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

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Chapter 13

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Chapter 13

Chapter 13

Integrative Physiology I: Control of Body Movement


About this chapter

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


Categories of skeletal muscle actions

Categories of skeletal muscle actions

  • CategoriesActions

  • Extensor Increases the angle at a joint

  • Flexor Decreases the angle at a joint

  • Abductor Moves limb away from midline of body

  • Adductor Moves limb toward midline of body

  • Levator Moves insertion upward

  • Depressor Moves insertion downward

  • Rotator Rotates a bone along its axis

  • Sphincter Constricts an opening


Neural reflexes overview

Neural Reflexes: Overview

  • Stimulus

  • Sensory receptor

  • Sensory (afferent) neuron

  • CNS integration

  • Efferent (motor) neuron

  • Effector (target tissue)

  • Response (movement)

  • Feedback to CNS


Neural reflexes overview1

Neural Reflexes: Overview

Figure 13-1a: Monosynaptic and polysynaptic somatic motor reflexes


Neural reflexes classification of pathways

Neural Reflexes: Classification of Pathways

  • Effector Division

    • Somatic

    • Autonomic

  • Integration site

    • Spinal

    • Brain

  • Neurons in pathway

    • Monosynaptic

    • Polysynaptic


Neural reflexes classification of pathways1

Neural Reflexes: Classification of Pathways

Figure 13-1: Monosynaptic and polysynaptic somatic motor reflexes


Autonomic reflexes visceral reflexes

Autonomic Reflexes: “visceral reflexes”

  • Regulate internal organs

  • Integrate in spinal cord or lower brain

  • Coordinate with hormones & pacemakers


Autonomic reflexes visceral reflexes1

Autonomic Reflexes: “visceral reflexes”

Figure 13-2: Autonomic reflexes


Examples of autonomic reflexes

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


Skeletal muscle reflex sensory receptors proprioceptors

Skeletal Muscle Reflex Sensory Receptors: Proprioceptors

  • Muscle spindle

    • In muscles

    • Sense stretch

  • Golgi tendon organ

    • Near tendon

    • Sense force

  • Joint receptors

    • Sense pressure

    • Position


Skeletal muscle reflex sensory receptors proprioceptors1

Skeletal Muscle Reflex Sensory Receptors: Proprioceptors

Figure 13-3: Sensory receptors in muscle


Chapter 13

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


Chapter 13

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


Muscle spindles mechanism

Muscle Spindles: Mechanism

  • Muscle tone

  • Stretch reflex


Stretch reflex and the muscle spindle apparatus

Stretch Reflex and the Muscle Spindle Apparatus

Figure 13-6b: Muscle reflexes


Golgi tendon reflex response to excessive force

Golgi Tendon Reflex: Response to Excessive Force

  • Force pulls collagen fibers which squeeze sensors

  • Overload causes inhibition of contraction


A myotactic unit

A Myotactic Unit

  • Myotactic unit: all pathways controlling a joint

  • Example: elbow joint – all nerves, receptors, muscles


Knee jerk reflex stretch reciprocal inhibition reflexes

Knee Jerk Reflex: Stretch & Reciprocal Inhibition Reflexes

  • Tendon strike stretches quads-reflexive contraction

  • Reciprocal (hamstring) muscle is inhibited


Knee jerk reflex stretch reciprocal inhibition reflexes1

Knee Jerk Reflex: Stretch & Reciprocal Inhibition Reflexes

Figure 13-7: The knee jerk reflex


Flexion reflex pull away from painful stimuli

Flexion Reflex: Pull away from Painful Stimuli

  • Pain stimulus

  • Nocioceptors

  • Spinal integration

  • Flex appendage away

  • Signal to brain (feel pain)


Chapter 13

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


Flexion reflex pull away from painful stimuli1

Flexion Reflex: Pull away from Painful Stimuli

Figure 13-8: Flexion reflex and the crossed extensor reflex


Cross extensor reflex to keep balance

Cross Extensor Reflex: To Keep Balance

  • Opposite leg

  • Extensors stimulated

  • Flexors inhibited

  • Body supported


Movement coordination of several muscle groups

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


Voluntary movement conscious

Voluntary Movement: “Conscious”

  • Cortex at top of several CNS integration sites

  • Can be initiated with no external stimuli

  • Parts can become involuntary: muscle memory


Voluntary movement conscious1

Voluntary Movement: “Conscious”

Figure 13-11: Control of voluntary movements


Rhythmic movements

Rhythmic Movements

  • Cortex initiation

  • Central pattern generators

    • In spine

    • Maintain motion

  • Combines movements

    • Reflexive

    • Voluntary

Figure 13-12: The corticospinal tract


Feed forward postural reflex

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


Visceral movement heart organs

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


Summary

Summary

  • Reflex pathways: spinal, cranial

    • Sensor, afferent, integration, efferent, effector

    • Classified by effector, integration site or synapses


Summary1

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


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