons and cerebellum Myelencephalon medulla oblongata Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Embryonic Development of the Brain Brain stem includes: The midbrain, pons, and medulla oblongata Ventricles Central cavity of the neural tube enlarges Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Embryonic Development of the Brain Figure 13.2a-e Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Embryonic Development of the Brain Brain grows rapidly, and changes occur in the relative position of its parts Cerebral hemispheres envelop the diencephalon and midbrain Wrinkling of the cerebral hemispheres More neurons fit within limited space Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Brain Development from Week 5 to Birth Figure 13.3a-d Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Basic Parts and Organization of the Brain Divided into four regions Cerebral hemispheres Diencephalon Brain stem: midbrain, pons, and medulla Cerebellum Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Basic Parts and Organization of the Brain Figure 13.4 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Basic Parts and Organization of the Brain Centrally located gray matter Externally located white matter Additional layer of gray matter external to white matter Due to groups of neurons migrating externally Cortex – outer layer of gray matter Formed from neuronal cell bodies Located in cerebrum and cerebellum Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Basic Parts and Organization of the Brain Figure 13.5 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Ventricles of the Brain Expansions of the brain’s central cavity Filled with cerebrospinal fluid Lined with ependymal cells Continuous with each other Continuous with the central canal of the spinal cord Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Ventricles of the Brain Lateral ventricles – located in cerebral hemispheres Horseshoe-shaped from bending of the cerebral hemispheres Third ventricle – lies in diencephalon Connected with lateral ventricles by interventricular foramen Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Ventricles of the Brain Cerebral aqueduct – connects 3rd and 4th ventricles Fourth ventricle – lies in hindbrain Connects to the central canal of the spinal cord Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Ventricles of the Brain Figure 13.6a, b Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Central Nervous System PART 2

The Cerebral Hemispheres Account for 83% of brain mass Fissures – deep grooves – separate major regions of the brain Transverse fissure – separates cerebrum and cerebellum Longitudinal fissure – separates cerebral hemispheres Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Cerebral Hemispheres Sulci – grooves on the surface of the cerebral hemispheres Gyri – twisted ridges between sulci Prominent gyri and sulci are similar in all people Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Cerebral Hemispheres Deeper sulci divide cerebrum into lobes Lobes are named for the skull bones overlying them Central sulcus separates frontal and parietal lobes Bordered by two gyri Precentral gyrus Postcentral gyrus Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Cerebral Hemispheres Figure 13.7a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Cerebral Hemispheres Parieto-occipital sulcus Separates the occipital from the parietal lobe Lateral sulcus Separates temporal lobe from parietal and frontal lobes Insula – deep within the lateral sulcus Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Cerebral Hemispheres Figure 13.7b, c Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Cerebral Hemispheres Frontal section through forebrain Cerebral cortex Cerebral white matter Deep gray matter of the cerebrum (basal ganglia) Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Cerebral Hemispheres Figure 13.8 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Home of our conscious mind Enables us to: The Cerebral Cortex Home of our conscious mind Enables us to: Be aware of ourselves and our sensations Initiate and control voluntary movements Communicate, remember, and understand Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Composed of gray matter Folds in cortex – triples its size The Cerebral Cortex Composed of gray matter Neuronal cell bodies, dendrites, and short axons Folds in cortex – triples its size Approximately 40% of brain’s mass Brodmann areas – 52 structurally distinct areas Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Functional and Structural Areas of the Cerebral Cortex Figure 13.11a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Functional and Structural Areas of the Cerebral Cortex Figure 13.11b Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Cerebral Cortex Functional regions Traditionally – studied brain-injured people and animals New discoveries – PET and fMRI Regions of the cerebral cortex Perform distinct motor and sensory functions Memory and language spread over wide area Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Three kinds of functional areas The Cerebral Cortex Three kinds of functional areas Motor areas Sensory areas Association areas Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Motor Areas – Primary Motor Cortex Controls motor functions Primary motor cortex (somatic motor area) Located in precentral gyrus (Brodmann area 4) Pyramidal cells – large neurons of primary motor cortex Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Motor Areas – Primary Motor Cortex Corticospinal tracts descend through brainstem and spinal cord Axons signal motor neurons to control skilled movements Contralateral – pyramidal axons cross over to opposite side of the brain Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Specific pyramidal cells control specific areas of the body Motor Areas Specific pyramidal cells control specific areas of the body Face and hand muscles – controlled by many pyramidal cells Motor homunculus – body map of the motor cortex Somatotopy – body is represented spatially in many parts of the CNS Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Motor Areas Figure 13.10 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Motor Areas – Premotor Cortex Located anterior to the precentral gyrus Controls more complex movements Receives processed sensory information Visual, auditory, and general somatic sensory Controls voluntary actions dependent on sensory feedback Involved in the planning of movements Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Central Nervous System PART 3

Cortical areas involved in conscious awareness of sensation Sensory Areas Cortical areas involved in conscious awareness of sensation Located in parietal, temporal, and occipital lobes Distinct area for each of the major senses Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Sensory Areas – Primary Somatosensory Cortex Located along the postcentral gyrus Corresponds to Brodmann areas 1-3 Involved with conscious awareness of general somatic senses Spatial discrimination – precisely locates a stimulus Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Sensory Areas – Primary Somatosensory Cortex Projection is contralateral Cerebral hemispheres Receive sensory input from the opposite side of the body Sensory homunculus – a body map of the sensory cortex Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Sensory Areas – Primary Somatosensory Cortex Figure 13.10 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Make associations between different types of sensory information Association Areas Make associations between different types of sensory information Associate new sensory input with memories of past experiences New name for association areas – higher order processing areas Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Association Areas – Prefrontal Cortex Large region of the frontal lobe anterior to motor areas Performs cognitive functions All aspects of thinking and perceiving Remembering and recalling information Also related to mood Has close links to the limbic part of the forebrain Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Association Areas – Prefrontal Cortex Anterior pole of frontal cortex Active in solving the most complex problems Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Lateralization of Cortical Functioning The two hemispheres control opposite sides of the body Hemispheres are specialized for different cognitive functions Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Lateralization of Cortical Functioning Left cerebral hemisphere – more control over: Language abilities, math, and logic Right cerebral hemisphere – more involved with: Visual-spatial skills Reading facial expressions Intuition, emotion, artistic and musical skills Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Different areas of the cerebral cortex communicate: Cerebral White Matter Different areas of the cerebral cortex communicate: With each other With the brainstem and spinal cord Fibers are usually myelinated and bundled into tracts Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Cerebral White Matter Types of tracts Commissures – composed of commissural fibers Allows communication between cerebral hemispheres Corpus callosum – the largest commissure Association fibers Connect different parts of the same hemisphere Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Cerebral White Matter Figure 13.13a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Types of tracts (continued) Cerebral White Matter Types of tracts (continued) Projection fibers – run vertically Descend from the cerebral cortex Ascend to the cortex from lower regions Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Cerebral White Matter Figure 13.13b Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Projection Tracts Figure 13.14a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Central Nervous System PART 4

Forms the center core of the forebrain The Diencephalon Forms the center core of the forebrain Surrounded by the cerebral hemispheres Composed of three paired structures: Thalamus, hypothalamus, and epithalamus Border the third ventricle Primarily composed of gray matter Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Diencephalon and Brainstem Figure 13.15 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Diencephalon Figure 13.16a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Diencephalon Figure 13.16b Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Diencephalon – The Thalamus Makes up 80% of the diencephalon Contains approximately a dozen major nuclei Send axons to regions of the cerebral cortex Nuclei act as relay stations for incoming sensory messages Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Diencephalon – The Thalamus Afferent impulses converge on the thalamus Synapse in at least one of its nuclei Is the “gateway” to the cerebral cortex Nuclei organize and amplify or tone down signals Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Thalamus Figure 13.17b Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Diencephalon – The Hypothalamus Lies between the optic chiasm and the mammillary bodies Pituitary gland projects inferiorly Contains approximately a dozen nuclei Main visceral control center of the body Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Diencephalon – The Hypothalamus Functions include the following: Control of the autonomic nervous system Control of emotional responses Regulation of body temperature Regulation of hunger and thirst sensations Control of behavior Regulation of sleep-wake cycles Control of the endocrine system Formation of memory Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Nuclei of the Hypothalamus Figure 13.18 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Diencephalon – The Epithalamus Forms part of the “roof” of the third ventricle Consists of a tiny group of nuclei Includes the pineal gland (pineal body) Secretes the hormone melatonin Under influence of the hypothalamus Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Central Nervous System PART 5

