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CAMPBELL AND REECE CHAPTER 49

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ability to react to stimuli originated billions of years ago with prokaryotes able to detect changes in environment that enhanced survival & reproductive success.

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Hydras, Jellies, & other cnidarians: radial symmetry interconnected nerve cells form a diffuse nerve net controls contractions & expansion of the central digestive compartment Hydra

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Invertebrate nervous systems range in complexity from simple nerve nets to highly centralized nervous systems having complicated brains & ventral nerve cords

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Central Nervous System: CNS Brain Spinal Cord Peripheral Nervous System: PNS Nerves

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functions of brain & spinal cord tightly coordinated Brain: integrative function Spinal Cord: conveys information to & from the brain & generates basic patterns of locomotion; spinal reflexes act independently of the brain Nerves: transmit sensory & motor signals between b

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automatic protective responses to certain stimuli thru simple nerve circuits

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http://www.sumanasinc.com/webcontent /animations/content/reflexarcs.html http://www.sumanasinc.com/webcontent /animations/content/reflexarcs.html

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Invertebrates have their nerve cord on ventrally (front) Vertebrates have spinal cord along dorsal side (back) segmental organization in arrangement of neurons w/in spinal cord, spinal nerves & ganglia just outside spinal cord

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CNS develops from a hollow dorsal nerve cord (hallmark of chordates, with a notochord)

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cavity of this nerve cord central canal of spinal cord + ventricles of brain both filled with CSF (cerebral spinal fluid) a filtrate of arterial blood CSF flows thru these spaces then drains into veins supplies brain with nutrients, hormones carries away waste in mammals: cushions brain & spinal cord (layer of CSF between these & surrounding bone)

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mainly neuron cell bodies, dendrites, & unmyelinated axons outside of brain inside spinal cord

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mainly bundled myelinated axons inside brain, outside spinal cord

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aka neuroglia cells that support, nourish, regulate, & augment functions of neurons Types: Ependymal cells Oligodendrocytes Astrocytes Microglia Schwann cells

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line ventricles ciliated promote circulation of CSF

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myelinate axons in the CNS (myelination greatly increases speed of action potentials)

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star-shaped facilitate information transfer @ synapses sometimes release neurotransmitter can cause blood vessels near neurons to dilate increasing oxygen & glucose delivery to neurons regulate extracellular concentrations of ions & neurotransmitters

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Immune cells that protect against pathogens

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myelinate axons in PNS

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Embryo: radial glia cells form tracks along which newly formed neurons migrate from neural tube Astrocytes induce cells lining capillaries to form tight jcts blood-brain barrier (bbb) controls the extracellular environment of CNS by restricting entry of most substances from blood

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Radial Glial cells & Astrocytes also thought to act as stem cells for CNSable to generate new neurons & glial cells..

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plays large role in regulating an animals movement & internal environment Afferent neurons: carry sensory signals CNS Efferent neurons: carry signals to skeletal muscle & glands & thru Autonomic Nervous system to smooth & cardiac muscle

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Sympathetic & Parasympathetic has antagonistic effects on a diverse set of target organs Efferent division: controls activity of many digestive organs

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Brain most complex organ of human body protected by thick bones of skull

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http://www.dnatube.com/video/12257/T he-human-embryonic-brain- development http://www.dnatube.com/video/12257/T he-human-embryonic-brain- development

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rapid expansion during 2 nd & 3 rd months of fetal development causes the outer portion, the cortex (gray matter) to extend over & around much of the rest of the brain Cerebral cortex: vital for perception, voluntary actions, & learning

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term includes cerebral cortex divided into hemispheres left hemisphere receives information from & controls movement of right side of body & vise versa Corpus callosum: thick band of axons connects hemispheres

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clusters of neurons deep w/in white matter of brain serve as centers for planning & learning movement sequences Damage during fetal development cerebral palsy (disruption of commands to muscles)

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part of forebrain Thalamus Hypothalamus Epithalamus

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main input center for sensory information cerebrum Sensory tracts from spinal cord thalamus which sorts info sending it to correct region of cerebrum for further processing

