PowerPoint Lecture Outlines
to accompany
Hole’s Human
Anatomy and Physiology
Tenth Edition
Shier w Butler w Lewis
Chapter
10
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
10-1
Chapter 10
Nervous System I
Cell Types of Neural Tissue
• neurons
• neuroglial cells
10-2
Divisions of the
Nervous System
• Central Nervous System
• brain
• spinal cord
• Peripheral Nervous System
• peripheral nerves
• cranial nerves
• spinal nerves
10-1
Divisions of Peripheral
Nervous System
Sensory Division
• picks up sensory information and delivers it to the CNS
Motor Division
• carries information to muscles and glands
Divisions of the Motor Division
• Somatic – carries information to skeletal muscle
• Autonomic – carries information to smooth muscle,
cardiac muscle, and glands
10-4
Divisions Nervous System
10-5
Functions of Nervous System
Sensory Function
• sensory receptors gather
information
• information is carried to the
CNS
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
• contains myelinated
axons
Gray Matter
• contains
unmyelinated
structures
• 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
• afferent
• carry impulse to CNS
• most are unipolar
• some are bipolar
Interneurons
• link neurons
• multipolar
• in CNS
Motor Neurons
• multipolar
• carry impulses away
from CNS
• carry impulses to
effectors
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
Types of Neuroglial Cells
10-12
Regeneration of A Nerve Axon
10-13
Resting Membrane Potential
• inside is negative
relative to the outside
• polarized membrane
• due to distribution of
ions
• Na+/K+ pump
10-14
Local Potential Changes
• occur on membranes of dendrites and cell bodies
• caused by various stimuli
• chemicals
• temperature changes
• mechanical forces
• if membrane potential becomes more negative, it has
hyperpolarized
• if membrane potential becomes more positive, it has
depolarized
• graded
• summation can lead to threshold stimulus that starts an action
potential
10-16
Resting Membrane Potential
• Charged ions that carry electric charges
across the membranes are sodium, chloride,
potassium, and calcium. Ion pumps and
channels generate resting and action
potentials.
• Sodium/potassium pump uses energy to
move the ions against their concentration
gradient.
• K+ leaks out, because the membrane is more
permeable to K+, and Na/K pump keeps the
concentration of K+ inside the cell higher
than that outside.
• This causes an excess of negative charges
inside the cell.
• There is a higher concentration of Na+
outside the membrane and higher K+
concentration inside. The Na+/ K+ pumps,
three sodium ions out for every two
potassium ions it pumps in.
• When voltage-gated channels open and
close the concentration of ions change,
causing a change in membrane potential.
Action Potential
• Sodium gates open in response to threshold
potential at the axon hillock. The channels are
depolarized to their threshold (5/10 mV more
positive).
• Sodium rushes In; causing the rising phase or
spike of an action potential.
• Repolarizing the membrane is due to rapid closing
of the sodium channels. Potassium gates open
more slowly and stay open longer, repolarizing
and hyperpolarizing the cell.
• All gated channels close.
• The cell returns to resting potential.
Potential Changes
• at rest membrane is
polarized
• threshold stimulus
reached
• sodium channels
open and membrane
depolarizes
• potassium leaves
cytoplasm and
membrane repolarizes
10-15
Action Potentials
• nerve impulse
• occur on axons
• all-or-none self-regenerating, because it spreads to
adjacent regions of the membrane.
•Summation- several subthreshold potential changes that
combine to reach threshold.
• refractory period
• absolute - time when threshold stimulus does not start another
action potential ( sodium gates are open)
• relative – time when stronger threshold stimulus can start
another action potential ( reestablishing its resting potential).
10-17
Action Potentials
10-18
Impulse Conduction
10-19
Saltatory Conduction
10-20
• In unmyelinated fibers, the axon potential
spreads smoothly along the axon.
• In myelinated fibers, action potential jump
across the myelin segments to nodes of
Ranvier. The hopping from node to node is
much faster than non-myelinated conduction.
• Additionally, ion channels are clustered at the
nodes.
• AP’s travel faster in large-diameter axons
than small-diameter axons.
The Synapse
Nerve impulses pass
from neuron to
neuron at synapses
10-21
Synaptic Transmission
Neurotransmitters are
released when impulse
reaches synaptic knob
10-22
• Chemical synapse is the most common type
of synapse.
• Acetylcholine is the neurotransmitter used
by neurons innervating skeletal muscle.
• It is released by exocytosis when the vesicle
fuses with membrane.
• Depolarization of the axon terminal causes
Ca+ to enter the cell triggering fusion of the
vesicles.
Synaptic Potentials
EPSP
• excitatory postsynaptic potential
• graded
• depolarizes membrane of postsynaptic neuron
• action potential of postsynaptic neuron becomes more
likely
IPSP
• inhibitory postsynaptic potential
• graded
• hyperpolarizes membrane of postsynaptic neuron
• action potential of postsynaptic neuron becomes less likely
10-23
Summation of
EPSPs and IPSPs
• EPSPs and IPSPs are
added together in a
process called
summation
• More EPSPs lead to
greater probability of
action potential
10-24
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