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Structure of a Vertebrate
Neuron
Basic Tasks of the Nervous
System
Sensory Input:
Monitor both
external and internal
environments.
Integration: Process
the information and
often integrate it with
stored information.
Motor output: If
necessary, signal
effector organs to
make an appropriate
response.
A system that controls all of the
activities of the body.
The nervous system is made of:
The brain
The spinal cord
The nerves
The senses
The Central Nervous System is made
of the brain and the spinal cord.
The Central Nervous System controls
everything in the body.
The Outer Nervous System is made of
the nerves and the sense organs.
Nerves
Sense organs
Myelinated Neurons
• Many vertebrate peripheral neurons have an insulating sheath around
the axon called myelin which is formed by Schwann cells.
• Myelin sheathing allows these neurons to conduct nerve impulses
faster than in non-myelinated neurons.
What is An Action Potential?
Saltatory Conduction in Myelinated
Axons
Myelin sheathing has bare patches of axon called nodes of Ranvier
Action potentials jump from node to node
Fig. 48.11
How does a signal move from
one neuron to another?
• A synape divides 2 neurons
• The action potential will not move
across the synape
• Neuro transmitters
–Released by the signal cell to the
receiver cell
–Move by diffusion
Detail of
Axon
Terminal
Transmission
Across the
Synapse
Source: Gray
A chemical synapse
Detail of the
Synapse Itself
Neurotransmitter
molecules
(e.g., Acetylcholine
or Dopamine)
Postsynaptic
membrane
Review the Synapse
• What is a synapse?
• A synapse is the “gap” between the axon
of one nerve and the dendrite of the next
one.
• The average neuron has 1,000 synapses
with other neurons.
Neurotransmitters
• There are dozens of different
neurotransmitters (NT) in the neurons of
the body.
• NTs can be either excitatory or inhibitory
• Each neuron generally synthesizes and
releases a single type of neurotransmitter
• The major neurotransmitters are indicated
on the next slide.
Major Neurotransmitters in the Body
Neurotransmitter
Role in the Body
Acetylcholine
A neurotransmitter used by the spinal cord neurons to control muscles and
by many neurons in the brain to regulate memory. In most instances,
acetylcholine is excitatory.
Dopamine
The neurotransmitter that produces feelings of pleasure when released by
the brain reward system. Dopamine has multiple functions depending on
where in the brain it acts. It is usually inhibitory.
GABA
(gamma-aminobutyric acid)
The major inhibitory neurotransmitter in the brain.
Glutamate
The most common excitatory neurotransmitter in the brain.
Glycine
A neurotransmitter used mainly by neurons in the spinal cord. It probably
always acts as an inhibitory neurotransmitter.
Norepinephrine
Norepinephrine acts as a neurotransmitter and a hormone. In the
peripheral nervous system, it is part of the flight-or-flight response. In the
brain, it acts as a neurotransmitter regulating normal brain processes.
Norepinephrine is usually excitatory, but is inhibitory in a few brain areas.
Serotonin
A neurotransmitter involved in many functions including mood, appetite,
and sensory perception. In the spinal cord, serotonin is inhibitory in pain
pathways.
NIH Publication No. 00-4871
Examples of chemical
neurotransmitters found in
synapse
• Acetylcholine: neuromuscular junctions,
glands, brain and spinal cord
• Norepinepherine: affects brain regions
concerned with emotions, dreaming
The Brain On Drugs
• http://www.thirteen.org/closetohome/scien
ce/html/animations.html
Higher
Brain
function
Spatial
Vision
Speech,
memory,
hearing
Motor control-Posture
& equilibrium
Autonomic Functions: breathing,
heartbeat, respiration, etc,
Put It all Together
- Stimulus- temperature/pressure on skin
light- sound- eyes and ears
correct shape molecule
taste buds /nose
- Action Potential proagates along axon
- Neurotransmitter released into synapse
- New action potential begins in adjoining
nerve or muscle cell