Flashcards
Nerval Tissue
Cards in this deck (176)
- 1DendritesHighly branched
dendritic spines
(0.5-1um long) - 2CNC Neurons receive infoat dendrites
from environment or other neurons - 3Cell body OrganellesContained within perikaryon
- 4Cell body Cytoskeletonneurofilaments
neurofibrils
extend into dendrites and axon - 5AxonCarries info toward other cells
transport of materials - 6Axoplasmic transporttransport enzymes and lysosomes using neurotubules
occurs in both directions - 7Retrograde flowback toward cell body
- 8Axon componentsAxon hillock
axolemma
axoplasm
collateral branches - 9Axon hillockbase
- 10Axolemmaplasma membrane of axon
- 11AxoplasmCytoplasm of axon with organelles
structural components
and
transport materials - 12Collateral branchesCommunicate with other cells
- 13TelodendriaAxonal extensions at end of axon trunk
terminate at synaptic terminals - 14Synaptic terminalswhere neurons communicate with other cells
- 15Synapsecommunication site between neuron and another cell
- 16Components of synapsePresynaptic cell
Postsynaptic cell
Synaptic cleft - 17presynaptic cellusually a neuron
may have synaptic know
Synaptic vesicles
neurotransmitters
presynaptic membrane - 18Synaptic vesiclescontain neurotransmitters
- 19neurotransmitterschemical messengers synthesized in cell body
- 20Presynaptic membranewhere neurotransmitters are released
- 21Post synaptic cellcan be neuron or other type of cell
- 22postsynaptic membranehas receptors for neurotransmitters
- 23Synaptic cleftnarrow space between cells
- 24Centriolsmost CNS neurons lack centriols and cannot divide
some neural stem cells exist - 25neural stem cellsmostly inactive
- 26neural stem cells exceptionsolfactory epithelium (smell)
Retina of eye
Hippocampus (memory storage) - 27Four major anatomical classes of neuronsAnaxonic
Bipolar
Unipolar
Multipolar - 28Anaxonic neuronsall processes look alike
located in brain and special sensory organs
functions poorly understood - 29Bipolar neuronsTwo distinct process
-one branching dendritic processes
-one axon
Rare (special sense organs)
Small (30um in length) - 30Unipolar neuronsDendrites and axon are continuous
Cell body lies off to one side
Initial segmant where dendrites converge - 31Unipolar neurons foundmost sensory of peripheral nervous system
may extend 1 meter or more - 32Multipolar neuronstwo or more dendrites and one axon
most common in CNS
can be as long as unipolar
Voluntary motor neurons - 33Three major functional classesSensory neurons (10 million)
Interneurons (20 million)
Motor neurons (500,000) - 34Sensory receptorsrelay stimuli to sensory neurons
- 35Types of sensory receptorsInteroceptors
Proprioceptors
Exteroceptors - 36InteroceptorsMotor sensations inside body from various systems
- 37ProprioceptorsMonitor body position and movement of joints and muscles
- 38ExteroceptorsMonitor sensations from external environment
- 39Afferent nerve fibersaxons from receptor to CNS
- 40Sensory gangliaContain cell bodies of unipolar sensory eurons
Somatic Sensory Neurons
Visceral sensory neurons - 41Somatic Sensory neuronsOutside world
- 42Visceral sensory neuronsinternal conditions
- 43Central nervous system Interneronsusually between sensory and motor neurons
responsible for highter functioning - 44Motor neuronsoriginate in CNS and transmit impulses to effectors through PNS
- 45Somatic motor neuronsSkeletal muscles
- 46Visceral motor neuronssmooth and cardiac
glands and adipose - 47Visceral motor neurons synapsewith 2nd set of neurons at autonomic ganglia
- 48neurogliasupport and protect neurons
abundant and diverse
half volume of nervous system - 49CNS gliaEpendymal
Microglia
Astrocytes
Oligodendrocytes
Oligodendrocytes - 50Ependymalform epithelia lining fluid filled passageway in brain and spinal cord
- 51cerebrospinal fluidsurrounds brain and spinal cord
- 52Microgliarelated to monocytes and macrophages
migrate to CNS
mobile phagocytic cells - 53phagocytic cellsremove debris, waste, pathogens
- 54Astrocytesmaintain blood-brain barrer
structural support
regulate ion nutrient and dissolved gas in interstitial fluid
absorbs recycles neurotransmitters
form scar tissue - 55blood-brain barrerisolates CNS from chemicals and hormones in blood
