Psychology 210 Cellular Anatomy Lecture 2. Cells of the Nervous System Neurons Neurons Information...
-
Upload
samson-richards -
Category
Documents
-
view
218 -
download
0
Transcript of Psychology 210 Cellular Anatomy Lecture 2. Cells of the Nervous System Neurons Neurons Information...
Psychology 210Psychology 210
Cellular Anatomy Cellular Anatomy
Lecture 2Lecture 2
Cells of the Nervous Cells of the Nervous SystemSystem
NeuronsNeurons Information processing and Information processing and
communicating nerve cellscommunicating nerve cells GliaGlia
Addressed laterAddressed later
What do you know about What do you know about neurons coming into this neurons coming into this
class?class? How does a neuron communicate How does a neuron communicate
with another neuron?with another neuron? What type of signal is processed in a What type of signal is processed in a
neuron?neuron? What are the parts of a neuron?What are the parts of a neuron?
Parts of a NeuronParts of a Neuron 3 main parts3 main parts
DendritesDendrites Receive Receive
informationinformation Soma (cell body)Soma (cell body)
Cellular Cellular maintenancemaintenance
AxonAxon Transmits Transmits
informationinformation
DendritesDendrites
Tree like processesTree like processes Receives information from other Receives information from other
neuronsneurons Dendritic spinesDendritic spines
Create more area for axons to transmit Create more area for axons to transmit informationinformation
Change depending on the amount of activityChange depending on the amount of activity This is one of the suggested bases for learning This is one of the suggested bases for learning
and memoryand memory A neuron can have multiple dendritesA neuron can have multiple dendrites
The somaThe soma
Nucleus- contains DNANucleus- contains DNA Nucleolus- constructs Nucleolus- constructs
ribosomesribosomes Endoplasmic reticulum- Endoplasmic reticulum-
contains ribosomes that contains ribosomes that construct proteinsconstruct proteins
Golgi apparatus- Golgi apparatus- “packages” proteins“packages” proteins
Mitochondria- produces Mitochondria- produces energyenergy
The AxonThe Axon Transmits information Transmits information
to other neuronsto other neurons Myelin sheath Myelin sheath
insulation that aids in insulation that aids in the speed of the neural the speed of the neural transmissiontransmission
Axon terminalAxon terminal End of the axon End of the axon Contains Contains
neurotransmittersneurotransmitters Also called terminal Also called terminal
buttonsbuttons
More on the AxonMore on the Axon
Axon hillockAxon hillock Where the Where the
action action potential potential beginsbegins
Nodes of Nodes of RanvierRanvier Segments of bare Segments of bare
axon not covered axon not covered by myelinby myelin
Giant SquidGiant Squid Used to study Used to study
axons in the axons in the 1930s-1940s1930s-1940s
Extra large Extra large axon visible axon visible to the eyeto the eye
Doesn’t have Doesn’t have myelin, so it myelin, so it is extra large is extra large to add to add conductanceconductance
Characterization of Characterization of neuronsneurons
Sensory neuronsSensory neurons Translates incoming sensory Translates incoming sensory
information into an electrical information into an electrical signalsignal
Afferent NeuronsAfferent Neurons Conduct information towards Conduct information towards
the brain from the muscles and the brain from the muscles and sensessenses
InterneuronsInterneurons Neurons in the spinal cord and Neurons in the spinal cord and
the brain that both the brain that both communicate a signal and communicate a signal and process that signal process that signal
Efferent NeuronsEfferent Neurons Conduct information away Conduct information away
from the brain to the muscles from the brain to the muscles and sensesand senses
Motor NeuronsMotor Neurons Translates electrical signal to Translates electrical signal to
the muscles and glandsthe muscles and glands
Not all neurons look the Not all neurons look the samesame
Named by the number Named by the number of extensions from the of extensions from the cell bodycell body
UnipolarUnipolar One extension that One extension that
branches into branches into dendrites and an axondendrites and an axon
BipolarBipolar Two extensions: one Two extensions: one
axon and one dendriteaxon and one dendrite MultipolarMultipolar
Many extensions: one Many extensions: one axon, many dendritesaxon, many dendrites
Unipolar NeuronsUnipolar Neurons
Found primarily in Found primarily in human embryos human embryos and invertebratesand invertebrates
Sensory neurons Sensory neurons that conduct that conduct impulses into the impulses into the brainbrain
Bipolar NeuronsBipolar Neurons
Found primarily as Found primarily as sensory neurons in sensory neurons in vision, audition vision, audition and olfactionand olfaction
