The Central Nervous System Part A Chapter 12 The Central Nervous System Part A

Objectives: • List, label and identify meninges, parts of the brain, match and select from a given list with 100% accuracy • List the functions of the different parts of the brain, match and select from a given list with 100% accuracy • Identify and label gross anatomy and sectional anatomy of the spinal cord • List some of the diagnostic procedures for assessing CNS dysfunction • Write short descriptions explaining the principles of EEG, brain wave patterns, memory, consciousness and their dysfunctions

Central Nervous System (CNS) CNS – composed of: The brain, and Spinal cord Evolutional Cephalization: involves: Elaboration of the anterior portion of the CNS Increase in number of neurons in the head Highest level is reached in the human brain

Embryonic Development First 26 days of development: Ectoderm thickens forming neural plate Neural plate invaginates, forming the neural groove Neural groove fuses dorsally and forms the neural tube Neural tube detaches, sinks deeper Neural tube forms the CNS

Primary Brain Vesicles Anteriorly the neural tube expands and constricts It forms three primary brain vesicles: Prosencephalon: The forebrain Mesencephalon: The midbrain Rhombencephalon: The hindbrain

Secondary Brain Vesicles In week 5, secondary brain vesicles form: Forebrain gives rise to: Telencephalon Diencephalon Midbrain remains as: Mesencephalon Hindbrain gives rise to: Metencephalon Myelencephalon

Adult Brain Structures Fates of the secondary brain vesicles: Telencephalon : Cerebrum: cortex, white matter, and basal nuclei Diencephalon: Thalamus, hypothalamus, and epithalamus Retina of the eye Mesencephalon: Brain stem: midbrain Metencephalon: Brain stem: pons Cerebellum (not part of brain stem) Myelencephalon: Brain stem: medulla oblongata

Adult Brain Structures Figure 12.2c, d

Adult Neural Canal Regions Adult structures derived from the neural canal: Telencephalon: Lateral ventricles Diencephalon: Third ventricle Mesencephalon: Cerebral aqueduct Metencephalon & myelencephalon: Fourth ventricle

Adult Neural Canal Regions Figure 12.2c, e

The Brain Composed of wrinkled, pinkish gray tissue Surface anatomy includes: Cerebral hemispheres Cerebellum Brain stem

Brain Lobes Figure 12.6a–b

Basic Pattern of the Central Nervous System Spinal Cord Central cavity surrounded by a gray matter core External white matter composed of myelinated fiber tracts Brain Similar to spinal cord but with additional areas of gray matter Cerebrum has grey matter in nuclei and additional gray matter in the cortex Cerebellum has gray matter in nuclei

Ventricles of the Brain The ventricles are: Expansions of the lumen of the embryonic neural tube Continuous with one another & with the central canal of the spinal cord Lined with ciliated ?????? cells Filled with cerebrospinal fluid

Ventricles of the Brain The ventricles include: The lateral ventricles: Paired C-shaped found in the telencephalon The third ventricle: Found in the diencephalon The fourth ventricle: found in the hindbrain (metencephalon & myelencephalon) dorsal to the pons

Ventricles of the Brain Figure 12.5

Major Lobes, Gyri, and Sulci of the Cerebral Hemisphere Shallow grooves divide the hemispheres into five lobes: Frontal Parietal Temporal Occipital insula Central sulcus: Separates the frontal and the parietal lobes

Brain Lobes Figure 12.6a–b

Major Lobes, Gyri, and Sulci of the Cerebral Hemisphere Parieto-occipital sulcus: Separates the parietal and occipital lobes, (can only be seen medially) Lateral sulcus: Separates both the frontal lobes from the temporal lobes Precentral and postcentral gyri: Border the central sulcus anteriorly & posteriorly, respectively.

