Chapter 48: The Nervous SystemChapter 48: The Nervous SystemThe nervous system & endocrine system work to The nervous system & endocrine system work to regulate the organism & maintain homeostasis.regulate the organism & maintain homeostasis.

Nervous systemNervous systemInvolves:Involves:

Sensory receptionSensory receptionStimulus (change in environment) triggers a responseStimulus (change in environment) triggers a responseconcentrated in sense organsconcentrated in sense organsSensitivity determined by density of receptorsSensitivity determined by density of receptors

IntegrationIntegrationInterneurons or associative neurons within the CNS relay Interneurons or associative neurons within the CNS relay messagemessage

Motor responseMotor responseA reaction or behavior resulting in response to a stimulusA reaction or behavior resulting in response to a stimulusEffecter- muscle or gland which carries out a responseEffecter- muscle or gland which carries out a response

NeuronsNeurons Nerve cellsNerve cells

Structure similar in all organismsStructure similar in all organisms Organization of cells varies among organismsOrganization of cells varies among organisms

PartsParts Dendrites Dendrites

receive signalreceive signal Cell bodyCell body

contains nucleus & other organellescontains nucleus & other organelles AxonAxon

transmits signaltransmits signal Myelin sheathMyelin sheath

encloses axon, insulating signalencloses axon, insulating signal aids in speed of action potentialaids in speed of action potential

Terminal branchesTerminal branches may contain neurotransmitters may contain neurotransmitters

Synaptic gapSynaptic gap site of communication between 2 neurons via neurotransmitterssite of communication between 2 neurons via neurotransmitters

*Impulse enters via dendrites & exits via terminal branches*Impulse enters via dendrites & exits via terminal branches Glia= supporting cellsGlia= supporting cells

TypesTypes AstrocytesAstrocytes

regulate ion & neurotransmitter concentration; dilation of blood vesselsregulate ion & neurotransmitter concentration; dilation of blood vessels Radial gliaRadial glia

act as stem cellsact as stem cells Oligodendrocytes (CNS) & Schwann cells (PNS)Oligodendrocytes (CNS) & Schwann cells (PNS)

form myelin sheathform myelin sheath

ReflexesReflexes Automatic, inborn, unlearnedAutomatic, inborn, unlearned Protective responses to stimulationProtective responses to stimulation Examples: blinking, sneezing, coughingExamples: blinking, sneezing, coughing Reflex arcReflex arc

Stimulus (receptors on sense organ)Stimulus (receptors on sense organ) sensory neuron sensory neuron interneuron within interneuron within CNS (analyze & interpret)CNS (analyze & interpret) motor neuron motor neuron effectors at neuromuscular effectors at neuromuscular junctionjunction

Instincts- automatic & inborn like reflexes Instincts- automatic & inborn like reflexes but not necessarily protective in functionbut not necessarily protective in function

HabitsHabits Automatic, learned behaviorsAutomatic, learned behaviors Examples: smoking, tying shoe laces, using Examples: smoking, tying shoe laces, using

profanity, writingprofanity, writing

Response of neuronsResponse of neurons Graded potentialsGraded potentials

Magnitude of depolarization or hyper-polarization varies with Magnitude of depolarization or hyper-polarization varies with stimulus strengthstimulus strength

Bigger stimuli= bigger changeBigger stimuli= bigger change Action potentialsAction potentials

All or none depolarizationAll or none depolarization Same strength regardless of stimulusSame strength regardless of stimulus

Nerve impulseNerve impulse Electrochemical signal; speeds of 100 meters/secondElectrochemical signal; speeds of 100 meters/second Resting stateResting state

both Naboth Na++ & K & K++ activation gate channels are closed activation gate channels are closed Resting potential- membrane more permeable to KResting potential- membrane more permeable to K++ so more K so more K++

moves out than Namoves out than Na++ moves in. moves in. Ion permeability must change to send an impulseIon permeability must change to send an impulse

Threshold must be achieved to depolarize neuron membrane Threshold must be achieved to depolarize neuron membrane & produce an action potential& produce an action potential

Depolarization: Na+ channels open & Na+ flows into neuron Depolarization: Na+ channels open & Na+ flows into neuron reversing polarityreversing polarity

Re-polarization: K+ ions allowed into neuron as Na+ is blockedRe-polarization: K+ ions allowed into neuron as Na+ is blocked Refractory: brief period of time when cell can not be stimulated Refractory: brief period of time when cell can not be stimulated

to carry an impulseto carry an impulse

The SynapseThe Synapse TypesTypes

Electrical synapsesElectrical synapses Gap junctions allow action potential to travel cell to cellGap junctions allow action potential to travel cell to cell

Chemical synapsesChemical synapses Neurotransmitters released from synaptic vesicles & bind to Neurotransmitters released from synaptic vesicles & bind to

dendrites of next neuron to start a new action potentialdendrites of next neuron to start a new action potential**Majority of synapses**Majority of synapses

NeurotransmittersNeurotransmitters Chemicals released into synaptic gap that diffuse & bind to Chemicals released into synaptic gap that diffuse & bind to

next neuronnext neuron CaCa+2+2 required for release required for release Excitatory neurotransmittersExcitatory neurotransmitters

Transmit impulsesTransmit impulses Examples: acetylcholine (to skeletal muscle), norepinephrine, Examples: acetylcholine (to skeletal muscle), norepinephrine,

dopamine, glutamate, aspartatedopamine, glutamate, aspartate Inhibitory neurotransmittersInhibitory neurotransmitters

