49 Nervous Systems Lecture Presentation by Nicole Tunbridge and

49 Nervous Systems Lecture Presentation by Nicole Tunbridge and
Kathleen Fitzpatrick

Command and Control Center
The human brain contains about 100 billion neurons, organized into circuits more complex than the most powerful supercomputers Powerful imaging techniques allow researchers to monitor multiple areas of the brain while the subject performs various tasks A recent advance uses expression of combinations of colored proteins in brain cells, a technique called “brainbow”

Figure 49.1 Figure 49.1 How do scientists identify individual neurons in the brain?

Concept 49.1: Nervous systems consist of circuits of neurons and supporting cells
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

The simplest animals with nervous systems, the cnidarians, have neurons arranged in nerve nets
A nerve net is a series of interconnected nerve cells More complex animals have nerves, in which the axons of multiple neurons are bundled together Nerves channel and organize information flow through the nervous system

(b) Sea star (echinoderm) (c) Planarian (flatworm) (d) Leech (annelid)
Figure 49.2 Eyespot Brain Radial nerve Brain Nerve cords Ventral nerve cord Nerve ring Nerve net Transverse nerve Segmental ganglia (a) Hydra (cnidarian) (b) Sea star (echinoderm) (c) Planarian (flatworm) (d) Leech (annelid) Brain Ganglia Brain Anterior nerve ring Spinal cord (dorsal nerve cord) Ventral nerve cord Brain Sensory ganglia Figure 49.2 Nervous system organization Ganglia Segmental ganglia Longitudinal nerve cords (e) Insect (arthropod) (f) Chiton (mollusc) (g) Squid (mollusc) (h) Salamander (vertebrate)

(b) Sea star (echinoderm)
Figure 49.2a Radial nerve Nerve ring Nerve net (a) Hydra (cnidarian) (b) Sea star (echinoderm) Eyespot Brain Brain Figure 49.2a Nervous system organization (part 1: cnidarian, echinoderm, flatworm and annelid) Nerve cords Ventral nerve cord Transverse nerve Segmental ganglia (c) Planarian (flatworm) (d) Leech (annelid)

(b) Sea star (echinoderm)
Figure 49.2a, b Radial nerve Nerve ring Nerve net (a) Hydra (cnidarian) (b) Sea star (echinoderm) Figure 49.2a, b Nervous system organization (cnidarian and echinoderm)

Bilaterally symmetrical animals exhibit cephalization, the clustering of sensory organs at the front end of the body The simplest cephalized animals, flatworms, have a central nervous system (CNS) The CNS consists of a brain and longitudinal nerve cords The peripheral nervous system (PNS) consists of neurons carrying information into and out of the CNS

(c) Planarian (flatworm)
Figure 49.2c Eyespot Brain Nerve cords Transverse nerve Figure 49.2c Nervous system organization (flatworm) (c) Planarian (flatworm)

Annelids and arthropods have segmentally arranged clusters of neurons called ganglia

(e) Insect (arthropod)
Figure 49.2d, e Brain Brain Ventral nerve cord Ventral nerve cord Segmental ganglia Segmental ganglia Figure 49.2d, e Nervous system organization (annelid and arthropod) (d) Leech (annelid) (e) Insect (arthropod)

Longitudinal nerve cords
Figure 49.2b Ganglia Brain Anterior nerve ring Ventral nerve cord Segmental ganglia Longitudinal nerve cords (e) Insect (arthropod) (f) Chiton (mollusc) Brain Brain Spinal cord (dorsal nerve cord) Figure 49.2b Nervous system organization (part 2: arthropod, mollusc, and vertebrate) Sensory ganglia Ganglia (g) Squid (mollusc) (h) Salamander (vertebrate)

Nervous system organization usually correlates with lifestyle
Sessile molluscs (for example, clams and chitons) have simple systems, whereas more complex molluscs (for example, octopuses and squids) have more sophisticated systems

Longitudinal nerve cords
Figure 49.2f, g Ganglia Anterior nerve ring Brain Ganglia Longitudinal nerve cords Figure 49.2f, g Nervous system organization (mollusc) (f) Chiton (mollusc) (g) Squid (mollusc)

Region specialization is a hallmark of both systems
In vertebrates The CNS is composed of the brain and spinal cord The peripheral nervous system (PNS) is composed of nerves and ganglia Region specialization is a hallmark of both systems

Spinal cord (dorsal nerve cord) Sensory ganglia
Figure 49.2h Brain Spinal cord (dorsal nerve cord) Sensory ganglia Figure 49.2h Nervous system organization (vertebrate) (h) Salamander (vertebrate)

Glia Glial cells, or glia have numerous functions to nourish, support, and regulate neurons Embryonic radial glia form tracks along which newly formed neurons migrate Astrocytes induce cells lining capillaries in the CNS to form tight junctions, resulting in a blood-brain barrier and restricting the entry of most substances into the brain

Capillary Neuron CNS PNS VENTRICLE Cilia Ependymal cells Astrocytes
Figure 49.3 Capillary Neuron CNS PNS VENTRICLE Cilia Figure 49.3 Glia in the vertebrate nervous system Ependymal cells Astrocytes Oligodendrocytes Microglia Schwann cells

Radial glial cells and astrocytes can both act as stem cells
Researchers are trying to find a way to use neural stem cells to replace brain tissue that has ceased to function normally

Figure 49.4 Figure 49.4 Newly born neurons in the brain of an adult mouse

Organization of the Vertebrate Nervous System
The CNS develops from the hollow nerve cord The cavity of the nerve cord gives rise to the narrow central canal of the spinal cord and the ventricles of the brain The canal and ventricles fill with cerebrospinal fluid, which supplies the CNS with nutrients and hormones and carries away wastes

Gray matter White matter Ventricles Figure 49.5
Figure 49.5 Ventricles, gray matter, and white matter

The brain and spinal cord contain
Gray matter, which consists of neuron cell bodies, dendrites, and unmyelinated axons White matter, which consists of bundles of myelinated axons

Central nervous system (CNS) Brain Cranial nerves Spinal cord
Figure 49.6 Central nervous system (CNS) Brain Cranial nerves Spinal cord Peripheral nervous system (PNS) Ganglia outside CNS Spinal nerves Figure 49.6 The vertebrate nervous system

The spinal cord also produces reflexes independently of the brain
The spinal cord conveys information to and from the brain and generates basic patterns of locomotion The spinal cord also produces reflexes independently of the brain A reflex is the body’s automatic response to a stimulus For example, a doctor uses a mallet to trigger a knee-jerk reflex

Cell body of sensory neuron in dorsal root ganglion
Figure 49.7 Cell body of sensory neuron in dorsal root ganglion Gray matter White matter Quadriceps muscle Spinal cord (cross section) Hamstring muscle Figure 49.7 The knee-jerk reflex Key Sensory neuron Motor neuron Interneuron

The Peripheral Nervous System
The PNS transmits information to and from the CNS and regulates movement and the internal environment In the PNS, afferent neurons transmit information to the CNS and efferent neurons transmit information away from the CNS

CENTRAL NERVOUS SYSTEM (information processing)
Figure 49.8 CENTRAL NERVOUS SYSTEM (information processing) PERIPHERAL NERVOUS SYSTEM Afferent neurons Efferent neurons Autonomic nervous system Motor system Sensory receptors Control of skeletal muscle Figure 49.8 Functional hierarchy of the vertebrate peripheral nervous system Internal and external stimuli Sympathetic division Parasympathetic division Enteric division Control of smooth muscles, cardiac muscles, glands

The PNS has two efferent components: the motor system and the autonomic nervous system
The motor system carries signals to skeletal muscles and is voluntary The autonomic nervous system regulates smooth and cardiac muscles and is generally involuntary

The autonomic nervous system has sympathetic and parasympathetic divisions
The sympathetic division regulates arousal and energy generation (“fight-or-flight” response) The parasympathetic division has antagonistic effects on target organs and promotes calming and a return to “rest and digest” functions

Parasympathetic division Sympathetic division
Figure 49.9 Parasympathetic division Sympathetic division Constricts pupil of eye Dilates pupil of eye Stimulates salivary gland secretion Inhibits salivary gland secretion Sympathetic ganglia Constricts bronchi in lungs Relaxes bronchi in lungs Cervical Slows heart Accelerates heart Stimulates activity of stomach and intestines Inhibits activity of stomach and intestines Thoracic Stimulates activity of pancreas Inhibits activity of pancreas Stimulates glucose release from liver; inhibits gallbladder Stimulates gallbladder Figure 49.9 The parasympathetic and sympathetic divisions of the autonomic nervous system Lumbar Stimulates adrenal medulla Promotes emptying of bladder Inhibits emptying of bladder Sacral Promotes erection of genitalia Promotes ejaculation and vaginal contractions Synapse

