PSY100H1 Chapter Notes - Chapter 3: Chemical Synapse, Resting Potential, Somatic Nervous System

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Published on 13 Sep 2012
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Chapter 3: Biological Foundations
What is the genetic basis of psychological science?
chromosomes: structures within the cell body that are made up of genes
gene: the unit of heredity that determines a particular characteristic in an organism.
Dominant gene: a gene that is expressed in the offspring whenever it is present
recessive gene: a gene that is expressed only when it is matched with a similar gene from the
other parent
genotype: the genetic constitution determined at the moment of conception
phenotype: observable physical characteristics that result from both genetic and environmental
influences
monozygotic twins: twin siblings who result from one zygote splitting in two and therefore share
the same genes (identical twins)
dizygotic twins: twin siblings who result from two separately fertilized eggs (fraternal twins)
heritability: a statistical estimate of the variation, caused by differences in heredity, in a trait
within a population.
+ depends on variation, the measure of the overall difference among a group of people for that
particular trait.
Neurons are specialized for communication:
neuron: the basic unit of the nervous system; it operates through electrical impulses, which
communicate with other neurons through chemical signals. Neurons receive, integrate, and
transmit information in the nervous system
sensory neurons: one of the three types of neurons, these afferent neurons detect information from
the physical world and pass it along to the brain
motor neurons: one of the three types of neurons, these efferent neurons direct muscles to contract
or relax, thereby producing movement
interneurons: one of the three types of neurons, these neurons communicate only with other
neurons, typically within a specific brain region.
Dendrites: branch-like extensions of the neuron that detect information from other neurons
cell body: in the neuron, where information from thousands of other neurons is collected and
processed
axon: a long narrow outgrowth of a neuron by which information is transmitted to other neurons
terminal buttons: small nodules, at the ends of axons, that release chemical signals from the
neuron to the synapse
synapse (synaptic cleft): the site for chemical communication between neurons, which contains
extracellular fluid
myelin sheath: a fatty material, made up of glial cells, that insulates the axon and allows for the
rapid movement of electrical impulses along the axon
nodes of ranvier: small gaps of exposed axon, between the segments of myelin sheath, where
action potentials are transmitted
resting membrane potential: the electric charge of a neuron when it is not active
Action Potentials cause neural communication:
action potential: the neural impulse that passes along the axon and subsequently causes the release
of chemicals from the terminal buttons
+ neuron respond to incoming stimulation by changing electrically and then passing along signals
to other neurons.
Excitatory: signals depolarize the cell membrane, increasing the likelihood that the neuron will
fire
inhibitory: signals that hyperpolarize the cell, decreasing the likelihood that the neuron will fire
two signals received by dendrites are integrated within the neuron.
+ if the total amount of excitatory input from the other neuron surpasses the receiving neuron's
threshold, an action potential is generated.
When a neuron fires, the sodium gates in cell membrane open, allowing sodium ions to rush into
neuron → inside of neuron become more positively charged than the outside. Change of charges
is basis of action potential.
Propagation: when neuron fires, the cell membrane's depolarization moves along the axon like a
wave.
Through natural restoration (repolarization), the electrical charges returns to its slightly negative
resting state.
All-or-none principle: the principle whereby a neuron fires with the same potency each time,
although frequency can vary; it either fires or not – it cannot partially fire.
Neurotransmitters bind to receptors across the synapse:
neurotransmitter: a chemical substance that carries signals from one neuron to another
presynaptic: sends the signal
postsynaptic: receives the signal
neurons do not touch each other; communicate by sending neurotransmitters from the axon across
the synaptic gap to the dendrites of the receiving neuron → neurotransmitters are stored in
vesicles → action potentials cause vesicles to fuse to the presynaptic membrane and release their
contents into the synapse → neurotransmission is terminated by reuptake, enzyme deactivation,
or autoreception → released neurotransmitters bind to the postsynaptic receptors
a neurotransmitter can bind only with its particular type of receptor, much as a key fits only with
the right lock
receptors: in neurons, specialized protein molecules, on the postsynaptic membrane, that
neurotransmitters bind to after passing across the synaptic cleft.
