Download Lecture 14 - Websupport1

Anatomy & Physiology
SIXTH EDITION
Chapter 12,
Neural tissue
PowerPoint® Lecture Slide Presentation prepared by
Dr. Kathleen A. Ireland, Biology Instructor, Seabury Hall, Maui, Hawaii
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Frederic H. Martini
Fundamentals of
Learning Objectives
• Describe the two major divisions of the nervous
system and their characteristics.
• Identify the structures/functions of a typical
neuron.
• Describe the location and function of neuroglia.
• Explain how resting potential is created and
maintained.
• Describe the events in the generation and
propagation of an action potential.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Learning Objectives
• Define the structure/function of a synapse.
• List the major types of neurotransmitters and
neuromodulators.
• Explain the processing of information in neural
tissue.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
SECTION 12-1
An Overview of the Nervous System
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
nervous system overview
• Nervous system
• Provides swift, brief responses to stimuli
• Endocrine system
• Adjusts metabolic operations and directs longterm changes
• Nervous system includes
• All the neural tissue of the body
• Basic unit = neuron
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Divisions of the Nervous system
• CNS (Central Nervous system)
• Brain and spinal cord
• PNS (Peripheral Nervous system)
• Neural tissue outside CNS
• Afferent division brings sensory information
from receptors
• Efferent division carries motor commands to
effectors
• Efferent division includes somatic nervous
system and autonomic nervous system
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.1 Functional Overview of the Nervous
System
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.1
SECTION 12-2
Neurons
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Neuron structure
• Perikaryon
• Neurofilaments, neurotubules, neurofibrils
• Axon hillock
• Soma
• Axon
• Collaterals with telodendria
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.2 The Anatomy of a Multipolar
Neuron
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.2b
Synapse
• Site of intercellular communication
• Neurotransmitters released from synaptic knob
of presynaptic neuron
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.3 The Structure of a Typical Synpase
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.3
Neuron classification
• Anatomical
• Anaxonic
• Unipolar
• Bipolar
• Multipolar
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.4 A Structural Classification of
Neurons
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.4
Functional
• Sensory neurons
• deliver information from exteroceptors,
interoceptors, or proprioceptors
• Motor neurons
• Form the efferent division of the PNS
• Interneurons (association neurons)
• Located entirely within the CNS
• Distribute sensory input and coordinate
motor output
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.5 A Functional Classification of
Neurons
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.5
SECTION 12-3
Neuroglia
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Neuroglia of the Central Nervous System
• Four types of neuroglia in the CNS
• Ependymal cells
• Related to cerebrospinal fluid
• Astrocytes
• Largest and most numerous
• Oligodendrocytes
• Myelination of CNS axons
• Microglia
• Phagocytic cells
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.6 An Introduction to Neuroglia
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.6
Figure 12.7 Neuroglia in the CNS
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.7a
Figure 12.7 Neuroglia in the CNS
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.7b
Neuroglia of the Peripheral Nervous System
• Two types of neuroglia in the PNS
• Satellite cells
• Surround neuron cell bodies within ganglia
• Schwann cells
• Ensheath axons in the PNS
PLAY
Animation: Nervous system anatomy review
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
The transmembrane potential
• Electrochemical gradient
• Sum of all chemical and electrical forces acting
across the cell membrane
• Sodium-potassium exchange pump stabilizes
resting potential at ~70 mV
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.11 An Introduction to the Resting
Potential
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.11
Figure 12.12 Electrochemical Gradients
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.12
Changes in the transmembrane potential
• Membrane contains
• Passive (leak) channels that are always open
• Active (gated) channels that open and close in
response to stimuli
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.13 Gated Channels
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.13
Three types of active channels
• Chemically regulated channels
• Voltage-regulated channels
• Mechanically regulated channels
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Graded potential
• A change in potential that decreases with
distance
• Localized depolarization or hyperpolarization
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.14 Graded Potentials
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.14.1
Figure 12.14 Graded Potentials
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.14.2
Figure 12.15 Depolarization and
Hyperpolarization
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.15
Action Potential
• Appears when region of excitable membrane
depolarizes to threshold
• Steps involved
• Membrane depolarization and sodium
channel activation
• Sodium channel inactivation
• Potassium channel activation
• Return to normal permeability
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.16 The Generation of an Action
Potential
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.16.1
Figure 12.16 The Generation of an Action
Potential
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.16.2
Characteristics of action potentials
• Generation of action potential follows allor-none principle
• Refractory period lasts from time action
potential begins until normal resting
