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Summary Biopsychologie

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Een samenvatting voor het vak Biopsychologie van het gehele boek. Geschreven in het Engels omdat de literatuur ook in het Engels is aangeleverd. Deze samenvatting heeft er in ieder geval voor gezorgd dat ik het vak heb gehaald.

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  • July 11, 2023
  • July 27, 2023
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Summary Biological Psychology
Chapter introduction: overview and major issues
The biological approach to behavior
Gottfried Leibniz posed the first extremely profound question: “why is there something
rather than nothing?”. That question is supremely baffling, but a subordinate question is
more amenable to discussion: given the existence of a universe, why this particular kind of
universe?
Beginning in the 1980s, specialist in a branch of physics known as string theory set out to
prove mathematically that this is the only possible way the universe could be. But they
concluded that this is not the only possible universe. The universe could have taken a vast
number of forms with different laws of physics.

Another profound question is the mind-brain problem, or the mind-body problem. So far, no
one has offered a convincing explanation of consciousness. Consciousness is something we
experience, and it balls for an explanation, even if we do not yet see how to explain it.
Researchers proposed that we regard consciousness as a fundamental property of matter. A
fundamental property is one that cannot be reduced to something else. But to say that
consciousness is a fundamental property would mean that we have given up on explaining it.

The field of biological psychology
Biological psychology is the study of the physiological, evolutionary, and developmental
mechanisms of behavior and experience. This is not only a field of study, but also a point of
view. It holds that we think and act as we do because of brain mechanisms, and that we
evolved those brain mechanisms because ancient animals built this way survived and
reproduced.

Biological explanations of behavior
In contrast to commonsense explanations, biological explanations of behavior fall into four
categories:
- Physiological: a behavior related to the activity of the brain and other organs. It deals
with the machinery of the body
- Ontogenetic: how a structure or behavior develops, including the influences of genes,
nutrition, experiences, and their interactions
- Evolutionary: the evolutionary history of a structure or behavior
- Functional explanation: why a structure or behavior evolved as it did

Why do researchers study nonhumans:
- The underlying mechanisms of behavior are similar across species and sometimes
easier to study in a nonhuman
- We are interested in animals for their own sake
- What we learn about animals sheds light on human evolution
- Legal or ethical restrictions prevent certain kinds of research on humans

,Chapter 1: nerve cells and nerve impulses
The nervous system consists of two kinds of cells, neurons, and glia. Neurons receive
information and transmit it to other cells. Glia cells serve many functions.
Two scientists of the late 1800s and early 1900s are widely recognized as the main founders
of neuroscience Charles Sherrington and Santiago Ramon y Cajal. Cajal’s early education was
not without any bumps in the road. In the end he combined two fields, he became an
outstanding anatomical researchers and illustrator. His detailed drawings of the nervous
system are still considered definitive today.

The structure of a neuron
Neurons have much in common with the rest of the body’s cells. The surface of a cell is its
membrane, a structure that separates the inside of the cell from the outside environment.
Most cells have a nucleus, the structure that contains the chromosomes. A mitochondrion is
the structure that performs metabolic activities, providing energy. Ribosomes are the sites
within the cell that synthesize new protein molecules. Some ribosomes float freely within the
cell, but others are attached to the endoplasmic reticulum, a network of thin tubes that
transport newly synthesized proteins
to other locations.

All neurons include a some (cell body),
dendrites, axon, and presynaptic
terminals. A motor neuron, with its
some in the spinal cord, receives
excitation through its dendrites and
conducts impulses along its axon to a
muscle.
A sensory neuron is specialized
at one end to be highly
sensitive to a particular type of
stimulation. The sensory
neuron conducts touch
information from the skin to
the spinal cord.

