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CAMPBELL
BIOLOGYReece • Urry • Cain • Wasserman • Minorsky • Jackson
© 2014 Pearson Education, Inc.
TENTH
EDITION
49Nervous Systems
Lecture Presentation by
Nicole Tunbridge and
Kathleen Fitzpatrick
© 2014 Pearson Education, Inc.
1. Organization of Animal
Nervous Systems
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Animal Nervous Systems
Nervous systems consist of circuits of neurons and
supporting cells
By the time of the Cambrian explosion more than
500 million years ago, specialized systems of
neurons had appeared that enables animals to
sense their environments and respond rapidly
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The simplest animals with nervous systems, the
cnidarians, have neurons arranged in nerve nets
A nerve net is a series of interconnected nerve cells
More complex animals have nerves, in which the axons
of multiple neurons are bundled together
Nerves channel and organize information flow through
the nervous system
Nerve net
(a) Hydra (cnidarian)
Radial
nerve
Nerve
ring
(b) Sea star (echinoderm)
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Bilaterally symmetrical animals exhibit cephalization, the
clustering of sensory organs at the front end of the body
The simplest cephalized
animals, flatworms, have a
central nervous system
(CNS)
The CNS consists of a brain and longitudinal nerve cords
The peripheral nervous system (PNS) consists of
neurons carrying information into and out of the CNS
Eyespot
Brain
Nerve
cords
Transverse
nerve
(c) Planarian (flatworm)
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Annelids and arthropods have segmentally
arranged clusters of neurons called ganglia
Brain
Ventral
nerve cord
Segmental
ganglia
(d) Leech (annelid)
Brain
Ventral
nerve
cord
Segmental
ganglia
(e) Insect (arthropod)
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Nervous system organization usually correlates with
lifestyle
Sessile molluscs (for example, clams and chitons)
have simple systems, whereas more complex molluscs
(for example, octopuses and squids) have more
sophisticated systems
Anterior
nerve ring
Longitudinal
nerve cords
Ganglia
(f) Chiton (mollusc)
Brain
Ganglia
(g) Squid (mollusc)
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In vertebrates:
The CNS is composed of the brain and spinal cord
The peripheral nervous system (PNS) is composed
of nerves and ganglia
Region specialization is a hallmark of both systems
Brain
Spinalcord(dorsalnervecord)
Sensory
ganglia
(h) Salamander (vertebrate)
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Glia
Capillary CNS Neuron PNS
Schwann cellsMicrogliaOligodendrocytesAstrocytesEpendymal
cells
VENTRICLE
Cilia
Glial cells, or glia have numerous functions to nourish,
support, and regulate neurons
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Figure 49.3
• Ependymal cells line the ventricles of the brain and
have cilia to promote circulation of the cerebral spinal
fluid (CSF)
• Oligodendrocytes myelinate axons in the CNS
which greatly increases the speed of action potentials
• Schwann cells perform the same function (the
myelination of axons) in the PNS
• Microglia are essentially immune cells in the CNS
that protect against pathogens
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Embryonic radial glia form tracks along which newly
formed neurons migrate
Astrocytes induce cells lining capillaries in the CNS to
form tight junctions, resulting in a blood-brain barrier
and restricting the entry of most substances into the brain
Radial glial cells and
astrocytes can both act
as stem cells that give
rise to neurons and
a variety of glial cells
newly generated neurons
in an adult mouse brain
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Organization of the Vertebrate Nervous System
The CNS (brain and spinal cord) develops from a
hollow nerve cord, the neural tube, during embryonic
development
The cavity of this nerve cord gives rise to the narrow
central canal of the spinal cord and the ventricles
of the brain
The canal and ventricles fill with cerebrospinal fluid,
which supplies the CNS with nutrients and hormones
and carries away wastes
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Figure 49.6
Central
nervous
system
(CNS)
Brain
Spinal
cord
Cranial nerves
Ganglia
outside CNS
Spinal nerves
Peripheral
nervous
system
(PNS)
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Gray matter
White
matter
Ventricles
The brain and spinal cord contain:
