Unit 3:Unit 3:

Biological Biological Bases Bases

of Behaviorof Behavior3-A (The Neuron)3-A (The Neuron)Mr. DebesMr. Debes

A.P. PsychologyA.P. Psychology

The NeuronThe Neuron Neuron:Neuron:

Nerve cellNerve cell Basic building block of the nervous systemBasic building block of the nervous system

The NeuronThe Neuron Types of NeuronsTypes of Neurons

Sensory Neurons:Sensory Neurons: Carry incoming information from sensory Carry incoming information from sensory

receptors to the brain/spinal cord; e.g. Perceiving receptors to the brain/spinal cord; e.g. Perceiving something as “hot”something as “hot”

Motor Neurons:Motor Neurons: Carry outgoing information from the brain/spinal Carry outgoing information from the brain/spinal

cord to the muscles/glands; e.g. Clenching a fistcord to the muscles/glands; e.g. Clenching a fist Interneurons:Interneurons:

Located within the brain/spinal cordLocated within the brain/spinal cord Communicate internally between sensory inputs Communicate internally between sensory inputs

and motor outputs; e.g. Reflexesand motor outputs; e.g. Reflexes

Parts of the NeuronParts of the Neuron Cell BodyCell Body

Cell’s life support centerCell’s life support center DendritesDendrites

Bushy extensions that receives messages from outside Bushy extensions that receives messages from outside & conducts impulses towards the cell body& conducts impulses towards the cell body

AxonAxon Fiber that extends from the neuron; it passes messages Fiber that extends from the neuron; it passes messages

through it’s branches to other neurons, muscles, and/or through it’s branches to other neurons, muscles, and/or glandsglands

Terminal branchesTerminal branches The ends of axon fibers, they form junctions with other The ends of axon fibers, they form junctions with other

cellscells Myelin SheathMyelin Sheath

Layer of fatty tissue that encases some axons to help Layer of fatty tissue that encases some axons to help speed neural impulsesspeed neural impulses

The Firing of a NeuronThe Firing of a NeuronResting Potential:Resting Potential:

When a neuron is not actively conducting When a neuron is not actively conducting an impulsean impulse

Difference in electrical charges on the Difference in electrical charges on the outside and inside of the cell membrane outside and inside of the cell membrane (positive charge outside & negative charge (positive charge outside & negative charge inside) inside)

This difference in charge is due to This difference in charge is due to different numbers of potassium ions (Kdifferent numbers of potassium ions (K++) ) and sodium ions (Naand sodium ions (Na++) on either side of the ) on either side of the membrane.membrane.

The Firing of a NeuronThe Firing of a NeuronSodium-potassium pump:Sodium-potassium pump:

Cellular mechanism that actively transports Cellular mechanism that actively transports (PUMPS) sodium ions outside the neuron’s (PUMPS) sodium ions outside the neuron’s cell bodycell body

Simultaneously transports (PUMPS) potassium Simultaneously transports (PUMPS) potassium ions into the neuron’s cell bodyions into the neuron’s cell body

3 sodium ions are pumped out for every 2 3 sodium ions are pumped out for every 2 potassium ions that are pumped inpotassium ions that are pumped in

This serves to keep the inside of the neuron This serves to keep the inside of the neuron negatively charged, compared to the outside negatively charged, compared to the outside (3 positive ions leave, 2 positive ions enter) (3 positive ions leave, 2 positive ions enter)

video

The Firing of a NeuronThe Firing of a Neuron Threshold: Level of stimulation required Threshold: Level of stimulation required

to trigger an action potential to trigger an action potential Neurons are constantly receiving hundreds of Neurons are constantly receiving hundreds of

signals from other neurons.signals from other neurons. Some signals are excitatory, some signals Some signals are excitatory, some signals

inhibitory inhibitory Excitatory signals “push the neuron’s Excitatory signals “push the neuron’s

accelerator,” while inhibitory signals “push the accelerator,” while inhibitory signals “push the neuron’s brakes.”neuron’s brakes.”

When the excitatory signals a neuron is When the excitatory signals a neuron is receiving exceeds the inhibitory signals by a receiving exceeds the inhibitory signals by a minimum intensity, the threshold has been minimum intensity, the threshold has been achieved and a brief change in the electrical achieved and a brief change in the electrical charge within the cell occurscharge within the cell occurs

The Firing of a NeuronThe Firing of a Neuron Action PotentialAction Potential

When the threshold is achieved, the electrical charge When the threshold is achieved, the electrical charge within the cell changes-Depolarization within the cell changes-Depolarization

Brief electrical charge that travels down an axonBrief electrical charge that travels down an axon As this action potential travels down the axon sections, As this action potential travels down the axon sections,

each axon section depolarizes in turn, further moving each axon section depolarizes in turn, further moving the action potential towards the axon terminals the action potential towards the axon terminals

““All-or-None”-action potential either occurs or does All-or-None”-action potential either occurs or does not. not.

