Chapter 9 The Nervous System: Central nervous System 1. General anatomy of the central nervous system ㄧ般解剖構造 2. The spinal cord 脊髓 3. The brain 腦 4. Integrated CNS function: Reflexes 中樞功能的整合 : 反射 5. Integrated CNS function: Voluntary motor control 隨意運動調控 6. Integrated CNS function: Language 語言 7. Integrated CNS function: Sleep 睡眠 8. Integrated CNS function: Emotion and motivation 情緒及動機 9. Integrated CNS function: Learning and memory 學習及記憶
I. General Anatomy of the Central Nervous System Glial cells 90% of CNS composed of glia Five types of glial cells Astrocytes 星狀細胞 -- numerous functions 許多功能 Ependymal cells 室管膜細胞 -- line cavities 形成管腔 Microglia 小神經膠質細胞 phagocytes 吞噬 Oligodendrocytes 寡樹突膠質細胞 -- form myelin 形成髓鞘 Schwann cells 許旺氏細胞 (located in PNS)-- form myelin P216
Glial Cells 中樞神經系統 Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings. 末梢神經系統 室管膜細胞 星狀細胞 小神經膠質細胞 寡樹突膠質細胞 許旺氏細胞 Figure 9.1 Glial cells in the nervous system. P217
Astrocytes Development of neural connections 神經之間的聯繫 Development of blood-brain barrier 血腦障壁 Possibly modulate synaptic activity 調控突觸的活性 Remove neurotransmitter from synaptic cleft 從突觸間隙移除神經傳導物質 Communicate to neurons through chemical messengers 釋放化學傳導物溝通兩個神經 Maintain normal electrolyte composition of ISF in CNS 維持中樞間質液間正常電解質組成 Protect neurons against toxic substances and oxidative stress 保護神經對抗有毒物質及氧化性壓力 P216
Microglia Protect CNS from foreign matter through phagocytosis 藉由吞噬作用保護中樞不受外來物攻擊 Bacteria Dead or injured cells Protect CNS from oxidative stress 保護中樞不受氧化性壓力 ( 自由基 ) 攻擊 P216
Glial cells in neurodegenerative diseases Multiple sclerosis 多發性硬化症 is an autoimmune disease 自體免疫疾病, a disease in which the immune system attacks a part of the body, in this case oligodendrocytes 寡樹突神經膠細胞 the loss of myelin 髓鞘 in the CNS slows down or stops communication along certain neural pathways Alzheimer s disease 阿茲海默症 ; 老年性癡呆 loss of cholinergic neurons 膽鹼性神經 in certain brain areas and replacement of the lost neurons with scar 疤 tissue called plaques 斑 during the degeneration of cholinergic neurons, astrocytes 星狀細胞 and microglia 小神經膠細胞 become overly active 過度活化 Parkinson s disease 帕金森氏病 is a degenerative disease involving the loss of dopaminergic neurons 多巴胺神經 glia cells are thought to enhance neural degeneration through the production of inflammatory agents P217
Physical Support of the CNS Bone outer structure Cranium 頭蓋骨 ; 頭顱 Vertebrae 脊椎骨節 ; 脊柱 Meninges 腦膜 located between the bony structures and the soft nervous tissues Dura mater 硬腦膜 Arachnoid mater 蜘蛛網膜 Pia mater 軟腦膜 Cerebrospinal fluid (CSF) 腦脊髓液 the cushioning 墊子 presence of CSF within the subarachnoid 蜘蛛網膜下 space provides yet another level of protection P217
Physical Support of the CNS 頭蓋骨 ; 頭顱 硬腦膜蜘蛛腦膜軟腦膜 腦膜 脊椎骨節 ; 脊柱脊髓 Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 9.1 Glial cells in the nervous system. (a,b) Sections of CNS protective structures. P218
Physical Support of the CNS 竇 No space exists between the dura and the arachnoid 蜘蛛網膜絨毛 蜘蛛網膜下空腔 後面 ( 背部 ) 脊髓 蜘蛛網膜 硬腦膜 The space between the pia and arachnoid, called the subarachnoid space, is filled with cerebrospinal fluid 軟腦膜 脊柱 Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings. 前面 ( 腹部 ) Figure 9.1 Glial cells in the nervous system. (a,b) Sections of CNS protective structures. P218
Cerebrospinal Fluid (CSF) CSF is a clear, watery fluid that bathes the CNS it is similar (but not identical) in composition to plasma CSF completely surrounds the CNS and it fills a number of cavities located within the brain and spinal cord The brain contains four such cavities, called ventricles 腦室, which are continuous with the central canal 中心管, a long thin cylindrical cavity that runs the length of the spinal cord The lining of the ventricles and central canal is composed of glial cells called ependymal cells 室管膜細胞, which are a type of epithelial cell Table 9.1 Compositions of plasma and CSF Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings. P219
