Chapter 2
Brain and Behavior
Neurons
-the brain consists of some 100 billion
neurons (individual nerve cells) which
carry and process information, activate
muscles and glands
-they form vast networks to produce
intelligence and consciousness
-linked to one another in tight clumps and
long chains
Parts of a Neuron
1. Dendrites -receive messages from other
neurons
2. Soma – they are the main body of a
neuron; also accepts incoming
information, but sends messages of its
own down a thin fiber called the axon
3. Axon – a thin fiber that carries
information away from the cell body of a
neuron.
4. Axon terminals – allows information to
pass from neuron to neuron.
The Nerve Impulse
1. Ions are electrically charged molecules found
in and around nerve cells
2. Resting potential is the electrical charge of an
inactive neuron at rest
3. Threshold is the point at which a nerve
impulse is triggered
4. Action potential is the nerve impulse, which
can travel up to 200 miles per hour. Once a
neuron reaches a certain point on the
threshold then it goes to the action potential.
5. The axon membrane is pierced by tiny
molecular tunnels called ion channels.
Salatory Conduction
-gaps in myelin that help impulses move
faster
Myelin – fatty tissue coating axons
Synapses and Neurontransmitters
1. nerve impulse is primarily electrical
2. communication between neurons is
chemical
3. Synapse is the microscopic space between
two neurons over which messages pass
4. When an action potential reaches the tips
of the axon terminals, neurotransmitters
are released into the synaptic gap
5. Neurotransmitter molecules cross the
synaptic gap and attach to special receptor
sites on the receiving neuron
6. Receptor sites are areas on the surface of
neurons and other cells that are sensitive
to neurotransmitters or hormones
7. Excite or inhibit the neurons
Neural Regulators
1. Neuropeptides are brain chemicals that
regulate the activity of neurons.
2.Enkephalins regulate reactions to pain and
stress
3.Endorphins -pain killing effect
Nervous System
Neurons are tiny cells; Nerves are large
bundles of axons and dendrites
1. Many nerves have a whitish color because
they contain axons coated with a fatty
layer of tissue called myelin
2. Neurilemma is a thin layer of cells that
encases many axons outside the brain and
spinal cord
Neural Networks
Central Nervous System and Peripheral
Nervous System
-the brain communicates with the rest of the
body through the spinal cord
Peripheral nervous system
-consists of all parts of the nervous system
outside the brain and spinal cord
-The peripheral nervous system can be
divided into two parts:
Somatic system which carries messages to
and from the sense organs and skeletal
muscles
Autonomic system serves the internal
organs and glands of the body
1. Sympathetic branch that arouses the
body
2. Parasympathetic branch that quiets the
body
Research Methods
Biopsychology - The study of how biological
processes, especially activity in the brain
and nervous system, relate to behavior.
Clinical studies – examining how brain
diseases or injuries affect personality,
behavior or sensory capacities
Ablation – surgical removal of parts of the
brain – causes changes in behavior or
sensations, which gives insight to the
purpose of the missing part
Cerebral Cortex
Cerebrum is the two large hemispheres that
cover the upper part of the brain.
Cerebral cortex is the outer layer of the
cerebrum
Gray matter is the areas in the nervous
system made up of mostly nerve cell
bodies
Cerbral Hemispheres
Corpus callosum is the bundle of fibers
connecting the cerebral hemispheres
The left side of the brain mainly controls the
right side of the body. The right side of the
brain mainly controls the left body areas
Damage to the right hem may cause Spatial
neglect: ignoring one side of the vision or
of the body after damage to a brain
hemisphere.
Left Brain
Roughly 95% of all adults use the left brain
for language (speaking, writing, and
understanding).
- superior at math, judging time and rhythm
and coordinating the order of complex
movements, such as those needed for
speech.
-mainly involved with analysis (breaking
information into parts)
-processes information sequentially
Right hemisphere can produce only the
simplest language and numbers
- Right brain is especially good at perceptual
skills, such as recognizing patterns, faces,
and melodies, putting together a puzzle, or
drawing a picture.
- detecting and expressing emotion
If the right brain is damaged people lose
their ability to understand jokes, irony,
sarcasm, implications, and other nuances
of language.
