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Chapter 13

Chapter 13. Integrative Physiology I: 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. Neural Reflexes. Table 13-1. Somatic Motor Reflexes.

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Chapter 13

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

  2. 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. Sensoryneuron Receptor Stimulus SpinalcordIntegrating center Skeletal muscle Somaticmotor neuron Onesynapse Target celleffector Efferentneuron Response Figure 13-1a

  5. Somatic Motor Reflexes (b) Polysynaptic reflexes have two or more synapses. Synapse 1 SpinalcordIntegrating center Sensoryneuron Receptor Stimulus Interneuron Synapse 2 Efferentneuron Target celleffector 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 Sensoryneuron Stimulus Receptor CNSintegratingcenter Preganglionicautonomicneuron Response Postganglionicautonomicneuron Targetcell Autonomicganglion Figure 13-2

  7. Skeletal Muscle Reflexes • Proprioceptorsare 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. Proprioceptors • Muscle spindle • Response to stretch • Within muscle fibers as intrafusalfibrer • 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 motorneuron Musclespindle Golgi tendon organ Tendon (a) Figure 13-3a

  10. Proprioceptors Gamma motor neurons Spindle fibers: Sense stretch To CNS Tonically active sensoryneurons Central regionlacks myofibrils. Gamma motor neuronsfrom CNS Musclespindle Intrafusal fibers Extrafusal fiber (b) Muscle spindle Figure 13-3b

  11. Proprioceptors Extrafusalmuscle fibers Afferent neuron Capsule Sensory neuron Collagenfiber Tendon (c) Golgi tendon organ Figure 13-3c

  12. Muscle Spindles • Muscle spindles monitor muscle length and prevent overstretching 1 Extrafusal musclefibers at resting length 1 3 Sensory neuronendings 2 2 Sensory neuron is tonically active. Sensoryneuron Intrafusal fibersof muscle spindle 3 Spinal cord integrates function. Alpha motorneuron Alpha motor neurons toextrafusal fibers receive tonicinput from muscle spindles. 4 Spinal cord 4 5 5 Extrafusal fibers maintain a certainlevel 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 Muscle shortens 1 Alpha motor neuron firesand gamma motor neuronfires. 1 2 Musclelength 2 Muscle contracts. 3 Intrafusal fibers do not slacken sofiring rate remains constant. 2 Action potentialsof spindlesensory neuron 3 Stretch on centers ofintrafusal fibers unchanged.Firing rate of afferentneuron remains constant. Muscle shortens 1 Time Figure 13-5a

  15. Without Gamma Motor Neurons (b) 1 1 Alpha motor neuron fires. Muscle shortens Musclelength 3 2 Muscle contracts. 2 4 Less stretch onintrafusal fibers Action potential 3 Less stretch on centerof intrafusal fibers Action potentialsof spindlesensory neuron 4 Muscle shortens Firing rate of spindlesensory neuron decreases. Time Figure 13-5b

  16. Muscle Reflexes Help Prevent Damage Muscle spindle reflex Sensory neuron Spindle Spinalcord 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. Parkinson’s Disease • Progressive neural disorder • Characterized by abnormal movements, speech difficulties, and cognitive changes • Loss of basal ganglia that release dopamine

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

  26. 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. 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

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