Left blank

1
Slide 1
Slide 2
Left blank
Your nervous system is a complex communication
network in which signals are constantly being
received, integrated, and transmitted. The
nervous system handles information, just as the
circulatory system handles blood.
Slide 3
Slide 4
There are two major types of cells in the nervous
system glia and neurons. Neurons are cells that
receive, integrate, and transmit information. In
the human nervous system, the vast majority are
interneurons neurons that communicate with
other neurons. There are also sensory neurons,
which receive signals from outside the nervous
system, and motor neurons, which carry messages
from the nervous system to the muscles that move
the body.
The soma, or cell body, contains the cell nucleus
and much of the chemical machinery common to most
cells.
Slide 5
Slide 6
The branched structure is called a dendritic
tree, and each individual branch is a dendrite.
Dendrites are the parts of a neuron that are
specialized to receive information.
The long fiber is the axon. Axons are specialized
structures that transmit information to other
neurons or to muscles or glands.
2
Slide 7
Slide 8
Most human axons are wrapped in a myelin sheath.
Myelin is a white, fatty substance that serves as
an insulator around the axon and speeds the
transmission of signals. In people suffering from
multiple sclerosis, some myelin sheaths
degenerate, slowing or preventing nerve
transmission to certain muscles.
The axon ends in a cluster of terminal buttons,
which are small knobs that secrete chemicals
called neurotransmitters. These chemicals serve
as messengers that may activate neighboring
neurons. The points at which neurons
interconnect are called synapses. A synapse is
a junction where information is transmitted from
one neuron to another.
Slide 9
Slide 10
Glia come in a variety of forms. Their main
function is to support the neurons by, among
other things, supplying them with nutrients and
removing waste material. In the human brain,
there are about ten glia cells for every neuron.
The neuron at rest is a tiny battery, a store of
potential energy. Inside and outside the axon are
fluids containing electrically charged atoms and
molecules called ions. Positively charged sodium
and potassium ions and negatively charged
chloride ions are the principal molecules
involved in the nerve impulse.
Slide 11
Slide 12
When the neuron is not conducting an impulse, it
is said to be in a resting state. The cell
membrane is polarizednegatively charged on the
inside and positively charged on the outside. The
charge difference across the membrane can be
measured with a pair of microelectrodes connected
to an oscilloscope. In a resting neuron, this
difference, called the resting potential, is
about 70 millivolts.
Click to play animation. Make sure volume is
turned up.
3
Slide 13
Slide 14
When the neuron is stimulated, channels in its
cell membrane open, briefly allowing positively
charged ions to rush in. For an instant, the
neurons charge is less negative, or even
positive, creating an action potential. An
action potential is a very brief shift in the
neurons electrical charge that travels along an
axon.
Click to play animation. Make sure volume is
turned up.
Slide 15
Slide 16
The size of an action potential is not affected
by the strength of the stimulus a weaker
stimulus does not produce a weaker action
potential. If the neuron receives a stimulus of
sufficient strength, it fires, but if it receives
a weaker stimulus, it doesnt. This is referred
to as the all-or-none law.
The neural impulse is a signal that must be
transmitted from a neuron to other cells. This
transmission takes place at special junctions
called synapses, where terminal buttons release
chemical messengers. The two neurons are
separated by the synaptic cleft, a microscopic
gap between the terminal button of one neuron and
the cell membrane of another neuron. Signals
have to cross this gap for neurons to
communicate.
Slide 17
Slide 18
The neuron that sends a signal across the gap is
called the presynaptic neuron. Click to
continue. The neuron that receives the signal is
called the postsynaptic neuron.
Neurotransmitters are chemicals that transmit
information from one neuron to another. Within
the buttons, most of these chemicals are stored
in small sacs, called synaptic vesicles.
4
Slide 19
Slide 20
The neurotransmitters are released when a vesicle
fuses with the membrane of the presynaptic cell
and its contents spill into the synaptic cleft.
After their release, neurotransmitters diffuse
across the synaptic cleft to the membrane of the
receiving cell.
When a neurotransmitter and a receptor molecule
combine, reactions in the cell membrane cause a
postsynaptic potential, or PSP a voltage change
at the receptor site on a postsynaptic cell
membrane. After producing postsynaptic
potentials, some neurotransmitters either become
inactivated by enzymes, or drift away. Most
neurotransmitters, however, are reabsorbed into
the presynaptic neuron through reuptake a
process in which neurotransmitters are sponged up
from the synaptic cleft by the presynaptic
membrane.
Slide 21
Slide 22
Most neurons are interlinked in complex chains,
pathways, circuits, and networks. Our
perceptions, thoughts, and actions depend on
patterns of neural activity in elaborate neural
networks. Click to see a video that shows how
neural networks work.
Specific neurotransmitters work at specific kinds
of synapses the study of which has led to
interesting findings about how specific
neurotransmitters regulate behavior. One
example is acetylcholine, which is released by
motor neurons controlling skeletal muscles, and
contributes to the regulation of attention,
arousal, and memory. An inadequate supply of
acetylcholine is associated with the memory
losses seen in Alzheimers patients. Here are a
few other examples of neurotransmitters, and how
their dysregulation is associated with certain
disorders.
Slide 23
Slide 24
The multitudes of neurons in your nervous system
have to work together to keep information flowing
effectively.
The peripheral nervous system is made up of all
the nerves that lie outside the brain and spinal
cord. Nerves are bundles of neuron fibers or
axons that are routed together in the
peripheral nervous system.
5
Slide 25
Slide 26
The peripheral nervous system can be divided into
two parts. The somatic nervous system is made up
of nerves that connect to voluntary skeletal
muscles and sensory receptors. They carry
information from receipts in the skin, muscles,
and joints to the CNS, and from the CNS to the
muscles. The autonomic nervous system is made up
of nerves that connect to the heart, blood
vessels, smooth muscles, and glands. It controls
automatic, involuntary, visceral functions that
people dont normally think about, such as heart
rate, digestions, and perspiration.
When a person is autonomically aroused, automatic
functions speed up. This speeding up is
controlled by the sympathetic division of the
autonomic nervous system the sympathetic
nervous system mobilizes the bodys resources for
emergencies and creates the fight-or-flight
response. The parasympathetic nervous system, on
the other hand, conserves bodily resources to
save and store energy.
Slide 27
Slide 28
The central nervous system, or CNS, consists of
the brain and spinal cord. It is protected by
enclosing sheaths called meninges, as well as
cerebrospinal fluid, which nourishes the brain
and provides a protective cushion for it. The
spinal cord houses bundles of axons that carry
the brains commands to peripheral.
Neuroscientists use many specialized techniques
to investigate connections between the brain and
behavior.
Slide 29
Slide 30
Lesioning involves the destruction of a piece of
the brain in order to observe what
happens. Electrical stimulation of the brain
sends a weak electric current into the brain to
stimulate it. Brain imaging devices allow
neuroscientists to look inside the human brain,
such as in a CT (computerized tomography or MRI
(magnetic resonance imaging) scan.
Another new research tool in neuroscience is
transcranial magnetic stimulation, which allows
scientists to temporarily enhance or depress
activity in a specific area of the brain. This
news video shows an example of how TMS may impact
patients with depression.
6
Slide 31
Slide 32
The hindbrain includes the cerebellum and two
structures found in the lower part of the
brainstem the medulla and the pons. The
cerebellum is critical to the coordination of
movement and to the sense of equilibrium, or
physical balance. Damage to the cerebellum
disrupts fine motor skills, such as those
involved in writing or typing. The pons contains
several clusters of cell bodies that contribute
to the regulation of sleep and arousal. The
medulla, which attaches to the spinal cord, has
charge of largely unconscious but essential
functions, such as regulating breathing,
maintaining muscle tone, and regulating
circulation.
The midbrain is concerned with certain sensory
processes, such as locating where things are in
space. The midbrain is the origin of an
important system of dopamine-releasing axons.
Among other things, this dopamine system is
involved in the performance of voluntary
movements. The abnormal movements associated with
Parkinsons disease are due to the degeneration
of neurons in this area.
Slide 33
Slide 34
Running through both the hindbrain and the
midbrain is the reticular formation. Lying at the
central core of the brainstem, the reticular
formation contributes to the modulation of muscle
reflexes, breathing, and the perception of
pain. It is best known, however, for its role in
the regulation of sleep and wakefulness. Activity
in the ascending fibers of the reticular
formation is essential to maintaining an alert
brain.
The forebrain is the largest and most complex
region of the brain, encompassing a variety of
structures, including the thalamus, hypothalamus,
limbic system, and cerebrum.
Slide 35
Slide 36
The thalamus is a structure in the forebrain
through which all sensory information, except
smell, must pass to get to the cerebral cortex.
This way station is made up of a number of
clusters of cell bodies, or nuclei. Each cluster
is concerned with relaying sensory information to
a particular part of the cortex. The
hypothalamus is made up of a number of distinct
nuclei. These nuclei regulate a variety of basic
biological drives, including the so-called four
Fs fighting, fleeing, feeding, and mating.
The limbic system is a loosely connected network
of structures involved in emotion, motivation,
memory, and other aspects of behavior.
7
Slide 37
Slide 38
The cerebrum is the largest and most complex part
of the human brain. It includes the brain areas
that are responsible for our most complex mental
activities, including learning, remembering,
thinking, and consciousness itself. The cerebrum
is divided into right and left halves, called
cerebral hemispheres. If we pry apart the two
halves of the brain, we see that this fissure
descends to a structure called the corpus
callosum.
