nervous systems - raylc.org · nervous systems originated from systems of sensory and motor...
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Nervous Systems
Basics of Life Science
Thursdays 9‐10:30
Ray Luo
A neuron (nervous system cell) receives signals at the denritesand propgates information (as action potential firing) to its
synapse via axons.
Dendrites
AxonhillockNucleus
Cellbody
Presynapticcell Axon
Synapse Synapticterminals
Synapticterminals
Postsynaptic cellNeurotransmitter
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Nervous systems originated from systems of sensory and motor neurons.
• Sea jelly nerve nets control contraction/expan.
• Sea star radial nerves for each arm contracts, connected to central nerve ring.
• Central nervous system integrate at anterior end & spine, peripheral system nerves ganglia.
• Glial cells (non‐neurons) protect and nourish neurons, e.g. Schwann cells produce myelin sheats surrounding axons in PNS for speed.
Nerve net
(a) Hydra (cnidarian)
RadialnerveNervering
Eyespot
Brain
Nervecords
Transversenerve
Brain
Ventralnerve cord
Segmentalganglia
(b) Sea star (echinoderm)
(c) Planarian (flatworm) (d) Leech (annelid)
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Capillary CNS Neuron PNS
Schwann cellsMicrogliaOligodendrocytesAstrocytesEpendymalcells
VENTRICLE
Cilia
Line ventricle,Promote circ.
Regulate O2, glucose,Ionic balance
Myelinate CNSaxons
Immune system protectors
Myelinate PNS axons
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Vertebrate nervous systems are grouped into circuits.
• Cavity of embryonic nerve cord becomes central canal of spinal cord and brain ventricles, filled with cerebrospinal fluid.
• Gray matter: neuron cell bodies.
• White matter: axon bundles myelinated, exterior in periphery, interior in CNS for region signaling.
• Spinal cord communicates CNS and PNS, but also indep in reflexes (bypassing CNS).
• Knee jerk reflex function at only spinal cord level.
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Gray matter
Whitematter
Ventricles
Centralnervoussystem(CNS)
Brain
Spinalcord
Cranial nerves
Gangliaoutside CNS
Spinal nerves
Peripheralnervoussystem(PNS)
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Quadricepsmuscle
Hamstringmuscle
Key Sensory neuron
Motor neuron
Interneuron
Cell body ofsensory neuron indorsal root ganglion Gray
matterWhitematter
Spinal cord(cross section)
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Peripheral nervous system consists of motor and autonomic systems.
• Afferent: PNS to CNS, efferent: CNS to PNS• PNS motor system: signal to skeletal muscles• PNS autonomic: involuntary, cardiac and smooth muscles, enteric digestive glands
• PNS autonomic sympathetic: arousal, digestion down, glucose conv, just outside spinal cord ganglia, post ganglia norephinephrine
• PNS autonomic parasympathetic: rest digest, glycogen prod, sex functions up along symp, base of brain to ganglia near organ, post ganglia ACh
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Afferent neurons
Sensoryreceptors
Efferent neurons
Internaland external
stimuli
Autonomicnervous system
Motorsystem
Control ofskeletal muscle
Sympatheticdivision
Parasympatheticdivision
Entericdivision
Control of smooth muscles,cardiac muscles, glands
PERIPHERAL NERVOUSSYSTEM
CENTRAL NERVOUSSYSTEM
(information processing)
e.g. exercise: symp up, parasymp down
Parasympathetic division Sympathetic division
Constricts pupil of eye Dilates pupil of eye
Stimulates salivarygland secretion
Inhibits salivarygland secretion
Relaxes bronchi in lungsConstrictsbronchi in lungs
Slows heart Accelerates heart
Inhibits activity ofstomach and intestines
Inhibits activityof pancreas
Stimulates activity ofstomach and intestines
Stimulates activity of pancreas
Stimulates gallbladder
Promotes emptyingof bladder
Promotes erectionof genitalia
Stimulates glucoserelease from liver;inhibits gallbladder
Stimulates adrenal medulla
Inhibits emptyingof bladder
Promotes ejaculation andvaginal contractions
Sympathetic ganglia
Cervical
Thoracic
Lumbar
Sacral
Synapse
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Regional specific components of evolved brain structures.