Gray matter, which consists of neuron cell bodies,
dendrites, and unmyelinated axons
White matter, which consists of bundles of myelinated
axons
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The spinal cord conveys information to and from the
brain and generates basic patterns of locomotion
The spinal cord also produces reflexes independently
of the brain
A reflex is the body’s automatic response to a
stimulus
For example, a doctor uses a mallet to trigger a knee-
jerk reflex
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Figure 49.7
Quadriceps
muscle
Hamstring
muscle
Key Sensory neuron
Motor neuron
Interneuron
Cell body of
sensory neuron in
dorsal root ganglion Gray
matter
White
matter
Spinal cord
(cross section)
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The Peripheral Nervous System
The PNS transmits information to and from the CNS
and regulates movement and the internal
environment
In the PNS, afferent neurons transmit information to
the CNS and efferent neurons transmit information
away from the CNS
“efferent” – conveying away from a center
“afferent” – conveying toward a center
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Figure 49.8
Afferent neurons
Sensory
receptors
Efferent neurons
Internal
and external
stimuli
Autonomic
nervous system
Motor
system
Control of
skeletal muscle
Sympathetic
division
Parasympathetic
division
Enteric
division
Control of smooth muscles,
cardiac muscles, glands
PERIPHERAL NERVOUS
SYSTEM
CENTRAL NERVOUS
SYSTEM
(information processing)
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The PNS has two efferent components: the motor system
and the autonomic nervous system
The motor system carries signals to skeletal muscles and
is voluntary
The autonomic nervous system regulates smooth and
cardiac muscles and is generally involuntary
The autonomic nervous system has sympathetic &
parasympathetic divisions
The sympathetic division regulates arousal and energy
generation (“fight-or-flight” response)
The parasympathetic division has antagonistic effects on
target organs and promotes calming and a return to “rest and
digest” functions
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Figure 49.9
Parasympathetic division Sympathetic division
Constricts pupil of eye Dilates pupil of eye
Stimulates salivary
gland secretion
Inhibits salivary
gland secretion
Relaxes bronchi in lungsConstricts
bronchi in lungs
Slows heart Accelerates heart
Inhibits activity of
stomach and intestines
Inhibits activity
of pancreas
Stimulates activity of
stomach and intestines
Stimulates activity
of pancreas
Stimulates gallbladder
Promotes emptying
of bladder
Promotes erection
of genitalia
Stimulates glucose
release from liver;
inhibits gallbladder
Stimulates
adrenal medulla
Inhibits emptying
of bladder
Promotes ejaculation and
vaginal contractions
Sympathetic
gangliaCervical
Thoracic
Lumbar
Sacral
Synapse
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2. The Vertebrate Brain
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Olfactory
bulbCerebrum
Cerebellum
Forebrain Midbrain Hindbrain
The vertebrate brain is regionally specialized
The vertebrate brain has three major regions: the
forebrain, midbrain, and hindbrain
The forebrain has activities including processing of
olfactory input, regulation of sleep, learning, and any
complex processing
The midbrain coordinates routing of sensory input
The hindbrain
controls involuntary
activities and
coordinates motor
activities
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Comparison of vertebrates shows that relative sizes
of particular brain regions vary
These size differences reflect the relative importance of
the particular brain function
Evolution has resulted in a close match between
structure and function
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Figure 49.10
Lamprey
Shark
Ray-finned
fish
Amphibian
Crocodilian
Bird
Mammal
ANCESTRAL
VERTEBRATE
Key
Forebrain
Midbrain
Hindbrain
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During embryonic development the anterior neural
tube gives rise to the forebrain, midbrain, and
hindbrain
The midbrain and part of the hindbrain form the
brainstem, which joins with the spinal cord at the base
of the brain
The rest of the hindbrain gives rise to the cerebellum
The forebrain divides into the diencephelon, which
forms endocrine tissues in the brain, and the
telencephalon, which becomes the cerebrum
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Figure 49.11b
