The introduction of psychological theories BOOK
Chapter 1, the science of psychology
Chapter 3, Biology and behaviour
3.1 neurons are the basic units of the nervous system
The nervous system is divided into two basic units:
- Central nervous system (CNS)
- The peripheral nervous system (PNS)
Their anatomically separate, but functions are highly interdependent
PNS sends information to CNS, CNS organizes and evaluates information and then
directs the PNS to perform specific behaviors or make bodily adjustments.
Central nervous system (CNS) consists of the brain and the spinal cord
Peripheral nervous system (PNS) consists of all the other nerve cells in the rest of the body
and includes the somatic and autonomic nervous systems.
Somatic component is involved in voluntary behavior, such as when you reach for an object
Autonomic component is responsible for the less voluntary actions of your body, such as
controlling your heart rate and other bodily functions.
Neurons (nerve cells), the basic units of the nervous systems receive, integrate, and
transmit information. They are powered by electrical impulses and communicate with other
nerve cells through chemical signals. During reception phase, neurons take in chemical
signals from neighboring neurons. During integration, incoming signals are assessed, during
transmission, neurons pass their own signals to yet other receiving neurons
neural network, neurons communicate selectively with other neurons forming circuits,
develop through genetic influence, maturation, and experience, repeated firing
,Functional basis of all psychological activity complex networks of neurons sending and
receiving signals
Types of neurons
- Sensory neurons detect information from the physical world and pass that.
Information along to the brain
- Somatosensory nerves the sensory nerves that provide information from the skin
and muscles
- Motor neurons direct muscles to contract or relax, thereby producing movement
- Interneurons act as relay stations facilitating communication between sensory and
motor neurons
Sensory and motor neurons work together to control movement
Reflexes automatic motor responses, occur before we even think about those responses
A typical neuron has four structural regions that participate in communication functions:
1. the dendrites, short branchlike appendages that detect chemical signals from
neighboring neurons
2. The cell body (soma), information received via dendrites collected and integrated
3. The axon, electrical impulses are transmitted along a long, narrow outgrowth,
carrying information between brain and other specific locations in the body
4. Terminal buttons, the end of each axon, knoblike structures
Synapse the site where chemical communication occurs between neurons. Neurons do not
touch, they communicate by sending chemicals into a synapse
Membrane the outer surface of a neuron, it regulates the concentration of electrically
charged molecules that are the basis of the neuron’s electrical activity
Within membrane are ion channels, these specialized pores allow ions to pass in and out of
the cell when neuron transmits signals down the axon.
3.2 Action potentials produce neural communication
Neural firing/ action potential is the electrical signal that passes along the axon. This causes
the terminal buttons to release chemicals that transmit signals to other neurons
,When neuron inactive, electrical charge inside neuron is slightly more negative than the
electrical charge outside = resting membrane potential. Occurs because the ratio of
negative to positive ions is greater inside the neuron than outside.
When neuron more negative ions inside than outside = polarized, this creates electrical
energy necessary to power the firing of the neuron.
Types of ions that contribute to a neuron’s resting membrane potential:
- Sodium ions
- Potassium ions
Sodium-potassium pump contributes to polarization: increases potassium and decreases
sodium inside neuron, helping to maintain the resting membrane potential
Signals arrive at the dendrites two types:
- Excitatory, signals depolarize the cell membrane (decrease polarization by
decreasing the negative charge inside the cell relative to outside the cell) increase
likelihood that neuron will fire opens gates sodium ions to rush into neuron
more positively charged
- Inhibitory signals hyperpolarize the cell (increase polarization by increasing the
negative charge inside the cell relative to outside cell) signals decrease likelihood
neuron will fire
Relative refractory period the sodium-potassium pomp restores the membrane potential to
its resting state.
All-or-none principle tells a neuron fire with the same potency each time, the stronger the
stimulation, the more frequently action potentials are generated.
Absolute refractory period short amount of time, an ion channel cannot open again.
Followed by a relative refractory period, in which it takes greater excitation to fire neuron
again.
Action potential always moves in one direction: down the axon away from the cell body to
the terminal buttons.
, Axons of many types of neurons are covered by myelin sheath: encases and insulates many
axons like the plastic tubing around wires in an electrical cord.
The presence of myelin
greatly increases the
sped with which an
action potential travels
down the axon
3.3 Neurotransmitters influence mental activity and behavior
Presynaptic neuron the neuron that sends the signal
Postsynaptic neuron the neuron that receives the signal
inside each terminal button of the presynaptic neuron are neurotransmitters, chemicals
that are made in the axon or cell body and stored in vesicles.
Common neurotransmitters and their major functions:
Acetylcholine motor control over muscles, learning, memory, sleeping and dreaming
Norepinephrine arousal, vigilance, and attention
Serotonin emotional states and impulsiveness dreaming
Dopamine reward and motivation, motor control over voluntary movement
GABA (gamma-aminobutyric acid) inhabitation of action potentials anxiety
reduction
Glutamate enhancement of action potentials, learning and memory
Endorphins pain reduction, reward
