Chapter The central nervous system • Identify and explain the function of different types of neurons, and structures in the central nervous system. • Explain the functional organization of the nervous system. • These will be measured by lecture exams and quizzes.
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Chapter The central nervous system Identify and explain the function of different types of neurons, and structures in the central nervous system. Explain.
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Chapter The central nervous system
• Identify and explain the function of different types of neurons, and structures in the central nervous system.
• Explain the functional organization of the nervous system. • These will be measured by lecture exams and quizzes.
Outline• Organization• Protection• Overview of components
– Important in repair of brain injuries and in neural scar formation
– Play role in neurotransmitter activity
– Take up excess K+ from brain ECF
– Along with other glial cells – enhance synapse formation and modify synaptic transmission
• Microglia– Immune defense
cells of the CNS– In resting state
release low levels of growth factors that help neurons and other glial cells survive and thrive. Can move.
• Oligodendrogytes
– Form myelin sheaths around axons in CNS
• Ependymal cells
– Line internal, fluid-filled cavities of the CNS
– In ventricles of brain, help form and circulate cerebrospinal fluid
Fig. 5-3, p. 138
Microglia
Space containingcerebrospinal fluid
Ependymalcell
NeuronsBraininterstitialfluid
Oligodendrocyte
Astrocyte
Capillary
• Enclosed by hard, bony structures
• Wrapped by three protective and nourishing membranes – meninges
– Dura mater
– Arachnoid mater
– Pia mater
• Floats in cushioning fluid – cerebrospinal fluid (CSF)
– Surrounds and cushions brain and spinal cord
– Shock absorbing
– Formed primarily by choroid plexuses
• Blood-brain barrier limits access of blood-borne materials into brain tissue
Protection of CNS
2
3
4
5
Brain stem
Fourth ventricle
Arachnoid villus
Cerebrospinal fluid
Subarachnoid space of brain
Dural sinus
Subarachnoid space of spinal cord
Pia mater
Dura materSpinal meningesArachnoid mater
Arachnoid materDura mater
Cranial meninges
Third ventricleChoroid plexus of third ventricleChoroid plexus of lateral ventricle
Vein
CerebrumVenous blood
Lateral ventricle
41
Spinal cordCentral canal
Choroid plexus of fourth ventricleAperture of fourth ventricleCerebellum
Pia mater
Fig. 5-6a, p. 141
Left lateralventricle
Right lateralventricle
Central canalof spinal cord
Fourth ventricle
Thirdventricle
Front of brain
Back of brain
Fig. 5-5a, p. 139
Blood-Brain Barrier (BBB)• Protects brain from chemical fluctuations in blood• Minimizes possibility that harmful blood-borne
substances might reach central nervous tissue• Prevents certain circulating hormones that could also act
as neurotransmitters from reaching brain• Limits use of drugs for treatment of brain and spinal cord
disorders– Many drugs cannot penetrate BBB
– Keeps K+ low and Na+ High
• Cells joined by tight junctions
• an anatomic-physiologic feature of the brain thought to consist of walls of capillaries in the central nervous system and surrounding astrocytic glial membranes.
• The barrier separates the parenchyma of the central nervous system from blood.
• The blood-brain barrier prevents or slows the passage of some drugs and other chemical compounds, radioactive ions, and disease-causing organisms such as viruses from the blood into the central nervous system.
Central Nervous System• Enables you to:
– Subconsciously regulate your internal environment by neural means
– Experience emotions
– Voluntarily control your movements
– Be consciously aware of your own body and your surroundings
– Engage in other higher cognitive processes such as thought and memory
Fig. 5-7b, p. 146
Pineal gland
Corpuscallosum
(b) Brain, sagittal view
MidbrainBrainstem
Top
Cerebrum (the righthemisphere, at thelongitudinal fissurebetween it and theleft hemisphere)
Hypothalamus Thalamus
Opticchiasm
Cerebellum
MedullaPons
Frontofbrain
Cerebrum (cortex)• Highly developed• Makes up about 80% of total brain weight (largest
portion of brain)• Inner core houses basal nuclei• Outer surface is highly convoluted cerebral cortex
– Highest, most complex integrating area of the brain– Plays key role in most sophisticated neural functions
– Organized into six well-defined layers
– Layers are organized into functional vertical columns
Right cerebralhemisphere
Longitudinal fissure
Left cerebralhemisphere
– Excels in logical, analytic, sequential, and verbal tasks
• Math, language forms, philosophy
– Excels in nonlanguage skills
• Spatial perception and artistic and musical talents
Cerebral Hemispheres
Frontallobe
Central sulcus
Parietallobe
Parietooccipitalnotch
Occipitallobe
Preoccipitalnotch
CerebellumBrain stem
Temporallobe
Lateralfissure
Fig. 5-8, p. 143
Carries out initial processing Of visual input
Initial reception of sound sensation
Somatosensory processingResponsible for
Voluntary motor activitySpeaking abilityElaboration of thought
Four major lobes
Fig. 5-9b, p. 144
Fig. 5-9a, p. 144
Cerebral Cortex• Primary areas of cortical specialization for
language– Broca’s area
• Governs speaking ability
– Wernicke’s area• Concerned with language comprehension• Responsible for formulating coherent patterns of
speech
• Language disorders– Aphasias– Speech impediments– Dyslexia
Cerebral Cortex• Primary motor cortex
– Located in frontal lobe
– Confers voluntary control over movement produced by skeletal muscles
– Primarily controls muscles on the opposite side of the body
– Motor homunculus• Depicts location and relative amount of motor cortex
devoted to output to muscles of each body part
Electroencephalogram (EEG)• Record of postsynaptic activity in cortical
neurons• “Brain waves”• Three major uses
– Clinical tool in diagnosis of cerebral dysfunction• epilepsy
– Used in legal determination of brain death
– Used to distinguish various stages of sleep
Electroencephalogram (EEG)
Cerebral Cortex
Schematic Linking
of Various Regions
of the Cortex
Flow of signals
Table 5-2 (1), p. 140
Hypothalamus
Brain stem
Cerebral cortex
Thalamus(medial)
Basal nuclei(lateral to thalamus)
Cerebellum
Spinal cord
Midbrain
Pons
Medulla
Brain component
Cerebral cortex
Basal nuclei
Thalamus
Hypothalamus
Cerebellum
Brain stem(midbrain, pons,and medulla)
*
Corpus callosum
Part of hypothalamus
Basalnucleigraymatter)
Caudate nucleus
Right cerebralhemisphere
Left cerebralhemisphere
Third ventricle
Thalamus
Lateral ventricle
Cerebral cortex(gray matter)
White matter
Claustrum
Globus pallidusPutamen
Fig. 5-14a, p. 154
Basal Nuclei (ganglia)• Act by modifying ongoing activity in motor pathways• Signals from the cortex reach the basal ganglia, the
signals are processed and the output is sent back to the motor cortex
• Primary functions– Inhibiting muscle tone throughout the body– Selecting and maintaining purposeful motor activity
while suppressing useless or unwanted patterns of movement
– Helps monitor and coordinate slow, sustained contractions, especially those related to posture and support
– Links cortex and thalamus
Disorders of the basal ganglia• Parkinson’s
– tremors of the hand
– dopamine deficiency
– Increased rigidity, resting tremors, slow initiation of motor behavior
– Incoordination of movements– Delay initiation of movements– Do not prevent their execution– Not significant unless a great portion of the cerebellum is