4 - 1 © 2000 Pearson Education Canada Inc., Toronto, Ontario Biology of Behaviour LECTURES # 4 & 5 BIOLOGY OF BEHAVIOUR I & II

Biology of Behaviour 4 - 1 © 2000 Pearson Education Canada Inc., Toronto, Ontario

LECTURES # 4 & 5 BIOLOGY OF BEHAVIOUR I

& II


Biology of Behaviour

1. The Brain and Its Components2. Study of the Brain3. Control of Behaviour4. Control of Internal Functions and

Automatic Behaviour5. Drugs and Behaviour


The Brain and Its Components

Structure of the Nervous System Cells of the Nervous System The Action Potential Synapses A Simple Neural Circuit


Structure of the Nervous System

(1) Central Nervous System (brain and spinal cord)

(2) Peripheral Nervous System (cranial and spinal nerves)


Structure of the Nervous System

F 4.2


Cells of the Nervous System

F 4.5


Basic Nerve Cell Structure & Function

A nerve cell is essentially a bag of chemicals. The bag is made of fat whose shape is

tailored by an interior scaffolding. The control of nerve cell function is by the

genetic material within the cell. The surface of the nerve cell contains pores

which permit the flow of ions through them The surface also contains structures that

pump ions in and out of the cell. At rest a nerve cell tends to “set” a net

negative charge.


What is an ion and what do nerve cells do with them?

An ion is a charged atom. In biology it always takes this form as a particle in dissolved in water Consider table salt

Table salt is sodium chloride or the chemical shorthand is written as NaCl

When it is dissolved in water it “breaks apart” to be Na and Cl but…here’s the important part

Its not just Na and Cl it is Na+ and Cl-

The Na is positively charged and the Cl has a negative charge.

This is also true for other important biological salts like potassium chloride and calcium chloride

Nerve cells always distribute these ions unevenly so that there is lots of potassium ion inside the cell. Whereas on the outside in the space surrounding nerve cells sodium, calcium and chloride ions are abundant


Basic nerve cell factsOverall this separation of charge creates a voltage across the cell membrane this is usually equal to about –70 mV (millivolts)

OUTSIDE

INSIDE

Na+K+

Na+K+

Cl-


The Action Potential

Ion channels and ion transporters regulate the number of ions inside and outside the axon.

F 4.6


The Action Potential

F 4.7

1. -70 mV (at rest)

3. Sodium ions “rush” into cell so membrane potential becomes more positive

2. Cell is excited

4. Potassium ions rush out of the cell and the membrane becomes more negative at same time the sodium channels close

Cell returns to resting state

http://faculty.washington.edu/chudler/ap.html


SynapsesIt is the site where the electrical activity of neuron is passed on to the next.

This results in the release of a chemical substance into the small space between the two nerves cells This space is called a synapse

This substance transmits a chemical message from one nerve to another and it is called a neurotransmitter

F 4.12


Synapses

F 4.11


There are basically two kinds of neurotransmitter action

Excitatory Release tends to

increase the likelihood that nerve cell receiving the transmitter will generate an action potential

Inhibitory Release tends to

decrease the likelihood that the nerve cell receiving the transmitter will generate an action potential

Modulatory neurotransmittersThese are transmitters which either increase or decrease the efficiency of the excitatory or inhibitory transmitters


Synapses

F 4.9


A Simple Neural CircuitF 4.13


A Simple Neural CircuitF 4.14


Neurotransmitters IGlutamate -excitatory

F 4.12

1. Glutamate is released by the arrival of the action potential in the nerve terminal

2. Opening of the ion channels on the next nerve cell creates excitation by inducing the flow of positive charge into the cell

3. After activation of the glutamate receptors the glutamate diffuses away and is “mopped up” by the termimal the active process of uptake

Na+


Why is glutamate important?

It is the “gas pedal” of the brain It keeps us awake… drugs that interfere with the

glutamate neurotransmission create hallucinations, sedation and unconsciousness

Drugs of use: Ketamine (anesthetic) MK-801 (prevents brain damage because of

stroke)

Drugs of Abuse: PCP or angel dust


Neurotransmitters IIGABA –inhibitory

F 4.12

1. GABA is released by the arrival of the action potential in the nerve terminal

2. Opening of the ion channels on the next nerve cell creates inhibitin by inducing the flow of negatively charged chloride ions in to the the cell

3. After activation of the GABA receptors the GABA diffuses awaya and is “mopped up” by the termimals and by helper cells called glia by the active process of uptakeCl-


Why is GABA important?

