Ch. 3: Biology and the Brain
Sec. 1: The Nervous System
Main Idea
The nervous system contains billions of cells called neurons. Neurons communicate with one
another through the central and peripheral nervous systems.
The nervous system has two parts. The central nervous system consists of the brain and spinal
cord. The peripheral nervous system is made up of nerve cells that send messages between the
central nervous system and other parts of the body. Nerve cells are called neurons.
•
The cell body
•
Dendrites
•
An axon transmits
•
Myelin is
•
Axon terminals branch
The Communication Process
•
Messages are sent from the axon terminals of one neuron to the dendrites of another
neuron.
•
In order for this process to happen, the message must cross a synapse.
•
A synapse
•
Messages travel in only one direction. Messages
–
enter the dendrites
–
travel through the cell body and axon to the axon terminals
–
cross the synapses to the dendrites of other neurons
Neurotransmitters: The Body’s Chemical Messengers
•
Neurons send messages across synapses through the release of neurotransmitters.
•
Neurotransmitters are
•
A neuron fires, or sends a message, by releasing neurotransmitters.
–
The message is converted into an electrical impulse that travels through the
neuron.
–
•
The message is transmitted to the next neuron by other neurotransmitters until
the message arrives at its destination.
There are several kinds of neurotransmitters.
–
Acetylcholine is
–
Dopamine is
The Central Nervous System
•
The central nervous systems
•
The spinal cord is a
•
The spinal cord transmits messages between the brain and the muscles and glands in
the body.
•
The spinal cord sends messages to specific muscles.
•
The spinal cord is involved in spinal reflexes.
The Peripheral Nervous System
The Somatic Nervous System
•
The somatic nervous system transmits
•
It carries messages from the voluntary muscles and sense organs.
•
It is activated by touch, pain, changes in temperature, and changes in body position.
The Autonomic Nervous System
•
The autonomic nervous system regulates
•
It has two divisions.
•
The sympathetic nervous system reacts to stress.
•
The parasympathetic nervous system restores peace to the body’s systems
Sec. 2: The Brain: Our Control Center
Main Idea
The human brain has many parts that work together to coordinate body movement,
create thought and emotions, and shape behaviors.
•
In ancient times, people did not attribute human psychological processes such as
thinking to the working of the brain.
•
Instead, people widely believed that the body was inhabited by souls or demons.
•
Ancient Egyptians believed that a little person dwelled within the skull and regulated
behavior.
•
The Greek philosopher Aristotle thought that the soul resided in the heart.
•
Today we recognize that the mind, or consciousness, dwells within the brain.
Parts of the Brain
The Hindbrain
•
The medulla is
•
The pons regulates
The cerebellum is
The Midbrain
•
Areas within the midbrain are
•
Contains part of the reticular activating system, which is important
The Forebrain
•
The thalamus serves
•
The hypothalamus is vital to the regulation of body temperature, the storage of
nutrients, and various aspects of motivation and emotion. It is also involved in hunger,
thirst, sexual behavior, caring for offspring, and aggression.
•
The limbic system is involved
•
The cerebrum makes up about
•
The cerebral cortex is the outer layer of the brain. It is the part that thinks, and it also
deals with memory, language, emotions, complex motor skills, perception, and more.
The Cerebral Cortex
•
The cerebral cortex has
•
Each side is called
•
The corpus callosum is
•
Information received by one side of the body is transmitted to the opposite hemisphere
of the brain.
•
Each hemisphere is divided into four parts:
–
frontal lobe
–
parietal lobe
–
temporal lobe
–
occipital lobe
Senses and Motor Behavior
•
The occipital lobe is the primary visual area of the cerebral cortex.
•
The temporal lobe is the hearing, or auditory, area of the cerebral cortex.
•
Messages received from the skin’s sensory receptors are projected to the sensory cortex
in the parietal lobe.
•
These sensations include warmth, cold, touch, and pain.
Association Areas
•
The association areas of the cerebral cortex
•
The association areas in the frontal lobes function as the brain’s executive center.
•
Association areas provide the core of the working memory.
•
The frontal region of the brain thus retrieves visual, auditory, and other kinds of
memories.
•
Other association areas make possible the psychological functions of language.
