Transcript Nervous System part 1

Essentials of Human Anatomy & Physiology
Seventh Edition
Elaine N. Marieb
Chapter 7
The Nervous SystemPage 200-215
(neurons, neuroglia, and
impulses)
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The Nervous System
• The master controlling and communicating
system of the body
• Uses electrical impulses to signal and communicate
• Impulses are rapid and specific
http://www.scienceclarified.com/Mu-Oi/Nervous-System.html
Structures of nervous system
Central Nervous
System (CNS)
Peripheral Nervous
System (PNS)
organs-
organs-
• Brain
• Peripheral nerves
• Spinal cord
• Sense organs
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Slide 7.3a
Functions of the Nervous System
• Sensory/Afferent: (PNS)
• Uses sensory receptors to monitor internal & external
changes/stimuli (input)
• Integration: (CNS)
• Processes and interprets and makes decisions about
what should be done (interprets)
• Motor/Efferent: (PNS)
• Is the response; an activated viscera, muscle or gland
(motor output or response)
• Involuntary (autonomic) and Voluntary (somatic)
Functions of nervous system
PNS
Affarent/
CNS
PNS
/Motor Receptor
Figure 7.1
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Slide 7.3a
Functions of the Nervous System
Integration
Sensory input
Motor output
Figure 7.2
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Slide 7.4
Anatomy of Nervous Tissue:
Support Cells in CNS
•called Neuroglia (page 205)
•support, insulate, protect neurons,
dispose of debris, circulate fluids
astrocyte
Figure 7.3: Types of
Neuroglia
oligodendrocyte
microglial cell
Ependymal cell
Slide 7.7b
Anatomy of Nervous Tissue:
Support Cells in PNS
 called Schwann Cells and Satellite Cells
 Schwann cells form myelin sheath around
nerve fiber of the PNS (insulate)
 Satellite Cells protect and cushion
Figure 7.3e
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Slide 7.7b
Anatomy of Nervous Tissue:
Structure of Neurons
 Neurons/Nerve Cells
 Highly specialized to transmit
messages (impulses)
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Slide 7.8
Anatomy of Nervous Tissue:
Structures of Neurons
• Cell body: metabolic
center, nissl
substance, nucleus
• Dendrite: slender
processes, convey
incoming messages to
cell body, vary in length
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Slide 7.8
Neuron Anatomy
• Nissl bodiesrough ER
Figure 7.4a
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Slide 7.9a
Neuron Anatomy
 Axon: conduct
impulse away
from cell body
 Myelin Sheath:
insulation
Axon Terminal
 Axon Terminals:
branching ends
of an axon
Figure 7.4a
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Slide 7.10
Neuron Anatomy
 Synaptic end
bulbs: swollen
end of axon,
contain synaptic
vesicles
Axon terminal
Synaptic end bulbs
Figure 7.4a
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Slide 7.10
Neuron Anatomy
• synaptic vesicles:
structure
containing neurotransmitters
 Neurotransmitter:
chemical
messenger
released when
impulse reaches the
synaptic vesicle,
carries impulse
across synaptic gap
synaptic
neurotransmitters
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Slide 7.10
Synaptic End Bulb
Neuron Anatomy
 Neurotransmitters:
chemical
messengers released
from synaptic
vesicles
 Carry impulse to
next neuron or to
the effector
Figure 7.4a
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Slide 7.10
Neuron Structural Classification
- All motor &
association neuron,
multiple processes
- Only in special sense
organs, 2 processes
Figure 7.8a
- In PNS ganglia, Short and
divides immediately, single
process
Slide 7.16a
Neuron Functional Classification
Figure 7.6
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Slide 7.15
Physiology of Neurons
 Irritability: ability to respond to stimuli
 Conductivity: ability to transmit an
electrical impulse
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Slide 7.17
