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Neuroanatomy
Chapter Two
A. Neurons
1. The long, thin cells of nerve tissue along
which messages travel to & from the brain
– About 100 billion neurons (nerve cells) in the
human brain
2. Transmission occurs whenever cells are
stimulated past a minimum point and emit a
signal.
– Either fires or does not fire
– Electrical impulses allow for transmission of info
within a neuron; chemical impulses allow for
transmission of info between neurons
B. Parts of a Neuron
1. Neurons have many of the same features as
other cells
– Nucleus
– Cytoplasm
– Cell membrane
2. What makes neurons unique is their shape
and function
Parts of a Neuron (cont.)
1. Cell Body (also called the soma)
– Contains the nucleus and produces the energy needed to fuel neuron activity
– Directs all cell activities including the nucleus
2. Axon
– Carries impulses away from the cell body toward surrounding neurons
3. Dendrite
– Receive impulses, or messages, from other neurons and send them to the cell body
Parts of a Neuron (cont.)
4. Myelin sheath- insulates and protects the axon
for some neurons
– speeds the transmission of impulses
– In cases of multiple sclerosis, the myelin sheath is
gone.
5. Axon terminals- release neurotransmitters to
stimulate dendrites of the next neurons
6. Neurotransmitters- chemicals contained in the
terminals that enable neurons to communicate
7. Synapse- Space between the terminals of one
neuron & the dendrites of the next neuron
Structures of a neuron
LO 2.3 Neuron communication
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C. How a Neuron “Fires”
1. Ions – charged particles.
– Inside neuron – negatively charged.
– Outside neuron – positively charged.
2. Resting potential - the state of the neuron when not firing
a neural impulse.
3. Action potential - the release of the neural impulse
consisting of a reversal of the electrical charge within the
axon.
– Allows positive sodium ions to enter the cell.
4. All-or-none - referring to the fact that a neuron either fires
completely or does not fire at all.
5. Return to resting potential.
D. Neurotransmitters
1. Types of neurotransmitters:
– Excitatory: causes a neuron to fire
– Inhibitory: stops a neuron from firing
2. In NS: called neurotransmitters
3. Outside of NS: called hormones
4. Often several NTs working at the same
terminal button
E. Neuron Activity
1. The intensity depends on whether the neurons are
ON or OFF
2. Types:
– Afferent
• Sensory neurons
• Relay messages from the sense organs to
spinal cord & brain
– Efferent
• Motor neurons
• Send signals from the brain to the glands and muscles
– Interneurons
• Carry information between other neurons only found in the brain
and spinal cord
I. The Nervous System
Chapter Two
The Big Picture: The Nervous System
Peripheral
Nervous System
Central Nervous
System
The Brain
The Spinal
Cord
Autonomic
NS
Sympathetic
NS
Skeletal
(Somatic) NS
Parasympathetic
NS
A. Nervous System
1. The Central Nervous System (CNS)
– The brain and the spinal cord.
2. Peripheral Nervous System (PNS)
– The smaller branches of nerves that stretch
throughout the body.
Spinal Cord
Sensory organs receive the message.
Sensory neurons connect in the back
of the spinal cord and send the
information to the spinal cord.
Interneurons take the information
and send it to the brain & to motor
neurons at the same time.
Motor neurons exit through the front of
the spinal cord and carry the message
back to the muscle.
B. Voluntary and Involuntary Activities
1. Somatic Nervous System
– The part of the peripheral nervous system that
controls voluntary movement of skeletal muscles.
• Example: raising your hand to turn a book page.
2. Autonomic Nervous System
– The part of the peripheral nervous system that
controls internal biological functions.
• Example: your heartbeat or blood pressure.
C. ANS
1. Two parts:
• Sympathetic
 Prepares the body for dealing with
emergencies or strenuous activity.
• Parasympathetic
Works to conserve energy and to
enhance the body’s ability to
recover from strenuous activity.
II. Parts of the Brain
Chapter Two
Exploring Psychology
• Early Greeks were not impressed with the brain. They
suggested that the brain’s main function was to cool the
blood. They were much more impressed by the heart. They
proposed that the heart was the source of feelings and
thoughts. Hippocrates, however, observed the effect of head
injuries on people’s thoughts and actions and noted, “[F]rom
the brain, and from the brain only, arise our pleasures, joys,
laughter and jests, as well as our sorrows, pains, griefs and
tears. Through it, in particular, we think, see, hear…Eyes,
ears, tongue, hands and feet act in accordance with the
discernment [judgment] of the brain.”
Adapted from Psychology by Peter Gray, 1999.
