Download Chapter 3 Lecture Notecards

:: 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.
The soma, or cell body, contains the cell nucleus and much of the chemical
machinery common to most cells.
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.
:: 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.
:: 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.
:: 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 polarized–negatively 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.
The points at which neurons interconnect are called synapses. A synapse
is a junction where information is transmitted from one neuron to another.
:: 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 neuron’s charge
is less negative, or even positive, creating an action potential.
Click to play animation. Make sure volume is turned up.
An action potential is a very brief shift in the neuron’s electrical charge that
travels along an axon.
:: 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 doesn’t. 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.
Neurotransmitters are chemicals that transmit information from one neuron
to another.
Click to continue.
Within the buttons, most of these chemicals are stored in small sacs, called
synaptic vesicles.
The neuron that receives the signal is called the postsynaptic neuron.
:: 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.
Specific neurotransmitters work at specific kinds of synapses – the study of
which has led to interesting findings about how specific neurotransmitters
regulate behavior.
Click to see a video that shows how neural networks work.
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 Alzheimer’s 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.
:: Slide 25 ::
:: Slide 26 ::
The peripheral nervous system can be divided into two parts.
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 body’s
resources for emergencies and creates the fight-or-flight response.
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 don’t normally think about, such as
heart rate, digestions, and perspiration.
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.
Neuroscientists use many specialized techniques to investigate connections
between the brain and behavior.
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 brain’s commands
to peripheral.
:: Slide 29 ::
:: Slide 30 ::
Lesioning involves the destruction of a piece of the brain in order to observe
what happens.
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.
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.
This news video shows an example of how TMS may impact patients
with depression.
:: 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 midbrain is concerned with certain sensory processes, such as locating
where things are in space.
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 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 Parkinson’s disease are due to the degeneration of neurons in this area.
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.
:: 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.
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.
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.
:: 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 limbic system is a loosely connected network of structures involved in
emotion, motivation, memory, and other aspects of behavior.
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.
:: 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.
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 cerebrum is divided into right and left halves, called cerebral hemispheres.
The occipital lobe includes the cortical area where most visual signals are
sent and visual processing is begun – the primary visual cortex.
If we pry apart the two halves of the brain, we see that this fissure descends to
a structure called the corpus callosum.
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.
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 Wernicke’s area can speak normally but
have difficulty understanding others.
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 man’s
frontal lobe. Since then, many similar cases have shown that this area of the brain –
which came to be known as Broca’s area – plays an important role in the production
of speech.
:: Slide 41 ::
:: Slide 42 ::
Each hemisphere’s 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.
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.
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.
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.
:: Slide 43 ::
:: Slide 44 ::
In another experimental procedure, split-brain subjects were asked to reach
under a screen to hold various 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.
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.
:: Slide 45 ::
:: Slide 46 ::
Eventually, researchers wondered whether it was safe to generalize from splitbrain subjects to normal individuals whose corpus callosum was intact.
The endocrine system consists of glands that secrete chemicals – known as
hormones – into the bloodstream that help control bodily functioning.
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.
Some hormones are released in response to changing conditions in the body
and act to regulate those conditions.
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.
:: 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.
:: 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.
Family studies, twin studies, and adoption studies are assess the impact of
heredity on behavior.
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.
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.
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.
Adoption studies are able to assess the influences of both nature and nurture,
as adopted children’s 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.
Left blank
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.
:: Slide XX ::
:: Slide XX ::
Left blank
Left blank