• Forebrain: complex processing, midbrain: routing inputs, hindbrain: involuntary activity movement
• Forebrain got bigger in evolution, region specific
• Human cerebral cortex: left control right, corpus callosum cross‐over, learning perception etc
• Cerebellum: error check move, eye‐hand coord
• Diencephalon: thalamus relay sensory info, hypothalamus hunger thirst, body temperature, bio clock, pituitary control, pineal gland: melatonin CSF
• Brainstem: pons and medulla, relay, breathing, heart, swallowing vital functions, cross‐over, vis reflex
Lamprey
Shark
Ray-finnedfish
Amphibian
Crocodilian
Bird
Mammal
ANCESTRALVERTEBRATE
Key
ForebrainMidbrainHindbrain
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Embryonic brain regions Brain structures in child and adult
Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephalon Medulla oblongata (part of brainstem)
Pons (part of brainstem), cerebellum
Midbrain (part of brainstem)
Diencephalon (thalamus, hypothalamus, epithalamus)
Cerebrum (includes cerebral cortex, basal nuclei)
Cerebrum DiencephalonMesencephalon
Metencephalon
MyelencephalonDiencephalon
TelencephalonSpinalcord
ChildEmbryo at 5 weeksEmbryo at 1 month
Forebrain
Midbrain
Hindbrain
Hindbrain
MidbrainPons
Medullaoblongata
Cerebellum
Spinal cord
Bra
ins
tem
Midbrain
Forebrain
Figure 49.11c
Cerebrum
Cerebellum
Basal nuclei
Corpus callosum
Cerebral cortex
Right cerebralhemisphere
Left cerebralhemisphere
Adult brain viewed from the rear
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Figure 49.11d
Diencephalon
ThalamusPineal glandHypothalamus
Pituitary gland
Spinal cord
Medullaoblongata
Pons
Midbrain
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Sleep, arousal, and circadian rhythms are regulated by midbrain control.
• Sleep: recording EEG waves, evidence for con‐solidation replay, midbrain reticular formation control REM rapid eye move dream filter input
• Dolphin: sleep one hemisphere at a time
• Biological clock sync to light and dark: hypothalamus
• Hypothalamic suprachiasmatic nucleus SCN transplant b/t 20 and 24 hr hamster strains ‐SCN as pacemaker
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Figure 49.12
Eye
Reticular formation
Input from touch,pain, and temperaturereceptors
Input fromnerves ofears
Figure 49.13
Key
Low-frequency waves characteristic of sleep
High-frequency waves characteristic of wakefulness
Location Time: 0 hours Time: 1 hour
Lefthemisphere
Righthemisphere
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Emotions rely on interplay within limbic system: amygdala, hippocampus
• Image followed by shock lead to autonomic arousal heart rate sweating, but amygdala damage ‐> no arousal but can recall image
• fMRI of human tracks change in local oxygen level, listen to happy or sad music: happy ‐> nucleus accumbens activated, sad ‐> amygdala
Thalamus
Hypothalamus
Olfactorybulb
Amygdala Hippocampus
Limbic system: emotions
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Nucleus accumbens Amygdala
Sad musicHappy music
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Team activity
Myelinated neurons are especially abundant in the _____.
• A) white matter of the brain and the gray matter of the spinal cord
• B) white matter in the brain and the white matter in the spinal cord
• C) gray matter of the brain and the gray matter of the spinal cord
• D) gray matter of the brain and the white matter of the spinal cord
If a patient has an injury in the brain stem, which of the following would be observed?
• A) an inability to regulate body temperature
• B) an inability to regulate heart function
• C) auditory hallucinations
• D) visual hallucinations
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Cerebral cortex consists of sensory, association, and motor areas.
