Chapter 11:Nervous System Basics and
Nervous System Tissues
Santiago Ramon Y. Cajal (1852-1934)Founding Scientist in the Modern Approach toNeuroscience. Received Nobel Prize in 1906
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.1: The nervous system’s functions, p. 388.
Sensory input
Motor output
Integration
Human Anatomy and Physiology, 7eby 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.
Central nervous system (CNS) Brain and spinal cord Integrative and control centers
Sensory (afferent) division Somatic and visceral sensory nerve fibers Conducts impulses from receptors to the CNS
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
Sympathetic division Mobilizes body systems during activity
Parasympathetic division Conserves energy Promotes housekeeping functions during rest
Peripheral nervous system (PNS) Cranial nerves and spinal nerves Communication lines between the CNS and the rest of the body
Somatic nervous System Somatic motor (voluntary) Conducts impulses from the CNS to skeletal muscles
= Structure= Function
Key:
Centralnervoussystem(CNS)
= Sensory (afferent)division of PNS= Motor (efferent)division of PNS
Key: Brain
SpinalcordSkin
Visceral organ
Skeletalmuscle
Peripheral nervous system(PNS)
Motor fiber ofsomatic nervoussystem
Somatic sensoryfiber
Sympatheticmotor fiber of ANS
Parasympatheticmotor fiber of ANS
Visceralsensory fiber
(a)
(b)
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.3: Neuroglia, p. 390.
(a) Astrocyte
(d) Oligodendrocyte
(e) Sensory neuron with Schwann cells and satellite cells
(b) Microglial cell
(c) Ependymal cells
Schwann cells(forming myelin sheath)
Cell bodyof neuronSatellite cells
Nerve fiber
Capillary
Neuron
Nerve fibers
Myelin sheath
Process ofoligodendrocyte
Fluid-filled cavity
Brain or spinal cord tissue
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.4: Structure of a motor neuron, p. 392.
(b)
(a)
Dendrites(receptiveregions)
Cell body(biosynthetic centerand receptive region)
Nucleolus
Nucleus
Terminal branches(telodendria)
Nissl bodies
Axon(impulse generatingand conductingregion)
Axon terminals(secretorycomponent)
Axon hillock
Neurilemma(sheath ofSchwann)
Node of Ranvier
Impulsedirection
Schwann cell(one inter-node)
Neuron cell body
Dendriticspine
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.5: Relationship of Schwann cells to axons in the PNS, p. 394.
(a)
(b)
(c)
(d)
Schwann cellcytoplasm
Axon
NeurilemmaMyelinsheath
Schwann cellnucleus
Schwanncell plasmamembrane
Myelin sheath
Schwann cellcytoplasm
Neurilemma
Axon
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.6: Operation of gated channels, p. 398.
(a) Chemically gated ion channel
Na+
K+K+
Na+
(b) Voltage-gated ion channel
Na+
Na+
Receptor
Neurotransmitter chemical attached to receptor
Closed Open
Membranevoltagechanges
Closed Open
Chemicalbinds
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.7: Measuring membrane potential in neurons, p. 399.
Voltmeter
Microelectrodeinside cell
Plasmamembrane
Ground electrodeoutside cell
Neuron
Axon
Human Anatomy and Physiology, 7eby 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.
Na+ Na+
K+
K+
K+
K+
Na+
Na+
Na+
Na+
Cell interiorNa+
15 mMK+
150 mMCl–
10 mM A–
100 mMNa+
150 mMA–
0.2 mM
Cell exterior
K+
5 mM Cl–
120 mM
Cellexterior
Cellinterior
Plasmamembrane
Na+–K+
pumpDif
fusi
on
K+ N
a+D
iffus
ion
-70 mV
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.9: Depolarization and hyperpolarization of the membrane, p. 400.
Depolarizing stimulus
Mem
bra
ne
po
ten
tial
(vo
ltag
e, m
V)
Time (ms)
0–100
–70
0
–50 –50
+50
1 2 3 4 5 6 7
Hyperpolarizing stimulus
Mem
bra
ne
po
ten
tial
(vo
ltag
e, m
V)
Time (ms)
0 1 2 3 4 5 6 7–100
–70
0
+50
Insidepositive
Insidenegative
(a) (b)
Restingpotential
DepolarizationRestingpotential
Hyper-polarization
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.10: The mechanism of a graded potential, p. 401.