Embryonic brain regions Brain structures in child and adult
Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephalon Medulla oblongata (part of brainstem)
Pons (part of brainstem), cerebellum
Midbrain (part of brainstem)
Diencephalon (thalamus, hypothalamus, epithalamus)
Cerebrum (includes cerebral cortex, basal nuclei)
Cerebrum DiencephalonMesencephalon
Metencephalon
MyelencephalonDiencephalon
Telencephalon
Spinal
cord
ChildEmbryo at 5 weeksEmbryo at 1 month
Forebrain
Midbrain
Hindbrain
Hindbrain
Midbrain
Pons
Medulla
oblongata
Cerebellum
Spinal cord
Bra
inste
m
Midbrain
Forebrain
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Figure 49.11c
Cerebrum
Cerebellum
Basal nuclei
Corpus callosum
Cerebral cortex
Right cerebral
hemisphereLeft cerebral
hemisphere
Adult brain viewed from the rear
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Figure 49.11d
Diencephalon
Thalamus
Pineal gland
Hypothalamus
Pituitary gland
Spinal cord
Medulla
oblongata
Pons
Midbrain
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Arousal and Sleep
The brainstem and cerebrum control arousal and
sleep
The core of the brainstem has a diffuse network of
neurons called the reticular formation
These neurons control the timing of sleep periods
characterized by rapid eye movements (REMs) and
by vivid dreams
Sleep is also regulated by the biological clock and
regions of the forebrain that regulate intensity and
duration
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Figure 49.12
Eye
Reticular formation
Input from touch,
pain, and temperature
receptors
Input from
nerves of
ears
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Sleep is essential and may play a role in the consolidation
of learning and memory
Some animals have evolutionary adaptations allowing for
substantial activity during sleep
e.g., Dolphins sleep with one brain hemisphere at a time
and are therefore able to swim while “asleep”Key
Low-frequency waves characteristic of sleep
High-frequency waves characteristic of wakefulness
Location Time: 0 hours Time: 1 hour
Left
hemisphere
Right
hemisphere
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Biological Clock Regulation
Cycles of sleep and wakefulness are examples of
circadian rhythms, daily cycles of biological activity
Such rhythms rely on a biological clock, a molecular
mechanism that directs periodic gene expression and
cellular activity
Biological clocks are typically synchronized to light and
dark cycles
In mammals, circadian rhythms are coordinated by a
group of neurons in the hypothalamus called the
suprachiasmatic nucleus (SCN)
The SCN acts as a pacemaker, synchronizing the biological
clock
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Emotions
Generation and experience of emotions involve many
brain structures, including the amygdala, hippocampus,
and parts of the thalamus
These structures are grouped as the limbic system
Thalamus
Hypothalamus
Olfactory
bulbAmygdala Hippocampus
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Generating and experiencing emotion often requires
interactions between different parts of the brain
The structure most important to the storage of
emotion in the memory is the amygdala, a mass of
nuclei near the base of the cerebrum
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Functional Imaging of the Brain
Brain structures are probed and analyzed with
functional imaging methods
Positron-emission tomography (PET) enables a
display of metabolic activity through injection of
radioactive glucose
Today, many studies rely on functional magnetic
resonance imaging (fMRI), in which brain activity is
detected through changes in local oxygen
concentration
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The range of applications for fMRI include
monitoring recovery from stroke, mapping
abnormalities in migraine headaches, and
increasing the effectiveness of brain surgery
Nucleus accumbens Amygdala
Sad musicHappy music
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The cerebral cortex
The cerebral cortex controls voluntary movement
and cognitive functions
The cerebrum, the largest structure in the human
brain, is essential for language, cognition, memory,
consciousness, and awareness of our surroundings
Four regions, or lobes (frontal, temporal, occipital,
and parietal), are landmarks for particular functions
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Figure 49.16
Motor cortex (control of
skeletal muscles) Somatosensory
cortex
(sense of touch)
Sensory association
