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