© 2017 Pearson Education, Inc.

12.6 Functional Brain Systems Networks of neurons that work together but span wide areas of brain Limbic system Reticular formation © 2017 Pearson Education, Inc.

Limbic System Structures on medial aspects of cerebral hemispheres and diencephalon Fornix: fiber tract that links limbic system regions Includes parts of diencephalon and some cerebral structures that encircle brain stem © 2017 Pearson Education, Inc.

Limbic System (cont.) Large part of emotional or affective brain Amygdaloid body: recognizes angry or fearful facial expressions, assesses danger, and elicits fear response Cingulate gyrus: plays role in expressing emotions via gestures and resolves mental conflict © 2017 Pearson Education, Inc.

Figure 12.17 The limbic system. Septum pellucidum Corpus callosum Fiber tracts connecting limbic system structures • Fornix Diencephalic structures of the limbic system • Anterior commissure • Anterior thalamic nuclei (flanking 3rd ventricle) Cerebral structures of the limbic system • Hypothalamus • Cingulate gyrus • Mammillary body • Septal nuclei • Amygdaloid body • Hippocampus • Dentate gyrus • Parahippocampal gyrus Olfactory bulb © 2017 Pearson Education, Inc.

Limbic System (cont.) Limbic system puts emotional responses to odors Example: skunks smell bad Most output relayed via hypothalamus Hypothalamus plays a role in psychosomatic illnesses © 2017 Pearson Education, Inc.

Limbic System (cont.) Limbic system interacts with prefrontal lobes Allows us to react emotionally to things we consciously understand to be happening Makes us consciously aware of emotional richness in our lives Hippocampus and amygdaloid body also play a role in memory © 2017 Pearson Education, Inc.

Reticular Formation Extends through central core of brain stem Three broad columns run length of 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 Connections allow it to govern brain arousal © 2017 Pearson Education, Inc.

Reticular Formation (cont.) Reticular activating system (RAS) Sends impulses to cerebral cortex to keep it conscious and alert Filters out repetitive, familiar, or weak stimuli (~99% of all stimuli is not relayed to consciousness) Inhibited by sleep centers, alcohol, drugs Severe injury can result in permanent unconsciousness (coma) © 2017 Pearson Education, Inc.

Reticular Formation (cont.) Motor function of reticular formation helps control coarse limb movements via reticulospinal tracts Reticular autonomic centers regulate visceral motor functions Vasomotor centers Cardiac center Respiratory centers © 2017 Pearson Education, Inc.

Figure 12.18 The reticular formation. The continuous stream of sensory stimuli keeps the cerebrum aroused and alert. 3 Radiations to cerebral cortex 2 RAS neurons relay sensory stimuli to the cerebrum through the thalamus. Reticular formation nuclei in brain stem Visual impulses 1 Sensory axons synapse on reticular activating system (RAS) neurons in the brain stem. Auditory impulses Descending projections Ascending general sensory tracts (touch, pain, temperature) • From reticular formation nuclei to the spinal cord • Help regulate skeletal and visceral muscle activity Reticular activating system (RAS) © 2017 Pearson Education, Inc.

Table 12.1-1 Functions of Major Brain Regions © 2017 Pearson Education, Inc.

Table 12.1-2 Functions of Major Brain Regions (continued) © 2017 Pearson Education, Inc.

Table 12.1-3 Functions of Major Brain Regions (continued) © 2017 Pearson Education, Inc.

Table 12.1-4 Functions of Major Brain Regions (continued) © 2017 Pearson Education, Inc.

12.7 Higher Mental Functions Analysis of higher mental functions include: Language Memory Brain waves and EEGs Consciousness Sleep and sleep-wake cycles © 2017 Pearson Education, Inc.

Language Language implementation system involves association cortex of left hemisphere Main areas include: Broca’s area: involved in speech production Patients with lesions in Broca’s understand words, but cannot speak Wernicke’s area: involved in understanding spoken and written words Patients with lesions in Wernicke’s can speak, but words are nonsensible Corresponding areas on right side are involved with nonverbal language components © 2017 Pearson Education, Inc.

Figure 12.7a Functional and structural areas of the cerebral cortex. Sensory areas and related association areas Motor areas Central sulcus Primary motor cortex Primary somatosensory cortex Premotor cortex Somatic sensation Frontal eye field Somatosensory association cortex Broca’s area (outlined by dashes) Gustatory cortex (in insula) Taste Anterior association area (prefrontal cortex) Wernicke’s area (outlined by dashes within the posterior association area) Working memory for spatial tasks Executive area for task management Primary visual cortex Solving complex, multitask problems Vision Visual association area Working memory for object-recall tasks Auditory association area Hearing Primary auditory cortex Lateral view, left cerebral hemisphere Primary motor cortex Motor association cortex Primary sensory cortex Sensory association cortex Multimodal association cortex © 2017 Pearson Education, Inc.

Memory Memory: storage and retrieval of information Different kinds of memory Declarative memory of facts (names, faces, words, dates) Procedural memory of skills (playing piano) Motor memory memory of motor skills (riding a bike) Emotional memory memory of experiences linked to an emotion (heart pounding when you hear rattlesnake) © 2017 Pearson Education, Inc.

Memory (cont.) Two stages of declarative memory 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 © 2017 Pearson Education, Inc.

Memory (cont.) Factors affecting transfer from STM to LTM Emotional state: best if alert, motivated, surprised, or aroused Rehearsal: repetition and practice Association: tying new information with old memories Automatic memory: subconscious information stored in LTM © 2017 Pearson Education, Inc.

Memory (cont.) Memory consolidation involves fitting new facts into categories already stored in cerebral cortex Hippocampus, temporal cortical areas, thalamus, and prefrontal cortex are involved in consolidation © 2017 Pearson Education, Inc.

Figure 12.19 Memory processing. Outside stimuli General and special sensory receptors Afferent inputs Temporary storage (buffer) in cerebral cortex Data permanently lost Data selected for transfer Automatic memory Forget Short-term memory (STM) Forget Data transfer influenced by: Excitement Retrieval Rehearsal Associating new data with stored data Long-term memory (LTM) Data unretrievable © 2017 Pearson Education, Inc.

Clinical – Homeostatic Imbalance 12.5 Damage to hippocampus or surrounding temporal lobe structures on either side result in only slight memory loss Bilateral destruction causes widespread amnesia Anterograde amnesia: consolidated memories are not lost, but new inputs are not associated with old one Person lives in the here and now Memory of conversations from just 5 minutes before would not be remembered © 2017 Pearson Education, Inc.

Clinical – Homeostatic Imbalance 12.5 Retrograde amnesia: loss of memories formed in the distant past © 2017 Pearson Education, Inc.

Brain Wave Patterns and the EEG Brain waves reflect electrical activity of higher mental functions Normal brain functions are continuous and hard to measure © 2017 Pearson Education, Inc.

Brain Wave Patterns and the EEG (cont.) Electroencephalogram (EEG) records electrical activity that accompanies brain function Used for diagnosing epilepsy and sleep disorders Localizes lesions, tumors, infarcts, infections, abscesses Used in research and also to determine brain death Electrodes placed on scalp measure electrical potential differences between various cortical areas © 2017 Pearson Education, Inc.

Figure 12.20a Electroencephalography (EEG) and brain waves. Scalp electrodes are used to record brain wave activity. © 2017 Pearson Education, Inc.

Brain Wave Patterns and the EEG (cont.) EEG measures patterns of neuronal electrical activity generated by synaptic activity in cortex Each person's brain waves are unique Patterns change with age, sensory stimuli, brain disease, and chemical state of body Measures wave frequency in Hertz (Hz), numbers of peaks per second (1 Hz = 1 peak per second) Can be grouped into four classes based on Hz: Alpha, beta, theta, or delta waves © 2017 Pearson Education, Inc.

Brain Wave Patterns and the EEG (cont.) Alpha waves: (8–13 Hz)—regular and rhythmic, low-amplitude, synchronous waves indicating an “idling” brain Beta waves: (14–30 Hz)—rhythmic, less regular waves occurring when mentally alert Theta waves: (4–7 Hz)—more irregular; common in children and uncommon in awake adults © 2017 Pearson Education, Inc.

Brain Wave Patterns and the EEG (cont.) Delta waves: (4 Hz or less)—high-amplitude waves of deep sleep and when reticular activating system is suppressed, as during anesthesia; indicates brain damage in awake adult © 2017 Pearson Education, Inc.

