Chapter 2: The Biological Basis of Behavior
Neuropsychologists: Psychobiologists who study the brain’s influence on
Neuroscience: The study of the brain and the nervous system.
Psychobiology: The area of psychology that focuses on biological foundations
of behavior and mental processes.
Neurons: Individual cells that are the smallest unit of the nervous system.
Dendrites: Short fibers that branch out from the cell body and pick up
Axon: Single long fiber extending from the cell body; it carries outgoing
Nerve (or tract): Group of axons bundled together.
Myelin sheath: White fatty covering found on some axons.
Sensory (or afferent) neurons: neurons that carry messages from sense
organs to the spinal cord or brain.
Motor (or efferent) neurons: neurons that carry messages from the spinal
cord or brain to the muscles and glands.
Interneurons (or association neuron): neurons that carry messages from one
neuron to another.
Glial cells (or glia): cells that insulate and support neurons by holding them
together, provide nourishment and remove waste products, prevent harmful
substances from passing into the brain, and from the myelin sheath.
Neural impulse: the firing of a nerve cell
Synaptic space (or synaptic cleft): Tiny gap between the axon terminal of one
neuron and the dendrites or cell body of the next neuron.
Synapse: area composed of the axon terminal of one neuron, the synaptic
space, and the dendrite or cell body of the next neuron.
Synaptic Transmission-Communication between neurons. When a neural
impulse reaches the end of an axon, tiny oval sacs, called synaptic vesicles, at
the end of most axons release varying amounts of chemical substances called
neurotransmitters. These substances travel across the synaptic space and
affect the next neuron.
Terminal button (or synaptic knob): structure at the end of an axon terminal
Synaptic vesicles: tiny sacs in a terminal button that release chemicals into
Neurotransmitters: chemicals released by the synaptic vesicles that travel
across the synaptic space and affect adjacent neurons.
Receptor sites: locations on a receptor neuron into which a specific
neurotransmitter fits like a key into a lock.
Major Neurotransmitters and Their Effects:
1. Acetylcholine (ACh) – distributed widely throughout the central
nervous system, where it is involved in arousal, attention,
memory, motivation, and movement. Involved in muscle action
through presence at neuromuscular junctions. Degeneration of
neurons that produce ACh has been linked to Alzheimer’s disease.
Too much ACh can lead to to spasms and tremors; too little, to
paralysis or torpor.
2. Dopamine – involved in a wide variety of behaviors and emotions,
including pleasure. Implicated in schizophrenia and Parkinson’s
3. Serotonin – involved in the regulation of sleep, dreaming, mood,
eating, pain, and aggressive behavior. Implicated in depression.
4. Norepinephrine – affects arousal, wakefulness, learning, memory,
5. Endorphins – involved in the inhibition of pain. Released during
strenuous exercise. May be responsible for “runner’s high.”
Neural plasticity: the ability of the brain to change in response to experience.
Neurogenesis: the growth of new neurons.
Central nervous system: division of the nervous system that consists of the
brain and spinal cord.
Peripheral nervous system: division of the nervous system that connects the
central nervous system to the rest of the body.
The divisions of the brain.
PARTS OF THE BRAIN AND THEIR FUNCTIONS:
Central Core Medulla: regulates respiration, heart rate,
Hind-brain Pons: regulates sleep-wake cycles
Cerebellum: regulates reflexes and balance;
Mid-brain Thalamus: major sensory relay center;
regulates higher brain centers and
peripheral nervous system.
Hypothalamus: influences emotion and
motivation; govern stress reactions.
Reticular formation: regulates attention and
Limbic System Hippocampus: regulates formation of new
Amygdala: governs emotions related to self-
Cerebral Cortex Frontal lobe: goal-directed behavior;
concentration; emotional control and
temperament; voluntary movements;
coordinates messages from other lobes;
complex problem solving; involved in many
aspects of personality.
Parietal lobe: receives sensory information;
Occipital lobe: receives and processes visual
Temporal lobe: smell and hearing; balance
and equilibrium; emotion and motivation;
some language comprehension; complex
visual processing and face recognition.
The limbic system: ring of structures that play a role in learning and
Cerebral cortex: the outer surface of the two cerebral hemispheres that
regulates most complex behavior.