Cerebrospinal Fluid (CSF) In some ventricles the lining is vascularized 血管化 and forms a tissue called the choroid plexus 脈絡膜叢, which consists of pia mater 軟腦膜, capillaries 微血管, and ependymal cells 室管膜細胞 and functions in the synthesis of CSF The total volume of CSF is only 125 150 ml, but because it is recycled approximately three times per day, the choroid plexus must produce 400-500 ml/day As CSF is produced it circulates through the ventricular system and enter the subarachnoid space through openings of the fourth ventricle The CSF in the subarachnoid space eventually gets reabsorbed into venous blood through special structures in the arachnoid mater called arachnoid villi 蜘蛛網膜絨毛 CSF production by choroid plexus & circulates to subarachnoid space and ventricles; reabsorbed by arachnoid villi Functions of CSF cushions brain 大腦的緩衝墊 & maintains stable interstitial fluid environment P219-210
Ventricular System of the CNS 大腦 腦幹 側腦室 竇 脊髓 蜘蛛網膜絨毛 蜘蛛網膜下空腔 小腦 中心管 第三腦室脈絡膜叢 第四腦室脈絡膜叢 小腦 腦幹 脊髓 中心管 第三腦室 第四腦室 硬膜蜘蛛網膜軟膜 Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 9.3 Ventricular system of the CNS. The brain s four ventricles two lateral ventricles, the third ventricle, and the fourth ventricle are continuous with the central canal of the spinal cord. (a) Lateral view. (b) Frontal view. (c) Relationships of the ventricles to other CNS structures. Note the presence of the choroid plexus within the ventricles. P219
Blood Supply to the CNS CNS comprises 2% of body weight (3-4 pounds) receives 15% of blood supply High metabolic rate Brain uses 20% of oxygen consumed by body at rest Brain uses 50% of glucose consumed by body at rest Depends on blood flow for energy Depends on aerobic glycolysis 依賴需氧性的糖解作用 Requires glucose and oxygen 需要葡萄糖及氧氣 No glycogen stores 沒有肝醣的儲存 Fatty acids not used for energy 脂肪酸不能作為能量來源 Ketones used during extreme conditions 在極端的情況下酮體可作為能量來源 P220
Stroke 中風 Caused by decreased blood supply 大腦血流供應量減少所造成 cause deficit in certain functions, such as the ability to speak or move an arm 造成大腦某些功能缺陷, 例如說話或移動手臂的能力缺陷 occlusion of cerebral blood vessel 腦血管阻塞引起 hemorrhage from cerebral blood vessel 腦血管出血引起 P220
Blood-Brain Barrier Capillaries 微血管 = Site of exchange between blood and interstitial fluid 血液與間質液進行物質交換的地方 一般微血管有孔洞 (pore) 可讓一些小分子 水溶性的物質自由進出, 例如葡萄糖 胺基酸等 ; 油溶性的物質則由細胞膜被動擴散 ; 大分子顆粒則是經由 transcytosis 運送 Special anatomy of capillaries in CNS limit exchange = bloodbrain barrier 中樞的血腦障壁是一種特殊的微血管構造, 可讓特定物質進行交換, 可保護中樞不會受到血液中一些有毒物質的攻擊 中樞的微血管內皮細胞之間以緊密結合 (tight junction) 連接在一起, 沒有孔洞 (pore) 存在, 形成所謂的血腦障壁 (BBB), 此緊密結合 (tight junction) 可能與星狀細胞 (astrocyte) 的存在有關 中樞因具有血惱障壁, 油溶性物質可被動擴散運送, 小分子 水溶性的物質則須經由媒介性運送 (mediated transport), 大分子顆粒則不能經由 transcytosis 運送進入中樞 P221,223
內皮細胞 孔洞 間質液 Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings. 內皮細胞 腦脊髓液 星狀細胞 油溶性溶質 孔洞 水溶性溶質 蛋白質 典型的微血管 特定的水溶性溶質 緊密結合 媒介物媒介性運送 蛋白質 大腦的微血管 內皮細胞 油溶性溶質 Figure 9.4 Blood-brain barrier. (a) Typical capillaries (found in most regions of the body). Whereas exchange of small hydrophilic molecules occurs by simple diffusion between blood and interstitial fluid through pores, proteins are too large to cross through pores; some proteins are transported across capillary walls by transcytosis. (b) Brain capillaries. Because endothelial cells in these capillaries are connected by tight junctions, hydrophilic molecules must be transported across the wall by mediated transport systems. Proteins cannot cross the blood-brain barrier because transcytosis does not occur in brain capillaries. Even though astrocytes are found in close association with brain capillaries, they do not constitute a functional barrier. P221
Gray Matter and White Matter Gray = cell bodies 細胞本體, dendrites 樹突, axon terminals 軸突末梢 灰質約佔中樞的 40%, 是中樞突觸訊息傳遞及神經整合的地方 White = axons 軸突 白質約佔中樞的 60%, 是訊息快速傳遞的地方 有髓鞘的軸突 在大腦, 大部分的灰質位於外層, 白質位於內層 在脊髓則相反, 白質位於外層, 灰質則位於內層 寡樹突神經膠質細胞 Figure 9.5 Makeup and arrangement of gray matter and white matter in the CNS. (a) Histology of gray matter and white matter. Whereas gray matter consists primarily of cell bodies and dendrites and is the site of neural integration, white matter consists primarily of myelinated axons. P222-223
Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings. 中間矢狀切面 冠狀切面 大腦皮質聯絡纖維聯合纖維投射纖維 ( 胼胝體 ) 白質灰質基底核丘腦 Figure 9.5 Makeup and arrangement of gray matter and white matter in the CNS. (b,c) Midsagittal and coronal sections of the brain, showing association fibers, commissural fibers, and projection fibers, tracts of white matter that connect different areas of the CNS.. Projection fibers 投射纖維 cerebral cortex with lower levels of brain or spinal cord Association fibers 聯絡纖維 connect two areas of cerebral cortex on same side of brain Commissural fibers 聯合纖維 connect same cortical regions on two sides of brain Corpus callosum 胼胝體 primary location of commissural fibers P222-223
II. Spinal Cord cylindrical nervous tissue 圓柱狀的神經纖維 surrounded by vertebral column 為脊椎管所環繞 31 pairs of spinal nerves branch off 有 31 對脊神經的分支 8 Cervical 頸脊神經 12 Thoracic 胸脊神經 5 Lumbar 腰脊神經 5 Sacral 骶脊神經 1 Coccygeal 尾脊神經 頸脊神經 胸脊神經 脊髓 脊椎 Figure 9.6 The spinal cord. (Left) Location of the spinal cord, as seen in a posterior view. (Right) Lateral view of the spinal cord, showing its position within the bony vertebral column. As shown are the 31 pairs of spinal nerves, which leave the spinal cord between adjacent vertebrae. 腰脊神經 骶脊神經 Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings. 尾脊神經 馬尾 P223-224
Dermatomes 皮節 Figure 9.7 Dermatomes. Each dermatome is a sensory region on the surface of the body that is served by the spinal nerve indicated by the abbreviations. Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings. P225
脊髓分成兩個區域 : 中央灰質區與白質 灰質區含有細胞本體與樹突 ; 白質環繞著中央灰質區並有髓鞘的軸突, 這些軸突形成上行及下形路徑 Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings. 傳入神經元與傳出神經元的軸突構成脊髓神經 和脊髓相連的 86 條 (43 對 ) 周邊神經 周邊神經系統共有 43 對神經, 分別為 12 對顱神經與 31 對脊神經 大部分神經同時含有傳入與傳出神經的軸突 周邊神經系統的傳出分支可以分成體神經及自律神經系統 體神經纖維支配骨骼肌細胞 ; 自律神經纖維支配各個腺體及臟器 Figure 9.8 Spinal cord gray matter and spinal nerves. This cross section of the spinal cord at the lumbar level reveals the two functional halves of spinal cord gray matter: dorsal and ventral. Axons of afferent neurons enter the spinal cord through the dorsal root and terminate in the dorsal horn; their cell bodies are located in dorsal root ganglia. Because they contain axons of both afferent and efferent neurons, spinal nerves are considered mixed nerves. P226
Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 9.9 Cross section of white matter in the spinal cord. Spinal cord white matter consists of longitudinal tracts that run between the brain and the spinal cord or between different spinal cord segments. Ascending tracts transmit information from spinal cord to brain, whereas descending tracts transmit information from brain to spinal cord. Only selected tracts are illustrated here. P227
Ascending Tracts Figure 9.10 Pathway of selected ascending and descending tracts. (a) The dorsal column and lateral spinothalamic tracts. Both of these ascending pathways originate with sensory receptors in the periphery and travel up the spinal cord, eventually communicating sensory information to the thalamus and then to the cerebral cortex. The dorsal column pathway crosses to the contralateral side in the brainstem (medial lemniscus), whereas the spinothalamic tract crosses to contralateral side in the spinal cord P228 Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Descending Tracts Figure 9.10 Pathway of selected ascending and descending tracts. (b) The pyramidal tracts. Both pyramidal tracts originate in the primary motor cortex. The lateral pyramidal tract crosses over in the medullary pyramids, whereas the anterior pyramidal tract crosses over in the spinal cord. Both tracts terminate in the ventral horn of the spinal cord, where they communicate to motor neurons innervating skeletal muscle. P228 Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
III. Brain Subdivisions of the Brain 1. Forebrain 前腦 Cerebrum 大腦 Cerebral Cortex 大腦皮質 Basal Nuclei 基底核 Diencephalon 間腦 Thalamus 丘腦 Hypothalamus 下視丘 2. Cerebellum 小腦 3. Brainstem 腦幹 Midbrain 中腦 Pons 橋腦 Medulla 延腦 腦部分成六個區域 : 大腦 間腦 中腦 橋腦 延腦與小腦 大腦由左右半部所構成, 再加上間腦, 共同成為前腦 大腦皮質是大腦的外層, 可分為頂葉 額葉 枕葉與顳葉 間腦包括視丘與下視丘 邊緣系統是前腦深部的構造, 與學習及情緒有關 小腦參與控制姿勢 運動與某些形式的記憶 中腦 橋腦與延腦共同形成腦幹, 其中有網狀構造 P227-229
External View of Divisions of the Brain Figure 9.11 The brain. The brain is composed of three main parts: forebrain, cerebellum, and brain stem. (a,b) External views of the brain, showing its three main parts and their relation to the spinal cord. P229
