The document describes the structure and function of neurons and the nervous system. It discusses how neurons are able to transmit signals via nerve impulses. When a neuron is stimulated, it causes depolarization of the membrane through ion exchange, initiating an action potential. This potential then propagates along the axon. At synapses, neurotransmitters transmit signals between neurons. The document also explains reflex arcs which allow for rapid involuntary responses through defined pathways and different types of reflexes.

1. PowerPoint® Lecture Slide Presentation
by Patty Bostwick-Taylor,
Florence-Darlington Technical College
The Nervous
System
7
PART B
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings

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

4. Nerve Impulses
Figure 7.9a–b
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

6. Nerve Impulses
Figure 7.9c–d
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

8. Nerve Impulses
Figure 7.9e–f
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