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Dr. Norris tries to explain the nervous system…. The OLLI Version. Anatomy (Construction). Physiology (Function). CNS. PNS. OUT. IN. CNS. PNS. Afferent (in coming). Efferent (out going). Sensory input. Sensor. Integration. Motor output. Effector. Central nervous system (CNS).
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Dr. Norris tries to explain the nervous system…. The OLLI Version
Anatomy (Construction) Physiology (Function)
CNS PNS OUT IN
CNS PNS Afferent (in coming) Efferent (out going)
Sensory input Sensor Integration Motor output Effector Central nervous system (CNS) Peripheral nervous system (PNS)
Dendrites Cell body Axon Neuron
Direction of signal Neuron
Neuron 3 types of Neurons
Sensory input Sensor Integration Motor output Effector Central nervous system (CNS) Peripheral nervous system (PNS)
Nerve net A little more concentration
Electrical potential across the membrane Microelectrode –70 mV Voltage recorder Reference electrode
Resting State OUTSIDE + + + + + + + + + + + + + + + + + + + + + + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - INSIDE Cell membrane neuron
Resting State Potassium channel Activation gates OUTSIDE Na+ Plasma membrane INSIDE Sodium channel Inactivation gate K+
Depolarization OUTSIDE Na+ Na+ K+ INSIDE
Rising phase of the action potential OUTSIDE Na+ Na+ K+ INSIDE
Falling phase of the action potential OUTSIDE Na+ Na+ K+ INSIDE
Action potential Na+ An action potential is generated as Na+ flows inward across the membrane at one location. Action potential K+ Na+ K+ The depolarization of the action potential spreads to the neighboring region of the membrane, re-initiating the action potential there. To the left of this region, the membrane is repolarizing as K+ flows outward. Action potential K+ Na+ K+ The depolarization-repolarization process is repeated in the next region of the membrane. In this way, local currents of ions across the plasma membrane cause the action potential to be propagated along the length of the axon.
Action potential propagation down the axon Schwann cell Depolarized region (node of Ranvier) Cell body Myelin sheath Axon Saltatory conduction
Invertebrate Vertebrate
Saltatory conduction Allows for very rapid transmission of action potential Vertebrate
Earthworm in cross-section Nerve cord
Earthworm nerve cord Giant escape axons
Myelinated neuron Schwann cells
Synaptic vesicles containing neurotransmitter Presynaptic membrane Voltage-gated Ca2+ channel Postsynaptic membrane Ca2+ Synaptic cleft Ligand-gated ion channels Action potential
Na+ Neuro- transmitter K+ Postsynaptic membrane Ligand- gated ion channel Ca2+
Ca2+ Stopping the signal e.g., Cholinesterase (enzyme)
Precursor Neurotransmitters
Neurotransmitter Mimic