reflex- para md2(2)
TRANSCRIPT
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1. ..
LabLAB
2. PRETEST LabLAB
3. BRIFT LAB ..
Lab
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Reflex:An automatic response to a stimulus
- same type of response (stereotypedresponse)
- subconscious
- conscious
Function of reflexes
- protection
- homeostasis: regulation of HR, BP, RR, GI
motility and secretion,.
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Reflex arc 1. receptors 2. afferent fiber
3. integrating center: CNS(brain and spinal cord),often receives signals (informations) from manyreceptors. The output from the center is the neteffect of the total afferent in puts.
4. efferent fiber 5. effectors: muscle, glands
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Properties of reflex
1. Adequate stimulus rods cones :light taste buds:taste
2. Reflex timebeginning of stimulation to thebeginning of response
3. Fatique of reflex: synapse
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Classification of reflexes1. Amount of synapse in the CNS
- monosynaptic reflex- disynaptic reflex- polysynaptic reflex
2. Kind of nerve fiber- somatic reflex- autonomic reflex
3. Origin of nerve fiber- cranial reflex
- spinal reflex
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Reflex arc 1. receptors 2. afferent fiber
3. integrating center: CNS(brain and spinal cord),often receives signals (informations) from manyreceptors. The output from the center is the neteffect of the total afferent in puts.
4. efferent fiber 5. effectors: muscle, glands
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4. Based on timing- inborn reflex
- acquired reflex (Pavlov reflex ,conditioned reflex)
5. Location of receptors- superficial reflex:corneal reflex, abdominal
reflex- deep reflex :patellar, ankle- visceral reflexes
6. Pathological reflex: Babinski sign
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Anterior motor neuron: each segment of thecord are located several thousand neurons;
MN, MN motor neuron (final common pathway) :to extrafusal muscle fibers.
A motor unit : an motor neuron, itsmotor axon, and all the skeletal musclefibers that its supplies, a few to several
hundred skeletal muscle fibers
motor neurons : to intrafusal muscle
fibers
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Musclesensory receptors1. Musclespindles : distributed throughout the
musclemuscle length, rate of change of its lengthstretch reflexesfine movements
2. Golgi tendon organs : muscle tendonstendon tension, rate of change of tension clasp knife reflex
Both receptors send signals to spinal cord,cerebellum, and cerebral cortex to control musclecontraction
subconscious level
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Musclespindles 3-10 mm long, 3-12intrafusal muscle fibers,
small skeletal muscle fibers central region: no or few actin myosin
filaments the end portions are supplied by MN
nuclear bag fiber, nuclear chain fiber Ia afferent fiber: primary ending (annulospiral
ending) on nuclear bag and nuclear chain fibers IIbafferent fiber : secondary ending, mostly
on nuclear chain fiberMuscle spindle can beexcited by
1. lengthening the whole muscle2. contraction of the end portions of the
intrafusal muscle fiber.
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Under normal conditions
motor neuron activity: action potentials
from muscle spindles
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Cerebellum, basal ganglia , cerebralcortex, bulboreticular area
+ -
MN
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Reflex arc 1. receptors 2. afferent fiber
3. integrating center: CNS(brain and spinal cord),often receives signals (informations) from manyreceptors. The output from the center is the neteffect of the total afferent in puts.
4. efferent fiber 5. effectors: muscle, glands
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Clinical application of thestretchreflex
1.To examine the intactness of thereflex arc.
2.To assess the degree offacilitation (excitation) or inhibition tospinal cord centers, i.e.,knee jerk reflex,ankle jerk reflex
facilitatory impulses hyperreflexia
facilitatory impulses hyporeflexia
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Reflex testing is a standard,
useful procedure in search ofneurological pathology. However,interpretation of reflexresponses is often subjective andrequires considerable experience
on the part of diagnosis
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The clinical significance of
deviations in the activity of muscle-stretch reflexes from normal willdepend on comparison on the
opposite side. And also otherneurological examination, i.e., motorpower, sensation, consciousness,are are used to make diagnosis.Moreover x-ray and MRI are very
helpfull.
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Grading of reflexes
Grade
0.Areflexia
.No response,any
lesion that interrupts the reflex arc.
Grade1. Hyporeflexia. A reflex may be
depressed by any lesion that interrupts the reflexarc.
Grade
2.Normal response
.
Grade3. Hyperreflexia with no pathology.
Grade4. Hyperreflexia with pathology.
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Clonus
Rhythmic contraction of muscles
Increased facilitatory impulses of
the brain to spinal cord centers
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Golgi tendon reflex
Golgi tendon organ(GTO), a sensory
receptor connected in series withmuscle fibers (GTO:muscle fiber= 1:10-15)
detect muscle tension (not muscle length
or rate of change of muscle length)
has both dynamic & static responses
type Ib nerve fibers connects toinhibitory interneuron,cerebellum,cerebral cortex
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Muscle tension + GTO + inhibitory
interneuron
muscle tension motor neuronactivity
Golgi tendon reflex- To prevent tearing of muscle , tendon
- To equalize the contractile force of
muscle fibers
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Flexor Reflex (Withdrawal reflex)
Stimulation of any cutaneous sensoryreceptor on a limb, i.e., touchreceptor,painreceptor(nociceptive receptor)
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Abnormal reflexesAbnormal reflexes
11. Babinski sign : UMN lesions. Babinski sign : UMN lesions
2. Clonus : excitatory impulses to spinal
cord centers, motor neuron activity,
hyperreflexia3. Hyperreflexia : motor neuron activity,
receptor sensitivity
4. Hyporeflexia : motor neuron activity,receptor sensitivity, LMN lesion,
abnormality of NMJ, muscle
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UMNlesions
weakn
ess,para
lysis
spasticity
tendon reflexes
+ Babinski sign
little,if any,muscle
atrophy
no fasiculation
LMNlesions
weakness, paralysis
flaccidity, hypotonia
Hypo- /no tendon
reflex
- Babinski sign
muscle atrophy
fasiculationof
involved muscle
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Light reflex (pupillary light reflex )
Accommodation reflex
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References1. Guyton AC, Hall JE. Textbook of medical physiology, 11 th
ed. Philadelphia: Elsevier Saunders, 2006: Chap 54.2. Ganong WF. Review of medical physiology, 22nd ed. Boston :
McGraw Hill, 2005: Chap 6.3. Rhoades R, Tanner. Medical physiology, 2 nd ed. New
York: Lippincot Williams & Wilkins, 2003: Chap 9.4. Aminoff MJ, Greenberg DA, Simson RP. Clinical neurology,
6 th ed. New York: Lange Medical Books/ McGraw Hill,2005: Chap 5.