Figure 12.20b Electroencephalography (EEG) and brain waves. 1-second interval Alpha waves — awake but relaxed Beta waves — awake, alert Theta waves — common in children Delta waves — deep sleep Brain waves shown in EEGs fall into four general classes. © 2017 Pearson Education, Inc.

Clinical – Homeostatic Imbalance 12.6 Epileptic seizure: torrent of electrical discharges by groups of neurons Prevent any other messages from getting through Victim of epilepsy may lose consciousness, fall stiffly, and have uncontrollable jerking Epilepsy is not associated with intellectual impairments Epilepsy occurs in 1% of population Genetic factors play a role, but brain injuries, stroke, infections, or tumors can also be causes © 2017 Pearson Education, Inc.

Clinical – Homeostatic Imbalance 12.6 Aura (sensory hallucination) may precede seizure Absence seizures (formerly petit mal) Mild seizures of young children: expression goes blank for few seconds Tonic-clonic seizures (formerly grand mal) Most severe; last few minutes Victim loses consciousness, bones broken during intense convulsions, loss of bowel and bladder control, and severe biting of tongue © 2017 Pearson Education, Inc.

Clinical – Homeostatic Imbalance 12.6 Control of epilepsy includes anticonvulsive drugs, vagus nerve stimulator or deep brain stimulator implantations that deliver pulses to vagus nerve or directly to brain to stabilize brain activity © 2017 Pearson Education, Inc.

Consciousness Consciousness involves: Perception of sensation Voluntary initiation and control of movement Capabilities associated with higher mental processing (memory, logic, judgment, etc.) Clinically defined on continuum that grades behavior in response to stimuli: alertness, drowsiness (lethargy), stupor, and coma © 2017 Pearson Education, Inc.

Consciousness (cont.) Current suppositions on consciousness Involves simultaneous activity of large cortical areas Superimposed on other neural activities Holistic and totally interconnected © 2017 Pearson Education, Inc.

Clinical – Homeostatic Imbalance 12.7 Except during sleep, loss of consciousness signals that brain function is impaired Fainting or syncopy: brief loss of consciousness Most often due to inadequate cerebral blood flow Due to low blood pressure or ischemia from hemorrhage or sudden, severe emotional stress Coma: unconsciousness for extended period Not the same as deep sleep; oxygen consumption is lowered © 2017 Pearson Education, Inc.

Clinical – Homeostatic Imbalance 12.7 Brain death: irreversible coma Ethical and legal issues surround decisions on whether person is dead or alive © 2017 Pearson Education, Inc.

Sleep and Sleep-Wake Cycles Sleep: state of partial unconsciousness from which person can be aroused by stimulation Cortical activity is depressed, but brain stem activity doesn’t change Types of sleep: Two major types of sleep (defined by EEG patterns) Non–rapid eye movement (NREM) sleep Broken into four stages Rapid eye movement (REM) sleep © 2017 Pearson Education, Inc.

Sleep and Sleep-Wake Cycles (cont.) Types of sleep (cont.): We pass through first two stages of NREM during the first 30–45 minutes of sleep, then move into stages 3 and 4, referred to as slow-wave sleep Frequency of waves declines, but amplitude increases EEG, heart rate, respiratory rate, blood pressure, and GI motility change © 2017 Pearson Education, Inc.

Sleep and Sleep-Wake Cycles (cont.) Types of sleep (cont.): At ~90 minutes in, fourth stage ends, and REM sleep begins abruptly Temporary paralysis, except for rapid eye movements Oxygen consumption, heart rate, and breathing increase; increase can be greater than when awake Most dreaming occurs in REM © 2017 Pearson Education, Inc.

Figure 12.21a Types and stages of sleep. Awake 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. Typical EEG patterns © 2017 Pearson Education, Inc.

Sleep and Sleep-Wake Cycles (cont.) How sleep is regulated Alternating cycles of sleep and wakefulness reflect natural circadian (24-hour) rhythm RAS activity is inhibited during sleep, but RAS also mediates sleep stages Suprachiasmatic and preoptic nuclei of hypothalamus time sleep cycle Hypothalamus releases orexins that help cortex to wake up Typical sleep pattern alternates between REM and NREM sleep © 2017 Pearson Education, Inc.

Figure 12.21b Types and stages of sleep. Awake REM Stage 1 Stage 2 NREM Stage 3 Stage 4 1 2 3 4 5 6 7 Time (hrs) Typical progression of an adult through one night’s sleep stages © 2017 Pearson Education, Inc.

