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Figure 49.1 CAMPBELL BIOLOGY Command and Control Center Concept 49.1: Nervous systems consist of circuits of neurons and supporting cells TENTH EDITION Reece • Urry • Cain • Wasserman • Minorsky • Jackson ! The human brain contains about 100 billion neurons, organized into circuits more complex than the most powerful supercomputers 49 ! By the time of the Cambrian explosion more than 500 million years ago, specialized systems of neurons had appeared that enables animals to sense their environments and respond rapidly ! Powerful imaging techniques allow researchers to monitor multiple areas of the brain while the subject performs various tasks Nervous Systems ! A recent advance uses expression of combinations of colored proteins in brain cells, a technique called “brainbow” Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick 2 © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. 3 © 2014 Pearson Education, Inc. Figure 49.2 Figure 49.2a Figure 49.2a, b Radial nerve Nerve ring Eyespot ! The simplest animals with nervous systems, the cnidarians, have neurons arranged in nerve nets Nerve net ! A nerve net is a series of interconnected nerve cells (a) Hydra (cnidarian) ! More complex animals have nerves, in which the axons of multiple neurons are bundled together Brain Ventral nerve cord ! Nerves channel and organize information flow through the nervous system Segmental ganglia (e) Insect (arthropod) Brain Brain Nerve cords Radial nerve Nerve ring Ventral nerve cord Transverse nerve (b) Sea star (echinoderm) Anterior nerve ring Brain Ganglia (d) Leech (annelid) (a) Hydra (cnidarian) Spinal cord (dorsal nerve cord) Eyespot (g) Squid (mollusc) Nerve net Brain Brain Nerve cords Sensory ganglia Longitudinal nerve cords (f) Chiton (mollusc) (b) Sea star (echinoderm) © 2014 Pearson Education, Inc. (a) Hydra (cnidarian) Segmental ganglia (c) Planarian (flatworm) (d) Leech (annelid) 7 © 2014 Pearson Education, Inc. Figure 49.2d, e ! Annelids and arthropods have segmentally arranged clusters of neurons called ganglia Eyespot Ventral nerve cord Transverse nerve Segmental ganglia (d) Leech (annelid) (c) Planarian (flatworm) ! The peripheral nervous system (PNS) consists of neurons carrying information into and out of the CNS 9 © 2014 Pearson Education, Inc. Brain Brain Nerve cords ! The CNS consists of a brain and longitudinal nerve cords 8 © 2014 Pearson Education, Inc. Figure 49.2c ! The simplest cephalized animals, flatworms, have a central nervous system (CNS) (b) Sea star (echinoderm) Ventral nerve cord Transverse nerve (h) Salamander (vertebrate) 6 ! Bilaterally symmetrical animals exhibit cephalization, the clustering of sensory organs at the front end of the body Radial nerve Nerve ring Brain 5 © 2014 Pearson Education, Inc. Nerve net Segmental ganglia (c) Planarian (flatworm) Ganglia 4 © 2014 Pearson Education, Inc. 10 © 2014 Pearson Education, Inc. Segmental ganglia (e) Insect (arthropod) 11 © 2014 Pearson Education, Inc. Figure 49.2b Brain Ventral nerve cord 12 © 2014 Pearson Education, Inc. Figure 49.2f, g Brain Ventral nerve cord Segmental ganglia Ganglia Anterior nerve ring ! Nervous system organization usually correlates with lifestyle Longitudinal nerve cords (e) Insect (arthropod) ! Sessile molluscs (for example, clams and chitons) have simple systems, whereas more complex molluscs (for example, octopuses and squids) have more sophisticated systems (f) Chiton (mollusc) Brain Brain Ganglia (g) Squid (mollusc) © 2014 Pearson Education, Inc. Spinal cord (dorsal nerve cord) ! In vertebrates Ganglia Sensory ganglia (h) Salamander (vertebrate) Anterior nerve ring ! Region specialization is a hallmark of both systems Longitudinal nerve cords 14 © 2014 Pearson Education, Inc. ! The peripheral nervous system (PNS) is composed of nerves and ganglia Ganglia (f) Chiton (mollusc) 13 ! The CNS is composed of the brain and spinal cord Brain (g) Squid (mollusc) 15 © 2014 Pearson Education, Inc. 16 © 2014 Pearson Education, Inc. Figure 49.2h Figure 49.3 Glia Capillary ! Glial cells, or glia have numerous functions to nourish, support, and regulate neurons Brain Spinal cord (dorsal nerve cord) Neuron CNS PNS ! Radial glial cells and astrocytes can both act as stem cells VENTRICLE Cilia ! Embryonic radial glia form tracks along which newly formed neurons migrate Sensory ganglia ! Researchers are