Psychology’sPsychology’sbiological roots:biological roots:

neurons andneurons andneural communicationneural communication

The neuronThe neuron

A cell that specializes in communicationA cell that specializes in communication

A neuron:A neuron:

a) receives information from other a) receives information from other neurons, through its neurons, through its dendritesdendrites

b) integrates those signals, and b) integrates those signals, and

c) sends messages to other neurons c) sends messages to other neurons through its through its terminal buttonsterminal buttons

Neural structureNeural structureThree main componentsThree main components

1) Cell Body – contains the nucleus1) Cell Body – contains the nucleus collects info from other cellscollects info from other cells cite of genetic activitycite of genetic activity

2) Axon - long, narrow outgrowth of a neuron2) Axon - long, narrow outgrowth of a neuron transmits messages to other neuronstransmits messages to other neurons through its through its terminal buttonsterminal buttons

3) Dendrites 3) Dendrites short outgrowths from the neuron’s short outgrowths from the neuron’s

cell body that receive signals from other cell body that receive signals from other neuron’s neuron’s terminal buttonsterminal buttons

An axon’s terminal buttons communicate An axon’s terminal buttons communicate with another cell’s dendrites across a tiny, with another cell’s dendrites across a tiny, but empty space known as the but empty space known as the synaptic synaptic cleft cleft

neuronal firingneuronal firing

Dendrites are constantly bombarded with Dendrites are constantly bombarded with messages from other neuronsmessages from other neuronsThese can be These can be excitatory, excitatory, prompting the prompting the neuron to fire off its own message, or neuron to fire off its own message, or inhibitory, inhibitory, decreasing the probability that decreasing the probability that the neuron will firethe neuron will fireThe power to restrain is just as crucial as The power to restrain is just as crucial as important as the power to engage in actionimportant as the power to engage in action

Neuronal firing iiNeuronal firing ii

After weighing the input it receives from After weighing the input it receives from other neurons, a neuron can decide to other neurons, a neuron can decide to send a message to another neuronsend a message to another neuron

It does so through an It does so through an electro-chemical electro-chemical process called process called action potential action potential or or neuronal firingneuronal firing

Neuronal firing iiiNeuronal firing iii

An An action potential action potential is the transmission of is the transmission of the signal down the axon through a the signal down the axon through a complex exchange of sodium and complex exchange of sodium and potassium ions potassium ions

When the action is over, the positive When the action is over, the positive sodium is pumped back out until next timesodium is pumped back out until next time

Neuronal firing ivNeuronal firing iv

In this manner, the signal passes at a In this manner, the signal passes at a steady rate, like a series of dominoes and steady rate, like a series of dominoes and is not slowed by electrical resistanceis not slowed by electrical resistanceThe message is sped along even faster if The message is sped along even faster if the axon is coated with the axon is coated with myelinmyelinIt insulates like the plastic tubing of an It insulates like the plastic tubing of an electric cordelectric cord

Neural communicationNeural communication

Neurons influence each other through the Neurons influence each other through the release of release of neurotransmitters neurotransmitters – – chemicalchemical

substances that carry signals across the substances that carry signals across the synaptic cleftsynaptic cleft

When the When the action potential action potential reaches the end reaches the end of the axon at its of the axon at its terminal button terminal button the the neurotransmitters neurotransmitters are released to travel are released to travel across the synaptic cleftacross the synaptic cleft

Neural comm. iiNeural comm. ii

After passing through the empty After passing through the empty synaptic synaptic cleft cleft the neurotransmitters attach or the neurotransmitters attach or bind bind to receptors on the postsynaptic neuronto receptors on the postsynaptic neuron

These neurotransmitters can then make These neurotransmitters can then make the receiving neuron either more or less the receiving neuron either more or less likely to firelikely to fire

It is in this infinitesimally small space that It is in this infinitesimally small space that irregularities can have profound effectsirregularities can have profound effects

neurotransmittersneurotransmitters

There are dozens (at least 60) types and There are dozens (at least 60) types and each activates many types of receptorseach activates many types of receptors

Once they contact the postsynaptic neuron Once they contact the postsynaptic neuron they can either:they can either:

a) go through a) go through reuptake reuptake (reabsorbtion)(reabsorbtion)

b) be swept away through diffusion, b) be swept away through diffusion,

c) or leave and then c) or leave and then reexcite reexcite the neuronthe neuron

Major neurotransmittersMajor neurotransmitters

Serotonin – while involved in many Serotonin – while involved in many behaviors, especially important for behaviors, especially important for emotional states, impulse control, and emotional states, impulse control, and dreamingdreamingLow levels lead to Low levels lead to sadness, anxiety, sadness, anxiety, aggression, and food cravingsaggression, and food cravingsLSD bears a close structural resemblance, LSD bears a close structural resemblance, when it binds to serotonin receptors when it binds to serotonin receptors involved in dreaming, involved in dreaming, hallucinations hallucinations resultresult

Ssri’sSsri’s

SSelective elective SSerotonin erotonin RReuptake euptake IInhibitorsnhibitors

Prevent serotonin from being quickly reabsorbedPrevent serotonin from being quickly reabsorbed

