CHAPTER 2: NEUROSCIENCENeurons and Neurotransmitters

ORIGINS OF STUDYING THE BRAIN

Plato believed that the mind was located in the spherical head

Aristotle believed that the mind was located in the heart

Phrenology – Studying bumps on the head to reveal a person’s mental abilities and character traits, Franz Gall invented phrenology Gall was correct to conclude

parts of the brain have specific functions. VIDEO: Racing and the brain.

BIOLOGY AND BEHAVIOR

Biology is the foundation for our behavior and mental processes

Biological Psychologists – study links between biology and behavior

Neuroscience – interdisciplinary field studying how biological processes relate to behavioral and mental processes.

NEURAL COMMUNICATION

Neuron – nerve cell, the building block of the nervous systemEach neuron consists of a cell body

(sometimes called the soma) and branching fibers

Neurons send out electrochemical communications to the brain and the rest of the body

Dendrite – receives information coming from the neuron

NEURAL COMMUNICATION

Axon – Passes information to other neurons, muscles and glandsAxons can be very long (unlike the

dendrite which is very short)Myelin Sheath – insulates the axon

Helps impulses travel quickly Importance of the myelin sheath is seen in

Multiple Sclerosis. Consider MS – the myelin sheath breaks down and

results in slow communication to the muscles.

NEURAL COMMUNICATION

Axon Terminal Buttons ( aka end buttons / branches, synaptic vessicles) –the branched end of the axon that contains the neurotransmitters. Reaches right up to another neuron, muscle, organ.

PARTS OF A NEURON

ACTION POTENTIAL

Neural impulses are called action potentialAction Potential is a brief electrical charge that

travels down an axon Where does an electrical charge come from?

During the resting potential axon gates are closed and do not allow positively charged ions in. negatively charged ions are on the inside.

Electrical activity must get past the threshold to fire.

ALL OR NOTHING

Neuron fires (aka Action Potential) --- + charged ion comes into axon. Negative ions rush out.(this depolarizes the axon) --- depolarizing causes the next gate to open and then the next… etc. (like dominoes)

Neuron’s Action PotentialAn “all or nothing response”

Like a gun firing or camera taking a picture… it does not go halfway

Refractory Period- When the positive ions are pumped outside of the

axon. During the phase the neuron can’t re-fire as in needs to recharge. FIELD TRIP TIME. YEAH!

FIELD TRIP

When you come back from our very brief field trip answer how the flushing of a toilet is analogous to the firing of a neuron. During which part of the demonstration did the following occur?

“all or nothing” principle Resting potential Threshold Action Potential (neural impulse) Refractory Period

ACTION POTENTIAL

NEURON COMMUNICATION Individual neurons function

as independent agents within the nervous system

Synapse – junction between the axon tip of the sending neuron and the dendrite of the receiving neuron (junction is called the synaptic gap)

From the axon terminal buttons, neurotransmitters travel across the synapse

ACTIVITY: Neural Network

NEURAL COMMUNICATION

LIVE!Psych (The Synapse and Neurotransmitters)

NEURON COMMUNICATION (CONT.)

When the action potential reaches the end of the axon, it triggers the release of neurotransmitters (chemical messengers)

Neurotransmitters cross the synaptic gap and binds to the receptor sites on the receiving neuron

Excess neurotransmitters are reabsorbed by the sending neuron – this is called reuptakeMany drugs today block the reuptake of

neurotransmitters. Ex Zoloft, prozac, Paxil for Serotonin.

AN EXAMPLE OF REUPTAKE …

NEUROTRANSMITTERS

Neurotransmitters – chemicals produced by neurons that travel across the synaptic gap and are then used for communication between neurons for the performance of mental and physical activities.

Q ANY EXAMPLES?

ACETYLCHOLINE (ACH)

Enables cognitive skill - learning and memory

Undersupply marks Alzheimer’s disease

DOPAMINE

Motor MovementOversupply is linked to schizophrenia.Undersupply is linked to tremors and

decreased mobility (ex. Parkinson’s disease)

Stem cellm Cell Reading

PARKINSON’S DISEASE AND DOPAMINE

Michael J Fox Parkinson's Disease Michael J. Fox has Parkinson's Michael j fox on family guy

SEROTONIN

Mood ControlUndersupply is linked to

clinical depression Selective Serotonin Reuptake

Inhibitors (SSRI) are a frequently used drug for depression (ex. Prozac, Paxil, Lexapro, Zoloft) These drugs increase the activity of Serotonin.

Anti-depressants and Placebo effect. VIDEO- Penn and Teller, Korea, college students and alcohol, talking to one person you can fully trust.

NOR EPINEPHRINE

Influences alertness and arousal

Undersupply can depress mood

ENDORPHINS

Released in response to pain and vigorous exercise – linked to pain and pleasure. Ex.- Donovan McNabb, Jack Youngblood.

“morphine within”. Runner’s high, exercisaholics Involved in addictions – Ex. Heroine

DRUGS AND HOW THEY AFFECT COMMUNICATION AT THE SYNAPSE

Agonist v. Antagonist DrugsAgonist – mimic neurotransmitters

(Excite) Blocks reuptake of neurotransmitters Fits into the receptor site and function as

neurotransmitters

Antagonist – blocks neurotransmitters (Inhibit) Inhibit neurotransmitters from releasing Block receptor sites LIVE!Psych

AGONIST V. ANTAGONIST EXAMPLE

Ex. DopamineUndersupply (Parkinson’s) – Agonist Drug.

Overdosage and hallucinations (grandfather)

Oversupply (Schizophrenia) – Antagonist. dyskenesia

Drugs such as heroine and morphine can take the place of natural neurotransmissionBrain stops producing natural opiatesBody is in pain until the natural production

of endorphins begins again.