Includes the midbrain, pons, and medulla oblongata The Brain Stem Includes the midbrain, pons, and medulla oblongata Several general functions Produces automatic behaviors necessary for survival Passageway for all fiber tracts running between the cerebrum and spinal cord Heavily involved with the innervation of the face and head 10 of the 12 pairs of cranial nerves attach to it Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Ventral View of the Brain – Diencephalon and Brain Stem Figure 13.19 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Brain Stem – The Midbrain Lies between the diencephalon and the pons Central cavity – the cerebral aqueduct Cerebral peduncles located on the ventral surface of the brain Contain pyramidal (corticospinal) tracts Superior cerebellar peduncles Connect midbrain to the cerebellum Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Brain Stem and Diencephalon Figure 13.20a, b Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Brain Stem – The Midbrain Periaqueductal gray matter surrounds the cerebral aqueduct Involved in two related functions Fright-and-flight reaction Mediates response to visceral pain Figure 13.21a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Brain Stem – The Midbrain Corpora quadrigemina – the largest nuclei Divided into the superior and inferior colliculi Superior colliculi – nuclei that act in visual reflexes Inferior colliculi – nuclei that act in reflexive response to sound Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Brain Stem – Dorsal View Figure 13.20c Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Brain Stem – The Pons Located between the midbrain and medulla oblongata Contains the nuclei of cranial nerves V, VI, and VII Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Brain Stem – The Pons Figure 13.21.b Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Brain Stem – The Medulla Oblongata Most caudal level of the brain stem Continuous with the spinal cord Choroid plexus lies in the roof of the fourth ventricle Pyramids of the medulla – lie on its ventral surface Decussation of the pyramids – crossing over of motor tracts Cranial nerves VIII–XII attach to the medulla Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Brain Stem – The Medulla Oblongata The core of the medulla contains: Much of the reticular formation Nuclei influence autonomic functions Visceral centers of the reticular formation include: Cardiac center Vasomotor center The medullary respiratory center Centers for hiccupping, sneezing, swallowing, and coughing Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Located dorsal to the pons and medulla The Cerebellum Located dorsal to the pons and medulla Smoothes and coordinates body movements Helps maintain equilibrium Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Consists of two cerebellar hemispheres The Cerebellum Consists of two cerebellar hemispheres Surface folded into ridges called folia Separated by fissures Hemispheres each subdivided into: Anterior lobe Posterior lobe Flocculonodular lobe Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Cerebellum Figure 13.22a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Composed of three regions The Cerebellum Composed of three regions Cortex – gray matter Internal white matter Deep cerebellar nuclei – deeply situated gray matter Cerebellum must receive information On equilibrium On current movements of limbs, neck, and trunk From the cerebral cortex Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Cerebellum – Cerebellar Peduncles Thick tracts connecting the cerebellum to the brain stem Superior cerebellar peduncles Middle cerebellar peduncles Inferior cerebellar peduncles Fibers to and from the cerebellum are ipsilateral Run to and from the same side of the body Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Central Nervous System PART 6

Functional Brain Systems Networks of neurons functioning together The limbic system – spread widely in the forebrain The reticular formation – spans the brain stem Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Functional Brain Systems – The Limbic System Location Medial aspect of cerebral hemispheres Also within the diencephalon The fornix and other tracts link the limbic system together Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Functional Brain Systems – The Limbic System Figure 13.23 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Functional Brain Systems – The Limbic System The “emotional brain” Cingulate gyrus Allows us to shift between thoughts Interprets pain as unpleasant Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Functional Brain Systems – The Reticular Formation Runs through the central core of the medulla, pons, and midbrain Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Functional Brain Systems – The Reticular Formation Figure 13.21c Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Functional Brain Systems – The Reticular Formation Widespread connections Ideal for arousal of the brain as a whole Reticular activating system (RAS) Maintains consciousness and alertness Functions in sleep and arousal from sleep Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Functional Brain Systems – The Reticular Formation Figure 13.24 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Protection of the Brain The brain is protected from injury by The skull Meninges Cerebrospinal fluid Blood-brain barrier Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Protection of the Brain – Meninges Cover and protect the CNS Enclose and protect the vessels that supply the CNS Contain the cerebrospinal fluid Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Strongest of the meninges Composed of two layers The Dura Mater Strongest of the meninges Composed of two layers Periosteal layer Meningeal layer Two layers are fused except to enclose the dural sinuses Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Dura Mater Figure 13.25a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Largest sinus – the superior sagittal sinus The Dura Mater Largest sinus – the superior sagittal sinus Dura mater extends inward to subdivide the cranial cavity Figure 13.26 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Located beneath the dura mater Subdural space Subarachnoid space The Arachnoid Mater Located beneath the dura mater Subdural space Potential space between dura and arachnoid mater Subarachnoid space Filled with CSF Contains the blood vessels that supply the brain Arachnoid villi Allow CSF to pass into the dural blood sinuses Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Delicate connective tissue Clings tightly to the surface of the brain The Pia Mater Delicate connective tissue Clings tightly to the surface of the brain Follows all convolutions of the cortex Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Central Nervous System PART 7

Protection of the Brain – Cerebrospinal Fluid (CSF) Provides a liquid cushion for the brain and spinal cord The brain “floats” in CSF Formed in choroid plexuses in the brain ventricles Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Protection of the Brain – Cerebrospinal Fluid (CSF) Figure 13.27a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Protection of the Brain – Cerebrospinal Fluid (CSF) Figure 13.27b Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Protection of the Brain – Blood-Brain Barrier Prevents most blood-borne toxins from entering the brain Impermeable capillaries Not an absolute barrier Nutrients such as oxygen pass through Allows alcohol, nicotine, and anesthetics through Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Runs through the vertebral canal The Spinal Cord Runs through the vertebral canal Extends from the foramen magnum to the level of the vertebra L1 or L2 Protected by bone, meninges, and CSF Dura mater of the spinal cord The spinal dural sheath – only one layer Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Conus medullaris – the inferior end of the spinal cord Filum terminale – long filament of connective tissue Attaches to the coccyx inferiorly Cervical and lumbar enlargements Where nerves for upper and lower limbs arise Cauda equina – collection of nerve roots Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Spinal Cord Figure 13.29a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Denticulate ligaments – anchor spinal cord to vertebrae The Spinal Cord Denticulate ligaments – anchor spinal cord to vertebrae Two deep grooves run the length of the cord Posterior median sulcus Anterior median fissure Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Anatomy of the Spinal Cord Figure 13.30a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Anatomy of the Spinal Cord Figure 13.30b Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Gray Matter of the Spinal Cord and Spinal Roots Shaped like the letter H Gray commissure – contains the central canal Anterior horns – contain cell bodies of motor neurons Posterior horns – consist of interneurons Gray matter – divided according to somatic and visceral regions Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Gray Matter of the Spinal Cord and Spinal Roots Figure 13.32 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Central Nervous System PART 8

White Matter of the Spinal Cord Composed of myelinated and unmyelinated axons Three types of fibers Ascending Descending Commissural Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

White Matter of the Spinal Cord Figure 13.33 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Sensory and Motor Pathways Most motor pathways: Decussate at some point along their course Consist of a chain of two or three neurons Exhibit somatotopy Tracts arranged according to the body region they supply All pathways are paired One of each on each side of the body Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Ascending (Sensory) Pathways Conduct general somatic sensory impulses Chains of neurons composed of: First-, second-, and third-order neurons Four main ascending pathways Dorsal column pathway Spinothalamic pathway Posterior spinocerebellar pathway Anterior spinocerebellar pathway Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Ascending Pathways Figure 13.34a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Ascending Pathways Figure 13.34b Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Descending (Motor) Pathways Deliver motor instructions from the brain to the spinal cord Divided into two groups Pyramidal, or corticospinal, tracts Other motor pathways Tectospinal tracts Vestibulospinal tract Rubrospinal tract Reticulospinal tract Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Descending Motor Pathways Figure 13.35a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Descending Motor Pathways Figure 13.35b Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Disorders of the Central Nervous System Brain dysfunction Traumatic brain injuries Concussion – brain injury is slight Contusion – marked destruction of brain tissue Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Disorders of the Central Nervous System Brain dysfunction (continued) Degenerative brain diseases Cerebrovascular accident (stroke) Blockage or interruption of blood flow to a brain region Alzheimer’s disease Progressive degenerative disease leading to dementias Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Disorders of the Central Nervous System Spinal cord damage Paralysis – loss of motor function Parasthesia – loss of sensation Paraplegia – injury to the spinal cord is between T1 and L2 Paralysis of the lower limbs Quadriplegia – injury to the spinal cord in the cervical region Paralysis of all four limbs Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

The Central Nervous System Throughout Life Congenital malformations Hydrocephalus Neural tube defects Anencephaly – cerebrum and cerebellum are absent Spina bifida – absence of vertebral lamina Cerebral palsy – voluntary muscles are poorly controlled Results from damage to the motor cortex Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings