Ch 09 Nervous System (a)
Transcript of Ch 09 Nervous System (a)
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The Nervous System : communication
A. Neurons = masses of nervecells that transmit information
1. Cell Body - contains the nucleus
and two extensions
2. Dendrites shorter, morenumerous, receive information
3. Axons single, long fiber whichconducts impulse away from the cellbody, sends information
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Nervous System
Central Nervous System (CNS): brain andspinal cord.
Peripheral Nervous System (PNS): nerves of
the body
-- Includes 31 pairs of spinal nerves
-- And 12 pairs of cranial nerves
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Basic Divisions of the Nervous System
Figure 12.2
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THREE BASIC FUNCTIONS OF THE NERVOUS SYSTEM
Sensory - gathers info
Integrative - information is brought togetherMotor - responds to signals, homeostasis
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Motor Functions
Somatic NervousSystem - skeletal(voluntary)
Autonomic NervousSystem - smoothmuscles, glands
(involuntary)
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Neuroglial Cells (p 208)
- support cellsfor the neurons
1. MicroglialCells: scatteredthroughout,digest debris or
bacteria
Microglial cells respond to
immunological alarms
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Neuroglial Cells (p 208)
2. Oligodendrocytes:
provide insulationaround the axons
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Neuroglial Cells (p 208)
3.
Astrocytes: connectblood vessels toneurons
I connect toblood
vessels
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Neuroglial Cells (p 208)
4. Ependymal Cells: form a membrane thatcovers brain-like parts
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5. Schwann cells: form the insulating myelinsheath around the neurons
Practice with neuroglia coloring!
http://www.biologycorner.com/anatomy/nervous/nerve_cells_coloring.htmlhttp://www.biologycorner.com/anatomy/nervous/nerve_cells_coloring.htmlhttp://www.biologycorner.com/anatomy/nervous/nerve_cells_coloring.html -
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Supporting Cells - NEUROGLIA
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Supporting Cells- NEUROGLIA
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Neurons
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Axon - long section,transmits impulses
Dendrite - smallextensions from thecell body; receive
information
Neurofibrils - fiberswithin the axon
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Chromatophilic substance (rough ER) - transport
system
Myelin -insulation surrounding axons
Nodes of Ranvier - gaps in the insulation
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White vs Grey Matter
Myelinated (white matter) myelinated axons
Unmyelinated (grey matter) - unmyelinated
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Label
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Interesting Facts about the Neuron
Longevity can live and function for a lifetime
Do not divide fetal neurons lose their ability to undergomitosis; neural stem cells are an exception
High metabolic rate require abundant oxygen and glucose
The nerve fibers of newbornsare unmyelinated - thiscauses their responses to
stimuli to be course andsometimes involve the wholebody. Try surprising a baby!
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Types of Neurons
Functional:Sensory, Motor,
Interneurons
Structural:
(A) Bipolar
(B) Unipolar
(C) Multipolar
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Cell Membrane Potential
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9.5 Cell Membrane Potential
At rest, the inside of a neuron's membrane
has a negative charge. As the figure shows,
a Na+ / K+ pump in the cell membrane
pumps sodium out of the cell and
potassium into it. However, more
potassium ions leak out of the cell. As a
result, the inside of the membrane builds
up a net negative charge relative to the
outside.
Animations of Nerve Impulses
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html -
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9.6 Nerve Impulse
Speed of an impulse is proportionate to the DIAMETER of the
AXON.
Greater diameter = faster speed
**Myelinated Axons conduct faster than unmyelinated ones"
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The Synapse
Synapse - junction between two
communicating neurons
Nerve pathway - nerve impulse
travels from neuron to neuron
Synaptic Transmission
Dendrite ->cell body -> along axon
-> synapse (gap)
To complete the signal, a
NEUROTRANSMITTER is
released at the gap to signal the
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http://www.youtube.com/watch?v=A0EyX4lRL2I -
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Structure of a Synapses
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Neurotransmitters
Excitatory - increase membrane permeability,
increases chance for threshold to be achieved
Inhibitory - decrease membrane permeability,
decrease chance for threshold to be achieved
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Types of Neurotransmitters
Acetylcholine - stimulates muscle contraction
Monoamines - Norepinephrine & Dopamine
(sense of feeling good, low levels = depression)
Serotonin (sleepiness) and mood
Endorphins (reduce pain, inhibit receptors)
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Drugs that Affect Synapses and Neurotransmitters
Curare - poison made from frog skinand causes paralysis by blocking
Ach receptors at the neuromuscularjunction.
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Drugs that Affect Synapses and Neurotransmitters
Strychnine poisoning can be fatal tohumans and animals and can occur byinhalation, swallowing or absorptionthrough eyes or mouth
Strychnine is a neurotoxin which acts as anantagonist of acetylcholine receptors. Itprimarily affects the motor nerves in thespinal cord which control musclecontraction. An impulse is triggered at one
end of a nerve by the binding ofneurotransmitters to the receptors.
Strychnine use by athletes?
http://en.wikipedia.org/wiki/Strychninehttp://en.wikipedia.org/wiki/Strychninehttp://en.wikipedia.org/wiki/Strychnine -
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Drugs that Affect Synapses and Neurotransmitters
Cocaine, morphine, alcohol, ether and chloroform
Ecstasy
LSD (hallucinogen)
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LSD (hallucinogen)
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Dangers of Ecstasy (MDMA) The most common cause ofEcstasy-related death isoverheating (hyperthermia).MDMA interferes with thebody's ability to regulate its
own body temperature andto see other warning signsallowing the body tooverheat without discomfortespecially when dancing forhours in hot clubs.
The neurotransmitterserotonin isvital in regulating many of our basic
functions. Serotonin is, among otherthings, the feel good neurotransmitterand helps to regulate body temp.
Our brain cells are constantly trying
to bring some amount of serotoninback into the cells and out of thesynapse using serotonin reuptaketransporters.
Ecstasy essentially takes theseupkeep transporters and reversestheir roles. This causes a massiveflood of serotonin from the brain cellsinto the synapse.
http://www.drugs.1emallway.com/mind-works/serotonin.htmhttp://www.drugs.1emallway.com/mind-works/serotonin.htm -
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LSD; lysergic acid diethylamide
Actions/Effects: LSD alters the action of the neurotransmitters serotonin,
norepinephrine, and dopamine, triggering extreme changes in brainfunction. Physical effects include increased body temperature, heart rate,and blood pressure. Psychological effects include perceptual and thoughdistortions, hallucinations, delusions, and rapid mood swings.
Cocaine blocks reuptakeof dopamine
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Antidepressants
Zoloft is part of a class of drugs called selective
serotonin reuptake inhibitors, or SSRIs for short. SSRIs act on a specific chemical
within the brain known as serotonin. This is one of
several chemicals used to send messages from onenerve cell to another.
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9.8 Impulse Processing
Neuronal pool - groups of neurons that make
hundreds of synaptic connections and worktogether to perform a common function
These "pools" help us
remember sequential tasks,like tying a shoe or riding abike.
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9.9 Types of Nerves
Sensory Nerves - conduct impulses into the brain or
spinal cord
Motor Nerves - carry impulses to muscles of glands
Mixed Nerves - contain both sensory and motor nerves
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Neurons Classified by Function: Sensory vs. Motor Neurons
Figure 12.11
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9.10 Nerve Pathways
Reflex arc - only includes a few neurons
Reflex Behavior - automatic, subconscious responses
Knee-jerk reflex - maintains uprightedness
Withdrawal reflex - avoidance of painful stimuli