Introduced in 1987- prozacIntroduced in 1987- prozac

Now wildly popular – even Now wildly popular – even

with dogswith dogs

Effective and relatively sideEffective and relatively side

effect freeeffect free

Should we all be “better than well”?Should we all be “better than well”?

dopaminedopamine

Essential influence on Essential influence on motivation motivation and and motor controlmotor control

Many think it “tells” us what we find Many think it “tells” us what we find pleasurable pleasurable

Kicks in when we are hungry, thirsty, and Kicks in when we are hungry, thirsty, and aroused to guide us to behaviors which aroused to guide us to behaviors which will satisfy our cravingswill satisfy our cravings

Do drugs enhance its effects (addiction) ?Do drugs enhance its effects (addiction) ?

epinephrineepinephrine

Formerly called Formerly called adrenalineadrenaline

Activated by our Activated by our sympathetic nervous sympathetic nervous system system when we need great bursts of when we need great bursts of energy to flee or stand and fightenergy to flee or stand and fight

endorphinsendorphins

Involved in the suppression of pain Involved in the suppression of pain Kicks in when pain becomes maladaptive, Kicks in when pain becomes maladaptive, helping animals feed and breed despite helping animals feed and breed despite discomfortdiscomfortAdministered through drugs like Administered through drugs like morphinemorphineMay account for the May account for the placebo effect –placebo effect – we we feel less pain because we convince feel less pain because we convince ourselves that we should, and release it, ourselves that we should, and release it, confirming our hopesconfirming our hopes

Neuronal Firing IINeuronal Firing II

An Action Potential is the transmission of An Action Potential is the transmission of the signal down the axon through a the signal down the axon through a complex exchange of sodium and complex exchange of sodium and potassium ionspotassium ions

When the action is over, the positive When the action is over, the positive sodium, is pumped back out until next timesodium, is pumped back out until next time

The nervous systemThe nervous system

From the perspective of From the perspective of contemporary psychologycontemporary psychology

Certain materials in this presentation are used under th Fair Use exemption of

The US Copyright Law and should not be used without the permission of their owner.

A survey of the nervous A survey of the nervous systemsystem

Within the broad heading of the Within the broad heading of the NervousNervous System System we find many component systems and subdivisionswe find many component systems and subdivisions

The first are: The first are:

a) The a) The Central Nervous System – Central Nervous System – the brain and the spinal cord, andthe brain and the spinal cord, and

b) The b) The Peripheral Nervous System Peripheral Nervous System – – bundles of axons connecting the spinal cord and bundles of axons connecting the spinal cord and the rest of the body.the rest of the body.

The spinal cordThe spinal cord

A rope of neural tissue that runs inside the A rope of neural tissue that runs inside the hollows of the vertebrae from just above hollows of the vertebrae from just above the pelvis into the base of the skullthe pelvis into the base of the skull

Connected to both Connected to both sensorysensory ( pain, touch, ( pain, touch, and pleasure)and pleasure) and and motor motor ( contract and ( contract and relax muscles)relax muscles) neuronsneurons

Facilitates Facilitates reflexes - reflexes - rapid, involuntary rapid, involuntary responses to stimulus responses to stimulus

Neuron typesNeuron types

Afferent – Afferent – sensorysensory

Efferent – Efferent – motormotor

Interneurons - Interneurons - connectiveconnective

Can neurons be repaired?Can neurons be repaired?

For decades, we thought notFor decades, we thought not

Now, as we begin to understand Now, as we begin to understand neuroplasticity, neuroplasticity, hope growshope grows

The promise and The promise and controversy of controversy of stem cellsstem cells

the peripheral nervous systemthe peripheral nervous system

Divides into :Divides into : a) the Somatic Nervous a) the Somatic Nervous

System – System – nerves which nerves which communicate with the skin and communicate with the skin and musclesmuscles and and

b) the Autonomic Nervous b) the Autonomic Nervous System – System – nerves which control nerves which control the involuntary muscles, internal the involuntary muscles, internal organs (heart, lungs, stomach, organs (heart, lungs, stomach, etc.) and glandsetc.) and glands

The autonomic nervous systemThe autonomic nervous system

Two divisions:Two divisions:

1) Sympathetic – prepares your body for 1) Sympathetic – prepares your body for action, action, fight or flightfight or flight

blood flows to musclesblood flows to muscles epinephrine epinephrine increases heart rateincreases heart rate lungs pull in more oxygenlungs pull in more oxygen sweat forms for coolingsweat forms for cooling

The autonomic nervous The autonomic nervous systemsystem

2) Parasympathetic – 2) Parasympathetic – returns your body to its returns your body to its resting state, conserves resting state, conserves energyenergy

heart rate slowsheart rate slows

epinephrine epinephrine cut offcut off

lungs relaxlungs relax

stomach resumes stomach resumes digestiondigestion

The endocrine systemThe endocrine system

A set of glands that produce and release A set of glands that produce and release hormoneshormones

These hormones influence thoughts, These hormones influence thoughts, behaviors and actionsbehaviors and actions

Transmitted through the bloodTransmitted through the blood

Have a Have a global global effect as compared to the effect as compared to the local local effect of neurotransmitterseffect of neurotransmitters

Include the Include the hypothalamus hypothalamus and and pituitarypituitary