• Visual auditory somatosensory receptors ‐> thalamus ‐> primary sensory area (particular feature) ‐> association area (recognition faces) ‐> prefrontal (action planning) ‐> motor cortex ‐> brainstem ‐> spinal cord ‐> motor neurons
• Topographical organization in sensory and motor cortices, proportional to amount of processing needed for that body part
• Broca’s area damage: can understand ‐ not speak, Wernicke’s damage: can’t comprehend ‐ can talk
Motor cortex (control ofskeletal muscles) Somatosensory
cortex(sense of touch)
Sensory associationcortex (integrationof sensory information)
Frontal lobe
Temporal lobe
Parietal lobe
Occipital lobe
Prefrontal cortex(decision making,planning)
Broca’s area(forming speech)
Auditory cortex(hearing)
Cerebellum
Visualassociationcortex (combiningimages and objectrecognition)
Visual cortex(processing visualstimuli and patternrecognition)
Wernicke’s area(comprehendinglanguage)
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Frontal lobe
Toes
LipsJaw
Tongue Primarymotorcortex
Parietal lobe
Genitalia
Primarysomatosensorycortex
Abdominalorgans
Hearingwords
Seeingwords
Max
Min
Generatingwords
Speakingwords
Wernicke’s area(left hemisphere)
Broca’s area(left hemisphere)
Visual cortex
Frontal (not speaking)
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• Left hemisphere: language, logic, math
• Right hemisphere: recognition, spatial, pattern
• Split brain severing of corpus callosum: cannot read word in left visual field since info cannot go from right hemisphere to language area
• Frontal lobe: Phineas Gage explosion caused iron rod behind left eye recovered, detached personality erratic behavior, no exec control
• Evolution: unconvoluted pallium in birds and convoluted cortex in humans from same ancestor? Birds can remember, tools, abstract
Skull of Phineas Gage, railroad construction crew
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Thalamus
Cerebrum(including pallium)
Cerebellum
Midbrain
(a) Songbird brain
Cerebrum (includingcerebral cortex)
(b) Human brain
Thalamus
Midbrain
Cerebellum
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Learning and memory are formed by changes in cell, synaptic connections.
• Competition for growth factors: cell death for half of cells who don’t reach proper location.
• Competition for right connections: half of synapses for a cell are eliminated in develop.
• Neuronal plasticity: activity of cell ‐> remodel, fire together ‐> wire together, autism defect.
• Hippocampus short term memory, cortex long term memory, damage to hippocampus: can recall past but not form new memories.
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Changes in synpatic strength at the hippocampus via LTP.
• More connections with existing knowledge the new knowledge is, easier it’s to remember
• New skill: new connects, new fact: use existing
• Long term potentiation in hippocampus: high freq presyn firing coincides with postsyndepolarization ‐> unblock NMDAR ‐> insertion of AMPAR glutamate receptors ‐> bigger postsyn potential with the usual presyn stim
(a) Connections between neurons are strengthened orweakened in response to activity.
(b) If two synapses are often active at the same time,the strength of the postsynaptic response mayincrease at both synapses.
N1N1
N2 N2
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(a) Synapse prior to long-term potentiation (LTP) (b) Establishing LTP
(c) Synapse exhibiting LTP
Glutamate
PRESYNAPTICNEURON
Mg2+
Ca2+
Na+
NMDA receptor(open)
StoredAMPAreceptorPOSTSYNAPTIC
NEURON
NMDAreceptor(closed)
1
2
3
1
2
4
3
Actionpotential
Depolarization
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Nervous system disorders can affect anyone.
• Family studies to identify genetic factors• Schizophrenia: disordered reality, hallucinates, delusions, dopamine block alleviates symptom
• Depression: major depressive, bipolar manic phase suicidal phase, Prozac amines up
• Addiction: manipulate VTA dopamine pathway• Alzheimer’s: can’t function can’t recognize, accumulate beta amyloid plagues that kill cells nearby, neurofibrillary tau tangles (early onset)
• Parkinson’s: tremors rigid shuffling, mitochondria genetic defect?, L‐Dopa and deep brain stim
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AddictionNicotinestimulatesdopamine-releasingVTA neuron.
Inhibitory neuron
Dopamine-releasingVTA neuron
Opium and heroindecrease activityof inhibitoryneuron.
Cocaine andamphetaminesblock removalof dopaminefrom synapticcleft.
Rewardsystemresponse
Cerebralneuron ofrewardpathway
Alzheimer’s disease: molecular aspects.
Amyloid plaque Neurofibrillary tangle 20 µm
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Team activity
The motor cortex is part of the _____.
• A) spinal cord
• B) cerebrum
• C) medulla oblongata
• D) cerebellum
Exercise and emergency reactions include _____.
• A) decreased activity in the sympathetic, and increased activity in the parasympathetic divisions
• B) increased activity in all parts of the peripheral nervous system
• C) increased activity in the enteric nervous system
• D) increased activity in the sympathetic, and decreased activity in the parasympathetic divisions