Figure 49.9a Parasympathetic division Sympathetic division Dilates pupil of eye Constricts pupil of eye Inhibits salivary gland secretion Stimulates salivary gland secretion Constricts bronchi in lungs Cervical Sympathetic ganglia Slows heart Stimulates activity of stomach and intestines Figure 49.9a The parasympathetic and sympathetic divisions of the autonomic nervous system (part 1: cervical) Stimulates activity of pancreas Stimulates gallbladder

Figure 49.9b Parasympathetic division Sympathetic division Relaxes bronchi in lungs Sympathetic ganglia Accelerates heart Inhibits activity of stomach and intestines Thoracic Inhibits activity of pancreas Stimulates glucose release from liver; inhibits gallbladder Lumbar Figure 49.9b The parasympathetic and sympathetic divisions of the autonomic nervous system (part 2: thoracic, lumbar and sacral) Stimulates adrenal medulla Promotes emptying of bladder Inhibits emptying of bladder Promotes erection of genitalia Sacral Promotes ejaculation and vaginal contractions Synapse

Concept 49.2: The vertebrate brain is regionally specialized
Specific brain structures are particularly specialized for diverse functions The vertebrate brain has three major regions: the forebrain, midbrain, and hindbrain

Forebrain Midbrain Hindbrain Cerebellum Olfactory bulb Cerebrum
Figure 49.UN01 Forebrain Midbrain Hindbrain Cerebellum Olfactory bulb Cerebrum Figure 49.UN01 In-text figure, vertebrate brain regions, p. 1085

The forebrain has activities including processing of olfactory input, regulation of sleep, learning, and any complex processing The midbrain coordinates routing of sensory input The hindbrain controls involuntary activities and coordinates motor activities

Comparison of vertebrates shows that relative sizes of particular brain regions vary
These size differences reflect the relative importance of the particular brain function Evolution has resulted in a close match between structure and function

Lamprey Shark ANCESTRAL VERTEBRATE Ray-finned fish Amphibian
Figure 49.10 Lamprey Shark ANCESTRAL VERTEBRATE Ray-finned fish Amphibian Crocodilian Key Figure Vertebrate brain structure and evolution Bird Forebrain Midbrain Hindbrain Mammal

During embryonic development the anterior neural tube gives rise to the forebrain, midbrain, and hindbrain The midbrain and part of the hindbrain form the brainstem, which joins with the spinal cord at the base of the brain The rest of the hindbrain gives rise to the cerebellum The forebrain divides into the diencephelon, which forms endocrine tissues in the brain, and the telencephalon, which becomes the cerebrum

Figure 49.11a Figure 49.11a Exploring the organization of the human brain (part 1: MRI)

Figure 49.11b Embryonic brain regions Brain structures in child and adult Telencephalon Cerebrum (includes cerebral cortex, basal nuclei) Forebrain Diencephalon Diencephalon (thalamus, hypothalamus, epithalamus) Midbrain Mesencephalon Midbrain (part of brainstem) Metencephalon Pons (part of brainstem), cerebellum Hindbrain Myelencephalon Medulla oblongata (part of brainstem) Mesencephalon Cerebrum Diencephalon Metencephalon Midbrain Myelencephalon Hindbrain Diencephalon Figure 49.11b Exploring the organization of the human brain (part 2: brain development) Midbrain Pons Brainstem Medulla oblongata Telencephalon Forebrain Cerebellum Spinal cord Spinal cord Embryo at 1 month Embryo at 5 weeks Child

Embryonic brain regions
Figure 49.11ba Embryonic brain regions Telencephalon Forebrain Diencephalon Midbrain Mesencephalon Metencephalon Hindbrain Myelencephalon Brain structures in child and adult Cerebrum (includes cerebral cortex, basal nuclei) Figure 49.11ba Exploring the organization of the human brain (part 2a: brain development, chart) Diencephalon (thalamus, hypothalamus, epithalamus) Midbrain (part of brainstem) Pons (part of brainstem), cerebellum Medulla oblongata (part of brainstem)

Mesencephalon Metencephalon Midbrain Myelencephalon Diencephalon
Figure 49.11bb Mesencephalon Metencephalon Midbrain Myelencephalon Diencephalon Hindbrain Telencephalon Figure 49.11bb Exploring the organization of the human brain (part 2a: brain development, embryo) Forebrain Spinal cord Embryo at 1 month Embryo at 5 weeks

