Download Neurons - Sonoma Valley High School

Unit #7 Nervous
System:
Neurons
Introduction
• Two systems of
communication
– Nervous system
• Rapid response
• Uses action potentials
– Endocrine system
• Slower response
• Uses hormones
Tortora
Pages 225
Did You Know?
• Many types of
mental illnesses
are related to
imbalances in
chemicals that
transmit
messages
between neurons
Tortora
Pages 225
Introduction
• Nervous system
– CNS
– PNS
Tortora
Pages 205 - 207
Introduction
• Endocrine
system
– Ductless glands
– Pituatary
(master gland)
Tortora
Pages 205 - 207
Functions of
Nervous System
• Sensory
Tortora
Pages 205 - 207
Functions of
Nervous System
• Integrative
Tortora
Pages 205 - 207
Functions of
Nervous System
• Motor
Tortora
Pages 205 - 207
Organization of
Nervous System
• Central
Nervous
System
– Brain
– Spinal cord
Tortora
Pages 205 - 207
Organization of
Nervous System
• Peripheral
Nervous System
– Cranial nerves
– Spinal nerves
Tortora
Pages 205 - 207
Organization of
Nervous System
• Sensory, Motor,
and Connecting
Neurons
– Sensory are
referred to as
afferent.
– Motor are referred
to as efferent.
– Connecting are
referred to as
association
Tortora
Pages 205 - 207
Organization of
Nervous System
• Somatic Vs
Autonomic
– Somatic is voluntary
• Sensory nerves and
motor nerves.
– Autonomic is
involuntary
• Mostly motor nerves
leading to smooth
muscle, cardiac
muscle, and glands.
Tortora
Pages 205 - 207
Organization of
Nervous System
• Symapathetic Vs
Parasymnpathetic
ANS
– Oppose each others
actions.
– Regulates
homeostasis.
Tortora
Pages 205 - 207
Histology
Tortora
Pages 207 - 210
• Two types of
cells
– Neurons conduct
impulses.
– Neuroglial cells
support and
protect neurons.
Neurons found in the
spinal cord.
Histology
Tortora
Pages 207 - 210
• Neuroglia
– Smaller than
neurons.
– Outnumber
neurons 5 to 50
times.
– Six different
types.
Neurons found in the
spinal cord.
Histology
Tortora
Pages 207 - 210
• Neurons.
– 3 distinct
areas
• Cell body.
• Dendrites.
• Axons.
Neurons found in the
spinal cord.
Histology
Tortora
Pages 207 - 210
• Cell body of
neuron.
– Nucleus
– Typical cell
organelles.
– No mitotic
spindle.
Neurons found in the
spinal cord.
Histology
• Neurons are
in three
forms.
– Multipolar
– Bipolar
– Unipolar
Tortora
Pages 207 - 210
Histology
Tortora
Pages 207 - 210
• Neurons are in three
sizes.
– Type A
• Largest diameters
• 130 M/sec
– Type B
• Middle sized
• 10 M/sec
– Type C
• Smallest
• .5 M/sec
• unmyelinated
Neurons and their
many branches
Histology
Tortora
Pages 207 - 210
• Dendrites
– Usually short and
thick.
– Usually highly
branched.
– Receives
impulses.
– Conducts
impulses towards
cell body.
Dendrites surrounded by
neuroglial cells.
Histology
Tortora
Pages 207 - 210
• Axons
– Neurons have a single
axon.
– Usually long and very
thin.
– Can be branched
(collaterals)
– Terminates in many
terminals.
– Terminals contain
vesicles.
– Vesicles contain
neurotransmitters.
Axon surrounded by
neuroglial cells
Histology
Tortora
Pages 207 - 210
• Myelin sheath
– Speeds impulse along
axon.
– Insulates axon .
– Composed of neuroglial
cells. (PNS)
– Schwann cells produce
myelin (lipoprotein)
– Nodes of Ranvier
create gaps in myelin
sheath.
Myelin sheath structure
Histology
• Grouping of
Neural tissue
– White matter
is myelinated.
– Gray matter
is
unmyelinated.
Tortora
Pages 207 - 210
Nerve Impulses
• Nerve impulse
– An imlpulse is a
change in the
electrical charge
(potential) on the
membrane of the
neuron.
– Due to ions moving
into and out of the
neuron.
Tortora
Pages 210-213
Nerve Impulses
– Ions move through
very selective
membrane channels.
– Channels are
transmembrane
proteins.
– Channels open or
close in response to
certain changes.
– Voltage gated
channels
Tortora
Pages 210-213
Nerve Impulses
• Membrane Potentials.
– Resting potential - no
impuse.
• Positive outside
• Negative inside.
– Action potential.
• Positive inside.
• Negative outside.
– Potentials are due to
ions.
• Na +
• K+
• Large negative ions
(proteins)
Tortora
Pages 210-213
Nerve Impulses
Tortora
Pages 210-213
• Resting potential
– No impulse.
– Positive outside
neurolemma
– Negative inside.
– 30x more K+ inside.
– 15x ore Na+ outside.
– Large negative ioins
trapped inside.
– Sodium - Potassium pump
creates these conditions.
– Membrane is “polarized”.
Creating An Impulse
Along An Axon
Caffeine & the
Nervous System
Histology
• Nerves are groups of
neurons.
– Mixed contain
dendrites and axons.
– Motor contain axons
only. (Efferent)
– Sensory contain
dendrites only.
(Afferent)
Tortora
Pages 207 - 210
Conduction
Across Synapses
• Impulses are sent
to:
– Glands
– Muscles
– Other neurons.
• Impulse must
bridge synapse
Tuesday 1/20/04
Pages 213-214
Conduction
Across Synapses
• Synapses have
ability to transmit
impulse or inhibit
impulse
transmission.
Tuesday 1/20/04
Pages 213-214
Conduction
Across Synapses
• Most brain
disorders
involve
disruption of
synaptic
communication.
Tuesday 1/20/04
Pages 213-214
Conduction
Across Synapses
Tuesday 1/20/04
Pages 213-214
• Presynaptic neuron
– Synaptic vesicles
– Neurotransmitter
– Role of calcium ions
• Synaptic cleft
• Postsynaptic
neuron.
– receptors
Voltage gated
channels
Na+/K+
Pump
Conduction
Across A Synapse
Saltatory Conduction
Tuesday 1/20/04
Pages 213-214
REGENERATION OF
NERVOUS TISSUE
• Neurons have limited
power of regeneration.
• Ability to reproduce
lost at 6 months of
age.
• A destroyed neuron is
lost.
• PNS neurons can
repair.
• CNS neurons cannot
repair.
Tuesday 1/20/04
Pages 213-214