The Question…
• How did Hippocrates help change the notion
that the brain, not the heart, was the source
of thoughts and feelings?
A. The Hindbrain
1. Location- Rear base of the skull
2. Role- Involved in most basic processes of life
– Includes:
•
Cerebellum- helps control posture, balance, and
voluntary movements
•
Medulla- controls breathing, heart rate, and a variety
of reflexes
•
Pons- functions as a bridge between the spinal cord
and the brain; produces chemicals the body needs for
sleep
B. The Midbrain
1. Location- Small part of the brain above the pons
2. Role- Collects information from the senses and sends
it upward
– Includes the medulla, pons, and midbrain (all make up the
brain stem)
– Reticular Activating System (RAS) spans across these
structures
• Alerts the rest of the brain to incoming signals and is involved in
the sleep/wake cycle
C. The Forebrain
1. Location- Covers the brain’s central core
– Includes:
• Thalamus- Relay station for information traveling to and
from the cortex (all sensory info except smell)
• Hypothalamus- Controls hunger, thirst, and sexual
behavior
– Makes us sweat when we are hot and shiver when
we are cold.
2. High thinking processes are also housed in the forebrain
– Cerebral cortex- outer layer of the forebrain
• Gives you the ability to learn and remember
– Cerebrum- inside layer of the forebrain
(Both go around the hindbrain and brain stem like a mushroom surrounds its stem)
D. The Limbic System
1. Location- Found in the core of the forebrain
(sits atop the brainstem but surrounded by
cerebral cortex)
2. Role- Composed of different structures in that
regulate emotions and motivations
– Includes the hypothalamus; amygdala (controls
violent emotions); thalamus; and hippocampus
(important in the formation of memories)
E. Cerebrum
1. Consists of two hemispheres, or halves
2. Resembles a small brain
2. The hemisphere is connected by a band of
fibers called the corpus callosum
3. Each hemisphere has deep grooves that mark
regions known as lobes
– Both hemispheres have the same four lobes
F. The Lobes
1.
Cerebral cortex– gray wrinkled surface; divided into 4 main
lobes
Occipital Lobe
•
–
–
•
Controls vision
Damage could cause visual problems
Parietal Lobe
–
•
Concerned with information from the senses all over the body
Temporal Lobe
–
•
Concerned with hearing, memory, emotion, and speaking
Frontal Lobe
–
Organization, planning, and creative thinking.
2. Some other sources say that frontal lobe controls behavior,
thought & emotion (instead of temporal lobe)
G. Other Parts of Cerebral Cortex
1. Prefrontal cortex: most frontal region of frontal
lobe (emotional control, planning)
2. Motor cortex: Strip of frontal lobe specialized for
controlling voluntary actions of muscles
3. Somatosensory cortex: Strip of parietal lobe
specialized for processing sensations of touch
4. Broca’s area: Portion of motor cortex found only
in the left hemisphere & specialized in
coordinating muscles used in speech
5. Wernicke’s area: Portion of temporal lobe found
only in the left hemisphere & involved in
processing & understanding speech
Overview of the Brain
Parts & Function
Sensory Homonculus
a map showing how different cortical segments
control parts of the body
The amount of cortex devoted to sensory, motor, and
association areas differs with more complex species.
Rats & cats rely on their
instincts more for survival.
Humans & chimpanzees rely on
integrating signals for survival.
III. Right/Left Brain
A. Hemisphere Lateralization
1. Each hemisphere controls & receives info
from the opposite side of body
2. Each hemisphere of the brain is
specialized to promote efficient work
•Left hemisphere– involved in tasks that
require logic, order, critical thinking or
analysis (writing, science, & math)
•Right hemisphere- require artistic or
creative skills (visual spatial skills); helps
with recognition of faces
B. Split-Brain Research
1. Patients with severe epilepsy had their
corpus callosum split to control seizures
2. They appear to be normal (cognitive, motor,
intellectual skills remain intact)
– Personality & mood are unaffected by surgery
3. Some unusual effects occur after surgery
– Patients cannot orally report info only presented
to the right hemisphere (since language centers
are in the left)
Language Areas of the Left Hemisphere
C. Important Figures Associated with the
Brain
1. Paul Broca- discovered that the speech
production center of the brain is located in
the frontal lobe
2. Carl Wernicke- studied the effects of brain
disease on speech & language
– All language deficits are result of damage to
Broca’s area
3. Roger Sperry- worked on split-brain research
4. Michael Gazzaniga- made advances in
understanding lateralization in the brain
IV. How Psychologists Study the
Brain
On September 13, 1848 Gage was a 25 year old
foreman of a blasting crew preparing a railroad bed
outside Cavendish, Vermont. He used his 3 foot 7
inches, 13 1/4 pound iron rod to tamp gunpowder
and sand into a hole in the rock. On this day
something went horribly wrong. The rod striking the
stone caused a spark and the resulting explosion sent
the rod flying up and through his left cheek and out
the top of his head. To the amazement of everyone
he was not killed and lived for more than eleven
years.