The right hemisphere appears to process
information simultaneously and
holistically
-Is better at assembling pieces of the world
into a coherent picture; it sees overall
patterns and general connections
Lobes of the Cerebral Cortex
Occipital lobes – the portion of the cerebral
cortex where vision registers in the brain
Parietal lobes – the area of the brain where
bodily sensations register
Somatosensory area is the receiving area for
bodily sensations within the Parietal lobe
Temporal lobes – the areas that include the
sites where hearing registers in the brain
Frontal lobes – the brain area associated
with movement, the sense of smell, and
higher mental functions
-Motor cortex – the brain area associated
with control of muscle movement
-Association cortex
-all areas of the cerebral cortex that are not
primarily sensory or motor in function
-Damage to association areas in the left
hemi may lead to Aphasia -a speech
disturbance resulting from brain damage
one type is related to Broca’s area: a
language area related to grammar and
pronunciation
Wernicke’s area is an area related to
language comprehension
Agnosia is the inability to grasp the meaning
of stimuli, such as words, objects, or
pictures
Facial agnosia is the inability to recognize
familiar faces
Subcortex
all brain structures below the cerebral cortex
The Hindbrain
Brainstem is the lowest part of the brain,
including the cerebellum, medulla, pons,
and reticular formation
Medulla is the structure that connects the
brain with the spinal cord and controls
vital life functions: heart rate, breathing,
swallowing
Pons is an area on the brainstem that acts as
a bridge between the medulla and other
structures
Cerebellum is a brain structure that controls
posture and coordination; stores
memories related to skills and habits
(walking, running, playing music
Reticular formation is a network of cells and
fibers within the medulla and brainstem;
associated with attention, alertness, and
some reflexes: breathing, sneezing,
coughing, vomiting
-as messages flow into the brain, the RF
gives priority to some with turning others
aside.
Reticular Activating System (RAS) is a part
of the reticular formation that activates the
cerebral cortex, stimulating it to keep it
active and alert
The forebrain contains two of the most
important parts of your body, the
thalamus and hypothalamus
Thalamus is a brain structure that relays
sensory information to the cerebral cortex
Hypothalamus is a small area of the brain
that regulates emotional behaviors and
motives
-behaviors are organized or “decided on”
before messages leave the brain, causing
the body to relax
Limbic system is a system in the forebrain
that is closely linked with emotional
response
Amygdala is a part of the limbic system
associated with fear responses
Hippocampus is a part of the limbic system
associated with storing memories
Endocrine System
Hormone is a glandular secretion that affects bodily
functions or behavior
Growth hormone is secreted by the pituitary gland
that promotes bodily growth
-Giantism is excessive bodily growth caused by too
much growth hormone
-Acromegaly is the enlargement of the arms, hands,
feet, and face caused by excess growth hormone
production late in the human growth period
-Hypopituitary dwarfism is shortness and smallness
caused by too little growth hormone
Pituitary gland is the “master gland” whose
hormones influence other endocrine
glands. The hypothalamus directs the
pituitary gland
Pineal gland helps regulate body rhythms
and sleep cycles
Melatonin is the hormone released by the
pineal gland in response to daily cycles of
light and dark; controls body rhythms and
sleep cycles
Thyroid gland is the endocrine gland that
helps regulate the rate of metabolism
-Hyperthyroidism is faster metabolism and
excitability caused by an overactive
thyroid gland
-Hypothyroidism is slower metabolism and
sluggishness caused by an underactive
thyroid gland
-Epinephrine is an adrenal hormone that
tends to arouse the body; norepinephrine
is associated with anger
5Adrenal glands is endocrine glands that arouse the
body, regulate salt balance, adjust the body to
stress, and affect sexual functioning
-Adrenal medulla is the inner core of the adrenal
glands; a source of epinephrine and
norepinephrine
-Adrenal cortex is the outer layer of the adrenal
glands; produces hormones that affect salt intake,
reactions to stress, and sexual development
-Virilism is the development of male sexual
characteristic in a female
-Premature puberty is the development of sexual
maturity in childhood
Plasticity
the brain’ s capacity to change its structure
and functions
the more you challenge and engage your
brain, especially by learning new skills, the
healthier it will be and the better it will
function
Neurogenesis
-the brain loses cells every day; it
simultaneously grows new neurons to
replace them