potential returns
• Continuous propagation
• spread of action potential across entire
membrane in series of small steps
• salutatory propagation
• action potential spreads from node to
node, skipping internodal membrane
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.17 Propagation of an Action Potential
along an Unmyelinated Axon
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.17
Figure 12.18 Saltatory Propagation along a
Myelinated Axon
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.18.1
Figure 12.18 Saltatory Propagation along a
Myelinated Axon
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.18.2
Axon classification
• Type A fibers
• Type B fibers
• Type C fibers
• Based on diameter, myelination and
propagation speed
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Muscle action potential versus neural action
potential
• Muscle tissue has higher resting potential
• Muscle tissue action potentials are longer lasting
• Muscle tissue has slower propagation of action
potentials
PLAY
Animation: The action potential
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Nerve impulse
• Action potential travels along an axon
• Information passes from presynaptic neuron to
postsynaptic cell
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
General properties of synapses
• Electrical
• Rare
• Pre- and postsynaptic cells are bound by
interlocking membrane proteins
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
General properties of synapses
• Chemical synapses
• More common
• Excitatory neurotransmitters cause
depolarization and promote action potential
generation
• Inhibitory neurotransmitters cause
hyperpolarization and suppress action potentials
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Cholinergic synapses
• Release acetylcholine (ACh)
• Information flows across synaptic cleft
• Synaptic delay occurs as calcium influx and
neurotransmitter release take appreciable
amounts of time
• ACh broken down
• Choline reabsorbed by presynaptic neurons
and recycled
• Synaptic fatigue occurs when stores of ACh are
exhausted
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.19 The Function of a Cholinergic
Synapse
PLAY
Animation: Overview of a cholinergic synapse
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.19.1
Figure 12.19 The Function of a Cholinergic
Synapse
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.19.2
Other neurotransmitters
• Adrenergic synapses release norepinephrine (NE)
• Other important neurotransmitters include
• Dopamine
• Serotonin
• GABA (gamma aminobutyric acid)
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Neuromodulators
• Influence post-synaptic cells response to
neurotransmitter
• Neurotransmitters can have direct or indirect
effect on membrane potential
• Can exert influence via lipid-soluble gases
PLAY
Animation: Synaptic potentials, cellular integration, and synaptic transmission
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.21 Neurotransmitter Functions
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.21a
Figure 12.21 Neurotransmitter Functions
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.21b
Figure 12.21 Neurotransmitter Functions
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.21c
SECTION 12-6
Information Processing
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Information processing
• Simplest level of information processing
occurs at the cellular level
• Excitatory and inhibitory potentials are
integrated through interactions
between postsynaptic potentials
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Postsynaptic potentials
• EPSP (excitatory postsynaptic potential) =
depolarization
• EPSP can combine through summation
• Temporal summation
• Spatial summation
• IPSP (inhibitory postsynaptic potential) =
hyperpolarization
• Most important determinants of neural activity
are EPSP / IPSP interactions
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.22 Temporal and Spatial Summation
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.22a
Figure 12.22 Temporal and Spatial Summation
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.22b
Figure 12.23 EPSP – IPSP Interactions
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.23
Presynaptic inhibition
• GABA release at axoaxonal synapse inhibits
opening calcium channels in synaptic knob
• Reduces amount of neurotransmitter released
when action potential arrives
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.24 Presynaptic Inhibition and
Facilitation
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.24
Presynaptic facilitation
• Activity at axoaxonal synapse increases amount
of neurotransmitter released when action
potential arrives
• Enhances and prolongs the effect of the
neurotransmitter
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.24 Presynaptic Inhibition and
Facilitation
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12.24
Rate of generation of action potentials
• Neurotransmitters are either excitatory or
inhibitory
• Effect on initial membrane segment reflects
an integration of all activity at that time
• Neuromodulators alter the rate of release of
neurotransmitters
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Rate of generation of action potentials
• Can be facilitated or inhibited by other
extracellular chemicals
• Effect of presynaptic neuron may be altered by
other neurons
• Degree of depolarization determines frequency
of action potential generation
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
You should now be familiar with:
• The two major divisions of the nervous system
and their characteristics.
• The structures/ functions of a typical neuron.
• The location and function of neuroglia.
• How resting potential is created and maintained.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
You should now be familiar with:
• The events in the generation and propagation of
an action potential.
• The structure / function of a synapse.
• The major types of neurotransmitters and
neuromodulators.
• The processing of information in neural tissue.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings