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Summary Nortman ALL CHAPTERS intro to psychology
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Chapter 1: The Science of Psychology1.1 What is psychological science?
Psychology is the study of mental activity and behaviour. A psychologist tries to understand
and predict behaviour. People do this intuitively in their daily lives. Often, people try to predict
the behaviour of others based on gut feelings and common sense. Psychological science is
the study of the mind (mental activity), the brain, and behaviour through research. Biological
processes within the brain create mental activity. Behaviour describes the observable actions of
people and animals. Psychologists have long focused on behaviour rather than on mental
activity. Now that the technology to observe the brain has advanced, psychologists are also able
to study mental states. Psychologists try to understand different concepts: normal and abnormal
mental activity, the biological basis of mental activity, how people change over time, how people
vary in response to certain circumstances and how people learn healthy and unhealthy
behaviour.
Psychological science teaches critical thinking
Many media reports contain distorted or false statements about psychological findings.
Therefore, an aspiring psychologist should always be sceptical about articles. A good scientist is
open to new ideas but cautious at the same time. Before believing something, a scientist
carefully weighs the facts. Critical thinking is the systematic interrogation and evaluation of
information with the help of sound evidence.
Fallacies
Non-critical thinking and thinking errors sometimes look like a lack of intelligence or motivation,
but nothing could be further from the truth. These errors often occur precisely because people
are motivated to use their intelligence and find connections that sometimes are not there.
Knowledge and an understanding of these mistakes is important to prevent them. The following
thinking errors are common:
● Ignoring evidence (confirmation bias): People tend to accept evidence that falls within
their expectations and ignore evidence that does not;
● Seeing connections that do not exist: There is a tendency to believe that things that
happen at the same time or shortly after each other are connected;
● Accepting after-the-fact explanations: There is a tendency to reinterpret old evidence
after an incident and use it as an explanation for the incident;
● Mental heuristics: people tend to use simple rules (heuristics) even when they are not
relevant to the current situation.
Chapter 3: Biology and Behaviour
How does the nervous system work?
The complete nervous system consists of the central nervous system (CNS) and the
peripheral nervous system (PNS). The CNS consists of the spinal cord and the brain. The
peripheral nervous system consists of all the other nerve cells in the rest of the body. The CNS
and PNS are therefore anatomically separate from each other. The PZS consists of the somatic
and autonomic nervous systems. The somatic component is responsible for voluntary
behaviour and the autonomic component is responsible for involuntary actions (e.g. controlling
the heartbeat).
3
,1 Neurons are the basic units of the nervous system
The basic unit of the nervous system is a neuron. Neurons receive, integrate and transport
information in the nervous system. Humans have billions of neurons. Neurons communicate
selectively with other neurons. This forms a circuit, which is also called a neural network.
Neurons are driven by electrical impulses and communicate through chemical signals. In the
receiving phase, neurons receive and absorb chemical signals from other neurons. During
integration these signals are evaluated and during transmission the neurons send out their
own chemical signals to other neurons.
Sensory neurons receive information from the physical world and transmit this information to
the brain via the spinal cord. There are different types of sensory neurons. For example,
somatosensory nerves receive information from the skin and muscles. Motor neurons send
signals from the brain to the muscles to contract or relax. Sensory and motor neurons work
together to control movements. Reflexes are automatic motor responses that occur without
thinking.
Structure of a neuron
Each neuron consists of four parts:
● Dendrites: detect chemical signals from surrounding neurons. They are short and
branched;
● Cell body (soma): the information from the dendrites is collected and integrated here;
● Axon: After incoming information is processed, electrical impulses are sent from the cell
body to the terminal buds via the axon. Axons are long and thin;
● Terminal buds: These are branches at the end of the axon. They send chemical signals
to the next neuron.
The chemical communication between neurons takes place in the synapse. This is a gap
between the sending neuron and the receiving neuron. In the synapse, chemical substances are
sent by one neuron and these substances are then detected by another neuron.
The whole neuron is covered with a membrane: a fatty protective layer that is insoluble in water.
The membrane is also semi-permeable. This means that only certain substances can pass
through it. The ion channels, for example, allow ions to pass through the membrane when the
neuron receives chemical signals. Ions are positively or negatively charged molecules. The
membrane thus regulates the flow of ions. This flow of ions forms the basis for the electrical
activity of the neuron.
3.2 Action potentials produce neural communication
An action potential (neural inflammation) is the electrical signal that passes along the axon.
This signal causes the terminal buds to release chemicals that transmit signals to other
neurons.
