PSYCH261 Chapter Notes - Chapter Intro, 1.1-1.2, 2.1-2.2: Active Transport, Stimulant, Schwann Cell

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Introduction
Main Ideas
oBiological explanations of behaviour fall into several categories, including physiology,
development, evolution and function
oNearly all current philosophers and neuroscientists reject the idea that the mind exists
independently of the brain. Still, the question remains as to how and why brain activity is
connected to consciousness
oThe expression of a given gene depends on the environment and on interactions with other
genes
oResearch with nonhuman animals yields important information, but it sometimes inflicts distress
or pain on the animals. Whether to proceed with a given experiment can be difficult ethical issue
oHard problem: given this universe composed of matter and energy, why is there such a thing as
consciousness?
oWhat is the relationship between mental experience and brain activity? This question is called the
mind-brain problem or the mind-body problem
oBiological psychology is the study of the physiological evolutionary, and developmental
mechanism of behavior and experience
oA physiological explanation relates a behaviour to the activity of the brain and other organs
oAn ontogenetic explanation describes how a structure or behavior develops, including the
influences of genes, nutrition, experiences, and their interactions.
oAn evolutionary explanation reconstructs the evolutionary history of a structure or behavior
oA functional explanation describes why a structure or behavior evolved as it did
Genetics and Behavior
oThe sequence of bases along a strand of DNA determines the order of bases along a strand of
RNA; RNA in turn controls the sequence of amino acids in a protein molecule
oDistinct from sex-linked genes are the sex-limited genes, which are present in both sexes,
generally on autosomal chromosomes, but active mainly in one sex. Example is breast size in
woman.
oPKU (phenylketonuria) a genetic inability to metabolize the amino acid phenylalanine. If PKU is
not treated, phenylalanine accumulates to toxic levels, impairing brain development and leaving
children mentally retarded, restless, and irritable.
oGenes are chemicals that maintain their integrity from one generation to the next and influence
the development of the individual. A dominant gene affects development regardless of whether a
person has pairs of that gene or only a single copy per cell. A recessive gene affects development
only in the absence of the dominant gene.
oGenes can change by mutations, microduplications, and microdeletions. Gene expression ca also
change in a process called epigenetics, as chemicals activate or deactivate parts of
chromosomes.
The Evolution of Behavior
oEvolution is a change over generations in the frequencies of various genes in a population
oEvolution includes any change in gene frequencies, regardless of whether it helps or harms the
species in the long run
oAltruistic behavior: an action that benefits someone other than the actor
oKin selection: selection for a gene that benefits the individual's relatives
oReciprocal altruism, the idea that individuals help those who will return the favor
The Use of Animals in Research
oThe underlying mechanisms of behavior are similar across species and sometimes easier to
study in a nonhuman species
oWhat we learn about animals sheds light on human evolution
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oWe are interested in animals for their own sake
oLegal or ethical restrictions prevent certain kinds of research on humans
oThe ethics of using animals in research is controversial. Some research does inflict stress or pain
on animals; however, many research questions can be investigated only through animal research
oAnimal research today is conducted under legal and ethical controls that attempt to minimize
animal distress
oUse of intimidation and violence by certain animal-rights extremists interferes with open
discussion of some difficult ethical issues
Neurons
Main Ideas
othe nervous system is composed nof two kinds of cells: neurons and glia. Only the neurons
transmit impulses from one location to another
othe larger neurons have branches, known as axons and dendrites, that can change their
branching pattern as a function of experience, age, and chemical influences
omany molecules in the bloodstream that can enter other body organs cannot enter the brain
othe action potential, an all-or-non change in the electrical potential across the membrane of a
neuron, is caused by the sudden flow of sodium ions into the neuron and is followed by a flow of
potassium ions out of the neuron
olocal neurons are small and do not have axons or action potentials. Instead they convey
information to nearby neurons by graded potentials
Anatomy of Neurons and Glia
oThe nervous system consist of two kinds of cells: neurons and glia
oNeurons receive information and transmit it to other cells
oThere are more neurons in the cerebellum than the cerebral cortex and spinal cor
The Structure of a Neuron
oThe most distinctive feature of neurons is their shape, which varies enormously from one neuron
to another
oNeurons have long branching extensions
oThe large neurons have these components: dendrites, a soma (cell body), an axon and
presynaptic terminals
oMotor neuron has its soma in the spinal cord. It receives excitation from other neurons through
its dendrites and conducts impulses along its axon to a muscle
oSensory neuron is specialized at one end to be highly sensitive to a particular type of
stimulation, such as light, sound or touch
oDendrites are branching fibers that get narrower near their ends
The greater the surface area of a dendrite, the more information it can receive
oMany contain dendritic spines, the short outgrowths that increase the surface area available for
synapses
oThe cell body, or soma contains the nucleus, ribosomes, and mitochondria
Most of the metabolic work of the neuron occurs here
The cell body is covered with synapses on its surface in many neurons
oThe axon is a thin fiver of constant diameter, in most cases longer than the dentrites
The axon is the neuron's information sender, conveying an impulse toward other neurons
or an organ or muscle
Many vertebrate axons are covered with an insulating material called a myelin sheath
with interruptions known as nodes of Ranvier
Invertebrate axons do not have myelin sheaths
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An axon has many branches, each of which swells at its tip, forming a presynaptic
terminal, also known as an end bulb or bouton
This is the point from which the axon releases chemicals that cross through the junction
between one neuron and the next
oAfferent axon brings information into a structure; efferent axon carries information away from a
structure
oIf a cell's dendrites and axon are entirely contained within a single structure, the cell is an
interneuron or intrinsic neuron of that structure
Glia
oOr neuroglia, the other major components of the nervous system, do not transmit information over
long distances as neurons do, although they perform many other functions
oThe star-shaped astrocytes wrap around the presynaptic terminals of a group of functionally
related axons
By taking up ions released by axons and then releasing them back to axons, an astrocyte
helps synchronize the activity of the axons, enabling them to send messages in waves
Astrocytes also remove waster material created when neurons die and control the
amount of blood flow to each brain area
During periods of heightened activity in some brain areas, astrocytes dilate the blood
vessels to bring more nutrients into that area
oNeurons communicate by releasing certain transmitters, such as glutamate
oAfter a neuron releases much glutatmate, nearby glia cells absorb some of the excess
oGlia convert most of this glutamate into a related chemical, glutamine, and then pass it back to
the neurons, which convert it back to glutamate, which they get ready for further release
oMicroglia, very small cells, also remove waste material as well as viruses, fungi, and other
microorganisms
In effect, they function like part of the immune system
oOgliodendrocytes in the brain and spinal cord and Schwann cells in the periphery of the body
are specialized types of glia that build the myelin sheaths that surround and insulate certain
vertebrate axons
oRadial glia guide the migration of neurons and their axons and dendrites during embryonic
development
When embryological development finishes, most radial glia differentiate into neurons, and
a smaller number differentiate into astrocytes and oligodendrocytes
The Blood-Brain Barrier
oMechanism that excludes most chemicals from the vertebrate brain
oDepends on the endothelial cells that form the walls of the capillaries
oSmall uncharged molecules, including oxygen and carbon dioxide, cross freely
oWater crosses through special protein channels in the wall of the endothelial cells
oMolecules that dissolve in the fats of the membrane also cross passively
oFew other chemicals, the brain uses active transport, a protein-mediated process that expends
energy to pump chemicals from the blood into the brain
oChemicals that are actively transported into the brain include glucose, amino acids, purines,
choline, a few vitamins, iron and certain hormones
Nourishment in Vertebrate Neurons
oMost cells use a variety of carbohydrates and fats for nutrition, but vertebrate neurons depend
almost entirely on glucose, a sugar
oGlucose is practically the only nutrient that crosses the blood-brain barrier after infancy, except for
ketones, and ketones are seldom available in large amounts
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Document Summary

Biological explanations of behaviour fall into several categories, including physiology, development, evolution and function. Nearly all current philosophers and neuroscientists reject the idea that the mind exists independently of the brain. Still, the question remains as to how and why brain activity is connected to consciousness. The expression of a given gene depends on the environment and on interactions with other genes. Research with nonhuman animals yields important information, but it sometimes inflicts distress or pain on the animals. Whether to proceed with a given experiment can be difficult ethical issue o o o o o o o o o o o o o o o o o o o. This question is called the mind-brain problem or the mind-body problem. Biological psychology is the study of the physiological evolutionary, and developmental mechanism of behavior and experience. A physiological explanation relates a behaviour to the activity of the brain and other organs.

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