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The Central Nervous System

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1 The Central Nervous System
PART 1

2 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

3 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

4 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

5 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

6 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

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

8 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

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

10 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

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

12 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

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

14 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

15 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

16 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

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

18 The Central Nervous System
PART 2

19 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

20 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

21 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

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

23 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

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

25 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

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

27 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

28 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

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

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

31 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

32 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

33 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

34 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

35 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

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

37 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

38 The Central Nervous System
PART 3

39 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

40 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

41 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

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

43 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

44 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

45 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

46 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

47 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

48 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

49 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

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

51 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

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

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

54 The Central Nervous System
PART 4

55 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

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

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

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

59 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

60 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

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

62 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

63 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

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

65 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

66 The Central Nervous System
PART 5

67 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

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

69 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

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

71 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

72 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

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

74 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

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

76 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

77 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

78 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

79 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

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

81 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

82 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

83 The Central Nervous System
PART 6

84 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

85 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

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

87 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

88 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

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

90 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

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

92 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

93 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

94 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

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

96 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

97 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

98 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

99 The Central Nervous System
PART 7

100 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

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

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

103 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

104 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

105 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

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

107 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

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

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

110 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

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

112 The Central Nervous System
PART 8

113 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

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

115 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

116 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

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

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

119 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

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

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

122 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

123 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

124 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

125 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


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