Chapter 2 Brain and Behavior

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Chapter 2Brain and Behavior
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Neuron and Its Parts

• Neuron Individual nerve cell
• Dendrites Receive messages from other neurons
• Soma Cell body body of the neuron
• Axon Fiber that carries information away from
  the cell body
• Axon Terminals Branches that link the dendrites
  and somas of other neurons

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Figure 2.1
FIGURE 2.1 A neuron, or nerve cell. In the right
foreground you can see a nerve cell fiber in
cross section. The upper left photo gives a more
realistic picture of the shape of neurons. Nerve
impulses usually travel from the dendrites and
soma to the branching ends of the axon. The nerve
cell shown here is a motor neuron. The axons of
motor neuron stretch from the brain and spinal
cord to muscles or glands of the body.
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Synapses

• Messages from one neuron to another pass over a
  microscopic gap called a synapse
• Synapse Microscopic gap between two neurons over
  which messages pass

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Figure 2.5
FIGURE 2.5 A highly magnified view of a synapse.
Neurotransmitters are stored in tiny sacs called
synaptic vesicles (VES-ihkels). When a nerve
impulse reaches the end of an axon, the vesicles
move to the surface and release
neurotransmitters. These molecules cross the
synaptic gap to affect the next neuron. The size
of the gap is exaggerated here it is actually
only about one millionth of an inch. Some
transmitter molecules excite the next neuron, and
some inhibit its activity.
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Neurotransmitters

• Chemicals that alter activity in neurons brain
  chemicals that carry messages.
• Acetylcholine Activates muscles
• Dopamine Muscle control
• Serotonin Mood and appetite control
• Receptor Site Areas on the surface of neurons
  and other cells that are sensitive to
  neurotransmitters

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Neural Regulators

• Neural Peptides Regulate activity of other
  neurons
• Endorphins Released by pituitary gland also
  help to relieve pain
• Do not send messages.

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Nerves and Neurons

• Nerves Large bundles of axons and dendrites (Not
  neurons)
• Myelin Fatty layer of tissue that coats axons
• Multiple Sclerosis (MS) occurs when myelin layer
  is destroyed numbness, weakness, and paralysis
  occur
• Neurogenesis Production of new brain cells

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Neural Networks

• Central Nervous System (CNS) Brain and spinal
  cord
• Peripheral Nervous System All parts of the
  nervous system outside of the brain and spinal
  cord
• Somatic System Links spinal cord with body and
  sense organs controls voluntary behavior
• Autonomic System Serves internal organs and
  glands controls automatic functions such as
  heart rate and blood pressure

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Figure 2.6
FIGURE 2.6 (a) Central and peripheral nervous
systems. (b) Spinal nerves, cranial nerves, and
the autonomic nervous system.
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Two Divisions of the Autonomic System

• Sympathetic Arouses body emergency system
• Parasympathetic Quiets body most active after
  an emotional event

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Figure 2.8
FIGURE 2.8 Sympathetic and parasympathetic
branches of the autonomic nervous system. Both
branches control involuntary actions. The
sympathetic system generally activates the body.
The parasympathetic system generally quiets it.
The sympathetic branch relays its messages
through clusters of nerve cells outside the
spinal cord.
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Figure 2.7
FIGURE 2.7 Subparts of the nervous system.
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Researching the Brain

• Computed Tomographic Scanning (CT)
  Computer-enhanced X-ray image of the brain or
  body
• Magnetic Resonance Imaging (MRI) Uses a strong
  magnetic field, not an X-ray, to produce an image
• Functional MRI (fMRI) MRI that also records
  brain activity
• Positron Emission Tomography (PET)
  Computer-generated color image of brain activity,
  based on glucose consumption in the brain

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Cerebral Cortex

• Definition Outer layer of the cerebrum
• Cerebrum Two large hemispheres that cover upper
  part of the brain
• Corticalization Increase in size and wrinkling
  of the cortex
• Cerebral Hemispheres Right and left halves of
  the cortex
• Corpus Callosum Bundle of fibers connecting
  cerebral hemispheres

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Split Brains

• Corpus Callosum is cut done to control severe
  epilepsy (seizure disorder).
• Result The person now has two brains in one
  body.
• This operation is rare and is often used as a
  last resort.