Block impulse transmissionBlock impulse transmission Examples: acetylcholine (to cardiac muscle), serotonin, Examples: acetylcholine (to cardiac muscle), serotonin,

epinephrine, glycine, GABA, endorphinsepinephrine, glycine, GABA, endorphins

Regulation in invertebratesRegulation in invertebrates ProtistsProtists

Sensitive to light, chemicals, temperatureSensitive to light, chemicals, temperature Cnideria (hydra)Cnideria (hydra)

Nerve netNerve net Whole organism responds to stimulusWhole organism responds to stimulus

Annelida (earthworm)Annelida (earthworm) Ventral nerve cordVentral nerve cord Fused ganglia (clusters of neurons) acting as brainFused ganglia (clusters of neurons) acting as brain

Arthropoda (insects)Arthropoda (insects) Ventral nerve cordVentral nerve cord Sensory organsSensory organs

AntennaeAntennae TympanumTympanum Compound eyesCompound eyes

Mammalian Nervous SystemMammalian Nervous System Central Nervous SystemCentral Nervous System

Cerebrospinal fluidCerebrospinal fluid helps supply nutrients & hormones to brain & removes wastehelps supply nutrients & hormones to brain & removes waste cushions brain & spinal cordcushions brain & spinal cord

Meninges- protective layers surrounding brain & spinal cordMeninges- protective layers surrounding brain & spinal cord BrainBrain

CerebrumCerebrum Largest, upper portion of brainLargest, upper portion of brain thinking, memory, body awareness, social behavior, languagethinking, memory, body awareness, social behavior, language EEG (electroencephalogram) detects brain wave activityEEG (electroencephalogram) detects brain wave activity Convolutions- folds in brainConvolutions- folds in brain Limbic system- lower part of brain that interacts with cerebral cortex to Limbic system- lower part of brain that interacts with cerebral cortex to

produce emotions, complex reasoning, & personalityproduce emotions, complex reasoning, & personality Includes:Includes: Amygdala- emotional memoriesAmygdala- emotional memories Hippocampus- emotional events, long term memoriesHippocampus- emotional events, long term memories Olfactory bulbOlfactory bulb

Corpus callosum- axons that enable communication between Corpus callosum- axons that enable communication between hemispheres of cerebrumhemispheres of cerebrum

Lobes:Lobes: Frontal- speech, motor functionFrontal- speech, motor function Temporal- smell, hearing, auditory associationTemporal- smell, hearing, auditory association Occipital- visionOccipital- vision Parietal- reading, somatosensory association, speech, tasteParietal- reading, somatosensory association, speech, taste

CerebellumCerebellum Lower, posterior portion of brainLower, posterior portion of brain Regulates muscle balance, tone, coordination, & error Regulates muscle balance, tone, coordination, & error

checking during motor, perceptual, & cognitive functionschecking during motor, perceptual, & cognitive functions BrainstemBrainstem

Primitive brain controlling involuntary activities includes:Primitive brain controlling involuntary activities includes: MidbrainMidbrain Pons- heart beat, swallowing, vomiting, digestionPons- heart beat, swallowing, vomiting, digestion Medulla oblongata- breathingMedulla oblongata- breathing

Reticular formationReticular formation network of neurons in the brainstem which selects network of neurons in the brainstem which selects

information being sent to cerebral cortexinformation being sent to cerebral cortex affects alertnessaffects alertness

DiencephalonDiencephalon IncludesIncludes

Epithalamus- pineal gland & choroid plexusEpithalamus- pineal gland & choroid plexus Thalamus- input center for sensory info & output Thalamus- input center for sensory info & output

center for motor info & emotionscenter for motor info & emotions Hypothalamus- homeostatic regulation; connection Hypothalamus- homeostatic regulation; connection

between nervous & endocrine systems; regulates between nervous & endocrine systems; regulates circadian rhythmscircadian rhythms

Spinal cord- connects the brain to the peripheral Spinal cord- connects the brain to the peripheral nervous systemnervous system

Peripheral nervous systemPeripheral nervous system System of branching nerves linking CNS to body System of branching nerves linking CNS to body

tissues & organstissues & organs Consists of:Consists of:

Somatic nervous systemSomatic nervous system Voluntary control or awareness of muscles, sense organs, & Voluntary control or awareness of muscles, sense organs, &

skinskin Allows for conscious control in response to external stimulationAllows for conscious control in response to external stimulation

Autonomic nervous systemAutonomic nervous system Automatic, unconscious or involuntary regulationAutomatic, unconscious or involuntary regulation Regulates internal environment by controlling smooth & cardiac Regulates internal environment by controlling smooth & cardiac

muscle & organsmuscle & organs IncludesIncludes

Sympathetic nervous system- increased heart beat, blood Sympathetic nervous system- increased heart beat, blood vessel constriction, bronchi open, pupils dilate, peristalsis vessel constriction, bronchi open, pupils dilate, peristalsis slows, bladder relaxesslows, bladder relaxes

Parasympatheic nervous system- reverse reactions of Parasympatheic nervous system- reverse reactions of sympathetic nervous systemsympathetic nervous system

Enteric nervous system- network of neurons to control Enteric nervous system- network of neurons to control organ secretions & smooth muscles; regulated through the organ secretions & smooth muscles; regulated through the sympathetic & parasympatheic nervous systemssympathetic & parasympatheic nervous systems

Diseases & DisordersDiseases & Disorders SchizophreniaSchizophrenia Bipolar disorder/Manic depressive Bipolar disorder/Manic depressive

disorderdisorder Major depressionMajor depression Alzheimer’s diseaseAlzheimer’s disease Parkinson’s diseaseParkinson’s disease