How does proprioceptive information influence our movements?. How are reflexes different from voluntary movements?
What are mirror neurons and what is their role in movement?
How do the cerebellum and basal ganglia contribute to voluntary movement?
What can we learn about motor control from disorders such as Parkinson’s disease and
Huntington’s disease? Haloperidol is a drug that blocks dopamine synapse. What effects would it be likely to have in someone suffering from Parkinson disease? Human infants are at first limited to gross movements of the trunk, arm, and legs. The ability to moive one finger at a time matures gradually over at least the first year.What hypothesis would you suggest about which brain areas controlling movement mature early and which area mature later
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Chapter 7
Movement
© Cengage Learning 2016
Sunday, April 9, 17
© Cengage Learning 2016
7.1 The Control of Movement
• Ultimately, the brain is linked to the
concept of doing something, that is,
movement
• Internal processing would be useless
without the ability to move
© Cengage Learning 2016
Sunday, April 9, 17
Muscles and Their Movements
• All animal movement depends on muscle
contractions
– Smooth muscles: control the digestive system
and other organs
– Skeletal muscles/striated muscles: control
movement of the body in relation to the
environment
– Cardiac muscles: heart muscles that have
properties of skeletal and smooth muscles
© Cengage Learning 2016
Sunday, April 9, 17
Three Categories of Vertebrate
Muscles
© Cengage Learning 2016
Sunday, April 9, 17
Muscle Fibers
• Muscles are composed of many individual
fibers
– Each muscle fiber receives information from
only one axon but a single axon may innervate
many muscle fibers
• A neuromuscular junction is a synapse
between a motor neuron axon and a
muscle fiber
• Release of acetylcholine causes the
muscle to contract
© Cengage Learning 2016
Sunday, April 9, 17
Muscles Fibers Receive Innervation from
One Axon
© Cengage Learning 2016
Sunday, April 9, 17
Antagonistic Muscles
• Movement requires the alternating
contraction of opposing sets of muscles
called antagonistic muscles
• Acetylcholine always excites skeletal
muscles to contract
• A flexor muscle is one that flexes or raises
an appendage
• An extensor muscle is one that extends an
appendage or straightens it
© Cengage Learning 2016
Sunday, April 9, 17
Flexor and Extensor Muscles: Work in Pairs
© Cengage Learning 2016
Sunday, April 9, 17
Fast and Slow Muscles, Part 1
• Skeletal muscle types range from:
– Fast-twitch: fibers produce fast contractions
but fatigue rapidly
– Slow-twitch: fibers produce less vigorous
contraction without fatigue
• People have varying percentages of fasttwitch and slow-twitch muscles
© Cengage Learning 2016
Sunday, April 9, 17
Fast and Slow Muscles, Part 2
• Slow-twitch fibers are aerobic and require
oxygen during movement and therefore do
not fatigue
– Nonstrenuous activities utilize slow-twitch and
intermediate fibers
• Fast-twitch fibers are anaerobic and use
reactions that do not require oxygen,
resulting in fatigue
– Behaviors requiring quick movements utilize
fast-twitch fibers
© Cengage Learning 2016
Sunday, April 9, 17
Temperature and Movement
© Cengage Learning 2016
Sunday, April 9, 17
Muscle Control by Proprioceptors, Part 1
• Proprioceptors: receptors that detect the
position or movement of a part of the body
• Muscle spindles are proprioceptors parallel
to the muscle that respond to a stretch:
cause a contraction of the muscle
• A stretch reflex occurs when muscle
proprioceptors detect the stretch and
tension of a muscle and send messages to
the spinal cord to contract it
© Cengage Learning 2016
Sunday, April 9, 17