- 56Oligodendrocytesframework by stabilizing axons
produce myelin/sheath - 57one oligodendrocyte wrapsaxonal segments of many neurons
- 58internodesmyelin-wrapped areas
- 59nodesgaps between internodes
- 60myelinatedaxons with myelin sheath
appear white due to lipid content
white matter - 61unmyelinatedgray matter: along with neuron cell body and dendrites
- 62Schwann cellsform sheath around peripheral axons
neurilemma
cover mylenated and unmyelinated axons - 63neurilemmaouter surface of schwann cells
- 64single schwann cellmyelinates an axon
can wrap many unmyelinated neurons - 65satellite cellssurround neuron cell bodies in ganglia
regulate intercellular environment - 66Repair of damaged nerves in PNS1. axon and myelin degenerate distal to injury
2. schwann cells proliferate along original path
3. axon grows along path
4. schwann cells wrap along elongated axon - 67if axon makes normal synaptic contactsnormal function may be regained
- 68if axon stops growing or wanders offnormal function may not return
- 69Wallerian degenerationrepair that does not restore full function
- 70limited repair can occur in CNS due to1. many axons involved
2. astrocytes produce scar tissue
3. release chemicals that block axonal growth - 71NeurophysiologyTransmembrane potential
- 72Transmembrane potentialunequal distribution of charge across membrane
- 73Transmembrane potential insideslightly negative
- proteins and ions - 74Transmembrane potential outsideslightly positive
+ions - 75Neural activity and transmemembrane potentialResting potential
graded potential
action potential
synaptic activity
information processing - 76change in transmembrane ptoentialcause muscle contraction
gland secretion
transfer of information - 77Resting potentialall neural activities begin with change in resting potential
- 78graded potentialtemporty, localized change in resting potential
decreases with distance from stimulus - 79Action potentialelectrical event involving location of axonal membrane
triggered by sufficiently large graded potential
propagates along axon toward synaptic terminals - 80Synaptic activityrelease of neurotransmitters py presynaptic cell
compounds bind to receptors on postsynaptic
change permeability- produces graded potential - 81Information processingintegration of stimuli at individual cell level
response of postsynatpic cell to stimulated receptors - 82Extracellular fluidhigh concentration of Na and Cl
- 83Cytosolhigh concentration of K+ and negatively charged proteins
- 84resting potential is usuallynear 0.07 volts
- 85Leak channelsalways open
size shape structure deterine which ions will pass
primariy causes the transmemebrane potential - 86Active transportsodium-potassium exchange pump
- 87sodium potassium ratio3 sodium- 2 potassium
maintains stable resting potential - 88Electrochemical gradientsChemical gradient
Electrical gradient
Equilibrium potential - 89Chemical gradientConcentration gradient for an ion across plasma membrane
- 90Electrical gradientAttraction between opposite charges or repulsion between like chrages
- 91Equilibrium potentialwhen electrial and chemical gradient are equal and opposite
resulting in no net movement across membrane - 92Potassium ion gradients at normal resting potentialelectrical and chemical graditns are ain in opposition but not equal
net electrochemical gradient is out of the cell - 93Sodium ion gradients at normal resting potentialboth chemical and electrical gradients cause na to move into cell
- 94Gated channelsresting potential remains stable until the cell is stimulated
- 95changes in transmembrane potential primarily due togated channels
- 96gated channelsChemically gated
Voltage-gated
Mechanically gated - 97Chemically gated channelsopen when they bind specific chemical
most abundant on dendrites and cell body - 98Chemical gated channels open exampeNMJ receptors that bind ACh
- 99Voltage-gated channeslcharacteristic of excitable membranes
capable of generateing and conducting action potential
open/close in response to changes in transmembrane potential - 100Most imporant voltage-gated channelspotassium
calcium
sodium - 101voltage-gated channels have two gatesthat function independently