Many vertebrate axons are covered with an insulating material called a myelin sheath with
interruptions known as nodes of Ranvier. The end of each branch has a swelling, called a
presynaptic terminal.
Other terms associated with neurons are:
- Afferent axon: brings information into structure (sensory)
- Efferent axon: carries information away from a structure (motor)
- Interneuron is if a cell’s dendrites and axon are entirely contained within a single
structure



Variations among neurons

,Glia cells perform many functions. The brain has several types of glia. The star-shaped
astrocytes wrap around the synapses of functionally related axons. By surrounding a
connection between neurons, as astrocyte shields it from chemicals circulating in the
surround. Astrocytes dilate the blood vessels to bring more nutrients into brain areas that
have heightened activity.
Tiny cells called microglia act as part of the immune system, removing viruses and fungi from
the brain.
Oligodendrocytes in the brain and the spinal cord and Schwann cells in the periphery of the
body build the myelin sheaths that surround and insulate certain vertebrate axons. They also
supply an axon with nutrients necessary for proper functioning.
Radial glia cells guide the migration of neurons and their axons and dendrites during
embryonic development.




The blood-brain barrier
The mechanism that excludes most chemicals from the vertebrate brain is known as the
blood-brain barrier. When the immune system cells discover a virus, they kill it and the cell
that contains it. This plan works fine if the virus-infected cell is a skin cell, which the body
replaced easily. The vertebrate brain does not replace damaged neurons. To minimize the
risk of irreparable brain damage, the body lines the brain blood vessels with tightly packed
cells that keep out most viruses, bacteria, and harmful chemicals.

If the blood-brain barrier is such a good defense, you might ask, why don’t we have similar
walls around all our other organs? The answer is that the barrier keeps out useful chemicals
as well as harmful ones. For these chemicals to cross the blood-brain barrier, the brain needs
special mechanisms not found in the rest of the body.
Molecules that dissolve in the fast of the membrane cross it easily. Water crosses through
special channels in the wall of the endothelial cells. For certain other chemicals (amino acids,
glucose), the brain sues active transport, a protein-mediated process that expends energy to
pump chemicals from the blood into the brain.

, The blood-brain barrier is essential to health. In Alzheimer’s disease the endothelial cells
lining the brain’s blood vessels shrink, and harmful chemicals enter the brain. But the barrier
poses a difficulty for treating brain cancers, because nearly all the drugs used for
chemotherapy fail to cross the blood-brain barrier.

Nourishment of vertebrate neurons
Most cells use a variety of carbohydrates and fats for nutrition, but vertebrate neurons
depend almost entirely on glucose, a sugar. Because metabolizing glucose requires oxygen,
neurons need a steady supply of oxygen. Glucose is the only nutrient that crosses the blood-
brain barrier in large quantities. A problem is the inability to use glucose. To use glucose, the
body needs vitamin B1, thiamine. Prolonged thiamine deficiency leads to death of neurons
and a condition called Korsakoff’s syndrome.

The resting potential of the neuron
Messages in a neuron develop from disturbances of the resting potential. All parts of a
neuron are covered by membrane about 8 nanometers thick. The membrane is composed of
two layers of phospholipid molecules, embedded among the phospholipids are cylindrical
protein molecules through which certain chemicals can pass. When at rest, the membrane
maintains an electrical gradient, known as polarization, a difference in electrical charge
between the inside and the outside of the cell. The potential inside is slightly negative with
respect to the outside. The difference in voltage is called the resting potential

The membrane has selective permeability. Some chemicals pass through it more freely than
others do. Oxygen, carbon dioxide, urea, and water cross freely. Several biologically
important ions, like sodium, potassium, calcium, and chloride, cross through the membrane
channels that are sometimes open and sometimes closed. When the membrane is at rest,
the sodium and potassium channels are closed. The sodium-potassium pump, a protein
complex, repeatedly transport three sodium (natrium) ions out of the cell while drawing two
potassium (kalium) ions into it.

When the neuron is at rest, two forces act on sodium, both tending to push it into the cell.
First, consider the electrical gradient. Sodium is positively charged, and the inside of the cell
is negatively charged, and opposites attract. Second, consider the concentration gradient, the
difference in distribution of ions across the membrane. Sodium is more concentrated outside
than inside, so just by the laws of probability, sodium is more likely to enter the cell than to
leave it. So, sodium would pass into the cell if it could. But when the membrane is at rest the
sodium channels are closed and almost no sodium flows except what the pump forces out of
the cell. Potassium is subject to competing forces. Potassium is positively charged, and the
inside of the cell is negatively charged, so the electrical gradient tends to pull potassium in.
however, potassium is more concentrated inside the cell than outside, so the concentration
gradient tends to drive it out. If the potassium channels were wide open, potassium would
have a small net flow out of the cell.

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