Transcript Chapter 11

Chapter 11:
Nervous System Basics and
Nervous System Tissues
Santiago Ramon Y. Cajal (1852-1934)
Founding Scientist in the Modern Approach to
Neuroscience. Received Nobel Prize in 1906
Figure 11.1: The nervous system’s functions, p. 388.
Sensory input
Integration
Motor output
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.2: Levels of organization in the nervous system, p. 389.
Key:
Central nervous system (CNS)
Brain and spinal cord
Integrative and
control centers
Key:
Brain
= Sensory (afferent)
division of PNS
= Motor (efferent)
division of PNS
= Structure
= Function
Visceral
sensory fiber
Peripheral nervous system (PNS)
Cranial nerves and spinal
nerves
Communication lines
between the CNS and the
rest of the body
Parasympathetic
motor fiber of ANS
Visceral organ
Sympathetic
motor fiber of ANS
Skin
Sensory (afferent) division
Somatic and visceral
sensory nerve fibers
Conducts impulses from
receptors to the CNS
Sympathetic division
Mobilizes body systems
during activity
Parasympathetic division
Conserves energy
Promotes housekeeping
functions during rest
Motor (efferent) division
Motor nerve fibers
Conducts impulses from
the CNS to effectors
(muscles and glands)
Autonomic nervous
system (ANS)
Visceral motor
(involuntary)
Conducts impulses
from the CNS to
cardiac muscles,
smooth muscles,
and glands
Somatic sensory
fiber
Spinal
cord
Motor fiber of
somatic nervous
system
Skeletal
muscle
Somatic nervous
System
Somatic motor
(voluntary)
Conducts impulses
from the CNS to
skeletal muscles
Central
nervous
system
(CNS)
Peripheral nervous system
(PNS)
(b)
(a)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.3: Neuroglia, p. 390.
Capillary
Neuron
(b) Microglial cell
(a) Astrocyte
Nerve fibers
Myelin sheath
Fluid-filled cavity
Process of
oligodendrocyte
(c) Ependymal cells
Schwann cells
(forming myelin sheath)
Brain or spinal cord tissue
Cell body
of neuron
Satellite cells
(d) Oligodendrocyte
Nerve fiber
(e) Sensory neuron with Schwann cells and satellite cells
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.4: Structure of a motor neuron, p. 392.
Dendrites
(receptive
regions)
Cell body
(biosynthetic center
and receptive region)
Neuron cell body
Nucleus
Dendritic
spine
(a)
Axon
(impulse generating
and conducting
region)
Nucleolus
Nissl bodies
Axon hillock
(b)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Impulse
direction
Node of Ranvier
Schwann cell
(one interNeurilemma node)
Terminal branches
(sheath of
(telodendria)
Schwann)
Axon terminals
(secretory
component)
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.5: Relationship of Schwann cells to axons in the PNS, p. 394.
Schwann cell
cytoplasm
Axon
Schwann
cell plasma
membrane
Schwann cell
nucleus
Myelin sheath
(a)
Schwann cell
cytoplasm
Axon
Neurilemma
(b)
(d)
Neurilemma
Myelin
sheath
(c)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.6: Operation of gated channels, p. 398.
Neurotransmitter
chemical attached
to receptor
Receptor
Na+
Na+
Chemical
binds
K+
K+
Closed
Open
(a) Chemically gated ion channel
Na+
Na+
Membrane
voltage
changes
Closed
Open
(b) Voltage-gated ion channel
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.7: Measuring membrane potential in neurons, p. 399.
Voltmeter
Plasma
membrane
Ground electrode
outside cell
Microelectrode
inside cell
Axon
Neuron
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.8: The basis of the resting membrane potential, p. 399.
Cell interior
Na+
15 mM
Cell
exterior
Na+
+
Na+ Na
K+
Na+–K+
pump
150 mM
Cl–
10 mM
Na+
Na+
A–
Na+
100 mM
150 mM
A–
0.2 mM
K+
5 mM
Cell exterior
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
K+
Cl–
120 mM
Cell
interior
Plasma
membrane
Na+
K+
K+
K+
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.9: Depolarization and hyperpolarization of the membrane, p. 400.