Sleep and Sleep-Wake Cycles (cont.) Importance of sleep Slow-wave sleep (NREM stages 3 and 4) presumed to be restorative stage People deprived of REM sleep become moody and depressed REM sleep may: Give brain opportunity to analyze day’s events and work through emotional events or problems Eliminate unneeded synapses that were formed (dream to forget) © 2017 Pearson Education, Inc.

Sleep and Sleep-Wake Cycles (cont.) Daily sleep requirements decline with age Stage 4 sleep declines steadily and may disappear after age 60 © 2017 Pearson Education, Inc.

Clinical – Homeostatic Imbalance 12.8 Sleep disorders include: Narcolepsy: abrupt lapse into sleep from awake state Orexins (“wake-up” chemicals from hypothalamus) may be being destroyed by immune system Offer key to possible treatment Insomnia: chronic inability to obtain amount or quality of sleep needed May be treated by blocking orexin action © 2017 Pearson Education, Inc.

12.8 Protection of Brain Meninges Function of meninges: Cover and protect CNS Protect blood vessels and enclose venous sinuses Contain cerebrospinal fluid (CSF) Form partitions in skull Consists of three layers (from external to internal): dura mater, arachnoid mater, and pia mater © 2017 Pearson Education, Inc.

Figure 12.22 Meninges: dura mater, arachnoid mater, and pia mater. Skin of scalp Periosteum Bone of skull Dura mater • Periosteal layer • Meningeal layer Superior sagittal sinus Arachnoid mater Pia mater Subdural space Arachnoid granulation Blood vessel Subarachnoid space Falx cerebri (in longitudinal fissure only) © 2017 Pearson Education, Inc.

Meninges (cont.) Dura mater Strongest meninx Made up of two layers of fibrous connective tissue Periosteal layer attaches to inner surface of skull Found only in brain, not spinal cord Meningeal layer: true external covering of brain Extends into vertebral canal as spinal dura mater Two layers are mostly fused, but separate in certain areas to form dural venous sinuses Sinuses collect venous blood from brain, empty into jugular veins of neck © 2017 Pearson Education, Inc.

Meninges (cont.) Dura mater (cont.) Dura mater extends inward in several areas to form flat partitions that divide cranial cavity Partitions referred to as dural septa Act to limit excessive movement of brain Three main septa: Falx cerebri: in longitudinal fissure; attached to crista galli Falx cerebelli: along vermis of cerebellum Tentorium cerebelli: horizontal dural fold over cerebellum and in transverse fissure © 2017 Pearson Education, Inc.

Figure 12.23a Dural septa and dural venous sinuses. Superior sagittal sinus Falx cerebri Straight sinus Tentorium cerebelli Crista galli of the ethmoid bone Falx cerebelli Pituitary gland Midsagittal view © 2017 Pearson Education, Inc.

Figure 12.23b Dural septa and dural venous sinuses. Superior sagittal sinus Parietal bone Scalp Falx cerebri Occipital lobe Tentorium cerebelli Dura mater Transverse sinus Falx cerebelli Cerebellum Temporal bone Arachnoid mater over medulla oblongata Posterior dissection © 2017 Pearson Education, Inc.

Meninges (cont.) Arachnoid mater Middle layer with spiderweb-like extensions Separated from dura mater by subdural space Subarachnoid space contains CSF and largest blood vessels of brain Arachnoid granulations protrude through dura mater into superior sagittal sinus Permit reabsorption of CSF back into venous blood © 2017 Pearson Education, Inc.

Figure 12.22 Meninges: dura mater, arachnoid mater, and pia mater. Skin of scalp Periosteum Bone of skull Dura mater • Periosteal layer • Meningeal layer Superior sagittal sinus Arachnoid mater Pia mater Subdural space Arachnoid granulation Blood vessel Subarachnoid space Falx cerebri (in longitudinal fissure only) © 2017 Pearson Education, Inc.

Meninges (cont.) Pia mater Delicate connective tissue that clings tightly to brain, following every convolution Contains many tiny blood vessels that feed brain © 2017 Pearson Education, Inc.

