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Chapter 10
Nervous System I
Cell Types of Neural Tissue
• neurons
• neuroglial cells
10-2
Divisions of the
Nervous System
• Central Nervous System
•
•
• Peripheral Nervous System
•
•
•
10-1
Divisions of Peripheral
Nervous System
Sensory Division
•
Motor Division
•
Divisions of the Motor Division
• Somatic –
• Autonomic –
10-4
Divisions Nervous System
10-5
Functions of Nervous System
Sensory Function
•
•
Integrative Function
• sensory information used to
create
• sensations
• memory
• thoughts
• decisions
Motor Function
• decisions are acted
upon
• impulses are
carried to effectors
10-6
Neuron Structure
10-7
Myelination of Axons
White Matter
•
Gray Matter
•
• cell bodies, dendrites
10-8
Classification of Neurons
Bipolar
• two processes
• eyes, ears, nose
Unipolar
• one process
• ganglia
Multipolar
• many processes
• most neurons of
CNS
10-9
Classification of Neurons
Sensory Neurons
•
• most are unipolar
• some are bipolar
Interneurons
• link neurons
• multipolar
•
Motor Neurons
• multipolar
•
•
10-10
Types of Neuroglial Cells
Schwann Cells
• peripheral nervous
system
• myelinating cell
Oligodendrocytes
• CNS
• myelinating cell
Microglia
• CNS
• phagocytic cell
Astrocytes
• CNS
• scar tissue
• mop up excess ions, etc
• induce synapse formation
• connect neurons to blood
vessels
Ependyma
• CNS
• ciliated
• line central canal of spinal cord
• line ventricles of brain 10-11
Resting Membrane Potential
•
• polarized membrane
• due to distribution of
ions
• Na+/K+ pump
0013.exe
10-14
Potential Changes
•
•
• sodium channels
open and membrane
depolarizes
• potassium leaves
cytoplasm and
membrane repolarizes
10-15
Local Potential Changes
• occur on membranes of dendrites and cell bodies
• caused by various stimuli
•
•
•
• if membrane potential becomes more negative, it has
hyperpolarized
• if membrane potential becomes more positive, it has
depolarized
• summation can lead to threshold stimulus that starts an action
potential
0014.exe
10-16
Action Potentials
• nerve impulse
• occur on axons
•
• refractory period
• absolute - time when threshold stimulus does not start another
action potential
• relative – time when stronger threshold stimulus can start
another action potential
10-17
Action Potentials
10-18
The Synapse
Nerve impulses pass
from neuron to
neuron at synapses
10-21
Synaptic Transmission
0015.exe
10-22
Neurotransmitters
10-25
Impulse Processing
Neuronal Pools
• groups of interneurons that make synaptic connections
with each other
• interneurons work together to perform a common
function
• each pool receives input from other neurons
• each pool generates output to other neurons
10-26
Convergence
• neuron receives input from
several neurons
• incoming impulses represent
information from different
types of sensory receptors
• allows nervous system to
collect, process, and respond
to information
• makes it possible for a
neuron to sum impulses from
different sources
10-27
Divergence
• one neuron sends
impulses to several
neurons
• can amplify an
impulse
• impulse from a
single neuron in
CNS may be
amplified to
activate enough
motor units
needed for muscle
contraction
10-28
Clinical Application
Multiple Sclerosis
Symptoms
• blurred vision
• numb legs or arms
• can lead to paralysis
Treatments
• no cure
• bone marrow transplant
• interferon (anti-viral drug)
• hormones
Causes
• myelin destroyed in
various parts of CNS
• hard scars
(scleroses) form
• nerve impulses
blocked
• muscles do not
receive innervation
• may be related to a
virus
10-29