Transcript Cells of the Nervous System

Structure of the nervous system
• @ Macroscopic level
– Brain & nerves
• @ Microscopic level
– Neurons & Glial Cells
Macroscopic: Divisions of the Nervous System
Central (inside skull & spine)
Brain
Spinal Cord
Peripheral (outside skull & spine)
Nerves
Central Nervous System
Brain
Divisions of the human brain
Specialization of function
Different regions of the brain are associated with different function
Ouch! That hurts, dude!
Spinal Cord Reflex
Spinal cord
lesion
- Would sensation be abolished by:
- a spinal cord lesion?
- polio?
- Would the reflex be abolished by:
- a spinal cord lesion?
- polio?
Peripheral Nervous System
Somatic System:
- controls voluntary muscle
Autonomic System:
- controls glands & internal organs
- has two subcomponents
- Sympathetic (adrenaline): arousal
- Parasympathetic: calm
Figure 3.28 The Autonomic Nervous System
Levels of
Investigation
Brain Areas
(visual system)
Cells
(neurons)
Molecules
(neurotransmitters)
Microscopic level: Neurons
Neurons: Its many shapes & sizes
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Neuron: basic parts
Cell Body
Dendrite
Axon
Axon
Cell membrane
Synaptic cleft
football field
Campus
wide a street
long as Philly - Ohio
thick as pinky finger
thick as thumb
axon terminals
# synapses
10.000 (same number as Villanova students)
Some axons are wrapped burrito-style by fatty cells (glial cells)
- increases speed at which neurons communicate)
- white in color (white matter vs gray matter
- is destroyed by multiple sclerosis
Neuron: its physiology
What makes neurons
different from other cells?
Neurons process and
transmit electrical impulses
Neuron’s cell membrane is
electrically charged
(interior is more negative)
Neurons influence each
other’s charge (‘communicate’)
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How do neurons
process and transmit
electrical impulses?
A. dendrites receive input
from other neurons
B. axon sends neural
impulse to axon terminal
C. a neurotransmitter (NT)
is release and makes
contact with another neuron
(synapse)
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Synapse
Communication Steps
•
NT is released from
pre-synaptic neuron
•
NT binds to receptors
in post-synaptic neuron
•
Opens Na+ channels
•
Sodium rushes in
(activation)
•
If enough Na+ rushes
in => depolarization
(action potential)
•
NT released by postsynaptic neuron
Pre-synaptic neuron
Post-synaptic neuron
Other important facts
Various Neurotransmitters (NT):
-
Dopamine
Adrenaline
Serotonin
Acetylcholine
For each NT,various receptors
- nicotine & muscarine
Drugs can act by
- modifying amount of NT, or
- binding to receptor (nicotine)
The net effect on neuron could be:
- activation (action potential)
- inhibition
Cells of the Nervous System
Glia (Greek=glue)
– Many types (oligodendrocites, schwann cells,
astrocytes, and microglia)
– More prevalent than neurons (10:1)
Complexity of CNS
• 1011 (100 billion) neurons
• each neuron interacts with 1,000 -7000 others
• => 100 -500 trillion connections (that’s a big #)
• Many other factors:
– Neurotransmitters
– Receptors
– Genes, Glial cells etc.
Glial Cells
• Functions: support, immunology (defense), nutrition for
neurons, guide migration of neurons during development,
maintain ion balance, etc.
• Form myelin which helps the speed of the action potential.
In Multiple Sclerosis, the myelin is broken down and
axons become less efficient.
Copyright © Allyn & Bacon 2004
Copyright © Allyn & Bacon 2004
Blood-brain barrier
Basal ganglia lesion
(hiperdensities) due to
increased bilirubin in newborn
(kernicterus)
Movement disorder
Spared images
Figure 3.3 The Nervous System
Figure 3.24 Spinal Column, Ventral View
Vertebra of Spinal column
Figure 3.26: Spinal Cord Cross Section
Figure 3.25 The Spinal Cord