trying to find a way to use neural stem cells to replace brain tissue that has ceased to function normally ! Astrocytes induce cells lining capillaries in the CNS to form tight junctions, resulting in a bloodbrain barrier and restricting the entry of most substances into the brain (h) Salamander (vertebrate) Ependymal cells 17 © 2014 Pearson Education, Inc. Astrocytes Oligodendrocytes Microglia Schwann cells 18 © 2014 Pearson Education, Inc. 19 © 2014 Pearson Education, Inc. Figure 49.4 20 © 2014 Pearson Education, Inc. Figure 49.5 Organization of the Vertebrate Nervous System ! The CNS develops from the hollow nerve cord 21 ! Gray matter, which consists of neuron cell bodies, dendrites, and unmyelinated axons White matter ! The canal and ventricles fill with cerebrospinal fluid, which supplies the CNS with nutrients and hormones and carries away wastes © 2014 Pearson Education, Inc. ! The brain and spinal cord contain Gray matter ! The cavity of the nerve cord gives rise to the narrow central canal of the spinal cord and the ventricles of the brain ! White matter, which consists of bundles of myelinated axons Ventricles 22 © 2014 Pearson Education, Inc. 23 © 2014 Pearson Education, Inc. Figure 49.6 24 © 2014 Pearson Education, Inc. Figure 49.7 Central nervous system (CNS) Brain Spinal cord Cell body of sensory neuron in dorsal root ganglion Cranial nerves Ganglia outside CNS ! The spinal cord conveys information to and from the brain and generates basic patterns of locomotion Peripheral nervous system (PNS) The Peripheral Nervous System Gray matter White matter Quadriceps muscle Spinal cord (cross section) Spinal nerves ! The spinal cord also produces reflexes independently of the brain ! For example, a doctor uses a mallet to trigger a knee-jerk reflex 25 © 2014 Pearson Education, Inc. ! In the PNS, afferent neurons transmit information to the CNS and efferent neurons transmit information away from the CNS Hamstring muscle ! A reflex is the body’s automatic response to a stimulus Key ! The PNS transmits information to and from the CNS and regulates movement and the internal environment Sensory neuron Motor neuron Interneuron 26 © 2014 Pearson Education, Inc. 27 © 2014 Pearson Education, Inc. 28 © 2014 Pearson Education, Inc. Figure 49.8 Figure 49.9 CENTRAL NERVOUS SYSTEM (information processing) Parasympathetic division PERIPHERAL NERVOUS SYSTEM Efferent neurons Afferent neurons Sensory receptors Autonomic nervous system Motor system Control of skeletal muscle Internal and external stimuli © 2014 Pearson Education, Inc. Sympathetic division Dilates pupil of eye Constricts pupil of eye Sympathetic Parasympathetic division division ! The PNS has two efferent components: the motor system and the autonomic nervous system ! The autonomic nervous system has sympathetic and parasympathetic divisions ! The motor system carries signals to skeletal muscles and is voluntary ! The sympathetic division regulates arousal and energy generation (“fight-or-flight” response) ! The autonomic nervous system regulates smooth and cardiac muscles and is generally involuntary ! The parasympathetic division has antagonistic effects on target organs and promotes calming and a return to “rest and digest” functions Constricts bronchi in lungs Cervical Sympathetic ganglia Accelerates heart Stimulates activity of stomach and intestines Inhibits activity of stomach and intestines Thoracic Inhibits activity of pancreas Stimulates glucose release from liver; inhibits gallbladder Stimulates gallbladder Lumbar Stimulates adrenal medulla Promotes emptying of bladder 29 30 © 2014 Pearson Education, Inc. 31 © 2014 Pearson Education, Inc. Relaxes bronchi in lungs Slows heart Stimulates activity of pancreas Enteric division Control of smooth muscles, cardiac muscles, glands Inhibits salivary gland secretion Stimulates salivary gland secretion Promotes erection of genitalia © 2014 Pearson Education, Inc. Inhibits emptying of bladder Sacral Synapse Promotes ejaculation and 32 vaginal contractions Figure 49.9a Figure 49.9b Parasympathetic division Sympathetic division Constricts pupil of eye Dilates pupil of eye Stimulates salivary gland secretion Inhibits salivary gland secretion Constricts bronchi in lungs Slows heart Figure 49.UN01 Parasympathetic division Relaxes bronchi in lungs Sympathetic ganglia ! Specific brain structures are particularly specialized for diverse