Internal View of Divisions of the Brain Figure 9.11 The brain. (c ) A midsagittal section of the brain, showing the structures of three main brain parts. Note the corpus callosum, the major fiber tract connecting the left and right cerebral hemispheres. P229
Cerebellum Bilaterally symmetrical Cortex + nuclei Functions Motor coordination and balance coordination of eye/body movements P228 Brainstem Connects forebrain and cerebellum to spinal cord Midbrain, connects to forebrain Pons, connects to cerebellum Medulla, connects to spinal cord Processing center for 10/12 cranial nerves Reticular formation P229
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Cerebral Cortex Figure 9.12 Organization of the cerebral cortex. (a) Convolutions of the cerebral cortex. (b) Layers of the cerebral cortex. The cell bodies are confined to a single layer, but axons and dendrites extend across layers. The actual arrangement of the layers depends on the area of cortex examined. P230
額葉 頂葉 枕葉 顳葉 Figure 9.13 Lobes of cerebrum. This lateral view of the left cerebrum shows its four distinct lobes: frontal, parietal, occipital, and temporal. The central sulcus separates the frontal and parietal lobes; the lateral sulus separates the temporal lobe from the frontal and parietal lobes. P231
Functional Areas of the Cerebrum Copyright 2008 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 9.14 Functional areas of the cerebral cortex. Some selected areas of the cerebral cortex and the specific functions associated with them are illustrated. P232
Figure 9.15 Motor and sensory homunculi. (a) Cross section of the primary somatosensory cortex, located just posterior to the central sulcus, and the corresponding somatotopic map of body parts. (b) Cross section of the primary motor cortex, located just anterior to the central sulcus, and the corresponding somatotopic map of body parts. P232
Brain Lateralization Sensory pathways cross Right brain perceives left input Left brain perceives right input Motor pathways cross Right brain controls muscles on left Left brain controls muscles on right Right brain specializations Creativity Spatial perception Left brain specializations Logic Analytical abilities Language P233-234
Subcortical Nuclei Functions of basal nuclei Inhibit unwanted movements Selecting purposeful movements Postural support Figure 9.16 Subcortical gray matter. A coronal section of the cerebrum at the level indicated reveals gray matter areas: the basal nuclei (caudate nucleus, putamen, and globus pallidus), thalamus, hypotalamus, and the amygdala (part of the limbic system). P234
Thalamus Diencephalon integrate sensory & motor info sensory relay to cortex Hypothalamus Food intake Thermoregulation Link between nervous & endocrine systems Circadian rhythms Suprachiasmatic nucleus Pineal gland P234-235
Limbic System Functions of limbic system Learning Emotions Behavior Figure 9.17 The limbic system. The major structures of the limbic system as depicted in this three-dimensional view. P235
IV. Integrated CNS Functions: Reflexes Reflexes: Automatic patterned response to a stimulus P236
Reflex Arc Figure 9.18 Schematic representation of a reflex arc. The five components of a reflex arc are a sensory receptor that detects a stimulus, an afferent neuron that transmits information from the receptor to the CNS, an integration center (which is generally the CNS), an efferent neuron that transmits information from the integration center to the periphery, and an effector organ, which produces a response to the thalamus. P237
Stretch Reflex Figure 9.19 The muscle spindle stretch reflex. The knee-jerk reflex, an example of the monosynaptic muscle spindle stretch reflex, by which a tap on the patellar tendon causes contraction of the quadriceps muscle. Muscle spindle afferent neurons make two synaptic communications in the spinal cord: excitatory synapse with efferent neurons to the quadriceps muscle, and synapses with inhibitory interneurons that communicate with efferent neurons to the hamstring muscles in the same leg. The afferent neurons also have collaterals that travel in the white matter of the spinal cord to the brainstem, where they form synapses with interneurons that transmit information about muscle length to various area of the brain. P237
