Contenu connexe Similaire à Ch7bppt nerve impulses and reflexes (20) Ch7bppt nerve impulses and reflexes1. PowerPoint® Lecture Slide Presentation
by Patty Bostwick-Taylor,
Florence-Darlington Technical College
The Nervous
System
7
PART B
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2. Functional Properties of Neurons
Irritability
Ability to respond to stimuli
Conductivity
Ability to transmit an impulse
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
3. Nerve Impulses
Resting neuron
The plasma membrane at rest is polarized
Fewer positive ions are inside the cell than
outside the cell
Depolarization
A stimulus depolarizes the neuron’s
membrane
A depolarized membrane allows sodium (Na+)
to flow inside the membrane
The exchange of ions initiates an action potential
in the neuron
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
5. Nerve Impulses
Action potential
If the action potential (nerve impulse) starts, it
is propagated over the entire axon (all or
none)
Impulses travel faster when fibers have a
myelin sheath
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
7. Nerve Impulses
Repolarization
Potassium ions rush out of the neuron after
sodium ions rush in, which repolarizes the
membrane
The sodium-potassium pump, using ATP,
restores the original configuration
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
9. Transmission of a Signal at Synapses
Impulses are able to cross the synapse to another
nerve
Neurotransmitter is released from a nerve’s
axon terminal
The dendrite of the next neuron has receptors
that are stimulated by the neurotransmitter
An action potential is started in the dendrite
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
10. Transmission of a Signal at Synapses
Axon of
transmitting
neuron
Axon
terminal
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Synapse
Figure 7.10, step 1
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
11. Transmission of a Signal at Synapses
Axon of
transmitting
neuron
Axon
terminal
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Synapse
Transmitting neuron
Vesicle
fuses with
plasma
membrane
Synaptic cleft
Ion channels
Receiving neuron
Figure 7.10, step 2
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
12. Transmission of a Signal at Synapses
Axon of
transmitting
neuron
Axon
terminal
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Synapse
Transmitting neuron
Vesicle
fuses with
plasma
membrane
Synaptic cleft
Ion channels
Neurotransmitter is released into
synaptic cleft
Neurotransmitter
molecules
Receiving neuron
Figure 7.10, step 3
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
13. Transmission of a Signal at Synapses
Axon of
transmitting
neuron
Axon
terminal
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Transmitting neuron
Vesicle
fuses with
plasma
membrane
Synaptic cleft
Ion channels
Neurotransmitter is released into
synaptic cleft
Synapse
Neurotransmitter binds
to receptor
on receiving
neuron’s
membrane
Neurotransmitter
molecules
Receiving neuron
Figure 7.10, step 4
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
14. Transmission of a Signal at Synapses
Axon of
transmitting
neuron
Axon
terminal
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Transmitting neuron
Vesicle
fuses with
plasma
membrane
Neurotransmitter is released into
synaptic cleft
Neurotransmitter binds
to receptor
on receiving
neuron’s
membrane
Neurotransmitter
molecules
Synaptic cleft
Ion channels
Synapse
Receiving neuron
Neurotransmitter
Receptor
Na+
Ion channel opens
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 7.10, step 5
15. Transmission of a Signal at Synapses
Axon of
transmitting
neuron
Axon
terminal
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Transmitting neuron
Vesicle
fuses with
plasma
membrane
Neurotransmitter is released into
synaptic cleft
Neurotransmitter binds
to receptor
on receiving
neuron’s
membrane
Neurotransmitter
molecules
Synaptic cleft
Ion channels
Synapse
Receiving neuron
Neurotransmitter
Receptor
Na+
Ion channel opens
Neurotransmitter
broken down
and released
Na+
Ion channel closes
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 7.10, step 6
16. Transmission of a Signal at Synapses
Axon
terminal
Axon of
transmitting
neuron
Action
potential
arrives
Vesicles
Synaptic
cleft
Receiving
neuron
Synapse
Transmitting neuron
Vesicle
fuses with
plasma
membrane
Neurotransmitter is released into
synaptic cleft
Neurotransmitter
molecules
Synaptic cleft
Ion channels
Neurotransmitter binds
to receptor
on receiving
neuron’s
membrane
Receiving neuron
Neurotransmitter
Receptor
Na+
Ion channel opens
Neurotransmitter
broken down
and released
Na+
Ion channel closes
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 7.10, step 7
17. The Reflex Arc
Reflex—rapid, predictable, and involuntary
response to a stimulus
Occurs over pathways called reflex arcs
Reflex arc—direct route from a sensory neuron, to
an interneuron, to an effector
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
18. The Reflex Arc
Skin
Spinal cord
(in cross section)
Stimulus at distal
end of neuron
Sensory neuron
Receptor
Motor neuron
(a)
Effector
Integration
center
Interneuron
Figure 7.11a
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
19. Simple Reflex Arc
Sensory receptors
(stretch receptors
in the quadriceps
muscle)
Spinal cord
(b)
Figure 7.11b, step 1
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
20. Simple Reflex Arc
Sensory receptors
(stretch receptors
in the quadriceps
muscle)
Sensory (afferent)
neuron
Spinal cord
(b)
Figure 7.11b, step 2
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
21. Simple Reflex Arc
Sensory receptors
(stretch receptors
in the quadriceps
muscle)
Sensory (afferent)
neuron
Spinal cord
Synapse in
ventral horn
gray matter
(b)
Figure 7.11b, step 3
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
22. Simple Reflex Arc
Sensory receptors
(stretch receptors
in the quadriceps
muscle)
Sensory (afferent)
neuron
Spinal cord
Synapse in
ventral horn
gray matter
Motor
(efferent)
neuron
(b)
Figure 7.11b, step 4
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
23. Simple Reflex Arc
Sensory receptors
(stretch receptors
in the quadriceps
muscle)
Sensory (afferent)
neuron
Spinal cord
Synapse in
ventral horn
gray matter
(b)
Motor
(efferent)
neuron
Effector
(quadriceps
muscle of
thigh)
Figure 7.11b, step 5
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
24. Simple Reflex Arc
Sensory receptors
(pain receptors in
the skin)
Spinal cord
(c)
Figure 7.11c, step 1
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
25. Simple Reflex Arc
Sensory receptors
(pain receptors in
the skin)
Spinal cord
Sensory (afferent)
neuron
(c)
Figure 7.11c, step 2
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
26. Simple Reflex Arc
Sensory receptors
(pain receptors in
the skin)
Spinal cord
Sensory (afferent)
neuron
Interneuron
(c)
Figure 7.11c, step 3
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
27. Simple Reflex Arc
Sensory receptors
(pain receptors in
the skin)
Spinal cord
Sensory (afferent)
neuron
Interneuron
Motor
(efferent)
neuron
(c)
Figure 7.11c, step 4a
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
28. Simple Reflex Arc
Sensory receptors
(pain receptors in
the skin)
Spinal cord
Sensory (afferent)
neuron
Interneuron
Motor
(efferent)
neuron
Effector
(biceps
brachii
muscle)
(c)
Figure 7.11c, step 4b
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
29. Types of Reflexes and Regulation
Somatic reflexes
Activation of skeletal muscles
Example: When you move your hand away
from a hot stove
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
30. Types of Reflexes and Regulation
Autonomic reflexes
Smooth muscle regulation
Heart and blood pressure regulation
Regulation of glands
Digestive system regulation
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
31. Types of Reflexes and Regulation
Patellar, or knee-jerk, reflex is an example of a
two-neuron reflex arc
Figure 7.11d
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings