Transcript Chapt13 Lecture 13ed Pt 2

Human Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 13
Nervous
System
Lecture Outline
Part 2
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13.1 Overview of the Nervous System
The nerve impulse: Stimulus causes
the axon to reach its threshold
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open
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Figure 13.3b Generation of
an action potential.
b. Stimulus causes the axon to reach its threshold;
the axon potential increases from −70 to −55.
The action potential has begun.
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13.1 Overview of the Nervous System
The nerve impulse: Action potential
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c. Depolarization continues as Na+ gates open
and Na+ moves inside the axon.
Figure 13.3c Generation of an action potential.
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13.1 Overview of the Nervous System
The synapse
• The synapse is a small gap between the
_________ neuron (presynaptic membrane) and
the________ neuron (postsynaptic membrane).
• Transmission is accomplished across this gap
by a _______________ (e.g., ACh, dopamine,
or serotonin).
• Neurotransmitters are stored in synaptic vesicles
in the axon terminals.
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13.1 Overview of the Nervous System
How does transmission across
the synapse occur?
• Nerve impulse reaches the axon terminal.
• Calcium ions enter the axon terminal and
stimulate the synaptic vesicles to fuse with the
presynaptic membrane.
• Neurotransmitters are released and diffuse
across the synapse, where they bind with the
postsynaptic membrane to inhibit or excite the
neuron.
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13.1 Overview of the Nervous System
A synapse and how it functions
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arriving action
potential
1. After an action
potential arrives
at an axon
terminal (arrow),
Ca2+ enters,
and synaptic
vesicles fuse
with the plasma
membrane of
the sending
neuron.
Sending neuron
Ca2+
axon of
sending
neuron
axon
terminal
Synaptic vesicles
enclose neurotransmitter.
Synapse
receiving
neuron
Receiving neuron Synaptic
cleft
2. Neurotransmitter
molecules
are released
and bind to
receptors
on the
membrane of
the receiving
neuron.
Receiving neuron
neurotransmitter
neurotransmitter
receptor
Na+
Figure 13.4 Signal transmission at
the synapse.
Receiving
neuron
ion
channel
3. When an
excitatory
neurotransmitter
binds to a
receptor,
Na+ diffuses
into the
receiving
neuron, and
an action
potential
begins.
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13.1 Overview of the Nervous System
Synaptic integration
• Integration is the _____________ of the
inhibitory and excitatory signals received by a
postsynaptic neuron.
• This occurs because a neuron receives many
signals.
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13.1 Overview of the Nervous System
Synaptic integration
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+20
0
excitatory signal
integration
inhibitory signal
20
Cell body of the
receiving neuron
axon branches of
sending neurons
 40
threshold
70
resting
potential
axon terminals
80
dendrite
Time (milliseconds)
b.
inhibitory
synapse
excitatory
synapse
a.
a: © Science VU/Lewis-Everhart-Zeevi/Visuals Unlimited
Figure 13.5 Integration of excitatory and inhibitory signals at the synapse.
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13.2 The Central Nervous System
The central nervous system
• The CNS consists of the brain and spinal cord.
• Both are protected by
• ________ – skull and vertebral column
• ___________ – 3 protective membranes that wrap
around CNS
• _______________ (CSF) – space between
meninges is filled with this fluid that cushions and
protects the CNS
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13.2 The Central Nervous System
The central nervous system
• Both the brain and spinal cord are made up of 2
types of nervous tissue.
• Gray matter – contains cell bodies and
_______________ fibers
• White matter – contains _____________ axons
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13.2 The Central Nervous System
The CNS: Spinal cord
• It extends from the base of the brain and along the
length of the vertebral canal formed by the vertebrae.
• The spinal cord functions to provide _____________
between the brain and most of the body.
• It is the center for ____________.
• Gray matter in the center is a __________ shape.
• White matter surrounds the gray matter.
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13.2 The Central Nervous System
What does the spinal cord look like?
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
white matter
gray matter
central canal
a.
gray matter
white matter
spinal cord
vertebra
Figure 13.7 The organization of white and gray matter in
the spinal cord and the spinal nerves.
dorsal root
dorsal root
ganglion
spinal
nerve
vertebra
ventral root
b.
central canal
dorsal root
dorsal root
ganglion
dorsal
dorsal root
branches
gray matter
white matter
dorsal root
ganglion
ventral
spinal
nerve
ventral root
cut vertebrae
meninges
c.
d. Dorsal view of spinal cord and dorsal roots of spinal nerves.
a: © Karl E. Deckart/Phototake; d: © The McGraw-Hill Companies, Inc./Rebecca Gray, photographer and Don Kincaid, dissections
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13.2 The Central Nervous System
The CNS: Brain
4 major parts
1.
2.
3.
4.
Cerebrum
Diencephalon
Cerebellum
Brain stem
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13.2 The Central Nervous System
The CNS: Overview of the brain
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lateral
third
ventricle ventricle
pineal
gland
Cerebrum
skull
meninges
corpus
callosum
Diencephalon
thalamus
(surrounds the
third ventricle)
hypothalamus
pituitary gland
Brain stem
midbrain
pons
Cerebellum
fourth ventricle
medulla
oblongata
spinal cord
b. Cerebral hemispheres
a. Parts of brain
Figure 13.8 The human brain.
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13.2 The Central Nervous System
The brain: Cerebrum
• Cerebral hemispheres
• Cerebral cortex
• Primary motor and sensory areas of
the cortex
• Association areas
• Processing centers
• Central white matter
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