Withdrawal & Crossed- Extensor Reflexes Figure 9.20 Withdrawal and crossextensor reflexes. In responses to the activation of a nociceptors, an afferent neuron synapses on an excitatory interneuron and an inhibitory interneuron, ultimately producing contraction of the hamstrings and relaxation of the quadriceps in the affected leg, and affecting in withdrawal. Simultaneously, the afferent neuron also synapses with an excitatory interneuron and an inhibitory neuron, which ultimately produces concentration of the quadriceps and relaxation of the hamstrings in the other leg. The afferent neuron also synapses with an interneuron that crosses to the opposite side of the spinal cord and travels to the thalamus to convey information about the painful stimulus to the brain. P238
Pupillary Light Reflex Cranial reflex Autonomic reflex Innate reflex Polysynaptic reflex Reflex arc: Photoreceptors Afferent neurons Midbrain nuclei Efferent neurons Pupils P239
V. Integrated CNS Function: Voluntary Motor Control Figure 9.21 Steps in voluntary movement. Voluntary movement requires coordinated activity of several neural structures to ensure smooth skeletal muscle movement. The process begins with the idea to move. P239
Innervation of Skeletal Muscle One motor neuron to skeletal muscle cell Also called lower motor neuron Always excitatory To contract muscle cell Activate motor neuron To relax muscle cell Do not activate motor neuron Input to Motor Neurons Afferents (as in reflexes) Pyramidal tract neurons Extrapyramidal tract neurons P240
Pyramidal Tracts Fine control of voluntary movement of the distal extremities Upper motor neurons Originate in primary motor cortex Direct input to motor neurons (some through interneurons) Most cross to contralateral side in medullary pyramids Figure 9.22 Pyramidal and extrapyramidal tracts. (a) Pyramidal tract. The lateral pyramidal tract is primarily a crossed pathway, whereas the anterior pyramidal tract is primarily uncrossed until it reaches the spinal cord. P240-241
Extrapyramidal Tracts All motor pathways outside pyramidal tracts Supportive voluntary movement of the proximal extremities Indirect input to motor neurons Several pathways Figure 9.22 Pyramidal and extrapyramidal tracts. (b) Extrapyramidal tracts. These tracts include all motor tracts except the pyramidal tracts; some cross, some do not, and some are bilateral. P240-241
Control of Posture Brainstem exerts involuntary control over posture (extrapyramidal tracts) Reticular formation Vestibular nuclei Red nuclei Input to brainstem from skin receptors eyes ears proprioceptors vestibular apparatus P240-241
The Role of the Cerebellum in Motor Coordination Feedback control of motor function Contributes to muscle tone Stores programs for remembered activities Figure 9.23 Major pathways for information flow to and from the cerebellum. The cerebellum receives information about the status of movement from sensory areas of the cortex, the brainstem, and the spinal cord. The cerebellum then transmits information to the cortex via the thalamus, enabling the cortex to alter its output to modify the movement (as needed) to accomplish the task smoothly. P241-242
Basal Nuclei in Motor Control The basal nuclei are thought to have functions similar to the cerebellum in that they provide feedback to the cortex for the development of motor strategies and smoothing out movements Some evidence also suggests that the basal nuclei are necessary for automatic performance of learned repetitive motions The basal nuclei receive input from the cortex and send output back to the cortex via relay in the thalamus One of the functions of this loop is to assist the cortex in the selection and initiation of purposeful movement while inhibiting unwanted movements P242
Huntington s Chorea Genetic disorder of basal nuclei pathway from basal nuclei to thalamus lost Symptoms Loss of motor coordination Increased involuntary motions twitches; jerking motions Advanced stages- loss of cognitive functions Parkinson s Disease Disease of basal nuclei lack of dopamine in substantia nigra Symptoms Rigidity- slow stiff movements Involuntary movements or tremors Stooped, shuffling gait Difficulty initiating/stopping movements P242
VI. Integrated CNS Functions: Language Two Language Areas Wernicke s Area Wernicke s Area Language comprehension Wernicke s aphasia Broca s Area Language expression Broca s aphasia Broca s Area P242-243
VII. Integrated CNS Function: Sleep Active process Theories on purpose of sleep Lets body rest Lets brain rest Enhances memory Enhances learning Mechanisms poorly understood P243
Slow Wave and REM Sleep There are two phases of sleep whose names depend on whether or not the eyes move behind the closed eyelids: NREM (non-rapid eye movement) 非快速動眼期 and REM (rapid eye movement) 快速動眼期 sleep The EEG waves during NREM sleep are of high amplitude and slow frequency, so NREM sleep is also referred to as slow-wave sleep 慢波睡眠 P244
Ascending Reticular Activating System Forebrain induces slow wave sleep adenosine (adenosine release blocked by caffeine) Pons induces REM sleep acetylcholine Figure 9.24 Ascending reticular activating system. The ascending reticular activating system is aprt of the reticular formation, a diffuse network of neurons spread throughout the heighlighted area of the brainstem. The arrows indicate the spread of excitation that arouses the cortex. P244-245
EEG Recording During Wakefulness and Sleep Figure 9.25 EEG recordings during wakefulness and sleep. These graphs are 20-second EEG samples recorded from a 21-year-old female subject. Amplitudes of EEG recordings are given in microvolts (mv), and frequencies are given in Hertz (Hz). (a) Waking EEG is characterized by high-frequency, low-amplitude waves. (b) During relaxed waking, alpha waves of 8-12 Hz are present in the EEG. (c) The EEG during stage 2 sleep is characterized by high-amplitude K-complex (seen here at 3 and 14 seconds) and sleep spindles (12- to 15-Hz waves seen here at 6, 10, and 12 seconds). (d, e) High-amplitude delta (0.3-3 Hz) waves are present in stage 3 sleep and occupy the entire 20-second period in the sample of stage 4 sleep. (f) EEG amplitude decrease and frequency increases in REM sleep. P245-246
Slow Wave and REM Sleep The initial phase of sleep NREM sleep is itself divided into four stages, each successive stage characterized by an EEG pattern with a slower frequency and higher amplitude than the preceding one 睡眠初期為非快速動眼期, 又可分四期, 每一期都比前一期的頻率更低, 振幅更高 Sleep begins with the progression from stage 1 to stage 4, which normally take 30 to 45 min If uninterrupted 沒有中斷, sleep continues in this cyclical fashion 循環週期, moving from stages 1, 2, and 3, to 4 then back up from 4 to 3, 2, and 1, where NREM sleep is punctuated 打斷 by an episode of REM sleep REM sleep is also called paradoxical sleep 弔詭睡眠 because the sleeper is difficult to arouse 很難叫醒 despite having an EEG characteristic of the alert, awake state 但腦電波卻是與警覺 清醒狀態ㄧ樣 Continuous recording of adults show that the average total night s sleep comprises 4 or 5 such cycles, each lasting 90 to min P246
Stages of Sleep During One Night Figure 9.26 Stages of sleep. During 8 hours of sleep, a person moves among the different sleep stages. Initially, the person progresses from stage 1 SWS to stage 4 SWS, then returns to REM sleep. As the period of sleep continues, REM sleep becomes longer and more frequent. P246
VIII. Integrated CNS Functions: Emotions & Motivation P247 Figure 9.27 The CNS structures. Various structures of the brain are involved in producing emotions, both the feeling and the responses associated with them. Cortical association areas integrate thoughts, memory, and sensory information and communicate to the limbic system. The limbic system creates the emotion, but we are not aware of the emotion until it is transmitted back to the cortex for perception. Meanwhile, the limbic system also communicates the emotion to the hypothalamus, which is responsible for bodily responses coupled with emotion, including hormonal changes (for example, adrenaline release), motor responses (for example, frowning), and autonomic responses (for example, changes in heart rate).
資料來源 :Vander s Human Physiology Motivation and emotion Those processes 過程 responsible for the goal-directed quality of behavior 目標導向特質 are the motivations 動機, or drives 驅動力 for that behavior Primary motivated behavior 原始動機行為 is behavior related directly stable internal environment 與內在環境恆定有關的行為, such as getting something to drink when you are thirsty 口渴 In many kinds of behavior, however, the relation between the behavior and the primary goal is indirect secondary motivated behavior 次級動機行為, 例如並沒有口渴時, 想喝某種口味的飲料 The concepts of reward 報償性 and punishment 懲罰性 are inseparable 不可分的 from motivation 動機 Rewards are things that organism work for or things that make the behavior that leads to them occur more often 重複性的行為 in other words, positive reinforces punishments are the opposite 相反
資料來源 :Vander s Human Physiology Chemical mediators Dopamine is a major neurotransmitter in the pathway that mediates the brain reward systems and motivation 多巴胺是腦部參予報償及動機的主要神經傳導物質 For this reason, drugs that increase synaptic activity in the dopamine pathways increase self-stimulation rates that is, they provide positive reinforcement 可增加多巴胺路徑突觸後活性的藥物, 即可增加自我刺激的速率 ( 正向強化作用 ) Amphetamines are an example of such a drug, since they increase the postsynaptic release of dopamine 安非他命即可促進突觸後釋放多巴胺 Conversely, drugs, such as chlorpromazine, an antipsychotic agent 抗精神病用藥 that blocks dopamine receptors and lowers activity in the catecholamine pathways, are negatively reinforcing 相反地, 抗精神病用藥阻斷多巴胺接受器及降低兒茶酚胺路徑, 造成負向的強化作用 The catecholamines are also implicated in the pathways involved in learning 學習 this is not unexpected 不意外 since rewards and punishments are believed to constitute incentives 動機 for learning
Altered states of consciousness 資料來源 :Vander s Human Physiology States of consciousness 意識狀態 may be different from the commonly experienced other, more bizarre sensations, such as those occurring with hypnosis 催眠, mind-altering drugs 改變精神狀態的藥物, and certain diseases 疾病, are referred to as altered states of consciousness 意識的改變狀態 Schizophrenia One of the diseases that induces altered states of consciousness is schizophrenia 精神分裂症, a disease in which information is not properly regulated in the brain The causes of schizophrenia remain unclear 原因不明 recent studies suggest that disease reflects a developmental disorder 發育性疾病 in which neurons migrate or mature abnormally during brain formation 在腦部形成過程中, 神經元的移動或成熟不正常
資料來源 :Vander s Human Physiology Schizophrenia The abnormality may be due to a genetic predisposition 遺傳因素 or multiple environmental factors 多重的環境因子 such as viral infections 病毒感染 and malnutrition 營養失調 during fetal life or early childhood 在胎兒或嬰兒時期 A widely accepted explanation for schizophrenia suggests that certain dopamine pathways are overactive 多巴胺路徑過度活化與精神分裂症有關 This hypothesis 假說 is supported by the fact that amphetamine-like drugs 與安非他命相類似的藥, which enhance dopamine signaling, make the symptoms worse, and by the fact that the most therapeutically beneficial drugs 治療藥物 used in treating schizophrenia block dopamine receptors 增加多巴胺訊息的藥物會惡化精神分裂症, 反之, 治療精神分裂症的藥物則是阻斷多巴胺接受器
資料來源 :Vander s Human Physiology The mood disorders: depressions and bipolar disorders The term mood 心情 ; 情感 refers to a pervasive 蔓延的 and sustained 持續的 inner emotion that affects a person s perception of the world 影響個人對環境的知覺 In the healthy people, moods can be normal, elated 興高采烈的, or depressed 抑鬱的, and people generally feel that they have some degree of control over their moods 健康的人對於心情有一定程度的控制能力 The sense of control is lost 失去控制的感覺, in the mood disorders 情感疾病, which include depressive disorders 憂鬱 and bipolar disorders 雙極性情感疾病 ( 躁鬱症 ) Along with schizophrenia, the mood disorders present the major psychiatric illness 精神疾病 today 精神分裂症及情感性疾病是目前主要的精神性疾病
資料來源 :Vander s Human Physiology Depressions and bipolar disorders Depressive disorders (depression) 憂鬱 is associated with decreased neuronal activity and metabolism in the anterior part of the limbic system 邊緣系統 and nearby prefrontal cortex 前額葉皮質 These same brain regions show abnormalities 相同的腦部區域不正常, albeit inconsistent ones 雖然不是同一個地方, in bipolar disorders The term bipolar disorders 雙極性情感疾病 describes swings 改變 between manna 躁症 and depression 鬱症 Although the major biogenic amine neurotransmitters (NE, dopamine, and 5-HT) and acetylcholine have all been implicated 都有參與, the causes of the mood disorders are unknown 原因未明 Current treatment 治療 of the mood disorders emphasizes drugs and psychotherapy 精神療法
Depressions and bipolar disorders The classical antidepressant drugs 抗憂鬱藥 are of three types: The tricyclic antidepressant drugs (TCA) 三環抗憂鬱藥 such as Elavil, Norpramin, and Sinequan interfere with 5-HT and/or NE reuptake by presynaptic endings 抑制 5-HT 及 NE 的再回收 The monoamine oxidase inhibitors (MAOI) 單胺氧化酶抑制劑 interfere with the enzyme responsible for the breakdown of these same two neurotransmitters 抑制 5-HT 及 NE 的代謝酶 The serotonin-specific reuptake inhibitors (SSRI) 選擇性的血清胺再回收抑制劑 are the most widely used antidepressant drugs and include Prozac ( 百憂解 ), Paxil, Zoloft In all three classes, the result is an increased concentration of 5-HT and (except for the SSRI) NE in the extracellular fluid at synapses 除了 SSRI 只增加 5-HT 的濃度外, 其餘兩類都是增加突觸 5-HT 及 NE 的濃度 Since the biochemical effects of antidepressant medications occur immediately but the beneficial antidepressant effects appear only after several weeks of treatment, the known biochemical effect must be only an early step in a complex sequence that leads to a therapeutic effect of these drugs 服用抗憂鬱藥會立即增加 5-HT 及 NE 的量, 但療效確要好幾個星期後才會呈現 資料來源 :Vander s Human Physiology
