PowerPoint ® Lecture Slides prepared by Vince Austin, Bluegrass Technical and Community College C H A P T E R Copyright © 2010 Pearson Education, Inc. 12 The Central Nervous System: Part C
Copyright © 2010 Pearson Education, Inc. Functional Brain Systems Networks of neurons that work together and span wide areas of the brain Limbic system Reticular formation
Copyright © 2010 Pearson Education, Inc. Limbic System Includes parts of the diencephalon and some cerebral structures that encircle the brain stem
Copyright © 2010 Pearson Education, Inc. Figure Corpus callosum Septum pellucidum Olfactory bulb Diencephalic structures of the limbic system Anterior thalamic nuclei (flanking 3rd ventricle) Hypothalamus Mammillary body Fiber tracts connecting limbic system structures Fornix Anterior commissure Cerebral struc- tures of the limbic system Cingulate gyrus Septal nuclei Amygdala Hippocampus Dentate gyrus Parahippocampal gyrus
Copyright © 2010 Pearson Education, Inc. Limbic System Emotional or affective brain Amygdala—recognizes angry or fearful facial expressions, assesses danger, and elicits the fear response Cingulate gyrus—plays a role in expressing emotions via gestures, and resolves mental conflict Puts emotional responses to odors Example: skunks smell bad
Copyright © 2010 Pearson Education, Inc. Limbic System: Emotion and Cognition The limbic system interacts with the prefrontal lobes, therefore: We can react emotionally to things we consciously understand to be happening We are consciously aware of emotional richness in our lives Hippocampus and amygdala—play a role in memory
Copyright © 2010 Pearson Education, Inc. Reticular Formation Three broad columns along the length of the brain stem Raphe nuclei Medial (large cell) group of nuclei Lateral (small cell) group of nuclei Has far-flung axonal connections with hypothalamus, thalamus, cerebral cortex, cerebellum, and spinal cord
Copyright © 2010 Pearson Education, Inc. Reticular Formation: RAS and Motor Function RAS (reticular activating system) Sends impulses to the cerebral cortex to keep it conscious and alert Filters out repetitive and weak stimuli (~99% of all stimuli!) Severe injury results in permanent unconsciousness (coma)
Copyright © 2010 Pearson Education, Inc. Reticular Formation: RAS and Motor Function Motor function Helps control coarse limb movements Reticular autonomic centers regulate visceral motor functions Vasomotor Cardiac Respiratory centers
Copyright © 2010 Pearson Education, Inc. Figure Visual impulses Reticular formation Ascending general sensory tracts (touch, pain, temperature) Descending motor projections to spinal cord Auditory impulses Radiations to cerebral cortex
Copyright © 2010 Pearson Education, Inc. Electroencephalogram (EEG) Records electrical activity that accompanies brain function Measures electrical potential differences between various cortical areas
Copyright © 2010 Pearson Education, Inc. Figure 12.20a (a) Scalp electrodes are used to record brain wave activity (EEG).
Copyright © 2010 Pearson Education, Inc. Brain Waves Patterns of neuronal electrical activity
Copyright © 2010 Pearson Education, Inc. Figure 12.20b Alpha waves —awake but relaxed Beta waves —awake, alert Theta waves —common in children Delta waves —deep sleep (b) Brain waves shown in EEGs fall into four general classes. 1-second interval
Copyright © 2010 Pearson Education, Inc. Epilepsy A victim of epilepsy may lose consciousness, fall stiffly, and have uncontrollable jerking Epilepsy occurs in 1% of the population not associated with intellectual impairments
Copyright © 2010 Pearson Education, Inc. Control of Epilepsy Anticonvulsive drugs
Copyright © 2010 Pearson Education, Inc. Consciousness Conscious perception of sensation
Copyright © 2010 Pearson Education, Inc. Consciousness Clinically defined on a continuum that grades behavior in response to stimuli Alertness Drowsiness (lethargy) Stupor Coma
Copyright © 2010 Pearson Education, Inc. Sleep State of partial unconsciousness from which a person can be aroused by stimulation Two major types of sleep (defined by EEG patterns) Nonrapid eye movement (NREM) Rapid eye movement (REM)
Copyright © 2010 Pearson Education, Inc. Figure 12.21a Awake (a) Typical EEG patterns REM: Skeletal muscles (except ocular muscles and diaphragm) are actively inhibited; most dreaming occurs. NREM stage 1: Relaxation begins; EEG shows alpha waves, arousal is easy. NREM stage 2: Irregular EEG with sleep spindles (short high- amplitude bursts); arousal is more difficult. NREM stage 3: Sleep deepens; theta and delta waves appear; vital signs decline. NREM stage 4: EEG is dominated by delta waves; arousal is difficult; bed-wetting, night terrors, and sleepwalking may occur.
