Download 4-Nervous system I: Structure and organization

4-Nervous system I: Structure and organization
GENERAL ORGANIZATION
NEURON STRUCTURE
BRAIN & CRANIAL NERVES
SPINAL CORD & NERVES
AUTONOMIC SYSTEM
Announcements
Andrew’s Office Hours: Friday 9:00-10:00, Higgins 520
Meghan’s Office Hours: Wednesday 6:30-7:30 (pm!), Higgins atrium
Quiz 1: Issued Today by 5:00, due Friday by 5:00
Scaling basics: geometric similarity
(large organisms could be (but are not
necessarily) just geometrically scaled-up
versions of small organisms)
Metabolism, as well as structure, is scaled….
Predicting LSD dosage for a large animal……
0.5-1.0 mg/kg is
the minimum to
cause a
“transient rage”
6.5 mg/kg is
lethal.
0.1 - 0.2 mg
causes mental
disturbance
QQ1: Is Tusko
especially
sensitive?
0.02 mg/kg
causes psychotic
symptoms
297 mg (= 0.10 mg/kg) was administered to “Tusko”,
a male Indian elephant (West et al. 1962).
West, L. J., C. M. Pierce and W. D. Thomas. 1962. Lysergic acid diethylamide: its effects on a male
Asiatic elephant. Science 138:1100-1103.
Harwood, P. 1963. Therapeutic dosage in small and large mammals . Science 139: 684-685.
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Q: What is the nervous system?
A network of billions of nerve cells linked together in a highly
organized fashion to form the rapid control center of the body
In the brain, roughly 100 billion (1011) neurons and 100 trillion
(1014) synapses (connections between nerve cells)
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Q: What does the nervous system do? (Next time)
Functions include:
–Integrating center for information coming into the body from the periphery
or internally; sensation
–Generation of movement
–Regulation of many body functions
–Locus of much of what makes us human – thought self-awareness, etc.
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NERVOUS STRUCTURE ORGANIZATION
Two major divisions:
1.Central Nervous System (CNS)
-Brain & spinal cord
2.Peripheral Nervous System (PNS)
-Nervous system outside of the
brain and spinal cord
-Carries information to and from the
CNS
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NERVOUS STRUCTURE ORGANIZATION
Two divisions to PNS:
i) Somatic; voluntary (afferent and
efferent)
-12 pairs of cranial nerves
-31 pairs of spinal nerves
ii) Autonomic; visceral;
involuntary; (efferent)
-Sympathetic component (“fight/
flight”; thoraco-lumbar)
-Parasympathetic component
(“rest/digest”; cranio-sacral)
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NERVOUS STRUCTURE ORGANIZATION
Another PNS classification
Sensory (afferent) PNS nerve cells
-impulses from receptors to the CNS
-Informs the CNS of the state of the
body interior and exterior
-Sensory nerve fibers can be somatic
(from skin, skeletal muscles or joints)
or visceral (from organs within the
ventral body cavity)
2. Motor (efferent) PNS nerve cells
-Conduct impulses from CNS to
effectors (muscles)
-Motor nerve fibers (both autonomic
and somatic/voluntary)
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MANY different types, shapes, and sizes
Functional types
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Among all types of neurons, myelinated neurons
conduct action potentials most rapidly
Schwann cells:
axons of PNS
Oligodendrocytes:
axons of CNS
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Neuroglia
Neural Crest!!!!
QQ2: What is function of neuroglia?
Schwann cells:
axons of PNS
Oligodendrocytes:
axons of CNS
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“Spines” on dendrites: change shape and strength of
connection with other nerve cells in response to
learning
Signal
Signal
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Brain Structure
Major Landmarks:
Forebrain
-Cerebrum
-Diencephalon
Corpus callosum
Brainstem
-Midbrain
-Pons
-Medulla oblongata
Cerebellum
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Cranial nerves: 12
pairs
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Spinal Nerves
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Spinal Nerves
Spinal nerve structure:
(simple version)
-“gray matter” = nerve cell
bodies
-“white matter” = nerve cell
axons
Anterior view of one
vertebra and the nearby
section of the spinal cord
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Spinal Nerves
QQ2: What integrates the afferent and efferent signals?
(code 6681)
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CNS
CNS = brain +
spinal cord; all
parts of
interneurons are in
the CNS
PNS
PNS: (1) afferent neurons (their activity
“affects” what will happen next) into the CNS &
(2) efferent neurons (“effecting” change:
movement, secretion, etc.) projecting out of
the CNS.
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Contrast autonomic and somatic
components of the nervous system
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Contrast autonomic and somatic
components of the nervous system
Voluntary
Command:
MOVE!
Involuntary
Command:
Rest/Digest
Involuntary
Command
FIGHT!
FLIGHT!
Skeletal
Muscle
Contraction
Heart,
smooth
muscle,
glands,
etc.
Heart,
smooth
muscle,
glands,
etc.
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Schematic diagram of the mammalian
autonomic nervous system
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Another schematic diagram of the
mammalian autonomic nervous system
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