activation gates
inactivation - 102Mechanically gated channelsopen in response to physical distortion of membrane
important sensory receptors
(touch, pressure, vibration) - 103Graded potential AKAlocal potential
cannot spread far from stimulation site - 104grated potentials examplechemically gated sodium channels
- 105Na+ graded potentialsresting potential = closed
binding of chemicals open (depolarization) - 106Depolarizationcaused by positively charged ions enter cell
shift to more positive - 107local currentintercellular Na spread out, attracted to negatively charged lining membrane
extra cellular Na moves to replace - 108degree of depolarizationdecreases with distance from stimulation site
- 109greater stimulus=more open channesl = more ion flow
change in transmembrane potential poportional to stimulus intensity - 110removal of chemical stimulusmembrane returns to resting potential
Na pumped out of sell (repolarizatoin) - 111Effects of chemically gated potassium channeslions leave cytoplasm
more negative transmembrane potential - 112Hyperpolariationmore negative transmembrane potential due to K ions leaving cytoplasm
- 113Acton potential generation Information transfer in neronsreceptrion of info as graded potentials on dendrties and cell bodies
at synaptic terminals- release neurotransmitters - 114Graded potentialsonly travel short distances
- 115distance between cell body and terminals can be largeaction potentials can travel longer distances
- 116leak channels responsible forresting potential
- 117Chemically gated channels producegraded potentials
- 118Voltage-gated channels produceaction potentials
- 119Prior to action potential generationtransmembrane potential- resting levels
sodium channels closed
potassium channel closed - 120Action potential sodium channelsactivation gate: closed
inactivation gate: open - 121Action potential potassium channelsingle gate closed
- 122Steps of action potential generation and propagation1. depolarization to threshold
2. activation of Na channels and rapid depolarization
3. Inactivation of Na channels and activation of K channels
4. Potassium channels close - 123Depolarization thresholdgraded depolarization large enough to open voltage-gated sodium channels=threshold
approximate trans membrane potential -60mV - 124activation of na channels and rapid depolarizationNa rush into cell
cause depolarization
from -60 to positive value - 125incativation of na channels and activatoin of k channelsat +30mV sodium inactivation gates close
voltage-gated potassium channels open - 126at +30mVSodium channel inactivation close
- 127voltage-gated potassium channels openbegins repolarization
- 128potassium channels closeas membrane reaches resting potential (-70 mV)
brief hyperpolarization - 129Grated potential is likepulling trigger of gun
enough pressure will cause gun to fire - 130Action potential is thefiring of gun
enough pressure will cause gun to fire the same way every time
stimulus triggers action potential or not at all - 131all or nothing principlestimulus triggers action potential or not at all
- 132Action potential propagationgenerated action potential does not itself move along axon
once generate at initial segment the action potential is regenerated at each adjacent axonal segment - 133Propagationonce generate at initial segment the action potential is regenerated at each adjacent axonal segment
not conduction - 134Two types of action potential propagationContinuous and
saltatory propagation - 135Continuous propagationoccurs along unmyelinated axons
move in series of tiny steps
propagation speed 1m/s - 136Steps of continous prpagation1. action potential develops at initial segment
2. na spreads away from voltage-gated channels
3. action potential occurs in adjacent segments (initial segment repolarizes)
4. na enters spreads to new segment - 137Action potential can onlymove forward because last axonal segment is in absolute refractory period
- 138Salatory propagationmyelinated axons
only exposed nodes can respond to depolarizing stimulus
must faster - 139Salatory prpagation speaddepends on axon diameter
large axon = faster current - 140internodesprevent ion flow across membrane