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bodys thermostat central biological clock controls release of hormones from pituitary source of posterior pituitary hormones

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includes pineal gland secretes melatonin clusters of capillaries produce CSF

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coordinates movement & balance helps in learning & remembering motor skills receives info on joint position & length of muscles + input from hearing & visual centers integrates information on motor commands from cerebrum as it carries out coordination & error checking during motor & perceptual functions

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controls eye-hand coordination if damaged: Eyes can follow moving object but eyes keep moving when object stops Hand movement toward the object will be erratic

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3 parts: 1. Midbrain 2. Pons 3. Medulla Oblongata

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receives & integrates several types of sensory information sends it to specific regions of forebrain all sensory axons from hearing either terminate in midbrain or pass thru it cerebrum coordinates visual reflexes Head turns towards object approaching from the side w/out brain having formed image of moving object

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transfers info from PNS midbrain & forebrain coordinates large-scale body movements (running, climbing) axon tracts cross from 1 side to other: right side of brain controls left side of body & vice versa

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contains several automatic, homeostatic functions: Respiratory center Cardiovascular center swallowing vomiting digestion

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transitions from wakefulness to sleep regulated by brainstem & cerebrum Arousal : state of awareness of external world Sleep: state in which external stimuli are received but not consciously perceived

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is an active state EEG (electroencephalogram): brain waves change as go thru stages of sleep hypothesis: sleep & dreams involved in consolidating learning & memory regions of brain involved in learning while awake also active during sleep those lacking sleep have more difficulty learning new task

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diffuse network of neurons in core of brainstem determines which sensory information makes it to cerebrum more info sent along to cerebrumthe more aware someone is Pons & Medulla also contain sleep centers & Midbrain has a center that causes arousal

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all birds & mammals Melatonin: hormone released by pineal gland peak secretion @ night, decrease in am

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Bottlenose Dolphins: Swim while sleeping Rise to surface to breathe Sleep with 1 eye open, 1 eye closed ? Does dolphin sleep with 1 hemisphere of brain awake/ 1 asleep? Proved by using EEG

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a molecular mechanism that directs periodic gene expression & cellular activity humans removed from any light/dark clues uniformly set a 24.2 hr cycle

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coordinated by a group of neurons in hypothalamus called: suprachiasmatic nucleus or SCN acts as pacemaker: synchronizes the biological clock in cells thru out body to natural cycles of day length

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their generation & experience involve many regions of brain but main area Limbic System Emotions Motivation Olfaction Behvior Memory Limbic System Parts Amygdala Hippocampus parts of the thalamus

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stored as memories that are recalled by similar circumstances Fear: memory is stored separate from the memory system that supports explicit recall of events Amygdala: stores emotional memories

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largest structure in human brain cortex: cognitive functions: sensory areas receive & process sensory info association areas integrate the info motor areas transmit instructions to other parts of the body

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1800s: Pierre Broca: autopsied brains of people that could understand language but could not speak Discovered many of them had defects in what is now called Brocas area: controls muscles in the face We now know this area is active during speech generation

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Karl Wernicke: damage to posterior portion of temporal lobe (Wernickes area) abolished ability to comprehend speech but not the ability to speak We now know this area is active when speech is heard.

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2 hemispheres make distinct contributions to some brain functions: Left side: Speech Math & Logical operations Right side: Recognition of faces & patterns Spatial relations Nonverbal thinking

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allows right & left hemispheres to work together If severed: split-brain

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In the somatosensory cortex (where somatosensory sensors like touch, pressure, pain, temperature, & position of muscles & limbs send impulses) & motor cortex (where motor commands generated) are arranged according to the part of the body that generates the sensory input or receives the motor commands.

