1. Integrative Physiology I: Control of Body Movement
Chapter 13
Integrative Physiology I: Control of Body Movement

2. Skeletal muscle reflexes The integrated control of body movement
About this Chapter
Neural reflexes
Autonomic reflexes
Skeletal muscle reflexes
The integrated control of body movement
Control of movement in visceral muscles

3. Neural Reflexes
Table 13-1

4. Somatic Motor Reflexes
Monosynaptic and polysynaptic somatic motor reflexes
(a) A monosynaptic reflex has a single synapse between the afferent and efferent neurons.
Sensory neuron
Stimulus
Receptor
Spinal cord Integrating center
Skeletal muscle
Somatic motor neuron
Target cell effector
One synapse
Efferent neuron
Response
Figure 13-1a

5. Somatic Motor Reflexes
(b) Polysynaptic reflexes have two or more synapses.
Synapse 1
Spinal cord Integrating center
Sensory neuron
Stimulus
Receptor
Interneuron
Synapse 2
Target cell effector
Efferent neuron
Response
Figure 13-1b

6. Autonomic Reflexes Some visceral reflexes are spinal reflexes
no brain involvement, or brain modulated
“bashful bladder” / toilet training / goose pimples
Sensory neuron
Stimulus
Receptor
CNS integrating center
Preganglionic autonomic neuron
Response
Postganglionic autonomic neuron
Target cell
Autonomic ganglion
Figure 13-2

7. 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 α
Effectors are contractile skeletal muscle fibers extrafusal muscle fibers

8. Muscle spindle Golgi tendon organ Joint receptors Proprioceptors
Response to stretch
Within muscle fibers as intrafusal fibrer
Automonic with gamma motor neurons
Golgi tendon organ
Muscle tension especially during isometric
Relaxation reflex - protective
Joint receptors
Are found in capsules and ligaments around joints

9. Proprioceptors
Muscle spindles and Golgi tendon organs are sensory receptors in muscle
Extrafusal muscle fibers
Alpha motor neuron
Muscle spindle
Golgi tendon organ
Tendon
(a)
Figure 13-3a

10. Spindle fibers: Sense stretch
Proprioceptors
Gamma motor neurons
Spindle fibers: Sense stretch
To CNS
Tonically active sensory neurons
Central region lacks myofibrils.
Gamma motor neurons from CNS
Muscle spindle
Intrafusal fibers
Extrafusal fiber
(b) Muscle spindle
Figure 13-3b

11. Proprioceptors Extrafusal muscle fibers Afferent neuron Capsule
Sensory neuron
Collagen fiber
Tendon
(c) Golgi tendon organ
Figure 13-3c

12. Muscle spindles monitor muscle length and prevent overstretching1 1
Extrafusal muscle fibers at resting length 3
Sensory neuron endings 2 2
Sensory neuron is tonically active.
Intrafusal fibers of muscle spindle
Sensory neuron 3
Spinal cord integrates function.
Alpha motor neuron
Spinal cord 4
Alpha motor neurons to extrafusal fibers receive tonic input from muscle spindles. 4 5 5
Extrafusal fibers maintain a certain level of tension even at rest.
(a) Spindles are firing even when muscle is relaxed.
Figure 13-4a

13. Muscle Spindles
Figure 13-4b

14. Alpha-Gamma Coactivation
(a) Alpha-gamma coactivation 1 1
Alpha motor neuron fires and gamma motor neuron fires.
Muscle shortens 1 2
Muscle length 2
Muscle contracts. 3
Intrafusal fibers do not slacken so firing rate remains constant. 2 3
Stretch on centers of intrafusal fibers unchanged. Firing rate of afferent neuron remains constant.
Action potentials of spindle sensory neuron
Muscle shortens 1
Time
Figure 13-5a

15. Without Gamma Motor Neurons
(b) 1 1
Alpha motor neuron fires.
Muscle shortens
Muscle length 3 2
Muscle contracts. 2 4
Less stretch on intrafusal fibers
Action potential 3
Less stretch on center of intrafusal fibers
Action potentials of spindle sensory neuron 4
Firing rate of spindle sensory neuron decreases.
Muscle shortens
Time
Figure 13-5b

16. Muscle Reflexes Help Prevent Damage
Muscle spindle reflex
Sensory neuron
Spindle
Spinal cord
Add load
Motor neuron
Muscle
(a) Load added to muscle.
Figure 13-6a

17. Muscle Reflexes Help Prevent Damage
Figure 13-6b

18. GTO’s
Figure 13-7

19. Movement
Types of movement
Reflex
Voluntary
Rhythmic

20. 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

21. CNS Integrates Movement
Table 13-3

22. CNS Control of Voluntary Movement
Figure 13-10

23. CNS Control of Voluntary Movement
Feedforward reflexes and feedback of information during movement
Figure 13-13

24. Progressive neural disorder
Parkinson’s Disease
Progressive neural disorder
Characterized by abnormal movements, speech difficulties, and cognitive changes
Loss of basal ganglia that release dopamine

25. Moves products in hollow organs Controlled by ANS
Visceral Movement
Moves products in hollow organs
Controlled by ANS
Some create own action potentials

26. Skeletal muscle reflexes
Summary
Neural reflexes
Somatic reflexes, autonomic reflexes, spinal reflexes, cranial reflexes, monosynaptic reflex, and polysynaptic reflex
Autonomic reflexes
Skeletal muscle reflexes
Extrafusal muscle fibers, alpha motor neurons, muscle spindles, intrafusal fibers, gamma motor neurons, muscle tone, and stretch reflex

27. Skeletal muscle reflexes (continued)
Summary
Skeletal muscle reflexes (continued)
Alpha-gamma coactivation, golgi tendon organs, myotatic unit, reciprocal inhibitions, flexion reflexes, crossed extensor reflex, and central pattern generator
Integrated control
Reflex movement, postural reflexes, voluntary movement, rhythmic movements, corticospinal tract, basal ganglia, and feedforward reflexes
Control of movement in visceral muscles