Download nervous system

Chapter 28
Nervous Systems
PowerPoint Lectures for
Campbell Biology: Concepts & Connections, Seventh Edition
Reece, Taylor, Simon, and Dickey
© 2012 Pearson Education, Inc.
Lecture by Edward J. Zalisko
Introduction
 Spinal cord injuries disrupt communication between
– the central nervous system (brain and spinal cord) and
– the rest of the body.
© 2012 Pearson Education, Inc.
Introduction
 Over 250,000 Americans are living with spinal cord
injuries.
 Spinal cord injuries
– happen more often to men,
– happen mostly to people in their teens and 20s,
– are caused by vehicle accidents, gunshots, and falls, and
– are usually permanent because the spinal cord cannot be
repaired.
© 2012 Pearson Education, Inc.
Figure 28.0_1
Chapter 28: Big Ideas
Nervous System
Structure and Function
Nerve Signals and
Their Transmission
An Overview of Animal
Nervous Systems
The Human Brain
NERVOUS SYSTEM
STRUCTURE
AND FUNCTION
© 2012 Pearson Education, Inc.
28.1 Nervous systems receive sensory input,
interpret it, and send out appropriate
commands
 The nervous system
– obtains sensory information, sensory input,
– processes sensory information, integration, and
– sends commands to effector cells (muscles) that carry out
appropriate responses, motor output.
© 2012 Pearson Education, Inc.
Figure 28.1A
Sensory input
Integration
Sensory receptor
Motor output
Brain and spinal cord
Effector cells
Peripheral nervous
system (PNS)
Central nervous
system (CNS)
28.1 Nervous systems receive sensory input,
interpret it, and send out appropriate
commands
 The central nervous system (CNS) consists of the
– brain and
– spinal cord (vertebrates).
 The peripheral nervous system (PNS)
– is located outside the CNS and
– consists of
– nerves (bundles of neurons wrapped in connective tissue) and
– ganglia (clusters of neuron cell bodies).
© 2012 Pearson Education, Inc.
28.1 Nervous systems receive sensory input,
interpret it, and send out appropriate
commands
 Sensory neurons
– convey signals from sensory receptors
– to the CNS.
 Interneurons
– are located entirely in the CNS,
– integrate information, and
– send it to motor neurons.
 Motor neurons convey signals to effector cells.
© 2012 Pearson Education, Inc.
Figure 28.1B
1
Sensory
receptor
2
Sensory
neuron
Brain
Ganglion
Motor
neuron
Spinal
cord
3
Quadriceps
muscles
4
Interneuron
Nerve
Flexor
muscles
PNS
CNS
28.2 Neurons are the functional units of nervous
systems
 Neurons are
– cells specialized for carrying signals and
– the functional units of the nervous system.
 A neuron consists of
– a cell body and
– two types of extensions (fibers) that conduct signals,
– dendrites and
– axons.
© 2012 Pearson Education, Inc.
28.2 Neurons are the functional units of nervous
systems
 Myelin sheaths
– enclose axons,
– form a cellular insulation, and
– speed up signal transmission.
© 2012 Pearson Education, Inc.
Figure 28.2
Signal direction
Cell body
Nucleus
Signal
pathway
Node of Ranvier
Layers of
myelin
Nodes of
Ranvier
Myelin
sheath
Dendrites
Cell
body
Schwann
cell
Synaptic
terminals
Nucleus
Axon
Schwann
cell
NERVE SIGNALS
AND THEIR TRANSMISSION
© 2012 Pearson Education, Inc.
28.3 Nerve function depends on charge differences
across neuron membranes
 At rest, a neuron’s plasma membrane has potential
energy—the membrane potential, in which
– just inside the cell is slightly negative and
– just outside the cell is slightly positive.
 The resting potential is the voltage across the
plasma membrane of a resting neuron.
© 2012 Pearson Education, Inc.
28.3 Nerve function depends on charge differences
across neuron membranes
 The resting potential exists because of differences in
ion concentration of the fluids inside and outside the
neuron.
– Inside the neuron
– K+ is high and
– Na+ is low.
– Outside the neuron
– K+ is low and
– Na+ is high.
© 2012 Pearson Education, Inc.
Animation: Resting Potential
Right click on animation / Click play
© 2012 Pearson Education, Inc.
Figure 28.3
Neuron
Axon
Plasma
membrane
Outside of neuron
Na
Na
Na
Na
K
K
Na
channel
Na
Plasma
membrane
Na
Na
Na
K
Na
Na
Na
Na
Na-K
pump
K
K
Na
Na
Na
Na
ATP
K channel
K
Na
K
K
Na
Na
K
K
Inside of neuron
K
K
K
K
K
K
K
28.4 A nerve signal begins as a change in the
membrane potential
 A stimulus is any factor that causes a nerve signal
to be generated. A stimulus
– alters the permeability of a portion of the membrane,
– allows ions to pass through, and
– changes the membrane’s voltage.
© 2012 Pearson Education, Inc.
28.4 A nerve signal begins as a change in the
membrane potential
 A nerve signal, called an action potential, is
– a change in the membrane voltage,
– from the resting potential,
– to a maximum level, and
– back to the resting potential.
© 2012 Pearson Education, Inc.
Animation: Action Potential
Right click on animation / Click play
© 2012 Pearson Education, Inc.
Figure 28.4
Na
Na
Na
Na
K
Additional Na channels
open, K channels are
closed; interior of cell
becomes more positive.
Na
Na
K
2
K
50
Membrane potential
(mV)
3
Action
potential
3
0
5
The K channels
close relatively
slowly, causing a
brief undershoot.
4
50 Threshold
1
Resting potential
100
5
1
Time (msec)
Sodium Potassium
Na channel channel
Na channels close
and inactivate; K
channels open, and
K rushes out;
interior of cell is more
negative than outside.
2
A stimulus opens some Na
channels; if threshold is reached,
an action potential is triggered.
Na
4
Outside
of neuron
Na
Na
Plasma membrane
K
1
K
Inside of neuron
Resting state: Voltage-gated Na
and K channels are closed;
resting potential is maintained by
ungated channels (not shown).
1
Return to resting
state.
Figure 28.4_s1
Membrane potential
(mV)
50
Action
potential
0
50 Threshold
1
100
Resting potential
Time (msec)
1
Resting state: Voltagegated Na and K
channels are closed;
resting potential is
maintained by ungated
channels (not shown).
Na
Na
Sodium Potassium
channel channel
Outside
of neuron
Plasma membrane
K
Inside of neuron
Figure 28.4_s2
Membrane potential
(mV)
50
Action
potential
0
2
50 Threshold
1
100
Resting potential
Time (msec)
2 A stimulus opens some Na
channels; if threshold is reached,
an action potential is triggered.
Na
Na
K
Figure 28.4_s3
Membrane potential
(mV)
50
Action
potential
3
0
2
50 Threshold
1
100
Resting potential
Time (msec)
3
Additional Na channels
open, K channels are
closed; interior of cell
becomes more positive.
Na
Na
K
Figure 28.4_s4
Membrane potential
(mV)
50
Action
potential
3
0
4
2
50 Threshold
1
100
Resting potential
Time (msec)
4
Na channels close
and inactivate; K
channels open, and
K rushes out;
interior of cell is more
negative than outside.
Na
Na
K
Figure 28.4_s5
Membrane potential
(mV)
50
Action
potential
3
0
2
50 Threshold
1
100
Resting potential
Time (msec)
5
The K channels
close relatively
slowly, causing a
brief undershoot.
4
5
Figure 28.4_s6
Membrane potential
(mV)
50
Action
potential
3
0
2
50 Threshold
1
1
100
5
Resting potential
Time (msec)
1 Return to resting
Na
4
Na
state.
K
28.5 The action potential propagates itself along
the axon
 Action potentials are
– self-propagated in a one-way chain reaction along a
neuron and
– all-or-none events.
© 2012 Pearson Education, Inc.
Figure 28.5_s1
Action
potential
Na
Plasma
membrane
Axon
segment
1
Na
Figure 28.5_s2
Action
potential
Na
Plasma
membrane
Axon
segment
1
Na
Action potential
Na
K
2
K
Na
Figure 28.5_s3
Action
potential
Na
Plasma
membrane
Axon
segment
1
Na
Action potential
Na
K
2
K
Na
Action potential
Na
K
3
K
Na
Figure 28.5
Axon
Plasma
membrane
Action

Na potential
Axon
segment
1
Na
Action potential
Na
K
2
K
Na
Action potential
Na
K
3
K
Na
28.5 The action potential propagates itself along
the axon
 The frequency of action potentials (but not their
strength) changes with the strength of the stimulus.
© 2012 Pearson Education, Inc.
28.6 Neurons communicate at synapses
 Synapses are junctions where signals are
transmitted between
– two neurons or
– between neurons and effector cells.
© 2012 Pearson Education, Inc.
28.6 Neurons communicate at synapses
 Electrical signals pass between cells at electrical
synapses.