Copyright © 2010 Pearson Education, Inc. Sleep Disorders Narcolepsy Lapsing abruptly into sleep from the awake state Insomnia Chronic inability to obtain the amount or quality of sleep needed Sleep apnea Temporary cessation of breathing during sleep
Copyright © 2010 Pearson Education, Inc. Language Language implementation system Broca’s area and Wernicke’s area (in the association cortex on the left side)
Copyright © 2010 Pearson Education, Inc. Memory Storage and retrieval of information Two stages of storage Short-term memory (STM, or working memory)—temporary holding of information; limited to seven or eight pieces of information Long-term memory (LTM) has limitless capacity
Copyright © 2010 Pearson Education, Inc. Figure Outside stimuli General and special sensory receptors Data transfer influenced by: Excitement Rehearsal Association of old and new data Long-term memory (LTM) Data permanently lost Afferent inputs Retrieval Forget Data selected for transfer Automatic memory Data unretrievable Temporary storage (buffer) in cerebral cortex Short-term memory (STM)
Copyright © 2010 Pearson Education, Inc. Transfer from STM to LTM Factors that affect transfer from STM to LTM Emotional state—best if alert, motivated, surprised, and aroused Rehearsal—repetition and practice Association—tying new information with old memories Automatic memory—subconscious information stored in LTM
Copyright © 2010 Pearson Education, Inc. Protection of the Brain Bone (skull) Membranes (meninges) Watery cushion (cerebrospinal fluid) Blood-brain barrier
Copyright © 2010 Pearson Education, Inc. Meninges Cover and protect the CNS Protect blood vessels and enclose venous sinuses Contain cerebrospinal fluid (CSF) Form partitions in the skull
Copyright © 2010 Pearson Education, Inc. Meninges Three layers Dura mater Arachnoid mater Pia mater
Copyright © 2010 Pearson Education, Inc. Cerebrospinal Fluid (CSF) Composition Watery solution Less protein and different ion concentrations than plasma Constant volume
Copyright © 2010 Pearson Education, Inc. Cerebrospinal Fluid (CSF) Functions Gives buoyancy to the CNS organs Protects the CNS from blows and other trauma Nourishes the brain and carries chemical signals
Copyright © 2010 Pearson Education, Inc. Figure 12.26a Superior sagittal sinus Arachnoid villus Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater Right lateral ventricle (deep to cut) Choroid plexus of fourth ventricle Central canal of spinal cord Choroid plexus Interventricular foramen Third ventricle Cerebral aqueduct Lateral aperture Fourth ventricle Median aperture (a) CSF circulation CSF is produced by the choroid plexus of each ventricle. 1 CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord. 2 CSF flows through the subarachnoid space. 3 CSF is absorbed into the dural venous sinuses via the arachnoid villi
Copyright © 2010 Pearson Education, Inc. Choroid Plexuses Hang from the roof of each ventricle Clusters of capillaries enclosed by pia mater and a layer of ependymal cells
Copyright © 2010 Pearson Education, Inc. Figure 12.26b Ependymal cells Capillary Connective tissue of pia mater Wastes and unnecessary solutes absorbed Section of choroid plexus (b) CSF formation by choroid plexuses Cavity of ventricle CSF forms as a filtrate containing glucose, oxygen, vitamins, and ions (Na +, Cl –, Mg 2+, etc.)
Copyright © 2010 Pearson Education, Inc. Blood-Brain Barrier Helps maintain a stable environment for the brain Separates neurons from some bloodborne substances
Copyright © 2010 Pearson Education, Inc. Figure 11.3a (a) Astrocytes are the most abundant CNS neuroglia. Capillary Neuron Astrocyte
Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of the Brain Cerebrovascular accidents (CVAs)(strokes) Blood circulation is blocked and brain tissue dies, e.g., blockage of a cerebral artery by a blood clot Typically leads to hemiplegia, or sensory and speed deficits Transient ischemic attacks (TIAs)—temporary episodes of reversible cerebral ischemia Tissue plasminogen activator (TPA) is the only approved treatment for stroke
Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of the Brain Degenerative brain disorders Alzheimer’s disease (AD): a progressive degenerative disease of the brain that results in dementia Parkinson’s disease: degeneration of the dopamine- releasing neurons of the substantia nigra Huntington’s disease: a fatal hereditary disorder caused by accumulation of the protein huntingtin that leads to degeneration of the basal nuclei and cerebral cortex