Reuptake: the process whereby a neurotransmitter is taken back into the presynaptic terminal
buttons, thereby stopping its activity.
Three major events that terminate the transmitters' influence in the synaptic cleft are reuptake,
enzyme deactivation, and autoreception
Neurotransmitters influence mind and behavior
agonist: any drug that enhances the actions of a specific neurotransmitter
+ can block the reuptake of neurotransmitters
antagonist: any drug that inhibits the action of a specific neurotransmitter
+ can destroy neurotransmitters in the synapse
acetylcholine (ACh): neurotransmitter responsible for motor control at the junction between
nerves and muscles; also involved in mental processes such as learning, memory, sleeping, and
dreaming
epinephrine: the neurotransmitter responsible for adrenaline rushes, bursts of energy caused by its
release throughout the body
+ known as adrenaline
norepinephrine: the neurotransmitter involved in states of arousal and awareness
serotonin: a monoamine neurotransmitter important for a wide range of psychological activity,
including emotional states, impulse control, and dreaming
dopamine: a monoamine neurotransmitter involved in reward, motivation, and motor control
Parkinson's disease (PD): a neurological disorder that seems to be caused by dopamine depletion,
marked by muscular rigidity, tremors, and difficulty initiating voluntary action
GABA (gamma-aminobutyric acid): the primary inhibitory transmitter in the nervous system
glutamate: the primary excitatory transmitter in the nervous system
endorphins: a neurotransmitter involved in natural pain reduction and reward
substance P: a neurotransmitter involved in pain perception
+ mood states and anxiety
Basic brain structures and functions:
central nervous system: the brain and spinal cord
+ information sent → organizes and evaluates the information
peripheral nervous system: all nerve cells in the body that are not part of the CNS. The PNS
includes the somatic and autonomic nervous systems
+ transmits a variety of information to the CNS
+ perform specific behaviors/make bodily adjustments
Broca's area: left frontal region of the brain, crucial for production of language
+ speech production
brain stem: a section of the bottom of the brain, housing the most basic programs of survival
breathing, swallowing, vomiting, urination, orgasm
cerebellum: a large, convoluted protuberance at the back of the brain stem, essential for
coordinated movement and balance
reticular formation: inducing and terminating the different stages of sleep.
+ sleep and arousal
hypothalamus: a small brain structure that is vital for temperature regulation, emotion, sexual
behavior, and motivation
+ affects many internal organs' functions.
Thalamus: the gateway to the brain; receives almost all incoming sensory information before that
information reaches the cortex
+ during sleep, shuts the gate on incoming sensations while the brain rests
hippocampus: a brain structure important for the formation of certain types of memory
+ storage of new memories
amygdala: a brain structure that serves a vital role in our learning to associate things with
emotional responses and in processing emotional information
+ fear
basal ganglia: a system of subcortical structures that are important for the initiation of planned
movement
+ receive input from the entire cerebral cortex and project to the motor centres of the brain stem
and thalamus
The cerebral cortex underlies complex mental activity
cerebral cortex: the outer layer of brain tissue, which forms the convoluted surface of the brain
frontal lobe: thought, planning movement
+ the region at the front of the cerebral cortex connected with planning and movement
+ premotor cortex & primary motor cortex
parietal lobe: touch, spatial relations
+ regions of the cerebral cortex, in front of the occipital lobes and behind the frontal lobes,
important for the sense of touch and of the spatial layout of an environment
+ include the primary somatosensory cortex, a strip running from the top of the brain down the
side
occipital lobe: vision.
+ regions of the cerebral cortex, at the back of the brain, important for vision

Document Summary

Chromosomes: structures within the cell body that are made up of genes. Gene: the unit of heredity that determines a particular characteristic in an organism. Dominant gene: a gene that is expressed in the offspring whenever it is present. Recessive gene: a gene that is expressed only when it is matched with a similar gene from the. Genotype: the genetic constitution determined at the moment of conception. Phenotype: observable physical characteristics that result from both genetic and environmental other parent influences. Monozygotic twins: twin siblings who result from one zygote splitting in two and therefore share the same genes (identical twins) Dizygotic twins: twin siblings who result from two separately fertilized eggs (fraternal twins) Heritability: a statistical estimate of the variation, caused by differences in heredity, in a trait within a population. + depends on variation, the measure of the overall difference among a group of people for that particular trait.