 At chemical synapses
– the ending (presynaptic) cell secretes a chemical signal, a
neurotransmitter,
– the neurotransmitter crosses the synaptic cleft, and
– the neurotransmitter binds to a specific receptor on the
surface of the receiving (postsynaptic) cell.
© 2012 Pearson Education, Inc.
Animation: Synapse
Right click on animation / Click play
© 2012 Pearson Education, Inc.
Figure 28.6
1
Sending cell
Axon of
sending
cell
Synaptic
terminal
of sending
cell
Action
potential
arrives
Synaptic
vesicles
Synaptic
terminal
2
3
Vesicle fuses
with plasma
membrane
Dendrite
of receiving
cell
Neurotransmitter
is released into
synaptic cleft
Synaptic
cleft
4
Neurotransmitter
binds to receptor
Receiving
cell
Ion channels
Neurotransmitter
molecules
Neurotransmitter
Receptor
Neurotransmitter broken
down and released
Ions
5
Ion channel opens
6
Ion channel closes
28.7 Chemical synapses enable complex
information to be processed
 Some neurotransmitters
– excite a receiving cell, and
– others inhibit a receiving cell’s activity by decreasing its
ability to develop action potentials.
© 2012 Pearson Education, Inc.
28.7 Chemical synapses enable complex
information to be processed
 A receiving neuron’s membrane may receive
signals
– that are both excitatory and inhibitory and
– from many different sending neurons.
 The summation of excitation and inhibition
determines if a neuron will transmit a nerve signal.
© 2012 Pearson Education, Inc.
Figure 28.7
Synaptic terminals
Dendrites
Inhibitory
Excitatory
Myelin
sheath
Receiving
cell body
Axon
Synaptic
terminals
28.8 A variety of small molecules function as
neurotransmitters
 Many small, nitrogen-containing molecules are
neurotransmitters.
– Acetylcholine is a neurotransmitter
– in the brain and
– at synapses between motor neurons and muscle cells.
– Biogenic amines
– are important neurotransmitters in the CNS and
– include serotonin and dopamine, which affect sleep, mood, and
attention.
© 2012 Pearson Education, Inc.
28.8 A variety of small molecules function as
neurotransmitters
– Many neuropeptides
– consist of relatively short chains of amino acids important in the
CNS and
– include endorphins, decreasing our perception of pain.
© 2012 Pearson Education, Inc.
28.9 CONNECTION: Many drugs act at chemical
synapses
 Many psychoactive drugs
– act at synapses and
– affect neurotransmitter action.
 Caffeine counters the effect of inhibitory
neurotransmitters.
 Nicotine acts as a stimulant by binding to
acetylcholine receptors.
 Alcohol is a depressant.
© 2012 Pearson Education, Inc.
Figure 28.9
AN OVERVIEW
OF ANIMAL
NERVOUS SYSTEMS
© 2012 Pearson Education, Inc.
28.11 Vertebrate nervous systems are highly
centralized
 In the vertebrates, the central nervous system (CNS)
– consists of the brain and spinal cord and
– includes spaces filled with cerebrospinal fluid
– forming ventricles of the brain,
– forming the central canal of the spinal cord, and
– surrounding the brain.
 The vertebrate peripheral nervous system (PNS)
consists of
– cranial nerves,
– spinal nerves, and
– ganglia.
© 2012 Pearson Education, Inc.
Figure 28.11A
Central
nervous
system
(CNS)
Brain
Spinal
cord
Cranial
nerves
Ganglia
outside
CNS
Spinal
nerves
Peripheral
nervous
system
(PNS)
Figure 28.11B
Gray matter
Brain
Cerebrospinal fluid
Meninges
White
matter
Central canal
Ventricles
Central canal
of spinal cord
Spinal cord
Dorsal root
ganglion
(part of PNS)
Spinal nerve
(part of PNS)
Spinal cord
(cross section)
28.12 The peripheral nervous system of
vertebrates is a functional hierarchy
 The PNS can be divided into two functional
components:
1. the motor system, mostly voluntary, and
2. the autonomic nervous system, mostly involuntary.
© 2012 Pearson Education, Inc.
28.12 The peripheral nervous system of
vertebrates is a functional hierarchy
 The motor nervous system
– carries signals to and from skeletal muscles and
– mainly responds to external stimuli.
 The autonomic nervous system
– regulates the internal environment and
– controls smooth and cardiac muscle and organs and
glands of the digestive, cardiovascular, excretory, and
endocrine systems.
© 2012 Pearson Education, Inc.
