Your Nervous SystemYour Nervous System

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Lorenzo’s Oil DiscussionLorenzo’s Oil Discussion

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Quick CommunicationsQuick CommunicationsNeuron ModelsNeuron Models

ExplainExplainNervous SystemNervous System

Four Major Parts of the Nervous SystemFour Major Parts of the Nervous System NeuronsNeurons NervesNerves BrainBrain Spinal CordSpinal Cord

Two Major Nervous SystemTwo Major Nervous System

CentralCentral Nervous System Nervous System PeripheralPeripheral Nervous System Nervous System

Nerves and Neurons are found in both and Nerves and Neurons are found in both and this is where we will beginthis is where we will begin

NeuronNeuron”Nerve Cell””Nerve Cell”

Functional Unit of Nervous SystemFunctional Unit of Nervous System1.1. Cell BodyCell Body – center part of the cell containing the – center part of the cell containing the

nucleusnucleus

2.2. DendritesDendrites Carries messages Carries messages towardtoward the cell body. the cell body. Fingerlike projections Fingerlike projections

3.3. AxonAxon Carries messages Carries messages awayaway from the cell body. from the cell body. Elongated extension of the cell body Elongated extension of the cell body End of the axon is divided into fingerlike projections called End of the axon is divided into fingerlike projections called

axon terminalsaxon terminals..

Neuron ModelNeuron Model

To check for understanding you will need To check for understanding you will need to construct a neuron model that contains to construct a neuron model that contains dendrites, a cell body (soma), axon, and dendrites, a cell body (soma), axon, and axon terminals.axon terminals.

Types of NeuronsTypes of Neurons

Sensory NeuronsSensory Neurons – picks up the stimuli – picks up the stimuli (nerve impulse) and carries it to the spinal (nerve impulse) and carries it to the spinal cord and brain.cord and brain.

Interneurons-Interneurons- Found within the brain and Found within the brain and spinal cord. Relays the message between spinal cord. Relays the message between the sensory neurons and the motor the sensory neurons and the motor neurons. neurons.

Motor NeuronsMotor Neurons – transfers impulses away – transfers impulses away from the brain to the spinal cordfrom the brain to the spinal cord

How Neurons WorkHow Neurons Work

1.1. Reception Reception Receptors in the skin sense stimuliReceptors in the skin sense stimuli

2.2. Transmission Transmission Sensory neurons transmit the touch messageSensory neurons transmit the touch message

3.3. Data InterpretationData Interpretation Information is sorted and interpretedInformation is sorted and interpreted

4.4. TransmissionTransmission Motor Neurons transmit a response message to a Motor Neurons transmit a response message to a

musclemuscle

5.5. ResponseResponse Muscles are activated causing a responseMuscles are activated causing a response

Impulse TransmissionImpulse Transmission

Start with a RESTING neuron – one NOT Start with a RESTING neuron – one NOT transmitting an impulsetransmitting an impulse

Plasma membrane controls [ ] of ions Plasma membrane controls [ ] of ions inside the cellinside the cell

NaNa++ and K and K++ on both sides of membrane on both sides of membraneNaNa++ Higher Conc Outside Higher Conc OutsideKK++ Higher Conc Inside Higher Conc InsideRemember NaRemember Na++/K/K++ ATPase Pump ATPase Pump

Sodium Potassium PumpSodium Potassium Pump

How an Impulse TravelsHow an Impulse Travels

Stimulus excites a neuronStimulus excites a neuron Na+ channels open, Na+ Na+ channels open, Na+

build up insidebuild up inside Inside more + that outsideInside more + that outside Change in charge Change in charge

(depolarization)(depolarization) Membrane immediately Membrane immediately

behind depolarization returns behind depolarization returns to RESTING STATEto RESTING STATE

RESTING STATE – inside RESTING STATE – inside negative, outside positivenegative, outside positive

1. Resting State1. Resting State

A neuron is not conducting an impulseA neuron is not conducting an impulseThe K+ concentration is much higher The K+ concentration is much higher

inside the cell than outinside the cell than outThe Na+ concentration is much higher The Na+ concentration is much higher

outside the cell than inoutside the cell than in

2. Depolarization2. Depolarization

A nerve cell is stimulatedA nerve cell is stimulatedMembrane becomes permeable to Na+ for Membrane becomes permeable to Na+ for

an instant and they quickly move into the an instant and they quickly move into the cellcell

The inner surface of the cell membrane is The inner surface of the cell membrane is now more positively charged then the now more positively charged then the outside.outside.

3. Repolarization3. Repolarization

When the cell membrane becomes When the cell membrane becomes depolarized, K+ automatically leaves the depolarized, K+ automatically leaves the cell until the cell is back to its resting state.cell until the cell is back to its resting state.

4. The Impulse Travels4. The Impulse Travels

““Wave” of depolarization – transmission of an Wave” of depolarization – transmission of an impulse along length of axonimpulse along length of axon

All or None PrincipleAll or None Principle – must reach a threshold – must reach a threshold level or the impulse dieslevel or the impulse dies

Covered by a white covering called a Covered by a white covering called a myelin myelin sheath (Schwann Cells)sheath (Schwann Cells), an insulator, an insulator

Myelin sheath causes the ion exchange to occur Myelin sheath causes the ion exchange to occur only at the only at the nodesnodes which speeds up the process which speeds up the process

For a short time after depolarization; the neuron For a short time after depolarization; the neuron cannot be stimulated cannot be stimulated

5. Transmission Across a Synapse5. Transmission Across a Synapse

Neurons do not actually touch. This gap Neurons do not actually touch. This gap between the two cells is call a between the two cells is call a SYNAPSESYNAPSE

Impulses are carried across a synapse by Impulses are carried across a synapse by chemical messengers called chemical messengers called neurotransmitters.neurotransmitters.

Approximately 30 different neurotransmitters; Approximately 30 different neurotransmitters; do one of two things: do one of two things:

1.1. Stimulate the action potential in a second cellStimulate the action potential in a second cell2.2. Inhibit the action potential in the next cellInhibit the action potential in the next cell

6. Refractory Period6. Refractory Period

The period of time it takes a neuron to The period of time it takes a neuron to return to its resting potential after being return to its resting potential after being stimulatedstimulated

A neuron cannot be stimulated during this A neuron cannot be stimulated during this periodperiod

This period of time is about 0.0004 of a This period of time is about 0.0004 of a secondsecond

ElaborationElaboration

Neurotransmission: Neurotransmission:

Nifty Neurons and Muscle MessagesNifty Neurons and Muscle Messages

EvaluationEvaluationParts of Nervous SystemParts of Nervous System

List the Four Major Parts of the List the Four Major Parts of the Nervous SystemNervous System

NeuronsNeurons NervesNerves BrainBrain Spinal CordSpinal Cord