Multipolar neuronsMultipolar neurons
Found everywhere Found everywhere elseelse BrainBrain Peripheral Peripheral
autonomic nervous autonomic nervous systemsystem
Spinal cordSpinal cord
What happens in a nerveWhat happens in a nerve
Neurons communicate information to Neurons communicate information to other neuronsother neurons
The signal itself is an electrical signal The signal itself is an electrical signal within the neuron within the neuron Action PotentialAction Potential
From neuron to neuron, communication From neuron to neuron, communication is chemicalis chemical
The Resting PotentialThe Resting Potential Two forces at work Two forces at work
in a neuronin a neuron Force 1: Force 1:
Equilibrium: the Equilibrium: the idea that the idea that the concentration of a concentration of a molecule tries to molecule tries to remain constant remain constant throughout the throughout the medium medium (substance)(substance)
Potassium Ions
The Resting PotentialThe Resting Potential
Ex. Smells: the garbage begins to Ex. Smells: the garbage begins to smell in one spot, but the smell smell in one spot, but the smell slowly expands throughout the slowly expands throughout the househouse The smell gets lighter and lighter as it The smell gets lighter and lighter as it
expands throughout the houseexpands throughout the house It tries to spread out as evenly as It tries to spread out as evenly as
possiblepossible
Status of the main Status of the main players (ions)players (ions)
Sodium (NaSodium (Na++): more of it outside of ): more of it outside of the neuronthe neuron
Potassium (KPotassium (K++): more of it inside of ): more of it inside of the neuronthe neuron
Chloride (ClChloride (Cl--): more of it outside of ): more of it outside of the neuronthe neuron
Based on equilibrium…Based on equilibrium…
What does NaWhat does Na++, K, K++, and Cl, and Cl-- want to want to do? Are they “happy” where they do? Are they “happy” where they are?are?
What direction will they move if What direction will they move if allowed?allowed?
Due to equilibrium…Due to equilibrium… NaNa++ wants to move inside the neuron wants to move inside the neuron KK++ wants to move outside the neuron wants to move outside the neuron ClCl-- wants to move inside the neuron wants to move inside the neuron
What about charge?What about charge?
Does charge play a role in things?Does charge play a role in things? According to charge, how might the According to charge, how might the
ions react?ions react?
How do charges react to How do charges react to each other?each other?
Opposites attractOpposites attract Like charges repelLike charges repel
One more piece to the One more piece to the puzzlepuzzle
There are large molecules inside the There are large molecules inside the neuron with negative chargesneuron with negative charges
Now which way do the ions Now which way do the ions want to go?want to go?
Potassium:Potassium: Which way does equilibrium push?Which way does equilibrium push? What about the charge?What about the charge?
Now which way do the ions Now which way do the ions want to go?want to go?
Chloride:Chloride: Which way does equilibrium push?Which way does equilibrium push? What about the charge?What about the charge?
Now which way do the ions Now which way do the ions want to go?want to go?
Sodium:Sodium: Which way does equilibrium push?Which way does equilibrium push? What about the charge?What about the charge?
At restAt rest Resting potentialResting potential
-70mV-70mV Potassium can cross the membranePotassium can cross the membrane Sodium and Chloride cannot cross the Sodium and Chloride cannot cross the
membranemembrane
What will potassium want to do at rest?
StimulationStimulation
When When stimulated stimulated by another by another neuron, neuron, some Nasome Na++ channels channels are openedare opened
KK++ channels channels closeclose
The action potentialThe action potential
If the signal is If the signal is strong enough, strong enough, it makes it to it makes it to the axon hillock the axon hillock
If strong If strong enough, an enough, an action potential action potential is generatedis generated ThresholdThreshold Begins an action Begins an action
potentialpotential
The action potentialThe action potential
DepolarizationDepolarization: occurs when : occurs when NaNa++ flows into flows into the cellthe cell Due to NaDue to Na++
channels channels openingopening
The action potentialThe action potentialAt the beginning of the AP, Na channels open and Na enters the cell
Now, there is more of a positive charge inside than outside (the Na stops coming in for the same reasons the K did originally, a balance of two forces) this represents the peak of the AP
How’s potassium feeling How’s potassium feeling now?now?