Refractory periodRefractory period After the action potential fires, the neuron pumps After the action potential fires, the neuron pumps

positively charged sodium ions back out, preparing to positively charged sodium ions back out, preparing to fire again. The action potential/refractory period fire again. The action potential/refractory period process repeats hundreds (sometimes thousands) of process repeats hundreds (sometimes thousands) of times a secondtimes a second

The Firing of a NeuronThe Firing of a Neuron

The Firing of a NeuronThe Firing of a Neuron

The Firing of a NeuronThe Firing of a Neuron

The Firing of a NeuronThe Firing of a Neuron

The Firing of a NeuronThe Firing of a Neuron

The Firing of a NeuronThe Firing of a Neuron

The Firing of a NeuronThe Firing of a Neuron

ReviewReview What is a What is a neuronneuron??

Differentiate Differentiate between the between the 33 types of types of neuronsneurons:: Sensory NeuronsSensory Neurons Motor NeuronsMotor Neurons InterneuronsInterneurons

Discuss the Discuss the functionsfunctions of the following parts of the of the following parts of the neuronneuron:: DendritesDendrites AxonAxon Myelin SheathMyelin Sheath Terminal BranchesTerminal Branches

What causes What causes neuronsneurons to to firefire??

Neural CommunicationNeural Communication Action potential is the mechanism Action potential is the mechanism

for communication WITHIN a single for communication WITHIN a single neuronneuron

How do neurons communicate with How do neurons communicate with other neurons?other neurons?

Neural CommunicationNeural Communication Synapse: meeting point between neuronsSynapse: meeting point between neurons

When an action potential reaches the axis terminal, When an action potential reaches the axis terminal, there is no direct contact there is no direct contact

There is a gap of 1 millionth of an inch, known as There is a gap of 1 millionth of an inch, known as the synaptic gap or synaptic cleftthe synaptic gap or synaptic cleft

Neurotransmitters (NTs): chemical messengers Neurotransmitters (NTs): chemical messengers that communicate between neuronsthat communicate between neurons When an action potential reaches the axis terminal, When an action potential reaches the axis terminal,

it triggers the release of chemical messengersit triggers the release of chemical messengers These NTs cross the synaptic gap & unlock channels These NTs cross the synaptic gap & unlock channels

in the receiving neuron, allowing ions to flow in, in the receiving neuron, allowing ions to flow in, either exciting or inhibiting this neuron’s readiness either exciting or inhibiting this neuron’s readiness to fireto fire

Reuptake: reabsorption of NTsReuptake: reabsorption of NTs The sending neuron reabsorbs any excess NTsThe sending neuron reabsorbs any excess NTs

Neural CommunicationNeural Communication

Neural CommunicationNeural Communication

Neural CommunicationNeural Communication

Neural CommunicationNeural Communication

Neural CommunicationNeural Communication

How Neurotransmitters How Neurotransmitters influence usinfluence us Influence of NTsInfluence of NTs

Dozens of different kinds of NTs Dozens of different kinds of NTs Many different ways NTs can influence Many different ways NTs can influence

our hunger, thinking, depression, our hunger, thinking, depression, euphoria, addictions, therapy, motions, euphoria, addictions, therapy, motions, emotions, etcemotions, etc****This unit, we will focus on the influence NTs have This unit, we will focus on the influence NTs have on motions/emotions**on motions/emotions**

Altering NeurotransmissionAltering Neurotransmission Artificial influencesArtificial influences

NTs are produced INSIDE the bodyNTs are produced INSIDE the body Outside influences can impact brain Outside influences can impact brain

chemistry at the synapseschemistry at the synapses Drugs & other chemicalsDrugs & other chemicals

Altering NeurotransmissionAltering Neurotransmission AgonistAgonist

Molecules that are similar to NTsMolecules that are similar to NTs This similarity allows them to mimic it & bind This similarity allows them to mimic it & bind

to NT receptors in neurons, replicating it’s to NT receptors in neurons, replicating it’s affectaffect Opiate drugs are agonists and produce a “high” Opiate drugs are agonists and produce a “high”

feeling by amplifying normal pleasurable sensationsfeeling by amplifying normal pleasurable sensations

AntagonistsAntagonists Molecules that are similar to NTsMolecules that are similar to NTs They also bind to NT receptors; instead of They also bind to NT receptors; instead of

replicating the affect of a NT, they block that replicating the affect of a NT, they block that responseresponse Botulin (botox) is an antagonists that blocks the Botulin (botox) is an antagonists that blocks the

release of a NT (ACh), that controls muscles; thus it release of a NT (ACh), that controls muscles; thus it temporarily paralyzes those musclestemporarily paralyzes those muscles

Agonist versus Antagonists

Agonist versus Antagonists

Agonist versus Antagonists

Agonist versus Antagonists

Agonist versus Antagonists

Agonist versus Antagonists

Agonist versus Antagonists

Agonist versus Antagonists

ReviewReview Explain how neurons communicate with Explain how neurons communicate with

other neurons.other neurons.

Explain how NTs influence behavior.Explain how NTs influence behavior.

Explain how drugs and other chemicals can Explain how drugs and other chemicals can influence neurotransmission. (make sure to influence neurotransmission. (make sure to differentiate between agonists & differentiate between agonists & antagonists.antagonists.