Depressions and bipolar disorders A major drug used in treating patients with bipolar disorder is the chemical element lithium 鋰, sometimes given in combination with anticonvulsant drugs 解痙攣劑 It is highly specific, normalizing both manic and depressing moods and slowing down thinking and motor behavior without causing sedation 鋰鹽專一性很高, 對躁症及鬱症都可將其正常化, 且減慢思考及運動行為, 但不會造成鎮靜作用 Lithium may interfere with the formation of signaling molecules of the inositol phosphate family, thereby decreasing the postsynaptic neurons response to neurotransmitters that utilize this signal transduction pathway 干擾 IP 3 次級訊息傳導物的生合成, 因而降低神經傳導物在突觸後訊息傳導的過程 Psychotherapy of various kinds can also be helpful in the treatment of depression an alternative treatment 取代療法 when drug therapy and psychotherapy are not effective is electroconvulsive therapy (ECT) 電痙療法 資料來源 :Vander s Human Physiology
Psychoactive substances, dependence, and tolerance Psychoactive substances 精神活性物質 are also used as recreational 改造 drugs in a deliberate attempt to elevate mood 提升心情 and produce unusually states of consciousness 不平常的意識狀態 ranging from meditational states 思考狀態 to hallucinations 幻覺幻聽 Virtually all the psychoactive substances exert their actions either directly or indirectly by altering neurotransmitter-receptor interactions 改變神經傳導物與接受器間的交互作用 in the biogenic amine particularly dopamine pathways ex. cocaine Substance dependence 物質依賴性, the term now preferred to addition 成癮性, has two facets that may occur either together or independently: a psychological dependence 心理性依賴 that is experienced as a craving 渴望 for a substance and inability 無能力 to stop using the substance at will a physical dependence 生理性依賴 that requires one to take the substance to avoid withdrawal 戒斷, which is the spectrum of unpleasant physiological symptoms that occurs with cessation 停止 of substance use 資料來源 :Vander s Human Physiology
Psychoactive substances, dependence, and tolerance 資料來源 :Vander s Human Physiology Several neuronal systems are involved in substance dependence, but most psychoactive substances act on the mesolimbic dopamine pathway Although the major neurotransmitter implicated in addiction is dopamine, other neurotransmitters, including GABA,, enkephalin, serotonin, and glutamate, are also involved Tolerance 耐受性 to a substance occurs when increasing doses of the substance are required to achieve effects that initially occurred in response to a smaller dose 需增加劑量才能產生跟之前小劑量即能產生的反應 Moreover, tolerance can develop to another substance as a result of taking the initial substance, a phenomenon called cross-tolerance 交叉耐受性
IX. Integrated CNS Function: Learning & Memory Learning = acquisition of new information Hippocampus important Associative Learning associate 2 stimuli Non-Associative Learning habituation; sensitization Memory = retention of information, skills, or thoughts Procedural Memory = Implicit Automatic response not requiring conscious effort Learned motor skills & behaviors Cerebellum involved Declarative Memory = Explicit Learned facts, events, & experiences Requires conscious effort for recall Hippocampus involved P247-248
Short Term and Long Term Memory Information first stored as short term memory lasts seconds to hours; information lost unless consolidated Consolidation from short term memory to long term memory mechanism unknown Long term memory lasts years to lifetime Plasticity in the Nervous System Learning & Memory involve plasticity development of new synapses long term modulation of existing synapses recently shown new neurons develop P248
Long-Term Potentiation Figure 9.28 A mechanism of longterm potentiation. Repetitive stimulation of a synapse increases the likelihood that synaptic input will produce an action potential. (a) At low levels of activity in the presynaptic cell, glutamate released from that cell binds to both receptor types, but the presence of magnesium in the NMDA receptor prevents calcium influx; the net effect is a depolarization of the postsynaptic cell. P249
Long-Term Potentiation Figure 9.28 A mechanism of longterm potentiation. (b) At high levels of activity in the presynaptic cell, increased glutamate release allows more sodium to enter the postsynaptic cell, producing a greater depolarization that forces magnesium out of the NMDA receptor channel. The resulting increased calcium inflow activates protein kinases. One protein kinase acts on the sodium channel, making it more sensitive to glutamate; a second protein kinase triggers production of a paracrine that causes the presynaptic cell to produce more glutamate. The net effect of more glutamate acting on a more sensitive postsynaptic cell is a prolong depolarization. P249