Each cerebral hemisphere is divided by deep
fissures into four parts called lobes. To some
extent, each of these lobes is dedicated to
specific purposes. The occipital lobe includes
the cortical area where most visual signals are
sent and visual processing is begun the primary
visual cortex. The parietal lobe includes the
area that registers the sense of touch the
primary somatosensory cortex. The temporal lobe
contains an area devoted to auditory processing,
the primary auditory cortex.
Slide 39
Slide 40
In recent decades, an exciting flurry of research
has focused on cerebral lateralization the
degree to which the left or right hemisphere
handles various cognitive and behavioral
functions. However, hints of cerebral
specialization were found as early as the late
1800s. In 1861, Paul Broca, a French surgeon,
performed an autopsy on a patient who had been
unable to speak. The autopsy revealed a lesion on
the left side of the mans frontal lobe. Since
then, many similar cases have shown that this
area of the brain which came to be known as
Brocas area plays an important role in the
production of speech.
In 1874, Paul Wernicke discovered that damage to
a portion of the temporal lobe of the left
hemisphere leads to problems with the
comprehension of language. Patients with damage
in Wernickes area can speak normally but have
difficulty understanding others.
Slide 41
Slide 42
Each hemispheres primary sensory and motor
connections are to the opposite side of the body
the left hemisphere controls and communicates
with the right hand, arm, etc. and the right
hemisphere controls and communicates with the
left side. Vision is more complex. Stimuli in
the right half of the visual field are
registered by receptors on the left side of each
eye that send signals to the left
hemisphere. Similarly, stimuli in the left half
of the visual field are registered by receptors
on the right side of each eye that send signals
to the right hemisphere.
Roger Sperry and his colleagues found that the
ability of split-brain subjects to name and
describe objects depended on which side of the
visual field the image was flashed in. When
pictures of common objects were flashed in the
right visual field and thus sent to the left
hemisphere, the split-brain subjects were able to
name and describe the objects depicted.
8
Slide 43
Slide 44
In another experimental procedure, split-brain
subjects were asked to reach under a screen to
hold various objects. When objects were placed
in the split-brain subjects right hand, which
communicates most directly with the left
hemisphere, the subjects had no problem naming
the objects. When the objects were placed in the
subjects left hand, which communicates most
directly with the right hemisphere, the subjects
had difficulty naming the objects.
Research with split-brain subjects provided the
first compelling evidence that the right
hemisphere has its own special talents. Based on
this research, investigators concluded that the
left hemisphere usually handles verbal
processing, whereas the right hemisphere usually
handles nonverbal processing, such as that
required by visual-spatial and musical tasks.
Slide 45
Slide 46
Eventually, researchers wondered whether it was
safe to generalize from split-brain subjects to
normal individuals whose corpus callosum was
intact. One method of studying cerebral
specialization in an intact brain is by looking
at perceptual asymmetries left-right imbalances
between the cerebral hemispheres in the speed of
visual or auditory processing. Subtle
differences in the abilities of the two
hemispheres can be detected by precisely
measuring how long it takes participants to
recognize different types of stimuli.
The endocrine system consists of glands that
secrete chemicals known as hormones into the
bloodstream that help control bodily
functioning. Some hormones are released in
response to changing conditions in the body and
act to regulate those conditions.
Slide 47
Slide 48
Hormones are secreted by the endocrine glands in
a pulsatile manner that is, several times per
day in brief bursts or pulses. The levels of many
hormones increase to a certain level, then
signals are sent to the hypothalamus or other
endocrine glands to stop secretion of that
hormone a negative feedback system.
Much of the endocrine system is controlled by the
nervous system through the hypothalamus, which
also connects with the pituitary gland. The
pituitary gland stimulates actions in the other
endocrine glands. For example, in the fight or
flight response, the hypothalamus sends signals
through the pituitary gland and autonomic nervous
system to the adrenal glands, which then secrete
stress hormones.
9
Slide 49
Slide 50
Every cell in your body contains information from
your parents, found on the chromosomes that lie
within the nucleus of each cell. Each chromosome
contains thousands of genes, which also occur in
pairs. Sometimes a member of a pair has a louder
voice, always expressing itself and masking the
other member of the pair this is a dominant
gene. A recessive gene is one that is masked
when the paired genes are different. When a
person has two genes in a specific pair that are
the same, the person is homozygous for that
trait. If the genes are different, they are
heterozygous.
Family studies, twin studies, and adoption
studies are assess the impact of heredity on
behavior. Family studies and twin studies focus
on genetic relatedness and how it affects various
traits in order to study the influence of nature
on behavior. Adoption studies are able to assess
the influences of both nature and nurture, as
adopted childrens traits can be evaluated in
relation to both their biological and adoptive
parents.
Slide 51
Slide XX
The field of evolutionary psychology is based on
the work of Charles Darwin and the ideas of
natural selection and reproductive
fitness. Evolutionary theorists study
adaptations, or inherited characteristics, that
increase in a population because they help solve
a problem of survival or reproduction during the
time they emerge.
Left blank
Slide XX
Slide XX
Left blank
Left blank