Frontal lobe: part of the cerebral cortex that is responsible for voluntary
movement; it is also important for attention, goal-directed behavior, and
appropriate emotional experiences.
Primary motor cortex: the section of each frontal lobe responsible for
Occipital lobe: receives and interprets visual information
Parietal lobe: receives sensory information from throughout the body.
Primary somatosensory cortex: area of the parietal lobe where messages
from the sense receptors are registered.
Temporal lobe: helps regulate hearing, balance and equilibrium, and certain
emotions and motivations.
The two cerebral hemispheres. Each hemisphere specializes in processing
specific types of information.
Corpus callosum: a thick band of nerve fibers connecting the left and right
Processing of speech and language. Broca’s and Wernicke’s areas, generally
found only on the left side of the brain, work together, enabling us to produce
and understand speech and language.
TOOLS FOR STUDYING THE NERVOUS SYSTEM:
Microelectrode Techniques – used to study the functions of
Macroelectrode Techniques – used to obtain a picture of the
activity in a particular region of the brain. The EEG is one such
Structural Imaging – family of techniques used to map structures
in a living brain.
o Computerized axial tomography (CAT or CT) – permits
three-dimensional imaging of a living human brain.
o Magnetic resonance imaging (MRI) – produces pictures
of inner brain structures.
Functional Imaging Techniques – family of techniques that can
image activity in the brain as it responds to various stimuli.
o EEG imaging – measures general brain activity on a
millisecond-by-millisecond basis through electrodes
pasted to the scalp.
o Magnetoencephalography (MEG) and Magnetic Source
Imaging (MSI) – two procedures that are similar to EEG
imaging but have greater accuracy.
o Positron Emission Tomography (PET) Scanning and
Single Photon Emission Computed Tomography
(SPECT) – two techniques that use radioactive energy
to map exact regions of brain activity.
o Functional Magnetic Resonance Imaging (fMRI) –
measures the movement of blood molecules in the
brain, pinpointing specific sites and details of neuronal
Spinal cord: complex cable of neurons that
runs down the spine, connecting the brain
to most of the rest of the body.
Peripheral nervous system (PNS) – links the
brain and spinal cord to the rest of the
body, including the sensory receptors,
glands, internal organs, and skeletal
Somatic nervous system: the part of the
PNS that carries messages from the senses
to the CNS and between the CNS and the
Autonomic nervous system: the part of the
PNS that carries messages between the CNS
and the internal organs.
The sympathetic and parasympathetic divisions of the autonomic nervous
system. The sympathetic division generally acts to arouse the body, preparing
it for “fight or flight.” The parasympathetic follows with messages to relax.
Endocrine system plays a key role in helping to coordinate and integrate
complex psychological reactions.
Endocrine glands: release hormones into the bloodstream.
Hormones: chemical substances released by the endocrine glands; they help
regulate bodily activities.
The glands of the endocrine system. Endocrine glands secrete hormones that
produce widespread effects on the body.
Genetics: study of how traits are transmitted from one generation to the
Behavior genetics: study of the relationship between heredity and behavior.
Genes: segments of DNA that control the transmission of traits; they are
found on the chromosomes.
Chromosomes: pairs of threadlike bodies within the cell nucleus that contain
Deoxyribonucleic acid (DNA): complex molecule in a double-helix
configuration that is the main ingredient of chromosomes and genes and
that forms the code for all genetic information.
Human genome: the full complement of genes within a human cell.
The 23 pairs of chromosomes found in every normal human cell. The 2
members of 22 of these pairs look exactly alike. The 2 members of the 23rd
pair, the sex chromosomes, may or may not look alike. Females have
equivalent X chromosomes, while males have one X and one Y chromosome,
which look very different.
1. Compare the operation of the endocrine system to that of the
2. Why are psychologists interested in hormones?
3. Explain the relative influence of heredity and environment in
Feldman, R. S. (2010). Understanding Psychology. 9th Edition. McGraw Hill Companies,
Morris, C.G.,et al. (2007). Psychology Concepts and Applications. Pearson Education, Inc.
Mrs. Maria Angela L. Diopol