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much more quickly than genetic evolution。
D。 Variation in the Human Genotype
1。 Basic Genetics
a） Genes： Organized packets of DNA that contain the instructions for the
production of proteins
b） Genes are found on rod like structures known as chromosomes。 Humans
contain 46 chromosomes； 23 from the mother and 23 from the father。
c） Estimates of the number of genes in the human genome range from 30；000
to 150；000
d） The X and Y sex chromosomes determine sex。 One X es from the
mother； and either an X or a Y es from the father。 XX = female。 XY =
male。
2。 Genes and Behavior： the interaction of psychology and genetics
a） Biology （genes） is （are） not destiny
b） Genes only determine the range of effects that the environment can have in
shaping phenotype and behavior
c） The person that you bee is jointly determined by genes and the
environment； by nature and nurture
3。 Sociobiology focuses on evolutionary explanations for social behavior and social
systems of humans and other animal species
II。Biology and Behavior
A。 Early Explanations of Behavior
1。 Rene Descartes argued that human physiology could be studied empirically； that
humans are just an animal machine； and that human action is a mechanical
response to the environment
2。 Sir Charles Sherrington provided evidence for Descartes’ ideas and suggested that
the human nervous system involves both excitatory and inhibitory processes
3。 Santiago Ramón y Cajal detected the physical gaps between adjacent neurons
4。 Donald Hebb proposed that the brain is not merely a mass of tissue but a highly
integrated series of structures； or cell assemblies； that perform specific functions
5。 Neuroscience is one of the most rapidly growing areas of research today
B。 Eavesdropping on the Brain
1。 Broca’s Area： The region of the brain that translates thoughts into speech
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PSYCHOLOGY AND LIFE
2。 Producing brain lesions
a） Not done on humans for obvious ethical reasons
b） Helpful in treating some neurological disorders such as epilepsy
3。 Electrical stimulation
a） Walter Hess found that sleep； sexual arousal； anxiety； and terror could be
turned on and off by electrically stimulating specific areas of the brain
4。 Recording and imaging brain activity
a） Electroencephalogram （EEG） records large； integrated patterns of brain
electrical activity
b） Positron…Emission Tomography （PET） scans construct a dynamic portrait
of the brain by detecting how radioactive （but safe） substances are
processed in the brain during different cognitive and behavioral activities
c） Magnetic Resonance Imaging （MRI） uses pulses of energy to cause atoms
to align with a magnetic field。 Special radio receivers then monitor the rate
at which atoms decay from alignment once the energy pulse is plete。
puters analyze this information to create dynamic models of brain
activity。
C。 The Nervous System
1。 prised of two major divisions
a） The central nervous system （CNS）； prised of all the neurons in the
brain and spinal cord
b） The peripheral nervous system （PNS）； prised of all the neurons
forming the nerve fibers that connect the CNS to the body
2。 The Central Nervous System （CNS）
a） Integrates and coordinates all bodily functions； processes all ining
neural messages； and sends mands to different parts of the body
b） Relies on PNS for information from sensory receptors
3。 The Peripheral Nervous System （PNS）
a） Provides the CNS with sensory information and relays mands from
the brain to the body’s organs and muscles
b） posed of two subdivisions
（1） The Somatic Nervous System （SNS）； which regulates the actions
of skeletal muscles
（2） The Autonomic Nervous System （ANS）； which sustains basic life
processes； further divided into two subdivisions：
（i） The Sympathetic Division governs response to
emergencies
（ii） The Parasympathetic Division governs routine operation
of internal bodily functions
D。 Brain Structures and Their Functions
1。 The brain is the most important ponent of the CNS and is posed of three
layers： the brain stem； the limbic system； and the cerebrum
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CHAPTER3： THE BIOLOGICAL BASES OF BEHAVIOR
2。 The Brain Stem
a） The Medulla； located at the top of the spinal cord； controls breathing； blood
pressure； and the heart
b） The Pons； located directly above the Medulla； provides inputs to other
structures of the brain stem and to the cerebellum
c） The Reticular Formation； located between the Medulla and Pons； arouses
the cerebral cortex to new stimulation and keeps the brain alert even
during sleep
d） The Thalamus； located above the Pons； receives input from the reticular
formation and channels ining sensory information to the appropriate
area of the cerebral cortex
e） The Cerebellum； located attached to the brain stem at the base of the skull；
coordinates bodily movements and plays a role in some types of learning
3。 The Limbic System mediates motivated behaviors； emotional states； and memory
processes and is posed of three structures：
a） The Hippocampus plays an important role in the acquisition of explicit
memories–memories that you are aware of retrieving
b） The Amygdala plays a role in emotional control and the formation of
emotional memories； especially those related to threat and danger
c） The Hypothalamus plays a role in maintaining homeostasis such as body
weight； temperature； and the endocrine system
4。 The Cerebrum regulates higher emotional and cognitive functions
a） The Cerebral Cortex is the thin outer layer of the cerebrum
b） The cerebrum is also divided into two symmetrical halves； the cerebral
hemispheres
c） The two cerebral hemispheres are connected by a thick mass of nerve fibers
called the corpus callosum； which relays messages between hemispheres
d） Grooves in the cerebrum； called the Central Sulcus and the Lateral Fissure；
help divide each cerebral hemisphere into four lobes
e） The Frontal lobe is located at the front of the cerebrum and is involved in
motor control and cognitive activities such as planning； decision making；
and goal setting
f） The Parietal lobe is located at the top of the cerebrum and is responsible for
the sensations of touch； pain； and temperature
g） The Occipital lobe is located at the back of the cerebrum and is responsible
for visual processing
h） The Temporal lobe is located at the side of the cerebrum and is responsible
for auditory processing
i） The hemispheres and lobes of the brain do not function independently；
rather they work as an integrated unit similar to an orchestra
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PSYCHOLOGY AND LIFE
j） The Motor Cortex； located in front of the central sulcus； controls movement
of the body’s voluntary muscles
k） The Somatosensory Cortex； located behind the central sulcus in the parietal
lobes； processes information about temperature； touch； body position； and
pain
l） The Auditory Cortex； located in the temporal lobes； processes auditory
information
m） The Visual Cortex； located in the occipital lobes； processes visual
information
n） Th