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Neural and Hormonal
Neuroscience and Behavior
Neural Communication
 Neurons
 How Neurons Communicate
 How Neurotransmitters Influence Us
The Nervous System
 The Peripheral Nervous System
 The Central Nervous System
History of Mind
Bettman/ Corbis
In 1800, German physician
Franz Gall suggested that
bumps of the skull
represented mental abilities.
His theory, though incorrect,
nevertheless proposed that
various brain regions have
particular functions.
Neural Communication
The body’s information system is built from
billions of interconnected cells called neurons or
nerve cells.
Neural Communication
Neurobiologists and other investigators
understand that humans and animals operate
similarly when processing information.
Note the similarities in the above brain regions, which are all
engaged in information processing.
A nerve cell, or a neuron, consists of many
different parts.
Parts of a Neuron
Cell Body: Life support center of the neuron.
Soma: the cell body of the neuron.
Dendrites: (tree) Branching extensions at the cell body.
Receive messages from other neurons. DENDRITES
Axon: Long single extension of a neuron, covered with
myelin sheath to insulate and speed up messages
through neurons. AXONS SPEAK
Terminal Branches of axon: Branched endings of an
axon that transmit messages (in neurotransmitters) to
other neurons.
Kinds of Neurons
Sensory Neurons (Afferent Neurons) carry incoming information from
the sense receptors to the CNS. Motor Neurons (Efferent Neurons)
carry outgoing information from the CNS to muscles and glands.
Interneurons connect the two neurons.
Interneuron Neuron
Sensory Neuron
Motor Neuron
Action Potential
A neural impulse. A brief
electrical charge that
travels down an axon and
is generated by the
movement of positively
charged atoms in and out
of channels in the axon’s
• Depending on the type of fiber, the neural
impulses travel at speeds ranging from a
sluggish 2 miles an hour to 200 miles per
• Even this top speed is still 3 million times
slower than that of electricity through a
• Brain is vastly more complicated than a
computer, but not faster at executing
simple responses.
Threshold: Each neuron receives
excitatory (like pushing the accelerator)
and inhibitory (like pushing the brake)
signals from many neurons. When the
excitatory signals minus the inhibitory
signals exceed a minimum intensity
(threshold) the neuron fires an action
Action Potential Properties
All-or-None Response:
A neuron always fires
with the same intensity.
A strong stimulus can
trigger more neurons to
fire, and to fire more
often, but it does not
affect the action
potentials strength or
Intensity of an action potential remains the same
throughout the length of the axon.
**Toilet flushing example
• The idea that either
the neuron fires or
it does not- no part
way firing.
• Like a gun
Steps of Action Potential
• Dendrites receive neurotransmitter from another
neuron across the synapse.
• Reached its threshold- then fires based on the all-ornone response.
• Opens up a portal in axon, and lets in positive ions
(Sodium) which mix with negative ions (Potassium)
that is already inside the axon (thus Neurons at rest
have a slightly negative charge).
• The mixing of + and – ions causes an electrical charge
that opens up the next portal (letting in more K) while
closing the original portal.
• Process continues down axon to the axon terminal.
• Terminal buttons turns electrical charge into
chemical (neurotransmitter) and shoots message to
next neuron across the synapse.
Synapse [SIN-aps] a junction between the axon
tip of the sending neuron and the dendrite or
cell body of the receiving neuron. This tiny gap
is called the synaptic gap or cleft.
(chemicals) released
from the sending
neuron travel across the
synapse and bind to
receptor sites on the
receiving neuron,
thereby influencing it to
generate an action
Neurotransmitters in
the synapse are
reabsorbed into the
sending neurons
through the process of
reuptake. This process
applies the brakes on
How Neurotransmitters Influence Us
Serotonin pathways are
involved with mood
From Mapping the Mind, Rita Carter, © 1989
University of California Press
Dopamine Pathways
Dopamine pathways
are involved with
diseases such as
schizophrenia and
Parkinson’s disease.
From Mapping the Mind, Rita Carter, © 1989
University of California Press
Lock & Key Mechanism
Neurotransmitters bind to the receptors of the
receiving neuron in a key-lock mechanism.
Agonists-a drug that boosts the
effects of a neurotransmitter
Antagonists-drug that blocks the
effect of a neurotransmitter
• Neurons have the ability to change—to
make new connections and strengthen old
• They can adapt/modify as a result of
• Ex. Violin player—motor area linked to
fingers in left had becomes bigger with
Glial Cells
• A support group for neurons.
• They provide the structural support for the
• They also help in forming new synapses
• Found to be crucial to learning and
• They are what form the myelin sheath.
Nervous System
The Nervous System
Nervous System: Consists of all the nerve cells. It
is the body’s speedy, electrochemical
communication system.
2 Major Parts
Central Nervous System (CNS): the brain and
spinal cord.
Peripheral Nervous System (PNS): the sensory and
motor neurons that connect the central nervous
system (CNS) to the rest of the body.
The Nervous System
Peripheral Nervous System
Its like the “pick up and delivery” service for the
Central Nervous System. It connects it with the
rest of the body through bundles of sensory/motor
The Nerves
Nerves consist of neural “cables” containing many
axons. They are part of the peripheral nervous
system and connect muscles, glands, and sense
organs to the central nervous system.
Somatic Nervous System: The division of
the peripheral nervous system that controls
the body’s skeletal muscles.
Afferent: sensory component
Efferent: Motor component
Autonomic Nervous System: Part of the
PNS that controls the glands and other
muscles. Fight/flight—self-regulating
Autonomic Nervous System (ANS)
Sympathetic Nervous System: Division of the
ANS that arouses the body, mobilizing its
energy in stressful situations. AROUSES
Parasympathetic Nervous System: Division of
the ANS that calms the body, conserving its
energy. CALMS
Opponent Process System: they work in
opposition create homeostasis.
Autonomic Nervous System (ANS)
Sympathetic NS
Parasympathetic NS
(rest and digest)
Central Nervous System
The Brain and Neural Networks:
Interconnected neurons form networks in the
brain. Theses networks are complex and modify
with growth and experience.
Complex Neural Network
Central Nervous System
The Spinal Cord and Reflexes
Simple Reflex
The Endocrine System
The Endocrine
System is the body’s
“slow” chemical
Communication is
carried out by
synthesized by a set
of glands.
Hormones are chemicals synthesized by the
endocrine glands that are secreted in the
bloodstream. Hormones affect the brain and many
other tissues of the body.
These hormones are the same chemical messengers
that are used in the nervous system
For example, epinephrine (adrenaline) increases
heart rate, blood pressure, blood sugar, and
feelings of excitement during emergency
situations. Fight or flight!
Pituitary Gland
Is called the “master gland.” The anterior pituitary
lobe releases hormones that regulate other glands.
The posterior lobe regulates water and salt
balance. It is at the base of your brain.
Pituitary Gland
• Although it is the “master gland” of the
endocrine system, it is really only a midlevel manager.
• It takes its orders from the brain…in
particular the Hypothalamus. More on this
soon 
Thyroid & Parathyroid Glands
Regulate metabolic and calcium rate.
Adrenal Glands
Adrenal glands consist of the adrenal medulla and
the cortex. The medulla secretes hormones
(epinephrine and norepinephrine) during stressful
and emotional situations, while the adrenal cortex
regulates salt and carbohydrate metabolism.
Sex glands are located in different places in men
and women. They regulate bodily development
and maintain reproductive organs in adults.