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POWERPOINT® LECTURE SLIDE PRESENTATION
by LYNN CIALDELLA, MA, MBA, The University of Texas at Austin
Additional text by J. Padilla exclusively for Physiology at ECC
UNIT 2
13
Integrative Physiology I:
Control of Body
Movement
HUMAN PHYSIOLOGY
AN INTEGRATED APPROACH
DEE UNGLAUB SILVERTHORN
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FOURTH EDITION
Neural Reflexes
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Somatic Motor Reflexes
Monosynaptic and polysynaptic somatic motor reflexes
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Figure 13-1a
Autonomic Reflexes
Some visceral reflexes are spinal reflexes
Stimulus
Receptor
Sensory
neuron
CNS
integrating
center
All autonomic reflexes are polysynaptic,
with at least one synapse in the CNS
and another in the autonomic ganglion.
Preganglionic
autonomic
neuron
Response
Postganglionic
autonomic
neuron
Target
cell
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Autonomic
ganglion
Figure 13-2
Skeletal Muscle Reflexes
 Proprioceptors are located in skeletal muscle, joint
capsules, and ligaments
 Proprioceptors carry input sensory neurons to CNS
 CNS integrates input signal
 Somatic motor neurons carry output signal
 Alpha motor neurons
 Effectors are contractile skeletal muscle fibers
 Examples of proprioceptors
 Muscle spindle
 Golgi tendon organ
 Joint receptors
 Are found in capsules and ligaments around joints
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Proprioceptors
Muscle spindles are sensory receptors in muscle that control muscle
tone and prevent injury from overstretching of the muscle. They are
found in all muscles and are tonically active, firing increases as the
muscle stretches.
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Figure 13-3a–b
Muscle Spindles
Muscle spindles monitor muscle length and prevent
overstretching of the same muscle. The tonic signaling
produces muscle tone.
(a)
1
Sensory
neuron
endings
3
Spinal
cord
1
Extrafusal muscle
fibers at resting length
2
Sensory neuron is
tonically active.
3
Spinal cord integrates
function.
4
Alpha motor neurons
to extrafusal fibers
receive tonic input
from muscle spindles.
5
Extrafusal fibers
maintain a certain
level of tension
even at rest.
2
Sensory
neuron
Intrafusal
fibers of
muscle spindle
4
5
Alpha motor
neuron
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Figure 13-4a
Muscle Spindles
During a stretch reflex increased firing by the sensory
neuron increases signaling by the alpha motor neuron
causing the muscle to contract.
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Figure 13-4b
Alpha-Gamma Coactivation***
Gamma motor neurons intervate the ends of intrafusal
fibers in muscle spindles and keep the sensory neuron
active even when the muscle contracts
(a)
If gamma motor axons are cut, the spindle loses activity when muscle contracts.
1
1
Alpha motor
neuron fires.
Muscle shortens
Muscle
length
3
2
Muscle contracts.
2
4
3
4
Stretch on center
of intrafusal fibers
is reduced.
Firing rate of
spindle sensory
neuron decreases.
Action
potentials
of
spindle
sensory
neuron
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Less stretch
on intrafusal
fibers
Action potential
Muscle shortens
Time
Figure 13-5a
Alpha-Gamma Coactivation
When an alpha motor neuron fires the muscle contracts and
shortens but the gamma motor neuron will also fire and thus
there will be stretching at the spindle fiber to keep the tonic
firing.
(b)
Alpha-gamma coactivation maintains spindle function when muscle contracts.
1
1
1
2
2
Alpha motor
neuron fires and
gamma motor
neuron fires.
Muscle
length
Muscle contracts.
3
2
3
1
Muscle shortens
Stretch on centers
of intrafusal fibers
unchanged. Firing
rate of afferent
neuron remains
constant.
Action
potentials
of
spindle
sensory
neuron
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Intrafusal fibers do not slacken, so
firing rate remains constant.
Muscle shortens
Time
Figure 13-5b, steps 1–3
Proprioceptors
Golgi tendon organs are sensory receptors in muscle that respond to
tension changes in the muscle and attempt to prevent injury from
excessively strong contractions. When golgi sensory neuron fibers
the efferent signal in inhibitory and thus there is a loss in
contraction strength
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Figure 13-3a, c
Muscle Reflexes: response to load and overload
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Patellar Tendon (Knee Jerk) Reflex
Receptor: Muscle
spindle stretches
and fires.
Afferent path: Action
potential travels through
sensory neuron.
Stimulus:
Tap to tendon
stretches
muscle.
The patellar tendon (knee jerk)
reflex illustrates a
monosynaptic stretch
reflex and reciprocal
inhibition of the
antagonistic muscle.
