Structure of the nervous system
• @ Macroscopic level– Brain & nerves
• @ Microscopic level– Neurons & Glial Cells
Central (inside skull & spine)
BrainSpinal Cord
Macroscopic: Divisions of the Nervous System
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
Spinal Cord Reflex
Spinal cord lesion
Ouch! That hurts, dude!
Group activity
- Would sensation be abolished by:- a spinal cord lesion?- polio?
- Would the reflex be abolished by: - a spinal cord lesion? - polio?
Somatic System:
- controls voluntary muscle
Autonomic System:
- controls glands & internal organs- has two subcomponents
- Sympathetic (adrenaline): arousal- Parasympathetic: calm
Peripheral Nervous System
Figure 3.28 The Autonomic Nervous System
Levels of Investigation Brain Areas
(visual system)
Cells (neurons)
Molecules (neurotransmitters)
Microscopic level: Neurons
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Neurons: Its many shapes & sizes
Neuron: basic parts
Cell Body football field
Dendrite Campus
Axon wide a street
Axon long as Philly - Ohio
Cell membrane thick as pinky finger
Synaptic cleft thick as thumb
# 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
axon terminals
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Neuron: its physiology
What makes neurons different from other cells?
Neuron’s cell membrane is electrically charged (interior is more negative)
Neurons influence each other’s charge (‘communicate’)
Neurons process and transmit electrical impulses
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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)
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 post-synaptic neuronPost-synaptic neuron
Synapse
Pre-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
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