functions Accelerates heart Inhibits activity of stomach and intestines Thoracic Cervical Concept 49.2: The vertebrate brain is regionally specialized Sympathetic division Sympathetic ganglia Stimulates activity of stomach and intestines Stimulates gallbladder 33 © 2014 Pearson Education, Inc. Hindbrain Olfactory bulb Cerebrum Stimulates adrenal medulla Promotes emptying of bladder Midbrain Cerebellum Stimulates glucose release from liver; inhibits gallbladder Lumbar Stimulates activity of pancreas Forebrain ! The vertebrate brain has three major regions: the forebrain, midbrain, and hindbrain Inhibits activity of pancreas Inhibits emptying of bladder Promotes erection of genitalia Sacral Promotes ejaculation and vaginal contractions 34 Synapse © 2014 Pearson Education, Inc. 35 © 2014 Pearson Education, Inc. 36 © 2014 Pearson Education, Inc. Figure 49.10 ! The forebrain has activities including processing of olfactory input, regulation of sleep, learning, and any complex processing Lamprey ! Comparison of vertebrates shows that relative sizes of particular brain regions vary ! The midbrain coordinates routing of sensory input ! These size differences reflect the relative importance of the particular brain function ! The hindbrain controls involuntary activities and coordinates motor activities ! Evolution has resulted in a close match between structure and function ANCESTRAL VERTEBRATE Ray-finned fish Crocodilian 37 39 © 2014 Pearson Education, Inc. Figure 49.11b Midbrain Midbrain Midbrain (part of brainstem) Metencephalon Pons (part of brainstem), cerebellum Myelencephalon Medulla oblongata (part of brainstem) Hindbrain Cerebrum Mesencephalon Myelencephalon Diencephalon Brain structures in child and adult Diencephalon Myelencephalon Cerebrum (includes cerebral cortex, basal nuclei) Midbrain Pons Medulla oblongata Telencephalon Pons (part of brainstem), cerebellum 42 Embryo at 1 month Arousal and Sleep Right cerebral hemisphere Corpus callosum ! The brainstem and cerebrum control arousal and sleep Brainstem Cerebrum Diencephalon ! The core of the brainstem has a diffuse network of neurons called the reticular formation Thalamus Pineal gland Hypothalamus Pituitary gland Basal nuclei Midbrain Pons Medulla oblongata Cerebellum Spinal cord Child © 2014 Pearson Education, Inc. Spinal cord Cerebellum 45 Adult brain viewed from the rear © 2014 Pearson Education, Inc. 44 © 2014 Pearson Education, Inc. Cerebral cortex Midbrain Pons Medulla oblongata Embryo at 5 weeks Figure 49.11d Left cerebral hemisphere Diencephalon Spinal cord 43 Medulla oblongata (part of brainstem) © 2014 Pearson Education, Inc. Figure 49.11c Telencephalon Midbrain (part of brainstem) Spinal cord Child Forebrain Diencephalon (thalamus, hypothalamus, epithalamus) Cerebellum Spinal cord Embryo at 5 weeks © 2014 Pearson Education, Inc. Figure 49.11bc Cerebrum Embryo at 1 month Myelencephalon Metencephalon Hindbrain Brainstem Forebrain Hindbrain Mesencephalon Diencephalon Metencephalon Midbrain Hindbrain Metencephalon Midbrain Diencephalon Diencephalon (thalamus, hypothalamus, epithalamus) Mesencephalon Mesencephalon Telencephalon Forebrain Cerebrum (includes cerebral cortex, basal nuclei) Forebrain Diencephalon Figure 49.11bb Embryonic brain regions Brain structures in child and adult Telencephalon 40 © 2014 Pearson Education, Inc. Figure 49.11ba Embryonic brain regions © 2014 Pearson Education, Inc. ! The forebrain divides into the diencephelon, which forms endocrine tissues in the brain, and the telencephalon, which becomes the cerebrum Mammal 38 © 2014 Pearson Education, Inc. 41 ! The rest of the hindbrain gives rise to the cerebellum Bird Forebrain Midbrain Hindbrain Figure 49.11a ! The midbrain and part of the hindbrain form the brainstem, which joins with the spinal cord at the base of the brain Amphibian Key © 2014 Pearson Education, Inc. ! During embryonic development the anterior neural tube gives rise to the forebrain, midbrain, and hindbrain Shark 46 47 © 2014 Pearson Education, Inc. ! These neurons control the timing of sleep periods characterized by rapid eye movements (REMs) and by vivid dreams ! Sleep is also regulated by the biological clock and regions of the forebrain that regulate intensity and duration 48 © 2014 Pearson Education, Inc. Figure 49.12 Figure 49.13 Biological Clock Regulation Key Low-frequency waves characteristic of sleep ! Sleep is essential