Figure 12.22 Meninges: dura mater, arachnoid mater, and pia mater. Skin of scalp Periosteum Bone of skull Dura mater • Periosteal layer • Meningeal layer Superior sagittal sinus Arachnoid mater Pia mater Subdural space Arachnoid granulation Blood vessel Subarachnoid space Falx cerebri (in longitudinal fissure only) © 2017 Pearson Education, Inc.

Clinical – Homeostatic Imbalance 12.9 Meningitis: inflammation of the meninges May spread to CNS, which would lead to inflammation of the brain, referred to as encephalitis Meningitis is usually diagnosed by observing microbes in a sample of CSF obtained via lumbar puncture © 2017 Pearson Education, Inc.

Cerebrospinal Fluid (CSF) Cerebrospinal fluid (CSF) forms a liquid cushion of constant volume around brain Functions Gives buoyancy to CNS structures Reduces weight of brain by 97% by floating it so it is not crushed under its own weight Protects CNS from blows and other trauma Nourishes brain and carries chemical signals Composed of watery solution formed from blood plasma, but with less protein and different ion concentrations from plasma © 2017 Pearson Education, Inc.

Cerebrospinal Fluid (CSF) (cont.) Choroid plexus: cluster of capillaries that hangs from roof of each ventricle, enclosed by pia mater and surrounding layer of ependymal cells CSF is filtered from plexus at constant rate Ependymal cells use ion pumps to control composition of CSF and help cleanse CSF by removing wastes Cilia of ependymal cells help to keep CSF in motion Normal adult CSF volume of ~150 ml is replaced every 8 hours © 2017 Pearson Education, Inc.

Figure 12.24 Formation, location, and circulation of CSF. Slide 2 Superior sagittal sinus Arachnoid granulation Choroid plexus Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater 1 Right lateral ventricle (deep to cut) Interventricular foramen Third ventricle Choroid plexus of fourth ventricle Cerebral aqueduct Lateral aperture Fourth ventricle Median aperture Central canal of spinal cord 1 The choroid plexus of each ventricle produces CSF. CSF circulation © 2017 Pearson Education, Inc.

Figure 12.24 Formation, location, and circulation of CSF. Slide 3 Superior sagittal sinus Arachnoid granulation Choroid plexus Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater 1 Right lateral ventricle (deep to cut) Interventricular foramen Third ventricle Choroid plexus of fourth ventricle Cerebral aqueduct Lateral aperture Fourth ventricle 2 Median aperture Central canal of spinal cord 1 The choroid plexus of each ventricle produces CSF. 2 CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. CSF circulation © 2017 Pearson Education, Inc.

Figure 12.24 Formation, location, and circulation of CSF. Slide 4 Superior sagittal sinus Arachnoid granulation Choroid plexus Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater 1 Right lateral ventricle (deep to cut) Interventricular foramen Third ventricle 3 Choroid plexus of fourth ventricle Cerebral aqueduct Lateral aperture Fourth ventricle 2 Median aperture Central canal of spinal cord 1 The choroid plexus of each ventricle produces CSF. 2 CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. 3 CSF flows through the subarachnoid space. CSF circulation © 2017 Pearson Education, Inc.

Figure 12.24 Formation, location, and circulation of CSF. Slide 5 4 Superior sagittal sinus Arachnoid granulation Choroid plexus Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater 1 Right lateral ventricle (deep to cut) Interventricular foramen Third ventricle 3 Choroid plexus of fourth ventricle Cerebral aqueduct Lateral aperture Fourth ventricle 2 Median aperture Central canal of spinal cord 1 The choroid plexus of each ventricle produces CSF. 2 CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. 3 CSF flows through the subarachnoid space. 4 CSF is absorbed into the dural venous sinuses via the arachnoid granulations. CSF circulation © 2017 Pearson Education, Inc.

Figure 12.24b Formation, location, and circulation of CSF. Ependymal cells Capillary Section of choroid plexus Connective tissue of pia mater Wastes and unnecessary solutes absorbed CSF forms as a filtrate containing glucose, oxygen, vitamins, and ions (Na+, Cl-, Mg2+, etc.) Cavity of ventricle CSF formation by choroid plexuses © 2017 Pearson Education, Inc.

Clinical – Homeostatic Imbalance 12.10 Hydrocephalus: obstruction blocks CSF circulation or drainage, resulting in increased pressure In newborns, skull bones are unfused, so increased pressure causes head to enlarge In adults, rigidity of the skull keeps pressure within, potentially leading to brain damage Can compress blood vessels and crush soft nervous tissue Treatment is to drain CSF with ventricular shunt to abdominal cavity © 2017 Pearson Education, Inc.

