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Introduction to Psychology: KCC
Brain and Behavior
Introduction to Psychology: KCC
Neuron and Its Parts
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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
– Myelin (Sheath): Protects Axon
– Axon Terminals: Branches that link the dendrites and
somas of other neurons
Introduction to Psychology: KCC
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.
Introduction to Psychology: KCC
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
Introduction to Psychology: KCC
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.
Introduction to Psychology: KCC
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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Introduction to Psychology: KCC
Nerves and Neurons
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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
Introduction to Psychology: KCC
Neural Networks
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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
Introduction to Psychology: KCC
Figure 2.6
FIGURE 2.6 (a) Central and peripheral nervous systems. (b) Spinal nerves, cranial nerves, and
the autonomic nervous system.
Introduction to Psychology: KCC
Two Divisions of the Autonomic System

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Sympathetic: Arouses body; emergency system
Parasympathetic: Quiets body; most active after an emotional
event
Introduction to Psychology: KCC
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.
Introduction to Psychology: KCC
Figure 2.7
FIGURE 2.7 Subparts of the nervous system.
Introduction to Psychology: KCC
Cerebral Cortex
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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
Introduction to Psychology: KCC
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.
Introduction to Psychology: KCC
Figure 2.22
Introduction to Psychology: KCC
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
Introduction to Psychology: KCC
Subcortex: Reticular Formation (RF)

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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
Introduction to Psychology: KCC
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.)
Introduction to Psychology: KCC
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
Introduction to Psychology: KCC
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.
Introduction to Psychology: KCC
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
Introduction to Psychology: KCC
Endocrine System Concluded
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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.
Introduction to Psychology: KCC
The Adrenal Glands
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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
Introduction to Psychology: KCC
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Parathyroid Glands – produces a hormone that increases
blood and decreases bone calcium levels.
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Thymus Gland – produces a hormone that stimulates the
immune response in children.
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Pancreas – produces hormones that control BSL (blood sugar
level).
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Ovaries – produces hormones that control female characteristics
and menstrual cycle.
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Testes – produces a hormone that control male characteristics and
sperm production.