NEURONS (TYPES OF NEURONS)

Sensory Neurons – picks up the stimuli (nerve impulse) and carries it to the spinal cord and brain.Interneurons- Found within the brain and spinal cord. Relays the message between the sensory neurons and the motor neurons. Motor Neurons – transfers impulses away from the brain to the spinal cord

1. Impulse Conduction In Impulse Conduction In
NeuronsNeurons
By : Gaurav PandeyBy : Gaurav Pandey

3. NeuronNeuron
”Nerve Cell””Nerve Cell”
Functional Unit of Nervous SystemFunctional Unit of Nervous System
1.1.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
1.1.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..

4. 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.

6. 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 – transfers impulses
away from the brain to the spinal cordaway from the brain to the spinal cord

7. How Neurons WorkHow Neurons Work
1.1.Reception Reception
Receptors in the skin sense stimuliReceptors in the skin sense stimuli
1.1.Transmission Transmission
Sensory neurons transmit the touch messageSensory neurons transmit the touch message
1.1.Data InterpretationData Interpretation
Information is sorted and interpretedInformation is sorted and interpreted
1.1.TransmissionTransmission
Motor Neurons transmit a response message to a Motor Neurons transmit a response message to a
musclemuscle
1.1.ResponseResponse
Muscles are activated causing a responseMuscles are activated causing a response

8. 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 membrane
NaNa
++
Higher Conc Outside Higher Conc Outside
KK
++
Higher Conc Inside Higher Conc Inside
Remember NaRemember Na
++
/K/K
++
ATPase Pump ATPase Pump

9. Sodium Potassium PumpSodium Potassium Pump

10. 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

11. 1. Resting State1. Resting State
A neuron is not conducting an impulseA neuron is not conducting an impulse
The K+ concentration is much higher The K+ concentration is much higher
inside the cell than outinside the cell than out
The Na+ concentration is much higher The Na+ concentration is much higher
outside the cell than inoutside the cell than in

12. 2. Depolarization2. Depolarization
A nerve cell is stimulatedA nerve cell is stimulated
Membrane 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.

13. 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.

14. 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

15. 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 cell
2.2.Inhibit the action potential in the next cellInhibit the action potential in the next cell

16. 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

18. ElaborationElaboration
Neurotransmission: Neurotransmission:
Nifty Neurons and Muscle MessagesNifty Neurons and Muscle Messages

19. EvaluationEvaluation
Parts 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

20. THANK YOUTHANK YOU