Cerebrum Diencephalon Midbrain Pons Brainstem Medulla oblongata
Figure 49.11bc Cerebrum Diencephalon Midbrain Pons Brainstem Medulla oblongata Figure 49.11bc Exploring the organization of the human brain (part 2c: brain development, child) Cerebellum Spinal cord Child

Left cerebral hemisphere Right cerebral hemisphere
Figure 49.11c Left cerebral hemisphere Right cerebral hemisphere Cerebral cortex Corpus callosum Cerebrum Basal nuclei Figure 49.11c Exploring the organization of the human brain (part 3: cerebrum and cerebellum) Cerebellum Adult brain viewed from the rear

Diencephalon Thalamus
Figure 49.11d Diencephalon Thalamus Pineal gland Hypothalamus Midbrain Pituitary gland Pons Figure 49.11d Exploring the organization of the human brain (part 4: diencephalon and brainstem) Medulla oblongata Spinal cord

Arousal and Sleep The brainstem and cerebrum control arousal and sleep
The core of the brainstem has a diffuse network of neurons called the reticular formation 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

Input from nerves of ears
Figure 49.12 Eye Input from nerves of ears Figure The reticular formation Reticular formation Input from touch, pain, and temperature receptors

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 Dolphins sleep with one brain hemisphere at a time and are therefore able to swim while “asleep”

Low-frequency waves characteristic of sleep
Figure 49.13 Key Low-frequency waves characteristic of sleep High-frequency waves characteristic of wakefulness Location Time: 0 hours Time: 1 hour Left hemisphere Figure Dolphins can be asleep and awake at the same time. Right hemisphere

Biological Clock Regulation
Cycles of sleep and wakefulness are examples of circadian rhythms, daily cycles of biological activity Such rhythms rely on a biological clock, a molecular mechanism that directs periodic gene expression and cellular activity Biological clocks are typically synchronized to light and dark cycles

In mammals, circadian rhythms are coordinated by a group of neurons in the hypothalamus called the suprachiasmatic nucleus (SCN) The SCN acts as a pacemaker, synchronizing the biological clock

Emotions Generation and experience of emotions involve many brain structures, including the amygdala, hippocampus, and parts of the thalamus These structures are grouped as the limbic system

Thalamus Hypothalamus Olfactory bulb Amygdala Hippocampus Figure 49.14
Figure The limbic system in the human brain Olfactory bulb Amygdala Hippocampus

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

Functional Imaging of the Brain
Brain structures are probed and analyzed with functional imaging methods 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

Nucleus accumbens Amygdala Happy music Sad music Figure 49.15
Figure Functional imaging in the working brain Happy music Sad music

Nucleus accumbens Happy music Figure 49.15a
Figure 49.15a Functional imaging in the working brain (part 1: happy music) Happy music

Amygdala Sad music Figure 49.15b
Figure 49.15b Functional imaging in the working brain (part 2: sad music) Sad music

The range of applications for fMRI include monitoring recovery from stroke, mapping abnormalities in migraine headaches, and increasing the effectiveness of brain surgery

Concept 49.3: The cerebral cortex controls voluntary movement and cognitive functions
The cerebrum, the largest structure in the human brain, is essential for language, cognition, memory, consciousness, and awareness of our surroundings Four regions, or lobes (frontal, temporal, occipital, and parietal), are landmarks for particular functions

Motor cortex (control of skeletal muscles)
Figure 49.16 Motor cortex (control of skeletal muscles) Sensory association cortex (integration of sensory information) Somatosensory cortex (sense of touch) Frontal lobe Parietal lobe Prefrontal cortex (decision making, planning) Visual association cortex (combining images and object recognition) Broca’s area (forming speech) Figure The human cerebral cortex Temporal lobe Occipital lobe Auditory cortex (hearing) Cerebellum Visual cortex (processing visual stimuli and pattern recognition) Wernicke’s area (comprehending language)

Information Processing
The cerebral cortex receives input from sensory organs and somatosensory receptors Somatosensory receptors provide information about touch, pain, pressure, temperature, and the position of muscles and limbs The thalamus directs different types of input to distinct locations

Information received at the primary sensory areas is passed to nearby association areas that process particular features of the input Integrated sensory information passes to the prefrontal cortex, which helps plan actions and movements In the somatosensory cortex and motor cortex, neurons are arranged according to the part of the body that generates input or receives commands

