Superficial and deep reflexes!

Reflex activity is the response to a peripheral stimulation that occurs without our consciousness.
Is an involuntary response to a stimulus.
It is a type of protective mechanism.

1. Superficial and D eep Reflexes !

2. Contents: Reflex? Reflex arc? Components of reflex arc Classification of reflexes Superficial reflexes and deep reflexes Muscle spindle Muscle tone & its types Disorders of muscle tone Summary References

3. Reflex Reflex activity is the response to a peripheral stimulation that occurs without our consciousness. Is an involuntary response to a stimulus. It is a type of protective mechanism .

4. Reflex arc A reflex arc is the neural pathway that mediates a reflex action. “OR” Reflex actions are mediated via the reflex arc. A simple reflex arc includes five components.

5. Components of reflex arc Receptor: site of stimulus Afferent nerve: transmit sensory impulses from the receptor to stimulus. Center: Center recieves the sensory impulses an in turn, it generates appropriate motor impulses. Efferent nerve: transmit motor impulses from the center to the effector organ. Effector organ: muscle or gland that respond to stimulus.

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7. CLASSIFICATION OF REFLEXES Reflexes are classified by six different methods depending upon various factors as given below: Depending upon whether inborn or acquired reflexes. Depending upon situation – anatomical classification. Depending upon purpose – physiological classification. Depending upon no of synapse. Depending upon whether visceral or somatic. Depending upon clinical basis. ( superficial and deep reflexes ).

8. Superficial reflexes Superficial reflexes are the reflexes, which are elicited from the surface of the body. These reflexes are motor responses to scraping of the skin. initiated by stimulating appropriate receptors of skin or mucous membrane. Are usually multisynaptic or polysynaptic.

9. Continue…! reflex Method of eliciting the reflex response Corneal reflex Touching cornea with cotton wisp. Closure of the eye (blinking). Conjunctival reflex Touching conjunctiva with cotton wisp. Closure of the eye. Nasal reflex (sneezing reflex) Irritiating the nasal mucosa with a cottin wasp. Sneezing. Planter reflex Stroking the sole Planter flexion and adduction of toes.

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11. deep reflex Deep reflex are elicited from deeper structures beneath the skin like tendon. Also known as tendon reflexes . Strech & Deep tendon reflexes: For skeletal muscles to perform normally: The Golgi tendon organs (proprioceptors) gives response to the change in the force or tension developed in the skeleton muscle during contraction. Stretch reflexes initiated by muscle spindles must maintain healthy muscle tone.

12. Muscle spindles Are composed of a few intrafusal muscle fibers that lack actin and myosin in their central regions, are noncontractile , and serve as receptive surfaces. Muscle spindles are wrapped with two types of afferent endings: primary sensory endings of type Ia fibers and secondary sensory endings of type II fibers . These regions are innervated by gamma efferent fibers. Note : contractile muscle fibers are extrafusal fibers and are innervated by alpha efferent fibers.

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14. How the muscle spindles works? Muscle spindle reflex oppose (correct for) increase in muscle length (stretch). Sensory information about muscle length is received by group Ia and group II afferent fibers. When a muscle is stretched ( lenghtened ) , the muscle spindle is also streched , stimulating group Ia and group II afferent fibers. Stimulation of group Ia afferents stimulates α - motorneurons in theb spinal cord. The stimulation in turn causes contraction and shortening of the muscle. Thus, the original stretch is opposed & muscle length is maintained.

15. Operation of the Muscle Spindles Stretching the muscles activates the muscle spindle There is an increased rate of action potential in Ia fibers Contracting the muscle reduces tension on the muscle spindle There is a decreased rate of action potential on Ia fibers

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17. Strech or deep tendon reflex Stretching the muscle activates the muscle spindle Excited motor neurons of the spindle cause the stretched muscle to contract Afferent impulses from the spindle result in inhibition of the antagonist Example : patellar reflex Tapping the patellar tendon stretches the quadriceps and starts the reflex action The quadriceps contract and the antagonistic hamstrings relax

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19. Golgi tendon reflex: The opposite of the stretch reflex. Contracting the muscle activates the Golgi tendon organs . Afferent Golgi tendon neurons are stimulated, neurons inhibit the contracting muscle, and the antagonistic muscle is activated. As a result, the contracting muscle relaxes and the antagonist muscle contracts

20. Deep reflexes Reflex Method of eliciting the reflex Response Jaw jerk Tapping the middle of the chin with slightly opened mouth. Closure of mouth. Bicep jerk Trapping the biceps tendon Flexion of forearm Triceps jerk Trapping the triceps tendon Extension of forearm Knee jerk or patellar tendon reflex Trapping the patellar tendon Extension of knee due to quadracips muscle Ankle jerk or achilles tendon reflex Trapping the achilles tendon Planter flexion of foot

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22. Muscle tone Muscle tone can be defined as the resistance of skeleton muscle to stretch. Muscle tone (residual muscle tension or tonus) is the continuous and passive part contraction of the muscles, or the muscle's resistance to passive stretch during resting state . It helps to maintain  posture.

23. Types of tone: Normal tone  --- means that there is the right amount of “tension” inside the muscle at rest, and that the muscle is inherently able to contract on command. High tone  --- means there is too much tension in the muscle at rest. In other words, the muscle is tight and tense even though it is not doing anything. Eg - spastic cerebral palsy. Low tone  --- means there is not enough tension in the muscle when it is at rest. The muscle may have a slightly mushy or floppy feel to it, and there is a lack of graded control of the muscle when it is being used (graded control means that just the right amount of movement and effort is used as appropriate to the task at hand). Eg - battle to sit upright at a desk for any period of time, and may slouch over.

24. Disorders of Muscle Tone Abnormalities of the tone : Hypertonia : abnormaly high muscle tone. Hypotonia : can present clinically as either spasticity or rigidity . Spasticity: is velocity-dependent resistance to passive stretch. can be in the form of the clasp-knife response, in which there is increased resistance only at the beginning or at the end of the movement.

25. Continue..! Rigidity: is velocity-independent resistance to passive stretch can be of the lead pipe type , in which there is resistance throughout to passive movement, or it may be of cogwheel type , in which the resistance to passive movement is in a jerky manner.

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27. Summary: What are the reflexes? role of reflex arc. Its components How the reflexes are classified? Depending over some various factors by different methods. What are the superficial and deep reflexes? Discussed about the muscle spindle, muscle tone & its disorder (hypertonia and hypotonia ).

28. References Essentials of medical physiology by k sembulingam ( jaypee , book). www.dartmouth.edu www.stanfordmedicine25.stanford.edu