Neuron Physiology: Transmission of
a Nerve Impulse
Figure 7.9a–c
a. Polarization = Resting potential
- lots of Na+ with some
negative ions outside, and
fewer K+ and lots of negative
ions on the inside
- overall negative charge is
greater on the inside of the
neuron
- neuron is inactive
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(b)
Slide 7.18
Neuron Physiology: Transmission of
a Nerve Impulse
Figure 7.9a–c
b. Depolarization = Action
Potential
– Na+ moves inward
- The inside becomes less
negative and more positive
- causes transmission of an
impulse
(b)
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Slide 7.18
Transmission of a nerve impulse
C. Repolarizationrestored resting state
- K+ moves out, Na+
still inside
(b)
- this outflow of
positive ions restores
the electrical
conditions of the
membrane
- but the neuron needs
to be reset to its
polarized state
(c)
Slide 7.19
Transmission of a nerve impulse
D. Na+/K+ pump- restores
polarized state
- another impulse cannot
be transmitted until Na+
and K+ are moved back
to their original
positions
- this is by active
transport, requires
ATP
Slide 7.19
All or none response
 Either all of neuron sends impulse, or
none of it does
Figure 7.9c–e
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Slide 7.20
Transmission of Nerve Impulse
http://www.britannica.com/EBchecked/topic/409665/nervoussystem/75842/Transmission-at-the-synapse(click on top video on left side of
screen)
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_imp
ulse.html
http://video.google.com/videoplay?docid=6890770586678681705&ei=KIX1Ss_OFZLSqQL1zJGpAw&hl=en
http://outreach.mcb.harvard.edu/animations/synaptic.swf
Synapse
synaptic end bulbs
cell body
dendrites
Presynaptic neuron
axon terminals
Synaptic cleft (gap)
Postsynaptic neuron
Slide 7.22
Synapse (up close)
neurotransmitter
receptor sites
Postsynaptic neuron
Gap or
Presynaptic
axon
Synaptic end bulbs
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Slide 7.22
Synapse (up close)
Figure 7.10
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Slide 7.22
Synapses & Synaptic transmission
 Stimulus causes electrical impulse AKA action
potential (via Na+ and K+) in neuron
 Impulse travels in presynaptic neuron
 Dendrites
 Cell body
 Axon, axon terminal, & synaptic end bulbs
 Synaptic vesicles
 Neurotransmitters- chemical impulse
released
 Synaptic gap
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 7.21
Synapses & Synaptic transmission
• In postsynaptic neuron
 Neurotransmitter receptor sites on dendrites
receive new stimulus
 Stimulus causes electrical impulse again
AKA action potential (via Na+ and K+)
 Impulse travels again from
Dendrites
Cell body
Axon, axon terminals, synaptic end
bulbs, Etc.
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Slide 7.21
The Reflex Arc
•Reflex – rapid, predictable, and
involuntary responses to stimuli
•Simplest reflex arc has 5 components
or interneuron
Reflex arc
Figure 7.11a
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Slide 7.23
Reflex Arc
Figure 7.6
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Slide 7.15
Simple Reflex Arc
Knee jerk reflex
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Withdrawal reflex
Figure 7.11b, c
Slide 7.24
Factors that Affects Synaptic
Transmission
Emotional state- excited, sad, etc
Physical state- exercise, sleep, etc
Environmental factors- drugs, alcohol,
etc
Number of synapses
Slide 7.22
Effects of Drugs on Synaptic
Transmission
Stimulants
Depressants
Cocaine
Marijuana
Crack
Alcohol
Ecstasy
Opium
Methamphetamine
Barbiturates
Amphetamine
Antipsychotics
Caffeine
Anticonvulsants
Nicotine
Opiates
Energy drinks
Nitrous oxide
Slide 7.22
Effects of Drugs on Synaptic
Transmission
http://teens.drugabuse.gov/mom/tg_effects.asp#
http://www.nida.nih.gov
http://www.drugabuse.gov/DrugPages/DrugsofAbuse.html
Slide 7.22