Resting membrane potential
When the membrane of the neuron is stable, there are more negatively charged ions on the
inside of the cell than on the outside. This is called the resting potential. At this point, the
neuron is inactive and its charge is -70 millivolts (mV). During the resting potential, the neuron is
polarised. Sodium and potassium ions contribute to the resting potential of a neuron. The ion
,channels are selective (semipermeable) for certain types of ions: sodium channels let through
sodium ions but not potassium ions and vice versa. The sodium-potassium pump is a
mechanism in the membrane that maintains polarisation. The pump increases potassium and
decreases sodium concentration in the neuron, thereby maintaining the resting membrane
potential.
Changes in the electric potential lead to action
A neuron receives chemical signals from nearby neurons through its dendrites. These
chemicals have an effect on polarisation and tell the neuron whether it should fire or not. The
dendrites can receive two types of signals:
● Excitatory (stimulus) signals: depolarise the cell membrane by reducing the negative
charge in the cell. This makes it more likely that a neuron will fire;
● Inhibitory signals: hyperpolarise the cell membrane by increasing the negative charge
in the cell. This makes it less likely that a neuron will fire.
The excitatory and inhibitory signals are combined in the neuron that receives them. When the
total input of the neuron exceeds the threshold value (-55 mV), an action potential is
generated. The action potential moves across the axon. When a neuron fires (an action
potential occurs) the following steps are taken:
1. Sodium channels in the cell membrane open and sodium ions flow into the neuron;
2. Potassium channels in the cell membrane open and potassium ions flow out of the
neuron;
3. The neuron is now more positively charged inside than outside (+40 mV);
4. The sodium channels close again;
5. The neuron begins to repolarize;
6. Potassium channels close;
7. The neuron eventually regains its original negative resting potential.
After repolarisation (reaching the resting potential again), there is a short period in which the cell
membrane cannot activate a new action potential.
, Action potentials distributed over the axon
An action potential always moves along the axon from the cell body to the terminal buds. Many
axons are covered by a fatty myelin sheath, which accelerates the transmission of electrical
signals. The myelin sheath is made up of glial cells. The myelin sheath is made up of segments
and between these are Ranvier's nodes, where an action potential can take place. The action
potential fires under an all-or-nothing principle. The whole neuron fires, or it doesn't fire; there
are no half fires. However, there can be a difference in the firing frequency: how quickly a
neuron fires successive action potentials.
3.3 Neurotransmitters influence mental activity and behaviour
The presynaptic neuron is the neuron that sends the signal. The postsynaptic neuron is the
neuron that receives the signal. Each terminal button contains neurotransmitters: chemicals
made in the axon and stored in vesicles. When the action potential has reached the terminal
button, the vesicle attaches to the presynaptic membrane and releases neurotransmitters into
the synapse. These neurotransmitters bind to the dendrites of the postsynaptic neuron. Each
receptor on a dendrite can be affected by only one type of neurotransmitter, creating either an
excitatory or an inhibitory effect. When a neurotransmitter binds to a receptor, it blocks new
signals until the neurotransmitter's influence is over.
There are three ways of ending the influence of neurotransmitters:
● Reuptake: a cycle of release and reuptake by the presynaptic neuron;
● Enzyme deactivation: an enzyme destroys the neurotransmitter in the synapse;
● Autoreceptors: Autoreceptors on the presynaptic neuron control the amount of
neurotransmitter in the synapse. When there is enough neurotransmitter in the synapse,
autoreceptors signal the presynaptic neuron to stop releasing the neurotransmitter.
Agonists are substances that enhance the action of the neurotransmitter by, for example,
mimicking the neurotransmitters and binding to receptors as if they were the real thing.
Substances that inhibit the action of neurotransmitters are antagonists.
Types of neurotransmitters
There are seven neurotransmitters that are important for thinking, feeling and behaviour:
● Acetylcholine (ACh) is responsible for motor control between nerves and muscles.
Botox suppresses ACh release, paralysing the muscles and reducing wrinkles. ACh is
also involved in complex mental processes such as learning, memory, sleep and
dreams. ACh antagonists cause temporary memory loss. Alzheimer's disease has also
been linked to impaired ACh function. ACh-agonists may slightly improve Alzheimer's
symptoms;
● Noradrenaline is involved in states of excitement, attention and alertness;
● Serotonin is involved in various psychological activities, mainly in emotional states,
impulse control and dreams. Low levels of serotonin cause sad and anxious moods,
hunger and aggressive behaviour. Drugs that block the reuptake of serotonin cause
more serotonin to remain in the synapses (Selective Serotonin Reuptake Inhibitors
(SSRIs)). This can be used for depression, OCD, eating disorders and obesity;
● Dopamine helps direct behaviour towards rewards. Low levels of dopamine cause
problems with movement. This is for example the case in Parkinson's disease, where the
dopamine-producing cells slowly die off;
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