Depolarizing stimulus
Hyperpolarizing stimulus
+50
Inside
positive
0
Inside
negative
Depolarization
–50
–70
Resting
potential
–100
0
1
2
3
4
5
6
Membrane potential (voltage, mV)
Membrane potential (voltage, mV)
+50
7
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
–50
Resting
potential
–70
Hyperpolarization
–100
0
Time (ms)
(a)
0
1
2
3
4
5
6
7
Time (ms)
(b)
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.10: The mechanism of a graded potential, p. 401.
Depolarized region
Stimulus
Plasma
membrane
(a) Depolarization
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
(b) Spread of depolarization
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Membrane potential (mV)
Figure 11.11: Changes in membrane potential produced by a depolarizing graded potential, p. 402.
Active area
(site of initial
depolarization)
–70
Resting potential
Distance (a few mm)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.12: Phases of the action potential and the role of voltage-gated ion channels, p. 403.
Outside
cell
Na+
Inside
cell
Inside
K+
cell
Repolarizing phase: Na+
channels inactivating, K+
channels open
K+
Membrane potential (mV)
2 Depolarizing phase: Na+
channels open
Action potential
+30
3
0
2
–55
–70
1
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
4
1
Sodium Potassium
channel channel
Activation
K+
gates
Inactivation gate
1 Resting state: All gated Na+
and K+ channels closed
(Na+ activation gates closed;
inactivation gates open)
Inside
cell
PNa
PK
0
Outside cell
Na+
Na+
Threshold
1
2
3
Time (ms)
Relative membrane
permeability
Outside
cell
4
Outside
cell
Na+
Inside
cell
K+
4 Hyperpolarization: K+
channels remain open;
Na+ channels resetting
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Membrane potential (mV))
Figure 11.13: Propagation of an action potential (AP), p. 405.
Voltage
at 2 ms
+30
Voltage
at 0 ms
Voltage
at 4 ms
–70
(a) Time = 0 ms
(b) Time = 2 ms
(c) Time = 4 ms
Resting potential
Peak of action potential
Hyperpolarization
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Voltage
Membrane potential (mV)
Figure 11.14: Relationship between stimulus strength and action potential frequency, p. 406.
Action
potentials
+30
–70
Threshold
Stimulus
amplitude
0
Time (ms)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.15: Refractory periods in an AP, p. 406.
Absolute refractory
period
Membrane potential (mV)
+30
Relative refractory
period
Depolarization
(Na+ enters)
0
Repolarization
(K+ leaves)
After-hyperpolarization
–70
Stimulus
0
1
2
3
4
5
Time (ms)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.16: Saltatory conduction in a myelinated axon, p. 407.
Node of Ranvier
Cell body
Myelin
sheath
Distal
axon
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.17: Synapses, p. 409.
Cell body
Dendrites
Axodendritic
synapses
Axosomatic
synapses
Axoaxonic
synapses
Axon
(a)
Axon
Axosomatic
synapses
(b)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Soma of
postsynaptic
neuron
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.18: Events at a chemical synapse in response to depolarization, p. 410.
Neurotransmitter
Ca2+
1
Axon terminal of
presynaptic neuron
Postsynaptic
membrane
Mitochondrion
Axon of
presynaptic
neuron
Na+
Receptor
Postsynaptic
membrane
Ion channel open
Synaptic vesicles
containing
neurotransmitter
molecules
5
Degraded
neurotransmitter
2
Synaptic
cleft
Na+
3
4
Ion channel closed
Ion channel
(closed)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Ion channel (open)
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.19: Postsynaptic potentials, p. 412.
+30
0
Threshold
–55
–70
10
20
Time (ms)
(a) Excitatory postsynaptic potential (EPSP)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Membrane potential (mV)
Membrane potential (mV)
+30
0
Threshold
–55
–70
10
20
Time (ms)
(b) Inhibitory postsynaptic potential (IPSP)
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.24: Types of circuits in neuronal pools, p. 422.
Input
Input
Input
Input 1
Input 2
Input 3
Output
Output
Output
(a) Divergence in same pathway (b) Divergence to multiple
pathways
Input
Output
(c) Convergence,
(d) Convergence,
multiple sources
single source
Input
Output
Output
(e) Reverberating circuit
(f) Parallel after-discharge circuit
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.
Figure 11.25: A simple reflex arc, p. 423.
Sensory neuron
Stimulus
Integration
center
Receptor
Interneuron
Response
Effector
Motor neuron
Spinal cord (CNS)
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.