Muscle Control by Proprioceptors, Part 2
• The Golgi tendon organ is another type of
proprioceptor that responds to increases in
muscle tension
– Located in the tendons at the opposite ends of
the muscle
– Acts as a “brake” against excessively vigorous
contraction by sending an impulse to the spinal
cord where motor neurons are inhibited
© Cengage Learning 2016
Sunday, April 9, 17
Two Kinds of Proprioceptors Regulate
Muscle Contractions
© Cengage Learning 2016
Sunday, April 9, 17
The Knee-Jerk Reflex
© Cengage Learning 2016
Sunday, April 9, 17
Voluntary and Involuntary Movements
• Reflexes are involuntary, consistent, and
automatic responses to stimuli
• Most movements are a combination of
voluntary and involuntary; reflexive and
nonreflexive
• Movements vary with respect to feedback
– Some are ballistic and cannot be changed
once initiated
– Others are guided by feedback
© Cengage Learning 2016
Sunday, April 9, 17
Sequences of Behaviors, Part 1
• Many behaviors consist of rapid sequences
of individual movements
• Central pattern generators are neural
mechanisms in the spinal cord or
elsewhere that generate rhythmic patterns
of motor output
– Example: wing flapping in birds or “wet dog
shake”
© Cengage Learning 2016
Sunday, April 9, 17
Sequences of Behaviors, Part 2
• A motor program refers to a fixed
sequence of movements that is either
learned or built into the nervous system
– Once begun, the sequence is fixed from
beginning to end
– Automatic in the sense that thinking or talking
about it interferes with the action
– Examples: mouse grooming itself; yawning
© Cengage Learning 2016
Sunday, April 9, 17
7.2 Brain Mechanisms of Movement
• Understanding how the brain controls
movement offers hope for spinal cord
damage or limb amputations
© Cengage Learning 2016
Sunday, April 9, 17
The Cerebral Cortex
• The primary motor cortex is located in the
precentral gyrus located in the frontal lobe
• Axons from the precentral gyrus connect to
the brainstem and the spinal cord, which
generate impulses that control the muscles
• Cerebral cortex is additionally involved in
complex movements
© Cengage Learning 2016
Sunday, April 9, 17
Muscle Control from the Primary Motor
Cortex
© Cengage Learning 2016
Sunday, April 9, 17
Motor Areas of the Human Cortex
© Cengage Learning 2016
Sunday, April 9, 17
Planning a Movement, Part 1
• Specific areas of the primary motor cortex
are responsible for control of specific areas
of the opposite side of the body
– Some overlap does exist
• The primary motor cortex is active when
people intend a movement
• The primary motor cortex “orders” an
outcome
© Cengage Learning 2016
Sunday, April 9, 17
The Primary Somatosensory Cortex and
Primary Motor Cortex
© Cengage Learning 2016
Sunday, April 9, 17
Planning a Movement, Part 2
• Other areas near the primary motor cortex
also contribute to movement
• Posterior parietal cortex: keeps track of the
position of the body relative to the world
– Damage to this area causes difficulty in
coordinating visual stimuli with movement
– Important for planning movement
© Cengage Learning 2016
Sunday, April 9, 17
Other Areas for Planning a Movement
• Premotor cortex
– Active during preparation for movement
– Receives information about a target
– Integrates information about position and
posture of the body; organizes the direction of
the movement in space
• Supplementary motor cortex
– Organizes rapid sequence of movements in a
specific order; inhibitory if necessary
– Active seconds before the movement
© Cengage Learning 2016
Sunday, April 9, 17
Inhibition of Movements
• Antisaccade task: inhibits a saccade, a
voluntary eye movement from one target to
another
• Performing this task well requires
sustained activity in parts of the prefrontal
cortex and basal ganglia before seeing the
moving stimulus
• Ability to perform this task matures through
adolescence
© Cengage Learning 2016
Sunday, April 9, 17
Mirror Neurons
• Neurons that are active during both
preparation of a movement and while
watching someone else perform the same
or similar movement
– May be important for understanding,
identifying, and imitating other people
– May be involved in social behaviors
– Unknown whether they cause or result from
social behavior
© Cengage Learning 2016
Sunday, April 9, 17
Imitating Facial Expressions
© Cengage Learning 2016
Sunday, April 9, 17
Connections from the Brain to the Spinal
Cord
• Messages from the brain must reach the
medulla and spinal cord to control the
muscles
• Corticospinal tracts are paths from the
cerebral cortex to the spinal cord
• Two such tracts:
– Lateral corticospinal tract
– Medial corticospinal tract
© Cengage Learning 2016
Sunday, April 9, 17
Lateral Corticospinal Tract
• A set of axons from the primary motor
cortex, surrounding areas, and red nucleus
to the spinal cord
– Controls movement in peripheral areas (hands
and feet)
– Red nucleus: a midbrain area with output
mainly to the arm muscles
• Axons extend from one side of the brain to
the opposite side of the spinal cord, and
control opposite side of the body
© Cengage Learning 2016
Sunday, April 9, 17
Medial Corticospinal Tract
• A set of axons from many parts of the
cortex
– Reticular formation, midbrain tectum, and
vestibular nucleus
• Vestibular nucleus is a brain area that
receives information from the vestibular
system
© Cengage Learning 2016
Sunday, April 9, 17
Axons and the Spinal Cord
• Axons go to both sides of the spinal cord
– Allows control of muscles of the neck,
shoulders, and trunk
– Enables movements such as walking, turning,
bending, standing up, and sitting down
© Cengage Learning 2016
Sunday, April 9, 17
Lateral and Medial Corticospinal Tracts
© Cengage Learning 2016
Sunday, April 9, 17
Touch Paths
© Cengage Learning 2016
Sunday, April 9, 17
Disorders of the Spinal Cord
Disorder
Paralysis
Description
Lack of voluntary movement in part of the body.
Paraplegia
Cause
Damage to spinal cord, motor neurons, or their
axons.
Cut through the spinal cord above the segments
attached to the legs.
Loss of sensation and voluntary muscle control in
both legs. Reflexes remain. Although no messages
pass between the brain and the genitals, the genitals
still respond reflexively to touch. Paraplegics have no
genital sensations, but they can still experience
orgasm
(Money 1967).
Quadriplegia
Loss
of sensation
and muscle control in all four
Cut through the spinal cord above the segments
extremities.
controlling the arms.
Hemiplegia
Loss of sensation and muscle control in the arm and Cut halfway through the spinal cord or (more
leg on one side.
commonly) damage to one hemisphere of the
cerebral cortex.
Tabes dorsalis Impaired sensation in the legs and pelvic region,
Late stage of syphilis.
impaired leg reflexes and walking, loss of bladder
Dorsal roots of the spinal cord deteriorate.
and
bowel
control.
Poliomyelitis
Paralysis.
Virus that damages cell bodies of motor neurons.
Amyotrophic
lateral
sclerosis
Gradual weakness and paralysis, starting with the
Unknown.
arms and later spreading to the legs.
Both motor neurons and axons from the brain to the
motor neurons are destroyed.
© Cengage Learning 2016
Sunday, April 9, 17
The Cerebellum, Part 1
• A structure in the brain often associated
with balance and coordination
– More neurons in the cerebellum than in all
other brain areas combined
• Damage to the cerebellum causes trouble
with rapid movements requiring aim/timing
– Examples: clapping hands, speaking, writing,
etc.