It is the “brakes ” of the brain It prevents excess excitation and maintains the proper

rhythmic activity of the brain… drugs that block GABA neurotransmission create convulsions and death.

Drugs of use: Benzodiazepines (Valium, Xanax, librium) potentiate GABA

action and reduce anxiety, panic attack syndrome (anxiolytic action)

it also induces sleep (sedative action). Pentobarbital amd Propofol used to induce unconsciousness

for surgery (PB also prevents brain damage because of stroke and child drowning incidents)


Why is GABA important?(continued)

Alcoholic beverages have as their primary site of action the GABA system

Muscle relaxantsEpilepsy treatmentDrugs of Abuse:

Alcohol Valium Valium and alcohol ( Jimi Hendrix, and many

other rock stars)


Dopamine – modulatory

1. Dopamine is released by the arrival of the action potential in the nerve terminal

2. Activation of dopamine receptors creates a secondary chemical signal within the nerve cell which modifies quality of the excitation and inhibition that the cells receives.

3. After activation of the dopamine is also mopped up by the termimal the active process of uptake

Neurotransmitters III


What is dopamine and why is it important?

Dopamine is another neurotransmitter which is very important for modulating the activity of the brain

Dopamine activity is implicated in the following diseases Parkinsons disease Schizophrenia Addiction Depression Attention deficit syndrome Obsessive compulsive disorder


Dopamine activity is compartmentalized

Two Broad classifications of dopamine action Affective behaviours

Attention Reward Addiction

Movement behaviours Initiating voluntary movement

These two types of behaviour are controlled by different parts of the brain.


Parkinson’s Disease

Manifested by Difficulty in initiating movements Difficulty in a executing smooth movement Loss of dopamine containing cells that are located in brain region

known as the substancia nigra SN It has occurred in younger people who took the drug

methamphetamine contaminated with a by product created through poor quality control MPTP, it is specifically toxic to SN.

Substancia nigra cells have axons that normally release dopamine and these axons project to another part of the brain called the striatum… this part of the brain which controls voluntary movement depends on the modulatory effects of dopamine and so movement is altered.

Treatment : give back dopamine artificially in the form of a pill (actually it is drug, Levodopa, that is converted to dopamine)


Schizophrenia Means split brain…but the disease rarely manifests itself a true or

mulitple personality (no matter what Jim Carey says) 1.1% of the population age 18 and older in a given year have

schizophrenia Usually characterised by paranoid delusions (Type 1)

Delusions (false beliefs) Hallucinations (perceiving the presence of something not really there) Disorganized speech Irrational or catatonic behavior, such as stupor, rigidity, or floppiness

of limbs.

OR…. Absence of thought or affect (Type II)

Negative symptoms, such as inaction, silence, or loss of will

Treated by neuroleptics drugs which block the action of dopamine in the cortex ie the disease appears to be caused by excess dopamine action

clozepine is an example of widely used antipsychotic for the treatment of schizophrenia


Schizophrenia“Good Day” “Bad Day”

Vincent Van Gogh


Drugs and Behaviour

Effects of Drugs on Synaptic Transmission –a few examples


Effects of Drugs on Synaptic Transmission

F 4.34


Effects of Drugs on Synaptic Transmission

F 4.35


Effects of Drugs on Synaptic Transmission F 4.36


www.addictionscience.net/ASNbiological.htm

What is drug addiction? Biological addiction refers to a state of physical dependence on a drug whereby discontinuing drug intake produces a withdrawal syndrome consisting of various somatic disturbances. A broader definition Addiction is a behavioral syndrome where drug procurement and use seem to dominate the individual’s motivation and where the normal constraints on behavior are largely ineffective.

•Sometimes this broader definition is described as a "psychological" addiction (thus distinguishing it from physical dependence archaically termed "physical" addiction),

•the condition commonly referred to as addiction is the ability of the drug to dominate the individual’s behavior, regardless of whether physical dependence is also produced by the drug.

Addiction and Dopamine


How does addiction happen? (biologically and psychologically)

What causes drug addiction? Many factors influence a person’s initial drug use. Personality

characteristics, peer pressure, and psychological stress can all contribute to the early stage of drug abuse.