Brain Lobes Figure 12.6a–b

Cerebral Hemispheres Superior part of the brain (83% of brain mass) Contain: elevated ridges called gyri shallow grooves called sulci deep grooves called fissures Separated into two parts by longitudinal fissure Separated from cerebellum by transverse fissure Have three basic regions: cortex white matter basal nuclei

Cerebral Cortex The cortex is the superficial gray matter It accounts for 40% of the brain mass It enables sensation, communication, memory, understanding, and voluntary movements Each hemisphere acts contralaterally (controls the opposite side of the body) Hemispheres are not equal in function Conscious behavior involves the entire cortex ( No functional area acts alone)

Functional Areas of the Cerebral Cortex The three types of functional areas are: Motor areas: Control voluntary movement Sensory areas: Conscious awareness of sensation Association areas: Integrate diverse information Note: All neurons in the cortex are interneurons

Functional Areas of the Cerebral Cortex Figure 12.8a

Cerebral Cortex: Motor Areas They control voluntary movements Lie in the posterior part of the frontal lobe They include: Primary (somatic) motor cortex Premotor cortex Frontal eye field Broca’s area

Primary Motor Cortex Located: Pyramidal cells: Allows: In the precentral gyrus Pyramidal cells: Large neurons called pyramidal cells Their axons: Descend to the spinal cord Make up the pyramidal (cortico-spinal) tracts Allows: Conscious control of the precise voluntary movements of skeletal muscles

Functional Areas of the Cerebral Cortex Figure 12.8a

Premotor Cortex Located: Controls motor skills that are: Involved in: Just anterior to precentral gyrus Controls motor skills that are: Learned Repetitious, or patterned Involved in: The planning of movements

Functional Areas of the Cerebral Cortex Figure 12.8a

Broca’s Area Broca’s area Located anteroinferiorly to the premotor area Present in one hemisphere (usually the left) A motor speech area (directs tongue muscles) Is active as one prepares to speak

Functional Areas of the Cerebral Cortex Figure 12.8a

Frontal Eye Field Frontal eye field Located: Controls: Anterior to the premotor cortex Superior to Broca’s area Controls: Voluntary eye movement

Functional Areas of the Cerebral Cortex Figure 12.8a

Cerebral Cortex: Sensory Areas Concerned with conscious awareness of sensation Found in insular, parietal, occipital, & temporal lobes They include: Primary somatosensory cortex Somatosensory association cortex Visual and auditory areas Olfactory (smell) gustatory (taste) vestibular (equilibrium) cortices

Functional Areas of the Cerebral Cortex Figure 12.8a

Lateralization of Cortical Function Each hemisphere has abilities not shared with its partner Cerebral dominance: Designates the hemisphere dominant for language Left hemisphere: Usually controls language, math, and logic i.e. dominant hemisphere Right hemisphere Controls conceptual skills, emotion, and artistic skills

Which side dominates Most right handed people (90%) use the left side hemisphere most The other 10% are either reversed or use both sides equally Some left handed people are ambidextrous (equal hemisphere use), This was once thought to result in dyslexia (hemisphere confusion)

Cerebral White Matter Consists of myelinated fibers bundled into large tracts Responsible for communication between: Various cerebral areas The cerebral cortex & the lower CNS centers

Cerebral White Matter Fibers and tracts: They include: Classified according to the direction they run They include: Commissures Association fibers Projection fibers

Cerebral White Matter Commissures: Association fibers: Run horizontally Connect corresponding gray areas of the two hemispheres Association fibers: Connect different parts of the same hemi- sphere

Cerebral White Matter (cont’d) Projection fibers: Run vertically Some enter hemispheres from the lower brain or cord centers Others leave the cortex to the lower centers Tie the cortex to: The rest of the nervous system The body’s receptors & effectors

Fiber Tracts in White Matter Figure 12.10a

Fiber Tracts in White Matter Figure 12.10b

Fiber Tracts in White Matter Figure 12.10b

Basal Nuclei Include: Basal nuclei are: Found: Masses of gray (cortical) matter Found: Deep within the cerebral white matter Include: The caudate, putamen, & globus pallidus Together the putamen & globus pallidus are called lentiform (lens-shaped) Collectively, the lentiform & caudate are called corpus striatum Striation appearance is due to internal capsule running through them

Break Slide Biol2401._______ Monday, April 01, ’13