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

2. About this Chapter Neural Reflexes: types & pathways
Autonomic Reflexes pathways and functions
Skeletal Muscle reflexes, myotactic units and movement
Combining reflexive and voluntary behavior into locomotion
Movement in visceral muscles

3. Neural Reflexes: Overview
Stimulus
Sensory receptor
Sensory (afferent) neuron
CNS integration
Efferent (motor) neuron
Effector (target tissue)
Response (movement)
Feedback to CNS

4. Neural Reflexes: Overview
Figure 13-1a: Monosynaptic and polysynaptic somatic motor reflexes

5. Neural Reflexes: Classification of Pathways
Effector Division
Somatic
Autonomic
Integration site
Spinal
Brain
Neurons in pathway
Monosynaptic
Polysynaptic

6. Neural Reflexes: Classification of Pathways
Figure 13-1: Monosynaptic and polysynaptic somatic motor reflexes

7. Autonomic Reflexes: “visceral reflexes”
Regulate internal organs
Integrate in spinal cord or lower brain
Coordinate with hormones & pacemakers

8. Autonomic Reflexes: “visceral reflexes”
Figure 13-2: Autonomic reflexes

10. Examples of Autonomic Reflexes
Cold Water Immersion causing tachycardia
Pupillary Reflex-Pupil Constricting in response to light
Baroreceptor Reflex- Low BP in carotid sinus results in tachycardia and blood vessel constriction
Carotid Sinus Reflex- Increased pressure within or external manipulation of carotid sinus results in bradycardia
Dilation of Blood vessels as body temperature increases
Secretion of epinephrine and norepinephrine from the adrenal medulla in response to fear or stress
Sweating in response to increased body temperature

13. Skeletal Muscle Reflex Sensory Receptors: Proprioceptors
Muscle spindle
In muscles
Sense stretch
Golgi tendon organ
Near tendon
Sense force
Joint receptors
Sense pressure
Position

14. Skeletal Muscle Reflex Sensory Receptors: Proprioceptors
Figure 13-3: Sensory receptors in muscle

16. Alpha motoneuronsextrafusal fibers
bigger and more numerous than intrafusal
myofibrils all along length
this causes muscle contraction
Gamma motoneurons intrafusal fibers
tightens spindles
enhances sensitivity of spindles

17. Upper motoneurons usually stimulate both
simultaneously ( Alpha-Gamma Coactivation)
Alpha motoneurons promote muscle contracting
Gamma motoneurons help maintain muscle tone
Reflexes are produced as an unconscious
response to particular stimuli
Can be simple or complex
Golgo tendon organs monitor tension

18. Muscle Spindles: Mechanism
Muscle tone
Stretch reflex

19. Stretch Reflex and the Muscle Spindle Apparatus
Figure 13-6b: Muscle reflexes

20. Golgi Tendon Reflex: Response to Excessive Force
Force pulls collagen fibers which squeeze sensors
Overload causes inhibition of contraction

22. A Myotactic Unit Myotactic unit: all pathways controlling a joint
Example: elbow joint – all nerves, receptors, muscles

23. Knee Jerk Reflex: Stretch & Reciprocal Inhibition Reflexes
Tendon strike stretches quads- reflexive contraction
Reciprocal (hamstring) muscle is inhibited

25. Knee Jerk Reflex: Stretch & Reciprocal Inhibition Reflexes
Figure 13-7: The knee jerk reflex

26. Flexion Reflex: Pull away from Painful Stimuli
Pain stimulus
Nocioceptors
Spinal integration
Flex appendage away
Signal to brain (feel pain)

27. Double reciprocal innervation
stimulus on one side of the body, reaction
on another
Step on tack- affected foot withdraws (flexes),
Other foot extends to support weight
(crossed-extensor reflex)
Take-home lesson: some reflexes are simple;
affect and are controlled by a small part
of the spinal cord
Some are more elaborate

28. Flexion Reflex: Pull away from Painful Stimuli
Figure 13-8: Flexion reflex and the crossed extensor reflex

29. Cross Extensor Reflex: To Keep Balance
Opposite leg
Extensors stimulated
Flexors inhibited
Body supported

30. Movement: Coordination of Several Muscle Groups
Reflexive Movement
Spinal integration
Input to brain
Postural reflexes
Cerebellum integration
Maintains balance
Input to cortex
Figure 13-9: Integration of muscle reflexes

31. Voluntary Movement: “Conscious”
Cortex at top of several CNS integration sites
Can be initiated with no external stimuli
Parts can become involuntary: muscle memory

32. Voluntary Movement: “Conscious”
Figure 13-11: Control of voluntary movements

33. Figure 13-12: The corticospinal tract
Rhythmic Movements
Cortex initiation
Central pattern generators
In spine
Maintain motion
Combines movements
Reflexive
Voluntary
Figure 13-12: The corticospinal tract

34. Feed Forward: Postural Reflex
Anticipates body movement
Reflexive adjustment to balance change
Prepares body for threat: blink, duck, "tuck & roll"
Combines with feedback
Figure 13-13: Feedforward reflexes and feedback of information during movement

35. Visceral Movement: Heart & Organs
Moves products in hollow organs
Act as valves (sphincters): digestive tract or blood vessels
Multiple controls: autonomic neurons, hormonal and paracrine

36. Summary Reflex pathways: spinal, cranial
Sensor, afferent, integration, efferent, effector
Classified by effector, integration site or synapses

37. Summary Proprioceptor types, functions, role in reflexes & balance
Motor reflex pathways: stretch, Golgi tendon, flexion, reciprocal inhibition & crossed extensor
Myotatic unit structure and coordination
Movement coordination: reflexive, voluntary, rhythmic
Feed forward and feedback coordination
Visceral movement of body organs