cortex (integration
of sensory information)
Frontal lobe
Temporal lobe
Parietal lobe
Occipital lobe
Prefrontal cortex
(decision making,
planning)
Broca’s area
(forming speech)
Auditory cortex
(hearing)
Cerebellum
Visualassociationcortex (combiningimages and objectrecognition)
Visual cortex(processing visualstimuli and patternrecognition)
Wernicke’s area(comprehendinglanguage)
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Information Processing
The cerebral cortex receives input from sensory
organs and somatosensory receptors
Somatosensory receptors provide information
about touch, pain, pressure, temperature, and the
position of muscles and limbs
The thalamus directs different types of input to
distinct locations
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Information received at the primary sensory areas
is passed to nearby association areas that process
particular features of the input
Integrated sensory information passes to the
prefrontal cortex, which helps plan actions and
movements
In the somatosensory cortex and motor cortex,
neurons are arranged according to the part of the
body that generates input or receives commands
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Figure 49.17
Frontal lobe
Toes
Lips
Jaw
Tongue Primarymotorcortex
Parietal lobe
Genitalia
Primary
somatosensory
cortexAbdominal
organs
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Language and Speech
Studies of brain activity have mapped areas
responsible for language and speech
Patients with damage in Broca’s area in the frontal
lobe can understand language but cannot speak
Damage to Wernicke’s area causes patients to be
unable to understand language, though they can still
speak
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Figure 49.18
Hearing
words
Seeing
words
Max
Min
Generating
words
Speaking
words
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Lateralization of Cortical Function
The two hemispheres make distinct contributions to brain
function
The left hemisphere is more adept at language, math, logic,
and processing of serial sequences
The right hemisphere is stronger at facial and pattern
recognition, spatial relations, and nonverbal thinking
The differences in hemisphere function are called
lateralization
The two hemispheres work together by communicating
through the fibers of the corpus callosum
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Frontal Lobe Function
Frontal lobe damage may impair decision making
and emotional responses but leave intellect and
memory intact
The frontal lobes have a substantial effect on
“executive functions”
Phineas Gage famously lost most
of his left frontal lobe in 1848
He survived seemingly intact but
had marked changes in his
personality
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Evolution of Cognition in Vertebrates
Previous ideas that a highly convoluted neocortex is
required for advanced cognition may be incorrect
The anatomical basis for sophisticated information
processing in birds (without a highly convoluted
neocortex) appears to be the clustering of nuclei in
the top or outer portion of the brain (pallium)
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Figure 49.19
Thalamus
Cerebrum
(including pallium)
Cerebellum
Midbrain
(a) Songbird brain
Cerebrum (including
cerebral cortex)
(b) Human brain
Thalamus
Midbrain
Cerebellum
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3. Memory & Learning
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Changes in synaptic connections underlie memory and learning
Two processes dominate embryonic development
of the nervous system
Neurons compete for growth-supporting factors in
order to survive
Only half the synapses that form during embryo
development survive into adulthood
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Neuronal Plasticity
Neuronal plasticity describes the ability of the
nervous system to be modified after birth
Changes can strengthen or weaken signaling at a
synapse
Autism, a developmental disorder, involves a
disruption in activity-dependent remodeling at
synapses
Children affected with autism display impaired
communication and social interaction, as well as
stereotyped, repetitive behaviors
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Figure 49.20
(a) Connections between neurons are strengthened or
weakened in response to activity.
(b) If two synapses are often active at the same time,
the strength of the postsynaptic response may
increase at both synapses.