prevents continuous propagation - 141Saltatory propagation steps1. action potential occurs at initial segment
2. local current produces graded depolarization to threshold at next node
3. action potential develops at node
4. local current flow produces graded depolarization to threshold at next node - 142Synaptic events-transmission of message within a neuron
-transfer of message between cells - 143Types of synapsesChemical
Electrical - 144Chemical Synapsesrely on neurotransmitter release
most abundant - 145chemical synapses most abundantmost between neurons
all between neurons and other cells - 146Chemical synapses that release AChCholinergic synapses
- 147Events at cholinergic synapse1. depolarization of synaptic knob by arriving action potential
2. opening of voltage-gate ca
3. ACh diffuses and binds to chemically gated Na
4. ACh enzyme breaks down ACh - 148Opening of voltage-gated calcium channelsinflux of Ca cause exocytosis of ACh from synaptic vesicles
ca quickly removed to end release of ACh - 149na diffuses into post synaptic cell and depolarizes membraneMore ACh bound= larger depolarization
- 150Break down of ACh20msec
- 151Chemical synapse physiologySynaptic fatigue
Synaptic delay - 152Synaptic fatigueextended stimulation: recycling of neurotransmitter unable to keep up with demand
weakens synapse (until neurotrnasmitter can be replensihed - 153Synaptic delayrelease and bind of neurotransmitter takes 0.2 to 0.5 msec
cumulative delay may be significant
rapid reflexes involve few synapses - 154Postsynaptic potentialsgraded potentials in postsynaptic cell in response to neurotransmitter
- 155Two types of Postsynaptic potentialsexcitatory Postsynaptic potentials
Inhibitory Postsynaptic potentials - 156excitatory Postsynaptic potentialsgraded depolarization caused by neurotransmitter
shifts tranmembrane potential to threshold (facilitated) - 157excitatory Postsynaptic potentials facilitaedmore facilitation = less additional stimulus needed to reach threshold
- 158inhibitoryPostsynaptic potentialsgrated hyperpolarization
shifts transmembrane potential farther from threshold (inhibited) - 159inhibitory Postsynaptic potentials exampleopening of chemically gated K channels
- 160More inhibitationlarger than usual stimulus needed to reach threshold
- 161SummationIntegration of graded potential effects on plasma membrane segment
- 162Summation may be combiningopposite stimulations
EPSP + IPSP
or similar stimulations ESPS + EPSP - 163Summation individual EPSP or IPSPsmall effect on transmembrane potential (.5mV)
- 164Summation of EPSP canlead to action potential
Threshold commonly 10mV - 165Two types of summationTemporary
and
Spatial - 166Temporal Summationsingle synapse stimulated repeatedly
- 167Example temporal summationbefore effects of one EPSP can dissipate another arrives
more ACh release= more postsynaptic cell depolarization
possibly to threshold at initial segment - 168Spatial summationinvolves multiple synapses activated simultaneously
- 169spacial summation exampleEPSP at multiple sites alling Na channels to open
may lead to action potential at initial segment - 170Spatial summation degree of depolarization dependent on1. number of synanpses activates at particular moment
2. distance from initial segment - 171Higher level information processinginvolves regulatory neurons
- 172regulatory neuronsfacilitate or inhibit synaptic neurons by
affecting cell body membrane or
altering sensitivity of synaptic knobs - 173Higher level information processing involvesdifferent neurotransmitters
more than 100 exist and work in different ways - 174neurotransmitters may havedirect or indirect effects on ion channels
- 175Indirect effects of neurotransmittersinvolve G proteins
trigger formation or release of second messengers - 176In nervous system, complex information processing is translated toaction potential
solely on frequency of action potential
example: muscle contraction changes in response to increasing action potential frequency
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- Flashcards on Nerval Tissue, created by E A on 19/11/2013.
- Created by
- E A · Nov 2013
- Updated
- Feb 19, 2016
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