Dr. Norris tries to explain the nervous system…. The OLLI Version

Anatomy (Construction) Physiology (Function)

CNS PNS OUT IN

CNSPNS Afferent (in coming) Efferent (out going)

Sensor Sensory input Motor output Integration Effector Peripheral nervous system (PNS) Central nervous system (CNS)

Neuron

Cell body Axon Dendrites

Neuron Direction of signal

Neuron 3 types of Neurons

Sensory Neuron

Association Neuron

Motor Neuron

Sensor Sensory input Motor output Integration Effector Peripheral nervous system (PNS) Central nervous system (CNS)

Nervous Systems

Nerve net A little more concentration

The vertebrate way

A Physiology (Function)

The Action Potential

Cell Membrane

Membrane with gates

Microelectrode Reference electrode Voltage recorder –70 mV Electrical potential across the membrane

OUTSIDE INSIDE Resting State Cell membrane neuron

Potassium channel Plasma membrane Na + Inactivation gate Activation gates Sodium channel K+K+ Resting State OUTSIDE INSIDE

Na + K+K+ Depolarization OUTSIDE INSIDE

Na + K+K+ Rising phase of the action potential OUTSIDE INSIDE

Na + K+K+ Falling phase of the action potential OUTSIDE INSIDE

An action potential is propagated

An action potential is generated as Na + flows inward across the membrane at one location. Na + Action potential Na + Action potential K+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. K+K+ Na + Action potential K+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. K+K+

The Action Potential

Vertebrate Neuron

Invertebrate Neuron – No myelin sheath

Cell body Schwann cell Depolarized region (node of Ranvier) Myelin sheath Axon Action potential propagation down the axon Saltatory conduction

VertebrateInvertebrate

Vertebrate Allows for very rapid transmission of action potential Saltatory conduction

Escape Neurons or Giant axons

Earthworm in cross-section Nerve cord

Earthworm nerve cord Giant escape axons

Myelinated neuron Schwann cells

Multiple sclerosis

Passing the signal on – The Synapse

Synaptic vesicles containing neurotransmitter Presynaptic membrane Voltage-gated Ca 2+ channel Ca 2+ Postsynaptic membrane Ligand-gated ion channels Synaptic cleft Action potential

Postsynaptic membrane Neuro- transmitter Ligand- gated ion channel Na + K+K+ Ca 2+

Major Neurotransmitters

Muscle Contraction

Ca 2+ Stopping the signal e.g., Cholinesterase (enzyme)

Playing with neurotransmitters

NeurotransmittersPrecursor

NeurotransmitterMimic

Adding a little extra

Playing with neurotransmitters

Cholinesterase Inhibition Pesticides

Transmission that doesn’t stop

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PRECAUTIONS KEEP OUT OF REACH OF CHILDREN IN CASE OF ACCIDENT CALL A DOCTOR MAY BE FATAL IF SWALLOWED May be absorbed through skin. May be irritant to the eyes and skin. Avoid contact with eyes and skin. Do not wear contaminated clothing until thoroughly washed. Wash thoroughly after handling. Keep away from food, feedstuffs and water supplies. PRECAUTIONS FOR MIXERS/LOADERS Mixers/loaders must wear: coveralls over a long-sleeved shirt and long pants chemical-resistant gloves chemical-resistant footwear and socks an air purifying respirator equipped with an -R or -P series filter a chemical-resistant apron PRECAUTIONS FOR APPLICATORS Do not apply with high-pressure handwand equipment. Applicators using ground application equipment with a closed cab must wear: a long-sleeved shirt and long pants chemical-resistant gloves when leaving cab for clean-up and repair (gloves must be removed and left outside when re-entering the cab) socks and shoes Applicators using ground application equipment with an open cab must wear: coveralls over a long-sleeved shirt and long pants chemical-resistant gloves socks and shoes Applicators using aerial application equipment must use enclosed cockpits and must wear: a long-sleeved shirt and long pants Dursban material safety sheet

Integration

Major Neurotransmitters Excitatory Inhibitory

Excitatory Inhibitory Stimulate action potential at site of application Inhibit action potential at site of application

An action potential is generated as Na + flows inward across the membrane at one location. Na + Action potential Na + Action potential K+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. K+K+ Na + Action potential K+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. K+K+ Inhibition Stronger stimulatory signals are needed to initiate action potential and keep it moving

Never this simple......

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The big picture Excitatory Inhibitory

To fire or not to fire Axon hillock

All or nothing