Primary somatosensory cortex
Figure 49.17 Frontal lobe Parietal lobe Shoulder Upper arm Forearm Elbow Trunk Knee Trunk Hip Head Neck Forearm Elbow Hip Leg Wrist Fingers Hand Hand Fingers Thumb Thumb Neck Eye Brow Nose Face Eye Lips Genitalia Face Toes Teeth Figure Body part representation in the primary motor and primary somatosensory cortices Gums Lips Jaw Jaw Tongue Pharynx Tongue Primary motor cortex Primary somatosensory cortex Abdominal organs

Language and Speech 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 Damage to Wernicke’s area causes patients to be unable to understand language, though they can still speak

Max Hearing words Seeing words Min Speaking words Generating words
Figure 49.18 Max Hearing words Seeing words Figure Mapping language areas in the cerebral cortex Min Speaking words Generating words

Lateralization of Cortical Function
The two hemispheres make distinct contributions to brain function The left hemisphere is more adept at language, math, logic, and processing of serial sequences The right hemisphere is stronger at facial and pattern recognition, spatial relations, and nonverbal thinking

The differences in hemisphere function are called lateralization
The two hemispheres work together by communicating through the fibers of the corpus callosum

Frontal Lobe Function Frontal lobe damage may impair decision making and emotional responses but leave intellect and memory intact The frontal lobes have a substantial effect on “executive functions”

Figure 49.UN03 Figure 49.UN03 In-text figure, Phineas Gage, p. 1092

Evolution of Cognition in Vertebrates
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)

Cerebrum (including pallium) Cerebellum Thalamus Midbrain
Figure 49.19 Cerebrum (including pallium) Cerebellum Thalamus Midbrain (a) Songbird brain Cerebrum (including cerebral cortex) Figure Comparison of regions for higher cognition in avian and human brains Thalamus Midbrain Cerebellum (b) Human brain

Concept 49.4: Changes in synaptic connections underlie memory and learning
Two processes dominate embryonic development of the nervous system Neurons compete for growth-supporting factors in order to survive Only half the synapses that form during embryo development survive into adulthood

Neuronal Plasticity Neuronal plasticity describes the ability of the nervous system to be modified after birth Changes can strengthen or weaken signaling at a synapse Autism, a developmental disorder, involves a disruption in activity-dependent remodeling at synapses Children affected with autism display impaired communication and social interaction, as well as stereotyped, repetitive behaviors

Figure 49.20 N1 N1 N2 N2 (a) Connections between neurons are strengthened or weakened in response to activity. Figure Neural plasticity (b) If two synapses are often active at the same time, the strength of the postsynaptic response may increase at both synapses.

Memory and Learning The formation of memories is an example of neuronal plasticity Short-term memory is accessed via the hippocampus The hippocampus also plays a role in forming long-term memory, which is later stored in the cerebral cortex Some consolidation of memory is thought to occur during sleep

Long-Term Potentiation
In the vertebrate brain, a form of learning called long-term potentiation (LTP) involves an increase in the strength of synaptic transmission LTP involves glutamate receptors If the presynaptic and postsynaptic neurons are stimulated at the same time, the set of receptors present on the postsynaptic membranes changes

NMDA receptor (closed) 2 Stored AMPA receptor 3
Figure 49.21 PRESYNAPTIC NEURON Ca2+ Na+ Mg2+ 1 Glutamate NMDA receptor (open) NMDA receptor (closed) 2 Stored AMPA receptor 3 POSTSYNAPTIC NEURON (a) Synapse prior to long-term potentiation (LTP) (b) Establishing LTP Figure Long-term potentiation in the brain 1 3 2 4 Action potential Depolarization (c) Synapse exhibiting LTP

NMDA receptor (closed) Stored AMPA receptor
Figure 49.21a PRESYNAPTIC NEURON Ca2+ Na+ Mg2+ Glutamate NMDA receptor (open) NMDA receptor (closed) Figure 49.21a Long-term potentiation in the brain (part 1: prior to LTP) Stored AMPA receptor POSTSYNAPTIC NEURON (a) Synapse prior to long-term potentiation (LTP)

1 2 3 (b) Establishing LTP Figure 49.21b
Figure 49.21b Long-term potentiation in the brain (part 1: establishing LTP) 3 (b) Establishing LTP