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Phineas Gage: 3 meter long, 3 cm diamter pipe thru his frontal lobe He survived but had personality changes; he became emotionally detached, impatient, erratic in behavior

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patients w/hx of tumors removed in same area as Gages injury have had similar changes: intellect & memory are intact decision making is flawed emotional responses diminished

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in humans: cerebral cortex ~80% of total brain mass 5 mm thick ~1,000 square cm outermost part called the neocortex

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until recently scientists thought a highly convoluted neocortex required for advanced cognition Primates & Cetaceans (whales, dolphins & porpoises) have very convoluted neocortex

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have region (pallium) contains clustered nuclei that carry out functions similar to those performed by our cerebral cortex Some birds solve problems & understand abstractions which indicates higher cognition

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during development more neurons and synapses form than will exist in the adult apoptosis of neurons & elimination of synapses in embryos establishes the basic structure of the nervous system

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In adult, reshaping of the nervous system can involve the loss or addition of synapses or the strengthening or weakening of signaling at synapses This capacity for remodeling is called neural plasticity defective remodeling of synapses is partly responsible for the developmental abnormalities of autism

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Connections between neurons strengthened or weakened in response to activity. High-level activity @ synapse of the post-synaptic neuron with presynaptic neuron leads to recruitment of more axon terminals from that neuron. Lack of activity @ synapse with presynaptic neuron loss of functional connections with that neuron

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If 2 synapses on the same postsynaptic cell are often active @ same time, the strength of the postsynaptic response may increase @ both synapses

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relies on temporary links in the hippocampus

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temporary links of short term memory replaced by connections w/in cerebral cortex

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transfer of information from short- term to long-term memory is enhanced by association of new data with that already in long-term memory (making connections to something you already have learned helps you learn new material)

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evidence shows they are involved in learning & memory After damage to CNS, surviving neurons can make new connections & sometimes compensate for lost cells. Stem cell research has long way to go at this time

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researchers have identified some genes that cause or contribute to disorders of nervous systemso better able to identify causes & predict outcomes environmental contributions also very significant but very difficult to identify

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1% worlds population See: psychotic episodes in which patient has distorted perception of reality hear voices delusional

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Causes (?): disruption in neuronal pathways that release dopamine Amphetamines which stimulate dopamine produce same set of symptoms meds used to alleviate symptoms block dopamine receptors

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Causes (?): alteration of glutamate signaling Street drug PCP blocks glutamate signaling & mimics symptoms of schizophrenia

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Characterized by: depressed mood alterations in sleep, appetite, energy level Nervous disorder with best chances of effective treatments with meds & therapy 2 broad forms: Major Depressive Disorder Bipolar Disorder

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1 of most common nervous system disorders Patients undergo periods of time when get no enjoyment out of things normally would Affects ~ 1/7 adults at some time in their lives; women: men 2:1

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aka Manic-Depressive Disorder ~1% of worlds population See: mood swings: very high to very low Highs: hi self-esteem, hi nrg, talkativeness, & increased risk taking Lows: less ability to feel pleasure, feel worthless, sleep disturbances

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characterized by compulsive consumption of drug & loss of control in limiting intake Drug increases activity of brains reward system (normally functions in pleasure, motivation & learning) Addictive Drugs Stimulants: cocaine, amphetamines Sedatives: heroin

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Normally: provides motivation for activities that enhance survival & reproduction Eating in response to hunger Drinking when thirsty In drug addict motivation is directed toward further drug consumption

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mental deterioration or dementia characterized by confusion & memory loss also, loss of ability to recognize people, treat others with suspicion &/or hostility incidence age-related: ~ 10% @ age 65 to ~ 35% @ age 85 No cure, drugs available that relieve some of symptoms or slow progression

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leads to death of neurons in many areas of the brain Brain shrinks See amyloid plaques & neurofibrillary tangles on post-mortem

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motor disorder, progressive disease more common with advancing edge (5% by age 85) See: Muscle tremors (pill-rolling) Poor balance Flexed posture Shuffling gait Facial mask: muscles rigid, unable to vary expression

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symptoms result from death of neurons in the midbrain that normally release dopamine in basal nuclei no cure: Brain surgery L-dopa

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most cases have no identifiable cause Except: disease that appears in relatively young adults has a clear genetic basis Find: disruption of genes required for certain mitochondrial functions

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