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Figure 2.19
FIGURE 2.19 Basic nerve pathways of vision.
Notice that the left portion of each eye connects
only to the left half of the brain likewise, the
right portion of each eye connects to the right
brain. When the corpus callosum is cut, a split
brain results. Then visual information can be
sent to just one hemisphere by flashing it in the
right or left visual field as the person stares
straight ahead.
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Figure 2.22
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When the Brain Fails to Function Properly

• Association Cortex Combine and process
  information from the five senses
• Aphasia Speech disturbance resulting from brain
  damage

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Figure 2.18
Spatial neglect resulting from a right hemisphere
stroke. Notice the neglect of the left side of
the pictures which were being reproduced.
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When the Brain Fails to Function Properly
(cont'd)

• Brocas Area Related to language and speech
  production
• If damaged, person knows what s/he wants to say
  but cant say the words
• Wernickes Area Related to language
  comprehension
• If damaged, person has problems with meanings of
  words, NOT pronunciation

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Subcortex

• Hindbrain (Brainstem)
• Medulla Connects brain with the spinal cord and
  controls vital life functions such as heart rate
  and breathing
• Pons (Bridge) Acts as a bridge between medulla
  and other structures
• Influences sleep and arousal
• Cerebellum Located at base of brain
• Regulates posture, muscle tone, and muscular
  coordination

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Subcortex Reticular Formation (RF)

• Lies inside medulla and brainstem
• Associated with alertness, attention and some
  reflexes (breathing, coughing, sneezing,
  vomiting)
• Reticular Activating System (RAS) Part of RF
  that keeps the cortex active and alert
• Its alarm clock

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Figure 2.25
FIGURE 2.25 This simplified drawing shows the
main structures of the human brain and describes
some of their most important features. (You can
use the color code in the foreground to identify
which areas are part of the forebrain, midbrain,
and hindbrain.)
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Forebrain

• Structures are part of the Limbic System System
  within forebrain closely linked to emotional
  response
• Thalamus Relays sensory information to the
  cortex switchboard
• Hypothalamus Regulates emotional behaviors and
  motives (e.g., sex, hunger, rage, hormone
  release)
• Amygdala Associated with fear responses
• Hippocampus Associated with storing memories
  helps us navigate through space

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Figure 2.26
FIGURE 2.26 Parts of the limbic system. Although
only one side is shown here, the hippocampus and
the amygdala extend out into the temporal lobes
at each side of the brain. The limbic system is a
sort of primitive core of the brain strongly
associated with emotion.
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Endocrine System

• Glands that pour chemicals (hormones) directly
  into the bloodstream or lymph system
• Pituitary Gland Regulates growth via growth
  hormone
• Too little means person will be smaller than
  average
• Hypopituitary Dwarfs As adults, perfectly
  proportioned but tiny
• Too much leads to giantism
• Excessive body growth

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Endocrine System (cont'd)

• Acromegaly Enlargement of arms, hands, feet, and
  facial bones
• Too much growth hormone released late in growth
  period
• Andre the Giant

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Endocrine System Concluded

• Pineal Gland Regulates body rhythms and sleep
  cycles.
• Releases hormone melatonin, which responds to
  daily variations in light.
• Thyroid In neck regulates metabolism.
• Hyperthyroidism Overactive thyroid person tends
  to be thin, tense, excitable, nervous.
• Hypothyroidism Underactive thyroid person tends
  to be inactive, sleepy, slow, obese.

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Figure 2.27
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The Adrenal Glands

• Adrenals Arouse body, regulate salt balance,
  adjust body to stress, regulate sexual
  functioning located on top of kidneys
• Releases epinephrine and norepinephrine (also
  known as adrenaline and noradrenaline)
• Epinephrine arouses body is associated with fear
• Norepinephrine arouses body is linked with anger
• Remember This has been a simplified view of the
  brain and nervous system.