(c) Synapse exhibiting LTP
Figure 49.21c 3 1 2 Figure 49.21c Long-term potentiation in the brain (part 1: exhibiting LTP) 4 Action potential Depolarization (c) Synapse exhibiting LTP

Concept 49.5: Many nervous system disorders can be explained in molecular terms
Disorders of the nervous system include schizophrenia, depression, drug addiction, Alzheimer’s disease, and Parkinson’s disease These are a major public health problem Genetic and environmental factors contribute to diseases of the nervous system To distinguish between genetic and environmental variables, scientists often carry out family studies

Genes shared with relatives of person with schizophrenia
Figure 49.22 50 Genes shared with relatives of person with schizophrenia 12.5% (3rd-degree relative) 40 25% (2nd-degree relative) 50% (1st-degree relative) 100% 30 Risk of developing schizophrenia (%) 20 10 Figure Genetic contribution to schizophrenia Individual, general population Parent Child First cousin Uncle/aunt Nephew/niece Grandchild Half sibling Full sibling Fraternal twin Identical twin Relationship to person with schizophrenia

Schizophrenia About 1% of the world’s population suffers from schizophrenia Schizophrenia is characterized by hallucinations, delusions, and other symptoms Evidence suggests that schizophrenia affects neuronal pathways that use dopamine as a neurotransmitter

Depression Two broad forms of depressive illness are known
In major depressive disorder, patients have a persistent lack of interest or pleasure in most activities Bipolar disorder is characterized by manic (high-mood) and depressive (low-mood) phases Treatments for these types of depression include drugs such as Prozac, which increase the activity of biogenic amines in the brain

The Brain’s Reward System and Drug Addiction
The brain’s reward system rewards motivation with pleasure Some drugs are addictive because they increase activity of the brain’s reward system These drugs include cocaine, amphetamine, heroin, alcohol, and tobacco Drug addiction is characterized by compulsive consumption and an inability to control intake

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 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

Nicotine stimulates dopamine- releasing VTA neuron.
Figure 49.23 Inhibitory neuron Nicotine stimulates dopamine- releasing VTA neuron. Opium and heroin decrease activity of inhibitory neuron. Dopamine- releasing VTA neuron Cocaine and amphetamines block removal of dopamine from synaptic cleft. Figure Effects of addictive drugs on the reward system of the mammalian brain Cerebral neuron of reward pathway Reward system response

Alzheimer’s Disease Alzheimer’s disease is a mental deterioration characterized by confusion and memory loss 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

Neurofibrillary tangle 20 µm
Figure 49.24 Amyloid plaque Neurofibrillary tangle 20 µm Figure Microscopic signs of Alzheimer’s disease

Parkinson’s Disease Parkinson’s disease is a motor disorder caused by death of dopamine-secreting neurons in the midbrain 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

Dopa decarboxylase Dopamine L-dopa Figure 49.UN04
Figure 49.UN04 In-text figure, L-dopa conversion, p. 1098

Before procedures After surgery and transplant
Figure 49.UN02 Wild-type hamster 𝜏 hamster Wild-type hamster with SCN from 𝜏 hamster 𝜏 hamster with SCN from wild-type hamster 24 23 Circadian cycle period (hours) 22 21 Figure 49.UN02 Skills exercise: designing an experiment using genetic mutants 20 19 Before procedures After surgery and transplant

Spinal cord (dorsal nerve cord) Sensory ganglia
Figure 49.UN05 Brain Spinal cord (dorsal nerve cord) Sensory ganglia Nerve net Figure 49.UN05 Summary of key concepts: nervous systems Hydra (cnidarian) Salamander (vertebrate)

CNS PNS VENTRICLE Astrocyte Ependy- mal cell Oligodendrocyte Cilia
Figure 49.UN06 CNS PNS VENTRICLE Astrocyte Ependy- mal cell Oligodendrocyte Cilia Figure 49.UN06 Summary of key concepts: CNS and PNS Schwann cells Capillary Neuron Microglial cell

Cerebrum Forebrain Thalamus Hypothalamus Pituitary gland Midbrain Pons
Figure 49.UN07 Cerebrum Forebrain Thalamus Hypothalamus Pituitary gland Midbrain Figure 49.UN07 Summary of key concepts: vertebrate brain regions Pons Spinal cord Hindbrain Medulla oblongata Cerebellum

Figure 49.UN08 Figure 49.UN08 Test your understanding, question 12 (public speaking)

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