(b)
Depolarized region Stimulus
Plasmamembrane
Depolarization Spread of depolarization(a)
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.11: Changes in membrane potential produced by a depolarizing graded potential, p. 402.
Distance (a few mm)
–70Resting potential
Active area(site of initialdepolarization)
Mem
bra
ne
po
ten
tial
(m
V)
Human Anatomy and Physiology, 7eby 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.
0 1 2 3 4
–70
–55
0
+30
Me
mb
ran
e p
ote
nti
al
(mV
)
Time (ms)
Re
lati
ve
me
mb
ran
e
pe
rme
ab
ilit
y
Na+Na+
K+
K+
Outsidecell
Insidecell
Outsidecell
Insidecell
Depolarizing phase: Na+
channels open
Repolarizing phase: Na+
channels inactivating, K+
channels open
Action potential
PNa
PKThreshold
Na+
Na+
K+K+
Outside cell
Insidecell
Outsidecell
Insidecell
Inactivation gate
Activationgates
Potassiumchannel
Sodiumchannel
Resting state: All gated Na+
and K+ channels closed (Na+ activation gates closed; inactivation gates open)
Hyperpolarization: K+
channels remain open; Na+ channels resetting
2
2
3
4
4
1
11
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.13: Propagation of an action potential (AP), p. 405.
–70
+30
(a) Time = 0 ms (b) Time = 2 ms (c) Time = 4 ms
Voltageat 2 ms
Voltageat 4 ms
Voltageat 0 ms
Resting potential
Peak of action potential
Hyperpolarization
Mem
bra
ne
po
ten
tial
(m
V))
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.14: Relationship between stimulus strength and action potential frequency, p. 406.
Time (ms)
Vo
ltag
eM
emb
ran
e p
ote
nti
al (
mV
)
–70
0
+30
Threshold
Actionpotentials
Stimulusamplitude
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.15: Refractory periods in an AP, p. 406.
Stimulus
Mem
bra
ne
po
ten
tial
(m
V)
Time (ms)
–70
0
+30
0 1 2 3 4 5
Absolute refractoryperiod
Relative refractoryperiod
Depolarization(Na+ enters)
Repolarization(K+ leaves)
After-hyperpolarization
Human Anatomy and Physiology, 7eby 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 bodyMyelinsheath
Distalaxon
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.17: Synapses, p. 409.
(a)
(b)
Cell body
Dendrites
Axon
Axodendriticsynapses
Axoaxonicsynapses
Axosomaticsynapses
Axosomaticsynapses
Soma of postsynaptic neuron
Axon
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.18: Events at a chemical synapse in response to depolarization, p. 410.
Synaptic vesiclescontaining neurotransmitter molecules
Axon of presynapticneuron
Synapticcleft
Ion channel(closed)
Ion channel (open)
Axon terminal of presynaptic neuron
PostsynapticmembraneMitochondrion
Ion channel closed
Ion channel open
Neurotransmitter
Receptor
Postsynapticmembrane
Degradedneurotransmitter
Na+
Na+
Ca2+
Action P
otential
1
2
34
5
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.19: Postsynaptic potentials, p. 412.
Threshold
Mem
bra
ne
po
ten
tial
(m
V)
Time (ms)
+30
0
–70
–55
10 20
(a) Excitatory postsynaptic potential (EPSP)
Threshold
Mem
bra
ne
po
ten
tial
(m
V)
Time (ms)
+30
0
–70
–55
10 20
(b) Inhibitory postsynaptic potential (IPSP)
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.24: Types of circuits in neuronal pools, p. 422.
(a) Divergence in same pathway
(e) Reverberating circuit
(f) Parallel after-discharge circuit
(b) Divergence to multiple pathways
(c) Convergence, multiple sources
(d) Convergence, single source
Input Input
Output Output
Input
OutputInput
Output
Input 1
Input 2 Input 3
Output
OutputInput
Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn
Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.
Figure 11.25: A simple reflex arc, p. 423.
Stimulus
Response
Receptor
Effector
Sensory neuron
Motor neuron
Integrationcenter
Spinal cord (CNS)
Interneuron