Transcript Slide 1

Chapter 21
Brain Structure and Function
Attention Deficit Disorder
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21.1 The Nervous System
The nervous system
 Neurons carry electrical and chemical
messages to and from the brain
 Neurons receive, process, and respond to
stimuli.
Three general categories of neurons
1. Sensory neurons
2. Interneurons
3. Motor neurons
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21.1 The Nervous System
Interneurons
(within brain or
spinal cord)
Motor
neurons
(from brain)
Sensory
neurons
(to brain)
See and
smell
cookies
Smile and
salivate
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Figure 21.2
21.1 The Nervous System
Sensory detectors can be either:
1. Sensory neurons
2. Specialized cells that communicate with
neurons
General Senses
•Temperature
•Pain
•Pressure
•Touch
•Proprioception
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Table 21.1
21.1 The Nervous System
Special Senses
•Smell
•Taste
•Vision
•Hearing
•Equilibrium
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Table 21.1
21.1 The Nervous System
Special Senses
•Smell
•Taste
•Vision
•Hearing
•Equilibrium
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Table 21.1
21.1 The Nervous System
The nervous system is divided
into two parts:
1. Central nervous system

brain and spinal cord
2. Peripheral nervous system

nerves extending from
vertebrae out to body
Interneuron
relays signal
Sensory neuron
senses heat
Motor neuron
withdraws hand
from heat
Hot stimulus
Reflex arc
 sensory neuron that synapses
to an interneuron and then
motor neuron
 action without higher
processing (e.g., knee jerk
reflex)
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Figure 21.4
21.1 The Nervous System
Focus on Evolution
 Muscle & Nervous
tissue is unique to
the animal kingdom
 Enables animals to
sense environment &
move in search of
food
 All animal nervous
systems have similar
properties.
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Brain
Spinal
cord
Sense
organs
Nerves
Figure 21.1
21.1 The Nervous System - Focus on
Evolution
Primitive Animal Nervous System
Nerve Nets
• Found in hydras, sea
anemones & jellyfish
•Limited travel
through environment
•No brain
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Figure E21.2
21.1 The Nervous System - Focus on
Evolution
Nerve Cords
•Found in insects
•Processing of
information
centralized in CNS
•Simple brain plus
many enlarged
‘ganglia’
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Figure E21.2
21.1 The Nervous System - Focus on
Evolution
Vertebrate Nervous
Systems
• Greater degree of
centralization
•Single large brain
•Regions of brain
become specialized for
specific tasks
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Figure E21.3
21.2 The Brain
Human Brain
 The brain rests in the skull in cerebrospinal
fluid, which bathes and cushions it.
Two major cell types in the brain
1. Neurons transmit nervous impulses
 Brain has 100-200 billion neurons
2. Glial cells support neurons by providing protection
& nutrients
 Almost 10 times as many glial cells as neurons
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Figure 21.6
21.2 The Brain
The brain is divided into 5 regions
1. Cerebrum
2. Cerebellum
3. Thalamus
4. Hypothalamus
5. Brain stem
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21.2 The Brain - Cerebrum
Lobes of the Cerebrum
1. Frontal lobe
2. Temporal lobe
3. Parietal lobe
4. Occipital lobe
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Other Important Structures
•Right & Left Hemispheres
•Central fissure
•Corpus callosum
•Caudate nuclei
Figure 21.7
21.2 The Brain - Cerebrum
Brain Hemispheres
•Many nerves cross over, so left brain
controls right side of body, and visa versa
•Left Hemispheres
•Controls speech, reading, & solving math
•Right Hemispheres
•Interprets spatial
relationships, music &
art
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Figure 21.7
21.2 The Brain - Thalamus and Hypothalamus
Thalamus and hypothalamus
 lie deep in the brain between the
hemispheres and act as control center.
 Thalamus relays information from spinal
cord to brain.
 Thalamus suppresses some information and
enhances other.
 Hypothalamus is the control center for
sex drive, pleasure, pain, hunger, and
other basic drives.
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21.2 The Brain - Cerebellum
Cerebellum
 Control of balance
 Coordination of muscular movement
 Damage to the cerebellum results in jerky,
awkward movements
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21.2 The Brain - Brainstem
Brainstem
 Controls involuntary activity.
 The brainstem is composed of the midbrain,
pons, and medulla oblongata
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Figure 21.8
21.2 The Brain
ADD and Brain Structure and Function
 Some researchers suggest there are
differences between brains of people with
ADD and people without.
 Corpus callosum smaller in individuals with
ADD
 Decreased folding on cerebrum in ADD
individuals
 Differences could be a result of genetics, or
development and life experiences
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21.3 Neurons
Neurons
 Neurons are highly
specialized cells
Parts of Neuron
 Dendrites
 Cell Body
 Axon
 Terminal Boutons
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Figure 21.9
21.3 Neurons - Neuron Structure
Myelin speeds up nervous impulses
 Many neurons have their axons covered by a
myelin sheath made by Schwann cells
 the unmyelinated patches are the nodes of
Ranvier.
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Figure 21.10
21.3 Neurons - Neuron Function
Neuron Function
 Cell accumulates K+ ions inside and Na+ ions
outside
(a) Resting nerve cell
Outside cell
Inside cell
All channels are closed.
The inside of the cell has
a more negative charge
than the outside of
the cell.
Nodes of
Ranvier
K+ channel
Na+ channel
Nerve cell
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Figure 21.11a
21.3 Neurons - Neuron Function
Nervous Impulse = Action Potential
 Stimulation of a neuron causes ion gates to open, and
Na+ rushes in, changing polarity (depolarization)
 Action potential (nervous Impulse) – a brief change in
polarity of the surface membrane, which moves down
the length of an axon
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Figure 21.11b
21.3 Neurons - Neuron Function
PLAY
Animation—Communication Within Neurons: The Axon
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21.3 Neurons - Neuron Function
How Neurons Work
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21.3 Neurons - Neuron Function
Synapse = junction between neurons
 Terminal boutons, space, & dendrites or
cell body
Synaptic transmission = Transmission of
impulses between neurons
 neurons use neurotransmitters to
communicate chemically across the
synapse
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21.3 Neurons - Neuron Function
Synaptic Transmission
1.
2.
3.
4.
5.
Action potential reaches terminal bouton of presynaptic cell
Calcium gates open, allowing Ca2+ to rush in
Ca2+ causes synaptic vesicles to release neurotransmitters
Neurotransmitter binds to receptors on postsynaptic cell
Opening or ion channels triggers action potential in
postsynpatic cell
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Figure 21.12
21.3 Neurons - Neuron Function
Two ways to stop synaptic transmission
1. Neurotransmitter is digested by enzymes
2. Reuptake of neurotransmitters by presynatpic cell
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Figure 21.12
21.3 Neurons - Neuron Function
PLAY
Animation—Communication Within Neurons: The Synapse
Copyright © 2010 Pearson Education, Inc.
21.3 Neurons
Alzheimer’s, Depression, Parkinson’s, and ADD
 Many mental diseases are linked to problems
with neurotransmitters.
 Alzheimer’s and Parkinson’s diseases seem
to be related to impaired neurotransmitter
production.
 Depression appears to be related to an
imbalance in several neurotransmitters, but its
unclear if this is a cause or a result of
depression.
 ADD may be result of lower levels of
neurotransmitter dopamine.
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21.3 Neurons - ADD Perscription Drug Action
Ritalin
•Blocks reuptake receptors
on presynaptic cells
•Increases dopamine in
synapse
Adderall & Dexedrine
•Both are amphetamines
•Increase levels of dopamine
in synapse
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Figure 21.13