and may play a role in the consolidation of learning and memory ! Some animals have evolutionary adaptations allowing for substantial activity during sleep Eye Reticular formation Location ! Dolphins sleep with one brain hemisphere at a time and are therefore able to swim while “asleep” Input from nerves of ears ! Cycles of sleep and wakefulness are examples of circadian rhythms, daily cycles of biological activity High-frequency waves characteristic of wakefulness ! Such rhythms rely on a biological clock, a molecular mechanism that directs periodic gene expression and cellular activity Time: 1 hour Time: 0 hours Left hemisphere ! Biological clocks are typically synchronized to light and dark cycles Right hemisphere Input from touch, pain, and temperature receptors 49 © 2014 Pearson Education, Inc. 50 © 2014 Pearson Education, Inc. 51 © 2014 Pearson Education, Inc. 52 © 2014 Pearson Education, Inc. Figure 49.14 Emotions Thalamus Hypothalamus ! In mammals, circadian rhythms are coordinated by a group of neurons in the hypothalamus called the suprachiasmatic nucleus (SCN) ! Generation and experience of emotions involve many brain structures, including the amygdala, hippocampus, and parts of the thalamus ! The SCN acts as a pacemaker, synchronizing the biological clock ! These structures are grouped as the limbic system ! Generating and experiencing emotion often require interactions between different parts of the brain ! The structure most important to the storage of emotion in the memory is the amygdala, a mass of nuclei near the base of the cerebrum Olfactory bulb Amygdala 53 © 2014 Pearson Education, Inc. Hippocampus 54 © 2014 Pearson Education, Inc. 55 © 2014 Pearson Education, Inc. Figure 49.15 56 © 2014 Pearson Education, Inc. Figure 49.15a Figure 49.15b Functional Imaging of the Brain ! Brain structures are probed and analyzed with functional imaging methods Nucleus accumbens Amygdala Nucleus accumbens Amygdala ! Positron-emission tomography (PET) enables a display of metabolic activity through injection of radioactive glucose ! Today, many studies rely on functional magnetic resonance imaging (fMRI), in which brain activity is detected through changes in local oxygen concentration Happy music Sad music 57 © 2014 Pearson Education, Inc. Happy music Sad music 58 © 2014 Pearson Education, Inc. 59 © 2014 Pearson Education, Inc. 60 © 2014 Pearson Education, Inc. Figure 49.16 Concept 49.3: The cerebral cortex controls voluntary movement and cognitive functions ! The range of applications for fMRI include monitoring recovery from stroke, mapping abnormalities in migraine headaches, and increasing the effectiveness of brain surgery Motor cortex (control of skeletal muscles) ! The cerebrum, the largest structure in the human brain, is essential for language, cognition, memory, consciousness, and awareness of our surroundings Somatosensory cortex (sense of touch) Frontal lobe Broca’s area (forming speech) © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. Cerebellum Wernicke’s area (comprehending language) © 2014 Pearson Education, Inc. ! The thalamus directs different types of input to distinct locations Occipital lobe Auditory cortex (hearing) 62 ! Somatosensory receptors provide information about touch, pain, pressure, temperature, and the position of muscles and limbs Visual association cortex (combining images and object recognition) Temporal lobe 61 ! The cerebral cortex receives input from sensory organs and somatosensory receptors Parietal lobe Prefrontal cortex (decision making, planning) ! Four regions, or lobes (frontal, temporal, occipital, and parietal), are landmarks for particular functions Information Processing Sensory association cortex (integration of sensory information) Visual cortex (processing visual stimuli and pattern recognition) 63 64 © 2014 Pearson Education, Inc. Figure 49.17 Figure 49.18 Language and Speech Frontal lobe er a rm Leg Hip Trunk Neck Head Toes Teeth Gums Jaw Tongue Pharynx Lips Jaw Tongue Primary motor cortex 65 © 2014 Pearson Education, Inc. Max ! Studies of brain activity have mapped areas responsible for language and speech ! Patients with damage in Broca’s area in the frontal lobe can understand language but cannot speak Eye Face ! In the somatosensory cortex and motor cortex, neurons are arranged according to the part of the body that generates input or receives commands Upp ! Integrated