These factors are less important as drug use continues and the person repeatedly experiences the potent pharmacological effects of the drug.

This chemical action, which stimulates certain brain systems, produces the addiction, while other psychological and social factors become less and less important in influencing the individual’s behavior.

When the pharmacological action of a drug dominates the individual’s behavior and the normal psychological and social control of behavior is no longer effective, the addiction is fully developed.


How is drug addiction related to "normal" behavior?

Specialized brain reward systems have evolved to ensure survival of the species. Directing behaviour that promotes survival of the individual and of the species. Fat & sex are good examples.

Activation of brain reward systems produces changes in affect ranging from slight mood elevation to intense pleasure and euphoria, and these psychological states help direct behavior toward natural rewards.

Some chemicals activate brain reward systems directly, bypassing the sensory receptors mediating natural rewards. Caffeine, alcohol, nicotine all activate brain reward mechanisms directly.

Moderate use of these substances has gained widespread acceptance over the centuries, although their use has been periodically prohibited

However other drugs much more potently activate brain reward systems. But the activation is so much more intense it causes the individual to crave the drug and to focus their activities around taking the drug.

The ability of addictive drugs to strongly activate brain reward mechanisms and their ability to chemically alter the normal functioning of these systems can produce an addiction.


The system that is usually associated with reward behaviour is the mesolimbic dopamine

system

Cells in the mesolimbic dopamine system are spontaneously active -- action potentials are constantly generated at a slow rate. This releases small amounts of dopamine into the synaptic cleft. The levels of dopamine produced when the cells are active at this low rate may be responsible for maintaining normal affective tone and mood. Some scientists speculate that some forms of clinical depression may result from unusually low dopamine levels.

Cocaine inhibits the reuptake of dopamine. This increases the availability of dopamine in the synapse and increases dopamine's action on the postsynaptic neurons. The enhanced dopamine activity produces mood elevation and euphoria. Cocaine's effect is usually quite short, prompting the user to repeatedly administer cocaine to re-experience its intense subjective effects.


The system that is usually associated with reward behaviour is the mesolimbic dopamine

system

Heroin increases the neuronal firing rate of dopamine cells. The increased number of action potentials produce an increase in dopamine release. Thus the heroin user experiences the enhanced dopamine activity as mood elevation and euphoria.

Neuroadpative Effects (Addictive) repeated use of psychomotor stimulants like cocaine and opiates like

heroin produces changes in the mesolimbic dopamine system causing the depletion of dopamine from this system.

These dopamine depletions may cause normal rewards to lose their motivational significance (i.e., produce motivational toxicity).

Also, the mesolimbic dopamine system becomes even more sensitive to pharmacological activation by psychomotor stimulants and by opiates (i.e., sensitization develops).

These neuroadpative changes are probably critical for producing an addiction. Substances that activate the mesolimbic dopamine system without producing these neuroadaptive effects are probably not truly addictive.


Study of the Brain

Research Methods of Physiological Psychology Anatomical Physiological Biochemical Pharmacological Genetic Behavioural


Research Methods of Physiological Psychology

F 4.15

How do we know that dopamine involved?

Hypothesis: That electrical stimulation of the mesolimbic dopamine area will cause the rat to addicted to the elctrical stimulation

Implant electrodes in brain of rat in mesolimbic area and use them to stimulate the “reward area”

So by training the rat to perform a task then stimulating this area this will re-inforce the performance



F 4.16



F 4.17

The rat does learn that pressing the bar causes a reward feeling to be felt.In fact the rat will repeated press the bar once it becomes addicted to performing the task


Control of Behaviour

Organization of the Cerebral Cortex

Lateralization of Function


Organization of the Cerebral CortexF 4.23


Organization of the Cerebral CortexF 4.24



F 4.25



F 4.26


Lateralization of Function

F 4.28


Control of Internal Functions and Automatic

Behaviour

The Brain Stem

The Cerebellum

Structures within the Cerebral Hemispheres


The Brain Stem and Cerebellum

F 4.30


Structures within the HemispheresF 4.31


Structures within the HemispheresF 4.33

Documents

4 - 1 © 2000 Pearson Education Canada Inc., Toronto, Ontario Biology of Behaviour LECTURES # 4 & 5 BIOLOGY OF BEHAVIOUR I & II