© Cengage Learning 2016
Sunday, April 9, 17
The Cerebellum, Part 2
• Important for the establishment of new
motor programs that allow the execution of
a sequence of actions as a whole, e.g.,
tasks that require timing
• Also critical for certain aspects of attention,
such as the ability to shift attention and
attend to visual stimuli
© Cengage Learning 2016
Sunday, April 9, 17
Cellular Organization of the Cerebellum,
Part 1
• The cerebellum receives input from the
spinal cord, from each of the sensory
systems and the cerebral cortex, and
sends it to the cerebellar cortex
• The cerebellar cortex is the surface of the
cerebellum
© Cengage Learning 2016
Sunday, April 9, 17
Cellular Organization of the Cerebellum,
Part 2
• Cerebellar cortex neurons are arranged in
precise geometrical patterns that provides
outputs of well-controlled duration
– Purkinje cells: flat parallel cells in sequential
planes
– Parallel fibers: axons parallel to one another;
perpendicular to planes of Purkinje cells
• The greater the number of excited Purkinje
cells, the greater their collective duration of
response
© Cengage Learning 2016
Sunday, April 9, 17
Cellular Organization of the Cerebellum,
Part 3
• Parallel fibers excite Purkinje cells
• Purkinje cells transmit inhibitory messages
to the cells in the nuclei of the cerebellum
(clusters of cell bodies in the interior of the
cerebellum) and the vestibular nuclei in the
brain stem
• Messages then sent to the midbrain and
the thalamus
© Cengage Learning 2016
Sunday, April 9, 17
Parallel Fibers and Purkinje Cells
© Cengage Learning 2016
Sunday, April 9, 17
The Basal Ganglia, Part 1
• The basal ganglia is a group of large
subcortical structures in the forebrain
– Responsible for initiating an action not guided
by a stimulus
• Comprises the following structures
– Caudate nucleus
– Putamen
– Globus pallidus
© Cengage Learning 2016
Sunday, April 9, 17
The Basal Ganglia, Part 2
© Cengage Learning 2016
Sunday, April 9, 17
The Basal Ganglia, Part 3
• Caudate nucleus and putamen receive
input from the cerebral cortex and send
output to the globus pallidus
• Globus pallidus connects to the thalamus,
which relays information to the motor areas
and the prefrontal cortex
– Inhibits the thalamus
• Basal ganglia select a movement to make
by ceasing to inhibit it
© Cengage Learning 2016
Sunday, April 9, 17
The Basal Ganglia, Part 4
© Cengage Learning 2016
Sunday, April 9, 17
Brain Areas and Motor Learning
• The learning of new skills requires multiple
brain areas involved in the control of
movement
– Basal ganglia are critical for learning motor
skills, organizing sequences of movement,
“automatic” behaviors, and new habits
• Example: driving a car
– The pattern of activity of the neurons in the
motor cortex becomes more consistent as a
new skill is learned
© Cengage Learning 2016
Sunday, April 9, 17
Conscious Decisions and Movement
• The conscious decision to move, and the
movement itself, occur at two different
times
• A readiness potential is a particular type of
activity in the motor cortex that occurs
before any type of voluntary movement
– Begins at least 200 ms before the movement
– Implies that we become conscious of the
decision to move after the process has already
begun
© Cengage Learning 2016
Sunday, April 9, 17
Libet’s Study of Conscious Decisions and
Movement
© Cengage Learning 2016
Sunday, April 9, 17
7.3 Movement Disorders
• Brain disorders, such as Parkinson’s
disease and Huntington’s disease not only
affect movement, but also impair mood,
memory, and cognition
© Cengage Learning 2016
Sunday, April 9, 17
Parkinson’s Disease
• A movement disorder characterized by
muscle tremors, rigidity, slow movements,
and difficulty initiating physical and mental
activity
– Associated with an impairment in initiating
spontaneous movement in the absence of
stimuli to guide the action
• Symptoms also include depression,
memory and reasoning deficits, loss of
olfaction, and other cognitive deficits
© Cengage Learning 2016
Sunday, April 9, 17
Immediate Cause of Parkinson’s
• Caused by gradual and progressive death
of neurons, especially in the substantia
nigra
– Substantia nigra usually sends dopaminereleasing axons to the caudate nucleus and
putamen
• Loss of dopamine leads to less stimulation
of the motor cortex and slower onset of
movements
© Cengage Learning 2016
Sunday, April 9, 17
A Comparison of Normal and Parkinson’s
Connections Within the Brain
© Cengage Learning 2016
Sunday, April 9, 17
Causes of Parkinson’s Disease, Part 1
• Studies suggest early-onset Parkinson’s
has a genetic link
• Genetic factors are only a small factor of
late onset Parkinson’s disease (after 50)
• Environmental influences such as
exposure to toxins
– Insecticides, herbicides, and fungicides
• Traumatic head injury
© Cengage Learning 2016
Sunday, April 9, 17
Causes of Parkinson’s Disease, Part 2
• Cigarette smoking and coffee drinking are
related to a decreased chance of
developing Parkinson’s disease
• Damaged mitochondria of cells seems to
be common to most factors that increase
the risk of Parkinson’s disease
© Cengage Learning 2016
Sunday, April 9, 17
Treatment of Parkinson’s Disease
• The drug L-dopa is the primary treatment
for Parkinson’s and is a precursor to
dopamine that easily crosses the bloodbrain barrier
– Often ineffective and especially for those in the
late stages of the disease
– Does not prevent the continued loss of
neurons
– Enters other brain cells, producing unpleasant
side effects
© Cengage Learning 2016
Sunday, April 9, 17
Other Possible Treatments for Parkinson’s
• Drugs that directly stimulate dopamine
receptors
• Implanting electrodes to stimulate areas
deep in the brain
• Experimental strategies such as:
– Transplanting brain tissue of aborted fetuses
– Implantation of stem cells that are
programmed to produce large quantities of Ldopa
© Cengage Learning 2016
Sunday, April 9, 17
Huntington’s Disease, Part 1
• A neurological disorder characterized by
various motors symptoms
– Affects 1 in 10,000 in the United States
– Usually onset occurs between age 30-50
• Associated with gradual and extensive
brain damage especially in the basal
ganglia but also in the cerebral cortex
© Cengage Learning 2016
Sunday, April 9, 17
Huntington’s Disease, Part 2
• Initial motor symptoms include arm jerks
and facial twitches
• Motors symptoms progress to tremors and
writhing that affect the persons walking,
speech, and other voluntary movements
• Also associated with various psychological
disorders:
– Depression, memory impairment, anxiety,
hallucinations/delusions, poor judgment,
alcoholism, drug abuse, sexual disorders
© Cengage Learning 2016
Sunday, April 9, 17
A Normal Brain vs. a Brain with Huntington’s
Disease
© Cengage Learning 2016
Sunday, April 9, 17
Heredity and Presymptomatic Testing
• Presymptomatic tests can identify with high
accuracy who will develop the disease
– Controlled by an autosomal dominant gene on
chromosome #4
– The higher the number of consecutive repeats
of the combination C-A-G, the more certain
and earlier the person is to develop the
disease
© Cengage Learning 2016
Sunday, April 9, 17
Base Pair Repeats and Onset of
Huntington’s
© Cengage Learning 2016
Sunday, April 9, 17
C-A-G Repeats and Huntingtin
• A variety of neurological diseases are
related to C-A-G repeats in genes
– For a variety of disorders, the earlier the onset,
the greater the probability of a strong genetic
influence
• Identification of the gene for Huntington’s
disease led to the discovery of the protein
that codes it (huntingtin)
– Mutant form impairs neurons in the brain;
future drug therapy may address huntingtin
© Cengage Learning 2016
Sunday, April 9, 17
C-A-G Repeats and Other Diseases
© Cengage Learning 2016
Sunday, April 9, 17
CHAPTER 7
MOVEMENT
Chapter Outline
I.
The Control of Movement
A. Muscles and Their Movements
1. All animal movement depends on the contractions of muscles. Vertebrate muscles
fall into three categories:
a. Smooth muscles: Control movements of the digestive system and other
internal organs.
b. Skeletal, or striated, muscles: Control movements of body in relation to the
environment.
c. Cardiac muscles: The heart muscles have properties intermediate between
those of smooth and skeletal muscles.
2. Each muscle is composed of many individual fibers and a given axon may
innervate more than one muscle fiber.
3. Neuromuscular junction: A synapse between a motor neuron axon and muscle
fiber. In skeletal muscles, acetylcholine is released at all axon terminals at the
neuromuscular junction.
4. Each muscle makes only one movement: a contraction; in the absence of excitation
it relaxes.
5. Antagonistic muscles: Are necessary for moving limbs in opposite directions.
a. Flexor muscles allow limbs to be flexed or raised.
b. Extensor muscles extend or straighten limbs.
7. Fast and Slow Muscles
a. Even though muscle contractions are chemical processes that are affected by
temperature, fish are able to swim fast rega …
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