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Chapter 3, 9.3

PSY100H1 Chapter Notes - Chapter 3, 9.3: Indirect Agonist, Periaqueductal Gray, Pituitary Gland


Department
Psychology
Course Code
PSY100H1
Professor
Michael Inzlicht
Chapter
3, 9.3

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Week 3-Biological Psychology
Ch 3.1-3.3, 9.3
Chapter 3.1
-Behavioural Genomics: the study of how genes are related to behaviour.
-Common misconception: a gene linked to a diseases doesn’t necessarily
mean everyone inheriting the gene develops disease. Complex diseases like
Alzheimer’s are a result of combinations of genes.
-One gene doesn’t only affect one trait. Example: gene linked to alcoholism
may also be linked to other drug dependences, anti-social behaviour, etc.
-Behavioral Genetic: the study of the influence of gene and environment on
behaviour.
-Best organisms’ to study behavioral genetics on is twins (mono—split
zygote—and di—two separate zygotes—zygotic)
-Heritability: number between 0-1 that represents the degree to which
genetic differences affects differences in behavior or trait in a population.
o0 value means genes do not contribute to individual differences in trait.
1.0 means genes account for all the individual differences in trait.
oEveryone has a mouth so heritability value for that would be 0, but the
taste buds (esp. For the bitter taste in cabbages, etc) could be because of
exposure to it during childhood OR due to genes.
- Epigenetics: the study of changes in gene expression due to environmental
factors.
-Example: maternal care (cuddling/licking) in humans and mice linked to
increased GR expression. It decreased in childhood abuse children.
-Seratonin related with mood. Low levels with depression.
-Evolutionary Psychology: the idea that our behavior now can be explained
with the understanding of how it may have helped increased the fitness of
our ancestors.
-Why humans are smarter than their ancestors and other species?
1) More folds/grooves on the brain cerebral cortex
2) More developed front brain frontal lobes
3) Cheating nature Neotony: human brains haven’t yet finished
developing at birth so human babies can’t start walking at birth. As they

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age, brain grows larger, thus making space for more skills and abilities
before the brains concludes growth.
Chapter 3.2
-Neuron: one of the major types of cells found in the nervous system, that are
responsible for sending and receiving messages throughout the body.
-its job is to ‘fire’, aka transmit impulse to another neural connection, which
eventually causes a response (behaviour)
- Neuron parts:
1) Soma: cell body containing nucleus containing genetic information.
2) Dendrites: small branches radiating from the cell body that receive messages
from other cells and transmit those messages toward the rest of the cell.
3) Axon: carries information in the form of electrochemical reactions from the
cell body to the end of the neuron.
- Neurotransmitters: the chemicals that function as a messenger allowing
neurons to communicate with each other.
-Types of neurons: sensory neurons bring info. to brain and spinal cord (like
neurons that sense touch/pain) and motor neurons bring info. away from
brain to muscles, etc.
-Glial cells: are specialized cells of the nervous system that are involved in
mounting immune responses in the brain, removing wasted, and
synchronising the activity of the billions of neurons that constitute the
nervous system.
-Myelin: fatty sheath that insulates the axon that increases the speed and
efficiency of communication.
-RESTING AND ACTION POTENTIAL
oWhen not fired, the cell outside has a + charge whereas the interior is
– charged. Difference is approx. -70millivolts.
oElectrostatic gradient and concentration gradient: just means that the
inside and outside differ in charge and the concentration of TYPES of
ions. More Na+ outside than in.
oFiring threshold= -55 millivolts
oAt action potential, the part of the axon turns ~35 millivolts.
oRepolarization: all the Na+ that came in, is rapidly pumped out to
restore the resting potential. Often becomes hyperpolarized, i.e too
much Na+ pumped out but then restored over 2-3 seconds the time
called refractory period
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-Synapses: the microscopically small space between the nerve cells. Cell
sending the signal is presynaptic cell and one receiving is postsynaptic cell.
oThe postsynaptic cell’s dendrites have specialized receptors that will
allow in certain neurotransmitters
oBinding neurotransmitter has one of two effects: a) if it creates
depolarization in postsynaptic cell’s axon called excitatory, b) if it
makes the axon more negative (thus less likely to fire) called
inhibitory.
oNeurotransmitters attach on postsynaptic receptors and detach. If they
stated attached for long, the cell fires less often. Once release, either
broken down by enzyme or re-uptaken into presynaptic cell.
-All or none principle: a neuron only either fires or doesn’t, there’s no such
thing has weak or strong impulse (OR sort-of fire or overfire).
-Mono-amines
oDopamine: mood control, voluntary movement and procession of
rewarding of experiences.
oNorepinephrine (noradrenaline): regulates stress responses
including increases arousal, attention and heart rate.
oSerotonin: regulates mood, sleep, aggression and appetite.
-Pain and Substance P: Discovered to be responsible for pain transmittance.
Receptors for this substance in periaqueductal grey, cerebral cortex,
amygdala, and hypothalamus. Pain is a combination of both sensation and
emotional response.
-Agonists: drugs that enhance or mimic the effects of a neurotransmitter’s
action. Ex: nicotine is agonist of acetylcholine.
oDirect agonist: physically binds to receptors at postsynaptic cells.
oIndirect agonist: facilitates indirectly without binding, eg, a drug that
block reuptake of a neurotransmitter.
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