His limbic system was separated from his frontal
lobe during this accident. He lost control of his
emotions & became impulsive & animalistic.
A. Ways of Studying Brain
1. Accidents- How does one behave after suffering
a brain injury (Ex. Phineas Gage)
2. Recording- Electrodes inserted into brain to
record neurons
3. Lesioning- removal or destruction of part of
brain
–
Two types:
»
»
Brain destruction to determine the “after” behavior as
compared to the “before” behavior
Most popular- frontal lobotomy
4. Stimulation
–
Electrodes used to “stimulate” brain to pinpoint problems
areas in order to repair
• Example: epilepsy and pain relieve
B. EEG
1. Stands for electroencephalograph
2. Created in 1929 by Hans Berger
3. Records brain’s electrical activity/firing of
neurons
4. Multiple electrodes are pasted to outside of
head
5. Adv- Detects rapid changes in electrical activity
6. Dis- Can not pinpoint exact source of activity
7. Can be done while the person is awake or even
sleeping
EEG
C. CAT/CT Scan
1. Stands for computerized tomography
2. Uses several X-ray cameras that rotate around
the brain & combine all the pictures into a 3-D
picture of the brain’s structure
3. Most commonly used when identifying tumors,
tissue degeneration & skull fractures
4. Adv- Provide greater clarity & reveal more
details than regular x-ray exams
5. Dis- Chance of getting radiation; not for
pregnant women
CAT
D. PET Scan
1. Stands for positron emission tomography
2. Lets researchers see what areas of brain are
most active during certain tasks
– Can do while brain is at rest, sleeping, etc.
3. Involves injection of radioactive dye into
bloodstream that can be traced & detected
to monitor blow flow to various regions of
brain
4. Useful for investigating abnormal brain
activity (seizures, following strokes, etc.)
PET
E. MRI
1. Stands for magnetic resonance imaging
2. Use magnetic fields to measure the density
& location of brain material
3. Computer then converts the signals into
highly detailed images of tissue & structures
in the brain (no function)
4. Adv- No exposure to radiation; brain, spinal
cord & nerves can be seen clear than x-rays
5. Dis– Some patients can’t have them; no
metal allowed in room
MRI
F. fMRI
1. Stands for Functional MRI
2. Combines elements of MRI & PET scans
3. Shows details of brain structure with info
about blood flow in brain, tying brain
structure to brain activity during cognitive
tasks
4. Adv- No exposure to radiation
5. Dis- Maps produced are not created in real
time
V. Endocrine System
A. Definition
1. Collection of glands which secrete
hormones into bloodstream that target &
have effects on specific organs in body
2. Allows for communication between the
brain & specific organs in the body (in
conjunction with ANS)
3. Under control of hypothalamus
B. Hormones vs. Neurotransmitters
1. Distance traveled between release &
target sites
– hormones travel longer distances
– neurotransmitters - travel across a synaptic cleft
2. Speed of communication
– hormones - slower communication
– neurotransmitters - rapid, specific action
C. Parts of the Endocrine System
1.
Pineal gland
–
Secretes melatonin which
regulates sleep-wake cycle
2. Pituitary gland
– Referred to as “master
gland” because it regulates
many other glands
3. Ovaries & testes
– Produce our sex hormones
– Estrogen for women;
testosterone for men
4. Adrenal glands– produce
adrenaline
– Signals rest of the body to
prepare for fight or flight
VII. Genetics
A. Definition
1. Affects human thought & behavior
2. Traits result from:
• Nature
– The characteristics one inherits
– Ones biological makeup
•
Nurture
– Environmental Factors
– Family, culture, education, individual
experiences
B. Basic Principles of Genetics
1. Chromosomes
– Strands of DNA molecules that
carry genetic information
2. The numbers:
– 46 chromosomes in each human body.
– Operate in 23 pairs (with one
chromosome of each pair contributed
by each parent).
– Organic molecule arranged in a doublehelix.
– Contains the “code of life”
C. Human Behavior Genetics
1. Family studies
– Assume that close family members share more of
a trait than non-relatives
– Used to assess heritability of psychological
disorders or traits
2. Twin studies
– Used to determine how heritable a trait or
disorder may be
– Identical twins would have highest heritability