Figure 12.25 Hydrocephalus in a newborn. © 2017 Pearson Education, Inc.

Blood Brain Barrier Helps maintain stable environment for brain Chemical variations could lead to uncontrollable neuron firings Exceptionally impermeable tight junctions keep brain separated from many bloodborne substances Substances must past through three layers before gaining entry into neurons Continuous endothelium of capillary walls Thick basal lamina around capillaries Feet of astrocytes surrounding neurons © 2017 Pearson Education, Inc.

Astrocytes are the most abundant CNS neuroglia. Figure 11.4a Neuroglia. Capillary Neuron Astrocyte Astrocytes are the most abundant CNS neuroglia. © 2017 Pearson Education, Inc.

Blood Brain Barrier (cont.) Barrier is selective, but not absolute Allows certain nutrients to move by facilitated diffusion Metabolic wastes, proteins, toxins, most drugs, small nonessential amino acids, K+ denied Allows any fat-soluble substances to pass, including alcohol, nicotine, and anesthetics Absent in some areas, such as vomiting center and hypothalamus Necessary to monitor chemical composition and temperature of blood © 2017 Pearson Education, Inc.

12.10 Brain Injuries and Disorders Traumatic Brain Injuries Brain injuries include: Concussion: temporary alteration in function Contusion: permanent damage Subdural or subarachnoid hemorrhage: pressure from blood may force brain stem through foramen magnum, resulting in death Cerebral edema: swelling of brain associated with traumatic head injury © 2017 Pearson Education, Inc.

Cerebrovascular Accidents (CVAs) Also referred to as “strokes” Ischemia: tissue deprived of blood supply, leading to death of brain tissue Can be caused by blockage of cerebral artery by blood clot Glutamate acts as excitotoxin, worsening condition Hemiplegia (paralysis on one side) or sensory and speech deficits may result © 2017 Pearson Education, Inc.

Cerebrovascular Accidents (CVAs) (cont.) Transient ischemic attacks (TIAs): temporary episodes of reversible cerebral ischemia Tissue plasminogen activator (TPA) is only approved treatment for stroke © 2017 Pearson Education, Inc.

Degenerative Brain Disorders Alzheimer’s disease (AD) Progressive degenerative disease of brain that results in dementia Key proteins appear to be misfolded and malfunction Memory loss, short attention span, disorientation, eventual language loss, irritability, moodiness, confusion, hallucinations Plaques of beta-amyloid peptides form in brain Neurofibrillary tangles inside neurons interfere with transport mechanisms, eventually killing neuron As brain cells die, brain shrinks © 2017 Pearson Education, Inc.

Figure 12.26 Brain activity is decreased by Alzheimer’s disease. Normal Alzheimer Anterior © 2017 Pearson Education, Inc.

Degenerative Brain Disorders (cont.) Parkinson’s disease Degeneration of dopamine-releasing neurons of substantia nigra Basal nuclei deprived of dopamine become overactive, resulting in tremors at rest Cause unknown, but theories include mitochondrial abnormalities or protein degradation pathways Treatment includes L-dopa (dopamine precursor), deep brain stimulation, gene therapy Research into stem cell transplants is promising © 2017 Pearson Education, Inc.

Degenerative Brain Disorders (cont.) Huntington’s disease Fatal hereditary disorder caused by accumulation of protein huntingtin in brain cells Leads to degeneration of basal nuclei and cerebral cortex Initial symptoms include wild, jerky “flapping” movements Later marked by mental deterioration Usually fatal within 15 years of onset Treated with drugs that block dopamine effects Stem cell implant research is promising © 2017 Pearson Education, Inc.

Diagnostic Procedures for Assessing CNS Dysfunction Simple test can include knee-jerk reflex with hammer tapped against quadriceps tendon Abnormal responses may indicate intracranial hemorrhage, multiple sclerosis, or hydrocephalus CT, MRI, and PET allow for quick identification of tumors, lesions, plaque, or areas of infarct Radioactive tracers help visualize specific areas Cerebral angiography uses X rays with dye to pinpoint any stroke causing clots Ultrasound can be used to evaluate blood flow through arteries feeding the brain © 2017 Pearson Education, Inc.