Transcript chapter_8_powerpoint_le07

Web sites
• Society for
Neuroscience
• www.sfn.org
• International Brain
Research
Organization
• www.ibro.org
The brain carries out
calculations at synapses, the
sites at which neurons interact.
While hundreds of neurotransmitters and receptors have
been identified, they can be
functionally classified into two
types: excitatory and inhibitory.
Excitatory neurotransmitters
increase the likelihood that the
postsynaptic neuron will
generate an action potential,
while inhibitory neurotransmitters make it less likely
that the postsynaptic neuron
will be active.
The balance of excitation and
inhibition determines how
information is processed in the
nervous system.
Some synapses are excitatory: An action potential in one (pink) neuron
releases a chemical that turns on the second (blue) neuron. The second
neuron therefore is more likely to transmit an action potential to other
neurons.
BCP 5-13
e.g. glutamate
Some synapses are inhibitory: An action potential in one (pink)
neuron releases a chemical that turns off the second (blue)
neuron. So the second neuron is less likely to send action
potentials to other neurons.
BCP 5-14
e.g. GABA
gamma-aminobutyric acid
Information is carried around the nervous
system as trains of action potentials
• At any given moment, the sum of excitatory &
inhibitory inputs to a neuron determines the
probability that it will generate an action
potential.
• Circuits of interconnected neurons represent
& process information in various ways.
• Information is represented as patterns of
electrical activity in groups of neurons.
Chapter 8
Vander’s
Human Physiology
The Mechanisms of Body Function
Tenth Edition
by
Widmaier • Raff • Strang
© The McGraw-Hill Companies, Inc.
Figures and tables from the book, with additional comments by:
John J. Lepri, Ph. D.,
The University of North Carolina at Greensboro
Chapter 8
Consciousness, Brain, and Behavior
Electroencephalography: a window on the brain
• States of wakefulness and sleep
• Limbic system: motivation and reward
• Neurochemistry of drug abuse
• Learning and memory
VOLTAGE
(typically 20-100 microvolts)
Figure 8-1
The electroencephalograph (EEG) is the printout of an
electronic device that uses scalp electrodes to monitor
the internal neural activity in the brain; this is a record
from the parietal or occipital lobes of an awake person.
19-3: Generation of very small electrical fields by synaptic currents in
pyramidal cells. When thousands of cells contribute their small voltages, the
signal is strong enough to see at the surface of the scalp.
19-4: (a) In a population of pyramidal cells under an EEG electrode, each neuron receives
many synaptic inputs. (b) If the inputs fire at irregular intervals, the pyramidal cell
responses are not synchronized, & the summed activity detected by the electrode has small
amplitude. (c) If the same inputs fire within a narrow time window so the pyramidal cell
responses are synchronized, the resulting EEG sum is much larger.
VOLTAGE
(20 to 100 microvolts)
Figure 8-2
EEGs provide diagnostic information about the
location of abnormal activity in the brain,
such as shown in this record typical of a patient
undergoing an epileptic seizure.
VOLTAGE
(20 to 100 microvolts)
VOLTAGE
(20 to 100 microvolts)
Figure 8-3
EEGs reflect mental state: contrasted here are
mental relaxation (a) versus concentration (b).
VOLTAGE
(20 to 100 microvolts)
Figure 8-4
EEG patterns undergo characteristic shifts in a
sleeping person, reflecting the four stages of sleep;
the duration of the series is typically ~90 minutes, and
the entire pattern cycles 4 to 8 times per night.
Figure 8-5
The EEG pattern was
analyzed to produce
this graph of a full
night’s sequence
of sleep stages;
also shown are cyclic
patterns in the periphery.
Figure 8-6
A model of some
of the neurochemical
changes across
the sleep-wake
continuum;
cause-and-effect
relationships are
under study.
19-20: In the SCN, clock
genes produce proteins
that inhibit further
transcription. Gene
transcription & the firing
rates of SCN neurons cycle
up & down over 24 hr. The
cycles are synchronized by
light exposure (input from
the retina.).
SCN = suprachiasmatic
nucleus
Figure 8-7
Neuronal changes
in these CNS
structures appear
to be essential
participants in
sleep-wake
transitions and in
biological rhythms.
Figure 8-8
Neural damage in the
right parietal lobe of
this patient results in the
unilateral visual neglect
seen in this drawing task.
Although patient is not
impaired visually, does not
perceive part of visual
world.
20-17: Self-portraits during
recovery from a R parietal
stroke that caused neglect
syndrome.
Upper L: 2 months after
stroke, virtually no L side
to face.
Upper R: After 3.5 months,
there is some detail on L.
Lower L & R: After 6 & 9
months, there is
increasing treatment of the
L side of the painting.
Figure 8-9
Alterations in the mesolimbic dopamine pathway
(shown here) appear to be a primary mechanism
by which psychoactive drugs change behavior.
Figure 8-10
stimulator
Animal models, such as this rat performing lever-presses
to receive rewarding neural stimulation through electrodes
implanted in its brain, have provided detailed insights into
the anatomical and neurochemical organization of the brain.
Figure 8-11
Changes in activity of the limbic system underlie some
of the primary needs of the organism, including
learning, motivation, appetite, and emotional response;
its malfunction is associated with affective disorders.
Figure 8-13
Psychoactive drugs
that affect serotoninreceptors share
structural similarities
with serotonin.
Psychoactive drugs
that affect dopaminereceptors share
structural similarities
with dopamine.
Figure 8-14
Declarative memory is associated with actual events
in a person’s direct experience.
Procedural memory is associated knowledge of the
sequence of events and relationships between events.
23-1: Types of memory.
23-8: Removing the medial temporal lobe from both sides to alleviate
severe epilepsy caused severe anterograde amnesia in H.M.
PET scan showing blood flow in the cortex during language tasks
Images of the active areas in the brain in a male (left) & a female (right) during
a language task.
Note that both sides of a woman’s brain are used in processing language,
but a man’s brain is more compartmentalized.
Figure 8-17
The primary loci underlying the comprehension
of speech are in Wernicke’s area, whereas
the primary loci for the production of speech are
located in Broca’s area.
20-p641: Wada test for hemispheric
dominance.
20-9: Language comprehension in R hemisphere of split-brain subject.
The End.