N1N1
N2 N2
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Memory and Learning
The formation of memories is an example of
neuronal plasticity
Short-term memory is accessed via the
hippocampus
The hippocampus also plays a role in forming long-
term memory, which is later stored in the cerebral
cortex
Some consolidation of memory is thought to occur
during sleep
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Long-Term Potentiation
In the vertebrate brain, a form of learning called
long-term potentiation (LTP) involves an
increase in the strength of synaptic transmission
LTP involves glutamate receptors
If the presynaptic and postsynaptic neurons are
stimulated at the same time, the set of receptors
present on the postsynaptic membranes changes
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Figure 49.21
(a) Synapse prior to long-term potentiation (LTP) (b) Establishing LTP
(c) Synapse exhibiting LTP
Glutamate
PRESYNAPTIC
NEURON
Mg2+
Ca2+
Na+
NMDA receptor
(open)Stored
AMPA
receptorPOSTSYNAPTIC
NEURON
NMDA
receptor
(closed)
1
2
3
1
2
4
3
Action
potential
Depolarization
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Many nervous system disorders can be explained in molecular terms
Disorders of the nervous system include
schizophrenia, depression, drug addiction,
Alzheimer’s disease, and Parkinson’s disease
Genetic and environmental factors contribute to
diseases of the nervous system
To distinguish between genetic and environmental
variables, scientists often carry out family studies
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Figure 49.22
Ris
k o
f d
eve
lop
ing
sc
hiz
op
hre
nia
(%
)
Relationship to person with schizophrenia
Genes shared with relatives of
person with schizophrenia
12.5% (3rd-degree relative)
25% (2nd-degree relative)
50% (1st-degree relative)
100%
50
40
30
20
10
0
Fir
st
co
us
in
Ind
ivid
ua
l,
ge
ne
ral
po
pu
lati
on
Ne
ph
ew
/nie
ce
Un
cle
/au
nt
Gra
nd
ch
ild
Ha
lf s
ibli
ng
Pa
ren
t
Fu
ll s
ibli
ng
Ch
ild
Fra
tern
al tw
in
Ide
nti
ca
l tw
in
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Schizophrenia
About 1% of the world’s population suffers from
schizophrenia
Schizophrenia is characterized by hallucinations,
delusions, and other symptoms
Evidence suggests that schizophrenia affects
neuronal pathways that use dopamine as a
neurotransmitter
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Depression
Two broad forms of depressive illness are known
In major depressive disorder, patients have a
persistent lack of interest or pleasure in most
activities
Bipolar disorder is characterized by manic (high-
mood) and depressive (low-mood) phases
Treatments for these types of depression include
drugs such as Prozac, which increase the activity
of biogenic amines in the brain
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The Brain’s Reward System and Drug Addiction
The brain’s reward system rewards motivation with
pleasure
Some drugs are addictive because they increase
activity of the brain’s reward system
These drugs include cocaine, amphetamine, heroin,
alcohol, and tobacco
Drug addiction is characterized by compulsive
consumption and an inability to control intake
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Addictive drugs enhance the activity of the
dopamine pathway
Drug addiction leads to long-lasting changes in the
reward circuitry that cause craving for the drug
As researchers expand their understanding of the
brain’s reward system, there is hope that their
insights will lead to better prevention and
treatment of drug addiction
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Figure 49.23
Nicotinestimulatesdopamine-releasingVTA neuron.
Inhibitory neuron
Dopamine-releasingVTA neuron
Opium and heroindecrease activityof inhibitoryneuron.
Cocaine andamphetaminesblock removalof dopaminefrom synapticcleft.
Rewardsystemresponse
Cerebralneuron ofrewardpathway
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Alzheimer’s Disease
Alzheimer’s disease is a mental deterioration
characterized by confusion and memory loss
Alzheimer’s disease is caused by the formation of
neurofibrillary tangles and amyloid plaques in the brain
There is no cure for this disease though some drugs are
effective at relieving symptomsAmyloid plaque Neurofibrillary tangle 20 µm
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Parkinson’s Disease
Parkinson’s disease is a motor disorder caused
by death of dopamine-secreting neurons in the
midbrain
It is characterized by muscle tremors, flexed
posture, and a shuffling gait
There is no cure, although drugs and various other
approaches are used to manage symptoms