Figure 28.12A
Peripheral nervous system
(to and from the central
nervous system)
Motor system
(voluntary and
involuntary; to and from
skeletal muscles)
Autonomic nervous system
(involuntary; smooth and
cardiac muscles, various glands)
Parasympathetic
division
(“Rest and digest”)
Sympathetic
division
(“Flight and fight”)
Enteric division
(muscles and glands
of the digestive system)
28.12 The peripheral nervous system of
vertebrates is a functional hierarchy
 The autonomic nervous system is composed of
three divisions.
1. The parasympathetic division primes the body for
activities that gain and conserve energy for the body.
2. The sympathetic division prepares the body for intense,
energy-consuming activities.
3. The enteric division consists of networks of neurons in
the digestive tract, pancreas, and gallbladder that control
secretion and peristalsis.
© 2012 Pearson Education, Inc.
Figure 28.12B
Sympathetic division
Parasympathetic division
Brain
Eye
Dilates pupil
Constricts pupil
Salivary
glands
Stimulates
saliva
secretion
Inhibits
saliva
secretion
Lung
Relaxes
bronchi
Constricts
bronchi
Slows
heart
Accelerates
heart
Heart
Adrenal
gland
Spinal
cord
Liver
Stomach
Stimulates
stomach,
pancreas,
and intestines
Pancreas
Stimulates
epinephrine
and norepinephrine release
Stimulates
glucose release
Inhibits
stomach,
pancreas,
and intestines
Intestines
Bladder
Stimulates
urination
Inhibits
urination
Promotes
erection of
genitalia
Promotes ejaculation and vaginal
contractions
Genitalia
28.13 The vertebrate brain develops from three
anterior bulges of the neural tube
 The vertebrate brain evolved by the enlargement
and subdivision of the
– forebrain,
– midbrain, and
– hindbrain.
 In the course of vertebrate evolution, the forebrain
and hindbrain gradually became subdivided
– structurally and
– functionally.
© 2012 Pearson Education, Inc.
Figure 28.13
Embryonic
Brain Regions
Brain Structures
Present in Adult
Cerebrum (cerebral hemispheres; includes
cerebral cortex, white matter, basal ganglia)
Forebrain
Diencephalon (thalamus, hypothalamus,
posterior pituitary, pineal gland)
Midbrain
Midbrain (part of brainstem)
Pons (part of brainstem), cerebellum
Hindbrain
Medulla oblongata (part of brainstem)
Cerebrum
Midbrain
Hindbrain
Diencephalon
Midbrain
Pons
Cerebellum
Medulla
oblongata
Forebrain
Embryo (1 month old)
Spinal cord
Fetus (3 months old)
28.13 The vertebrate brain develops from three
anterior bulges of the neural tube
 In birds and mammals the cerebrum
– is much larger and
– correlates with their sophisticated behavior.
© 2012 Pearson Education, Inc.
THE HUMAN BRAIN
© 2012 Pearson Education, Inc.
28.14 The structure of a living supercomputer:
The human brain
 The human brain is
– more powerful than the most sophisticated computer and
– composed of three main parts:
1. forebrain,
2. midbrain, and
3. hindbrain.
© 2012 Pearson Education, Inc.
Figure 28.14A
Cerebral cortex
(outer region
of cerebrum)
Cerebrum
Forebrain
Thalamus
Hypothalamus
Pituitary gland
Midbrain
Hindbrain
Pons
Medulla
oblongata
Cerebellum
Spinal
cord
28.14 The structure of a living supercomputer:
The human brain
 The midbrain, subdivisions of the hindbrain, the
thalamus, and the hypothalamus
– conduct information to and from higher brain centers,
– regulate homeostatic functions,
– keep track of body position, and
– sort sensory information.
© 2012 Pearson Education, Inc.
Figure 28.14B
Left cerebral
hemisphere
Right cerebral
hemisphere
Thalamus
Cerebrum
Cerebellum
Basal
nuclei
Corpus
callosum
Medulla
oblongata
Table 28.14
28.14 The structure of a living supercomputer:
The human brain
 The cerebrum is
– part of the forebrain and
– the largest and most complex part of the brain.
– Most of the cerebrum’s integrative power resides in the
cerebral cortex of the two cerebral hemispheres.
© 2012 Pearson Education, Inc.
28.15 The cerebral cortex is a mosaic of
specialized, interactive regions
 The cerebral cortex
– is less than 5 mm thick and
– accounts for 80% of the total human brain mass.
 Specialized integrative regions of the cerebral cortex
include
– the somatosensory cortex and
– centers for vision, hearing, taste, and smell.