Language Abilities
•
For nearly all right-handed people,
•
Language functions are also based in the left hemisphere of about two out of three lefthanded people.
•
Wernicke’s area connects sounds and sights. When this area is damaged, people find it
difficult to understand speech.
•
Broca’s area is involved in speech. When this area is damaged, people speak slowly and
use simple sentences.
Left and Right Hemispheres
•
The left hemisphere
•
The right hemisphere is more
•
Split-brain operations have taught psychologists much of what they know about leftand right-hemisphere functioning.
Methods of Studying the Brain
Accidents
•
Researchers are able to learn how the brain is related to psychological functions through
the study of brain damage due to accidents.
Electrical Stimulation
•
Electrical stimulation of the brain has shown that specific areas are associated with
specific types of sensations.
•
It is not a reliable research tool.
Lesions
•
Scientists can study a brain by cutting, removing, or destroying parts of it.
•
This method is used on laboratory animals.
Electroencephalogram
•
The EEG is a device that records electrical activity of the brain.
•
EEG readings can help diagnose certain psychological disorders and to help locate
tumors.
Brain Imaging
•
•
Brain imaging can provide information about
–
brain damage
–
cancers
–
difficult surgeries
Brain imaging techniques include
–
CAT scans
–
MRI scans
–
PET scans
–
fMRI scans
Sec. 3: The Endocrine System
Main Idea
The endocrine system produces hormones that affect growth, development, and some
behaviors.
•
The endocrine system consists of glands that secrete substances called hormones.
The Pituitary Gland
•
It lies just below
•
It secretes hormones that include human growth hormone, prolactin, and oxytocin.
•
Some pituitary hormones stimulate other endocrine glands such as the adrenals,
thyroid, and ovaries or testes.
The Thyroid Gland
•
It produces
•
Thyroxin affects
•
Too little thyroxin can cause hypothyroidism and cretinism.
•
Too much thyroxin can cause hyperthyroidism.
The Adrenal Glands
•
They are located
•
The outer layer, or cortex,
•
Cortical steroids increase resistance to stress, promote muscle development, and make
the liver release stored sugar to provide energy during emergencies.
•
The adrenal glands produce adrenaline and noradrenaline.
Ovaries and Testes
Ovaries in females and testes in males produce hormones that influence sexual
development and functions.
Both glands produce estrogen, progesterone, and testosterone.
Estrogen and Progesterone
•
Estrogen and progesterone are female sex hormones that regulate the menstrual cycle.
•
Estrogen has psychological as well as biological effects.
•
Low levels of estrogen and progesterone are found in males.
•
Testosterone
•
Testosterone is the primary male sex hormone.
•
It aids the growth of muscle and bone.
•
It aids development of primary and secondary sex characteristics.
•
Small amounts are found in females.
Sec. 4: Heredity: Our Genetic Background
Main Idea
Heredity is the transmission of characteristics from parents to offspring. Both heredity
and environment shape an individual’s personal traits.
Heredity, Genes, and Chromosomes
•
Heredity is the
•
Psychologists study heredity to understand people’s behavior.
•
Genes are the
•
Genes are found in threadlike structures called chromosomes.
–
Genes are
–
Most normal human cells have
–
In each pair, one chromosome is
–
The twenty-third pair determines gender.
–
When a child is born without all 46 chromosomes, physical and behavioral
disorders may result.
Nature and Nurture
•
The debate over the role of biology in determining who we are as people is called the
“nature-nurture” issue.
•
Nature refers to what people inherit.
•
Nurture refers to environmental factors.
•
“Nature” supporters argue that biological makeup primarily determines people’s traits
and personalities.
•
“Nurture” supporters argue that the environment and everyday experiences determine
how we behave and think.
•
Both views are extreme.
•
Most psychologists think that both nature and nurture determine psychological traits.
•
The role of heredity is still a controversial topic.
Kinship Studies
•
Kinship studies focus on the roles that heredity and environment play in determining a
trait.
•
Kinships refers to the degree to which people are related.
•
Twin Studies Studies of
•
Adoptee Studies Psychologists
•
Twins Reared Apart One of the most useful types of kinship studies focuses on twins
who have been reared apart.
–
Lack of common experiences makes it more likely that similarities are
attributable to genetic factors.