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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 
36 


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 

37 


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) The Association Cortex; which includes all of the cortex that is unlabeled; 
works to interpret and integrate information from many parts of the brain 

5。 Hemispheric Lateralization 
a) Roger Sperry and Michael Gazzaniga devised situations that could allow 
visual information to be presented separately to each hemisphere。 

b) Information from the right visual field goes to the left hemisphere; and 
information from the left visual field goes to the right hemisphere 

c) Speech may be the most highly lateralized of all brain functions。 For most 
people; speech is a left hemisphere function。 

d) The left hemisphere tends to be more analytical; processing information bit 
by bit 

e) The right hemisphere tends to be more holistic; processing information in 
global patterns 

f) There may be gender differences in lateralization。 When making 
judgments; the left hemispheres of males showed more activity; while both 
hemispheres of females showed activity 

E。 The Endocrine System 
1。 A highly plex munication system prised of a network of glands that 
supplements the work of the nervous system 
a) Hormones–“the messengers of life”–are chemicals secreted by the glands of 
the endocrine system。 They influence sexual development; physical 
growth; moods; arousal level; immune functioning; and metabolism rate。 

2。 The Hypothalamus serves as an intermediary between the endocrine system and the 
nervous system。 Messages from the brain cause the hypothalamus to release 
hormones to the pituitary gland。 
3。 The Pituitary Gland; the “master gland;” secretes about ten different types of 
hormones; which influence the functioning of all other endocrine system glands; and 
influences growth 
a) In males; the pituitary gland activates secretion of testosterone; which leads 
to sperm production 

b) In females; the pituitary gland activates secretion of estrogen; which is 
essential to the release of eggs from the ovaries 

38 


CHAPTER3: THE BIOLOGICAL BASES OF BEHAVIOR 

III。 The Nervous System in Action 
A。 The Neuron 
1。 The neuron is a cell specialized to receive; process; and transmit information to other 
cells。 There are at least 200 different types of neurons; which are typically prised 
of dendrites; soma; axon; and terminal buttons。 

a) Dendrites are branched fibers that extend outward from the body of the 
neuron and that receive messages from other neurons 

b) The Soma; or cell body; integrates information received by the dendrites 
and passes it along to the axon 

c) The Axon is a single extended fiber that conducts information to terminal 
buttons 

d) Terminal buttons are bulblike structures that secrete neurotransmitters 
which influence other neurons 

2。 There are three major classes of neurons: sensory neurons; motor neurons; and 
interneurons 
a) Sensory neurons carry messages from sense receptors toward the CNS 
b) Motor neurons carry messages from the CNS to the muscles and glands 
c) Interneurons carry messages between different neurons 

3。 Glia cells; derived from the Greek word for “glue;” outnumber neurons in the brain by 
about five or ten to one and perform three primary functions: housekeeping; 
insulation; and protection of the brain 
a) Development: Glia cells help guide newborn neurons to appropriate 
locations in the brain 

b) Housekeeping: Glia cells clean up after neurons die and absorb excess 
neurotransmitters 

c) Insulation: Glia cells form a myelin sheath around the axon of some types 
of neurons; greatly increasing the conduction speed of the axon 

d) Protection: Glia cells form a blood…brain barrier that prevents toxins from 
reaching the brain 

B。 Action Potentials 
1。 Neurons send messages in an all…or…none fashion through action potentials traveling 
down the axon; and they receive messages in the form of graded potentials through 
the dendrites 
a) Excitatory input increases the likelihood that a neuron will fire 

b) Inhibitory input decreases the likelihood that a neuron will fire 

c) Graded Potentials are generated by excitatory inputs and vary in size 
according to the magnitude of the stimulation。 One graded potential is 
often 

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