sensory information passes to the prefrontal cortex, which helps plan actions and movements Parietal lobe Knee Hip Trunk lder Shou w Elbo ! Information received at the primary sensory areas is passed to nearby association areas that process particular features of the input Abdominal organs Hearing words Seeing words Speaking words Generating words ! Damage to Wernicke’s area causes patients to be unable to understand language, though they can still speak Genitalia Min Primary somatosensory cortex 66 © 2014 Pearson Education, Inc. 67 © 2014 Pearson Education, Inc. 68 © 2014 Pearson Education, Inc. Figure 49.UN03 Lateralization of Cortical Function Frontal Lobe Function ! The two hemispheres make distinct contributions to brain function ! The differences in hemisphere function are called lateralization ! The left hemisphere is more adept at language, math, logic, and processing of serial sequences ! The two hemispheres work together by communicating through the fibers of the corpus callosum ! The right hemisphere is stronger at facial and pattern recognition, spatial relations, and nonverbal thinking 69 © 2014 Pearson Education, Inc. ! The frontal lobes have a substantial effect on “executive functions” 70 © 2014 Pearson Education, Inc. Figure 49.19 Cerebrum (including pallium) Evolution of Cognition in Vertebrates Cerebellum ! Previous ideas that a highly convoluted neocortex is required for advanced cognition may be incorrect ! The anatomical basis for sophisticated information processing in birds (without a highly convoluted neocortex) appears to be the clustering of nuclei in the top or outer portion of the brain (pallium) ! Frontal lobe damage may impair decision making and emotional responses but leave intellect and memory intact 71 © 2014 Pearson Education, Inc. Concept 49.4: Changes in synaptic connections underlie memory and learning Neuronal Plasticity ! Two processes dominate embryonic development of the nervous system Thalamus Midbrain (a) Songbird brain Cerebrum (including cerebral cortex) ! Changes can strengthen or weaken signaling at a synapse ! Only half the synapses that form during embryo development survive into adulthood ! Autism, a developmental disorder, involves a disruption in activity-dependent remodeling at synapses Midbrain 73 (b) Human brain Cerebellum ! Neuronal plasticity describes the ability of the nervous system to be modified after birth ! Neurons compete for growth-supporting factors in order to survive Thalamus © 2014 Pearson Education, Inc. 72 © 2014 Pearson Education, Inc. 74 75 © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. Memory and Learning Long-Term Potentiation ! Children affected with autism display impaired communication and social interaction, as well as stereotyped, repetitive behaviors 76 © 2014 Pearson Education, Inc. Figure 49.20 Figure 49.21 N1 N1 ! The formation of memories is an example of neuronal plasticity N2 N2 ! In the vertebrate brain, a form of learning called long-term potentiation (LTP) involves an increase in the strength of synaptic transmission ! Short-term memory is accessed via the hippocampus (a) Connections between neurons are strengthened or weakened in response to activity. © 2014 Pearson Education, Inc. Glutamate NMDA receptor (open) POSTSYNAPTIC NEURON ! LTP involves glutamate receptors ! The hippocampus also plays a role in forming long-term memory, which is later stored in the cerebral cortex (b) If two synapses are often active at the same time, the strength of the postsynaptic response may increase at both synapses. PRESYNAPTIC NEURON Mg2+ Stored AMPA receptor 1 NMDA receptor (closed) 3 2 (b) Establishing LTP ! If the presynaptic and postsynaptic neurons are stimulated at the same time, the set of receptors present on the postsynaptic membranes changes 3 1 2 78 © 2014 Pearson Education, Inc. Na+ (a) Synapse prior to long-term potentiation (LTP) ! Some consolidation of memory is thought to occur during sleep 77 Ca2+ Depolarization 79 © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. (c) Synapse exhibiting LTP 4 Action potential 80 Figure 49.21a Figure 49.21b PRESYNAPTIC NEURON Figure 49.21c Concept 49.5: Many nervous system disorders can be explained in molecular terms Ca2+ Na+ ! Disorders of the nervous system include schizophrenia, depression, drug addiction, Alzheimer’s disease, and Parkinson’s disease Mg2+ Glutamate NMDA receptor (open) 1 