Sodium moving Sodium moving inside the cell inside the cell made the inside made the inside of the cell more of the cell more positivepositive
This repels This repels potassium to potassium to move outsidemove outside
The action potentialThe action potential
K+ channels open at the peak and K+ K+ channels open at the peak and K+ flows out of the cellflows out of the cell
This repolarizes the cell and even This repolarizes the cell and even overshoots the resting potential of beforeovershoots the resting potential of before Called hyperpolarizationCalled hyperpolarization
Then the Na/K pump brings the K back Then the Na/K pump brings the K back inside the cell and the Na back outside inside the cell and the Na back outside the cellthe cell 2 K for every 3 Na2 K for every 3 Na Uses energy (ATP)Uses energy (ATP)
The action potentialThe action potentialAt the peak, K+ channels open and K+ exits the cell
Conditions are now back where they started in terms of potential and charge, but the ions are in opposite positions
The action potentialThe action potential The Sodium The Sodium
Potassium pump Potassium pump restores the restores the original original environment of environment of the resting the resting potential so that potential so that the neuron can the neuron can fire yet againfire yet again
This is known as This is known as the refractory the refractory periodperiod
Graded PotentialsGraded Potentials Action Potentials are Action Potentials are
referred to as “all-or-none”referred to as “all-or-none” Either get an action potential Either get an action potential
or notor not Inputs that don’t reach Inputs that don’t reach
threshold: Graded Potentialsthreshold: Graded Potentials Can add up across Can add up across
synapses/inputs to reach synapses/inputs to reach thresholdthreshold
Saltatory ConductionSaltatory Conduction Insulation is not perfectInsulation is not perfect
Signal loses strength down the axonSignal loses strength down the axon Regeneration of the Action Potential occurs at Regeneration of the Action Potential occurs at
each break in the myelineach break in the myelin
At the Axon TerminalAt the Axon Terminal Vesicles containing Vesicles containing
neurotransmitters are neurotransmitters are presentpresent
When an action When an action potential reaches the potential reaches the axon terminal, Caaxon terminal, Ca2+2+ channels open up and channels open up and this causes the fusing of this causes the fusing of the vesicles to the the vesicles to the membrane and the membrane and the release of the release of the neurotransmitters into neurotransmitters into the synaptic cleftthe synaptic cleft
In the Synaptic CleftIn the Synaptic Cleft Neurotransmitters cross the Neurotransmitters cross the
membrane and bind to membrane and bind to receptors on the receiving receptors on the receiving neuronneuron
Depending on the Depending on the neurotransmitter, it can neurotransmitter, it can either excite or inhibit the either excite or inhibit the post-synaptic neuronpost-synaptic neuron
Excitatory Postsynaptic Excitatory Postsynaptic Potential (EPSP)- the Potential (EPSP)- the excitation of the receiving excitation of the receiving neuronneuron
Inhibitory Postsynaptic Inhibitory Postsynaptic Potential (IPSP)- the Potential (IPSP)- the inhibition of the receiving inhibition of the receiving neuronneuron
NeurotransmittersNeurotransmitters
Various chemicalsVarious chemicals Can either excite the receiving Can either excite the receiving
neuron or inhibit itneuron or inhibit it Acetylcholine- an excitatory NT Acetylcholine- an excitatory NT
typically found in the musclestypically found in the muscles GABA- an inhibitory NT typically GABA- an inhibitory NT typically
found elsewhere in the nervous found elsewhere in the nervous systemsystem
How transmission occursHow transmission occurs
Multiple synapses on each neuronal Multiple synapses on each neuronal dendritedendrite
Some can excite while others inhibitSome can excite while others inhibit Axon potentials can be created by Axon potentials can be created by
multiple EPSPs from multiple multiple EPSPs from multiple neuronsneurons
Called Spatial SummationCalled Spatial Summation
How transmission occursHow transmission occurs
One synapse can fire repeatedly on One synapse can fire repeatedly on the same dendrite within a short the same dendrite within a short temporal window (time period)temporal window (time period)
Axon potentials can be created by Axon potentials can be created by multiple EPSPs from a single neuronmultiple EPSPs from a single neuron
Called Temporal SummationCalled Temporal Summation
Summary: One last thingSummary: One last thing
Transmission within the neuron is Transmission within the neuron is electricelectric Via action potentialsVia action potentials
Transmission between neurons is Transmission between neurons is chemicalchemical Via neurotransmittersVia neurotransmitters
Glial cellsGlial cells Astrocytes- Astrocytes-
structural support structural support and blood brain and blood brain barrierbarrier
Oligodendrocytes- Oligodendrocytes- myelination of myelination of axons CNSaxons CNS
Schwann cells- Schwann cells- myelination of myelination of axons PNSaxons PNS
Microglia- clean upMicroglia- clean up