Chapter 8 The Nervous System. Organization of nervous system Central Nervous System Central Nervous System Peripheral Nervous System Peripheral Nervous.
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Chapter 8Chapter 8
The Nervous System
Organization of nervous Organization of nervous systemsystem
Central Nervous SystemCentral Nervous System
Peripheral Nervous Peripheral Nervous SystemSystem
Integration of CNS and PNSIntegration of CNS and PNS
The Neuron is theThe Neuron is the
Functional unit of the nervous systemFunctional unit of the nervous system
The “model” neuron
Peripheral Nervous SystemPeripheral Nervous System
Afferent NeuronsAfferent Neurons
Sensory Receptors send information to Sensory Receptors send information to CNSCNS
Efferent NeuronsEfferent Neurons Carry information to effector cells of the bodyCarry information to effector cells of the body
PNS is divided intoPNS is divided into
1. Autonomic Division1. Autonomic Division
– Sympathetic branchSympathetic branch
– Parasysmpathetic branchParasysmpathetic branch
PNS is divided intoPNS is divided into
2. 2. Somatic Motor divisionSomatic Motor division
– Controls skeletal muscleControls skeletal muscle
PNS divided into PNS divided into
3. Enteric division3. Enteric division
Glial cells of the PNSGlial cells of the PNS
Schwann CellsSchwann Cells Satellite CellsSatellite Cells
The PNS and Schwann CellThe PNS and Schwann Cell
Nodes of Ranvier: Are not Nodes of Ranvier: Are not covered by myelincovered by myelin
Central Nervous SystemCentral Nervous System
Glial cells of CNSGlial cells of CNS
AstrocytesAstrocytes– NutritionNutrition
EpendymalEpendymal– barrierbarrier
MicrogiliaMicrogilia– ImmuneImmune
OligodendrocyteOligodendrocytess– MyelinMyelin
An overview of glial cellsAn overview of glial cells
Remember the neuron… Remember the neuron…
Communicates information Communicates information throughout the body, but how?throughout the body, but how?
Another picture of vertebrate Another picture of vertebrate neuronneuron
By Action Potentials!By Action Potentials!
Action Potentials Action Potentials areare our our nerve impulses. nerve impulses.
It’s all to do with communication.
We can look at an action We can look at an action potential as an electrical potential as an electrical
event.event.
First we remember First we remember howhow ions ions influence the membrane influence the membrane potential (Em) of a cell.potential (Em) of a cell.
K+
Large non-diffusible anionic proteins
Is the charge across this cell zero?
K+
Chemical gradient
Electrical Force
Permeable only to K+
Volt meter
No! No!
It is –90 mV! Why?It is –90 mV! Why?
Now let’s try to think about a Now let’s try to think about a living excitable cell…living excitable cell…
Resting Neuron Membrane Resting Neuron Membrane PotentialPotential
Volt meter
Now what does the volt meter read?
-70 mV at rest -70 mV at rest butbut the Em the Em can change when a nerve is can change when a nerve is
“excited”.“excited”.
But why do we care about But why do we care about these values?these values?
A change in Em results in NT A change in Em results in NT release!release!
But But howhow does this change does this change in charge occur so that the in charge occur so that the neurotransmitter neurotransmitter cancan be be
released?released?
A simple flow chart of electrical A simple flow chart of electrical eventsevents
Graded potentialsGraded potentials
Action potentialsAction potentials
Neurotransmitter releaseNeurotransmitter release
Graded potentials decrease in Graded potentials decrease in strength as they spread out from the strength as they spread out from the
point of originpoint of originbut may bring about an action but may bring about an action
potential.potential.
The end of Part 1
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