© 2012 Pearson Education, Inc.
28.15 The cerebral cortex is a mosaic of
specialized, interactive regions
 The motor cortex directs responses.
 Association areas
– make up most of the cerebrum and
– are concerned with higher mental activities such as
reasoning and language.
 In a phenomenon known as lateralization, right and
left cerebral hemispheres tend to specialize in
different mental tasks.
© 2012 Pearson Education, Inc.
Figure 28.15
Frontal lobe
Parietal lobe
Frontal
association
area
Speech
Somatosensory
association
area
Reading
Speech
Hearing
Smell
Auditory
association
area
Visual
association
area
Vision
Temporal lobe
Occipital lobe
28.16 CONNECTION: Injuries and brain
operations provide insight into brain
function
 Brain injuries and surgeries reveal brain functions.
– After a 13-pound steel rod pierced his skull, Phineas
Gage appeared to have an intact intellect but his
associates noted negative changes to his personality.
– Stimulation of the cerebral cortex during surgeries caused
patients to recall sensations and memories.
– Cutting the corpus callosum revealed information about
brain lateralization.
© 2012 Pearson Education, Inc.
Figure 28.16A
28.18 Several parts of the brain regulate sleep and
arousal
 Sleep and arousal involve activity by the
– hypothalamus,
– medulla oblongata,
– pons, and
– neurons of the reticular formation.
© 2012 Pearson Education, Inc.
28.18 Several parts of the brain regulate sleep and
arousal
 Sleep
– is essential for survival,
– is an active state, and
– may be involved in consolidating learning and memory.
© 2012 Pearson Education, Inc.
28.19 The limbic system is involved in emotions,
memory, and learning
 The limbic system is
– a functional group of integrating centers in the
– cerebral cortex,
– thalamus,
– hypothalamus, and
– involved in
– emotions, such as nurturing infants and bonding emotionally to
other people,
– memory, and
– learning.
© 2012 Pearson Education, Inc.
Figure 28.19
Thalamus
Cerebrum
Hypothalamus
Prefrontal
cortex
Smell
Olfactory
bulb
Amygdala
Hippocampus
You should now be able to
1. Describe the structural and functional subdivisions
of the nervous system.
2. Describe the three parts of a reflex, distinguishing
the three types of neurons that may be involved in
the reaction.
3. Describe the structures and functions of neurons
and myelin sheaths.
4. Define a resting potential and explain how it is
created.
© 2012 Pearson Education, Inc.
You should now be able to
5. Explain how an action potential is produced and
the resting membrane potential restored.
6. Explain how an action potential propagates itself
along a neuron.
7. Compare the structures, functions, and locations of
electrical and chemical synapses.
8. Compare excitatory and inhibitory
neurotransmitters.
9. Describe the types and functions of
neurotransmitters known in humans.
© 2012 Pearson Education, Inc.
You should now be able to
10. Explain how drugs can alter chemical synapses.
11. Describe the diversity of animal nervous systems
and provide examples.
12. Describe the general structure of the brain, spinal
cord, and associated nerves of vertebrates.
13. Compare the functions of the motor nervous
system and autonomic nervous system.
© 2012 Pearson Education, Inc.
You should now be able to
14. Compare the structures, functions, and
interrelationships of the parasympathetic,
sympathetic, and enteric divisions of the
peripheral nervous system.
15. Explain how the vertebrate brain develops from an
embryonic tube.
16. Describe the main parts and functions of the
human brain.
17. Explain how injuries, illness, and surgery provide
insight into the functions of the brain.
© 2012 Pearson Education, Inc.
You should now be able to
18. Explain how fMRI scans help us understand brain
functions.
19. Explain how the brain regulates sleep and
arousal.
20. Describe the structure and functions of the limbic
system.
21. Describe the causes, symptoms, and treatments
of schizophrenia, depression, Alzheimer’s
disease, and Parkinson’s disease.
© 2012 Pearson Education, Inc.
Figure 28.UN01
Sensory
receptor
Sensory input
Integration
Effector
cells
Motor output
Peripheral nervous
system
Central nervous
system
Figure 28.UN02
Dendrites
Cell Axon
body
Myelin sheath
(speeds signal
transmission)
Synaptic
terminals
Figure 28.UN03
Central Nervous
System
(CNS)
Brain
Spinal cord:
nerve bundle that
communicates
with body
Peripheral Nervous
System
(PNS)
Motor system:
voluntary control
over muscles
Autonomic
nervous system:
involuntary control
over organs
• Parasympathetic
division:
rest and digest
• Sympathetic division:
fight or flight