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Figure 13-7
Patellar Tendon (Knee Jerk) Reflex
Receptor: Muscle
spindle stretches
and fires.
Afferent path: Action
potential travels through
sensory neuron.
Stimulus:
Tap to tendon
stretches
muscle.
The patellar tendon (knee jerk)
reflex illustrates a
monosynaptic stretch
reflex and reciprocal
inhibition of the
antagonistic muscle.
Efferent path 1:
Somatic motor neuron
Integrating
center:
Sensory neuron
synapses in
spinal cord.
onto
Efferent path 2: Interneuron
inhibiting somatic motor neuron
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Figure 13-7
Patellar Tendon (Knee Jerk) Reflex
Receptor: Muscle
spindle stretches
and fires.
Afferent path: Action
potential travels through
sensory neuron.
Stimulus:
Tap to tendon
stretches
muscle.
The patellar tendon (knee jerk)
reflex illustrates a
monosynaptic stretch
reflex and reciprocal
inhibition of the
antagonistic muscle.
Efferent path 1:
Somatic motor neuron
Integrating
center:
Sensory neuron
synapses in
spinal cord.
onto
Effector 1: Quadriceps
muscle
Efferent path 2: Interneuron
inhibiting somatic motor neuron
Response: Quadriceps
contracts, swinging lower
leg forward.
Effector 2: Hamstring
muscle
Response: Hamstring
stays relaxed, allowing
extension of leg
(reciprocal inhibition).
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Figure 13-7
Flexion Reflex and
the Crossed Extensor Reflex
Spinal cord
3a
2
1 Painful stimulus
activates nociceptor.
Sensory
neuron
Ascending pathways to brain
Gray
matter
Spinal
White cord
matter
2 Primary sensory
neuron enters spinal
cord and diverges.
Nociceptor
Painful
stimulus
1
3a One collateral activates
ascending pathways for
sensation (pain) and postural
adjustment (shift in center of gravity).
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Figure 13-8, steps 1–3a
Flexion Reflex and
the Crossed Extensor Reflex
Spinal cord
3a
2
1 Painful stimulus
activates nociceptor.
Sensory
neuron
Ascending pathways to brain
Gray
matter
Spinal
White cord
matter
3b
2 Primary sensory
neuron enters spinal
cord and diverges.
Nociceptor
Painful
stimulus
1
Extensors
3a One collateral activates
inhibited
ascending pathways for
sensation (pain) and postural
Flexors contract,
adjustment (shift in center of gravity).
moving foot
away from
3b Withdrawal reflex pulls foot away
painful
from painful stimulus.
stimulus.
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Alpha motor
neurons
Figure 13-8, steps 1–3b
Flexion Reflex and
the Crossed Extensor Reflex
Spinal cord
3a
2
1 Painful stimulus
activates nociceptor.
Sensory
neuron
3b
Ascending pathways to brain
Gray
matter
Spinal
White cord
matter
3c
2 Primary sensory
neuron enters spinal
cord and diverges.
Nociceptor
Painful
stimulus
1
Extensors
3a One collateral activates
inhibited
ascending pathways for
sensation (pain) and postural
Flexors contract,
adjustment (shift in center of gravity).
moving foot
away from
3b Withdrawal reflex pulls foot away
painful
from painful stimulus.
stimulus.
3c Crossed extensor reflex supports
body as weight shifts away from
painful stimulus.
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Alpha motor
neurons
Extensors contract
as weight shifts to
left leg.
Flexors inhibited
Figure 13-8, steps 1–3c
Movement Classification
Three types of movement: Reflex (simplest)
voluntary (most complex) Rhythmic (a combination
of relex and voluntary).
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CNS Integrates Movement
 Spinal cord integrates spinal reflexes and contains
central pattern generators
 Brain stem and cerebellum control postural reflexes
and hand and eye movements
 Cerebral cortex and basal ganglia
 Voluntary movement- can become reflexive once well
learned
Rhythmic movement is initiated at the cerebrum but
maintained by interneurons in the spinal cord
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Integration of Muscle Reflexes
Reflexes are
managed by the
spinal cord,
cerebellum, and
brain stem. They
do not require
input from the
cerebrum.
However, sensory
input is send to
the cerebrum so
we aware of what
happens.
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Figure 13-9
CNS Control of Voluntary Movement
Voluntary movement can be planned
based on postural reflex information.
There are 3 phases, sensory feed back is
used in the first two.
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Figure 13-10
Voluntary Movement
Feedforward reflexes and feedback of information
during movement
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Figure 13-13
Visceral Movement
 Contraction of cardiac and smooth muscle
 Moves material in hollow organs by changing the
shape of the organ
 Controlled by ANS as a reflex
 Some create own action potentials
 Muscle can respond to hormones or signaling from
neighboring cells through gap junction
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