NMDA receptor (closed) Stored AMPA receptor POSTSYNAPTIC NEURON 3 ! These are a major public health problem 3 1 2 2 4 ! Genetic and environmental factors contribute to diseases of the nervous system Action potential ! To distinguish between genetic and environmental variables, scientists often carry out family studies Depolarization (a) Synapse prior to long-term potentiation (LTP) 81 © 2014 Pearson Education, Inc. (b) Establishing LTP 82 (c) Synapse exhibiting LTP 83 84 © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. Schizophrenia Depression The Brain’s Reward System and Drug Addiction Figure 49.22 40 Genes shared with relatives of person with schizophrenia 12.5% (3rd-degree relative) 25% (2nd-degree relative) 50% (1st-degree relative) 100% ! About 1% of the world’s population suffers from schizophrenia 30 Identical twin Child Fraternal twin Parent Full sibling Grandchild Half sibling Uncle/aunt Nephew/niece Individual, general population Relationship to person with schizophrenia 85 © 2014 Pearson Education, Inc. Nicotine stimulates dopaminereleasing VTA neuron. ! Addictive drugs enhance the activity of the dopamine pathway ! Drug addiction leads to long-lasting changes in the reward circuitry that cause craving for the drug ! Treatments for these types of depression include drugs such as Prozac, which increase the activity of biogenic amines in the brain ! Drug addiction is characterized by compulsive consumption and an inability to control intake 87 Alzheimer’s Disease Opium and heroin decrease activity of inhibitory neuron. Cerebral neuron of reward pathway Reward system response Neurofibrillary tangle 20 µm ! Alzheimer’s disease is caused by the formation of neurofibrillary tangles and amyloid plaques in the brain ! There is no cure for this disease though some drugs are effective at relieving symptoms 90 © 2014 Pearson Education, Inc. 91 © 2014 Pearson Education, Inc. Figure 49.UN04 92 © 2014 Pearson Education, Inc. Figure 49.UN02 Figure 49.UN05 Parkinson’s Disease Wild-type hamster ! hamster Wild-type hamster with SCN from ! hamster ! hamster with SCN from wild-type hamster Circadian cycle period (hours) Brain Dopa decarboxylase ! It is characterized by muscle tremors, flexed posture, and a shuffling gait ! There is no cure, although drugs and various other approaches are used to manage symptoms L-dopa Dopamine 24 23 22 94 © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. Nerve net Spinal cord (dorsal nerve cord) Sensory ganglia 21 Hydra (cnidarian) 20 19 93 © 2014 Pearson Education, Inc. Amyloid plaque ! Alzheimer’s disease is a mental deterioration characterized by confusion and memory loss Cocaine and amphetamines block removal of dopamine from synaptic cleft. ! Parkinson’s disease is a motor disorder caused by death of dopamine-secreting neurons in the midbrain 88 © 2014 Pearson Education, Inc. Figure 49.24 Inhibitory neuron ! As researchers expand their understanding of the brain’s reward system, there is hope that their insights will lead to better prevention and treatment of drug addiction © 2014 Pearson Education, Inc. ! These drugs include cocaine, amphetamine, heroin, alcohol, and tobacco © 2014 Pearson Education, Inc. Dopaminereleasing VTA neuron 89 ! Some drugs are addictive because they increase activity of the brain’s reward system ! Bipolar disorder is characterized by manic (highmood) and depressive (low-mood) phases 86 © 2014 Pearson Education, Inc. Figure 49.23 ! The brain’s reward system rewards motivation with pleasure ! In major depressive disorder, patients have a persistent lack of interest or pleasure in most activities ! Evidence suggests that schizophrenia affects neuronal pathways that use dopamine as a neurotransmitter 10 0 ! Two broad forms of depressive illness are known ! Schizophrenia is characterized by hallucinations, delusions, and other symptoms 20 First cousin Risk of developing schizophrenia (%) 50 Before procedures After surgery and transplant 95 Salamander (vertebrate) 96 © 2014 Pearson Education, Inc. Figure 49.UN06 Figure 49.UN07 CNS Figure 49.UN08 PNS VENTRICLE Ependymal cell Cilia Astrocyte Oligodendrocyte Cerebrum Forebrain Thalamus Hypothalamus Pituitary gland Midbrain Schwann cells Capillary Neuron Pons Hindbrain Microglial cell 97 © 2014 Pearson Education, Inc. Medulla oblongata Cerebellum Spinal cord 98 © 2014 Pearson Education, Inc. 99 © 2014 Pearson Education, Inc.