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Sensation and Reflex Arcs -A&P Lab #11

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icorojo's version from 2017-04-04 13:29

Section 1 (Introduction)

Question Answer
Exteroceptorssensitive to changes in the body's EXTERNAL environment
Exteroceptors sensestaste, smell, vision, hearing, pain, touch, pressure, temperature, and hair movement
Interoceptorsrespond to changes in body's INTERNAL environment
Interoceptors respond tochanges in blood pressure, fluid composition, balance, acceleration, and body position, and movement
Reflex Arcs arerapid, predictable, and involuntary motor responses to stimuli that are medicated over neural pathways
Reflex Arca basic structural and functional unit of the nervous system. It allows the body to react automatically and involuntarily to a variety of internal and external stimuli.
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Section 2

Question Answer
Adequate Stimulusthe type of stimulus to which a receptor is most sensitive to
Adequate Stimulus exceptionmost receptors will respond to a stimulus other than the adequate stimulus if its STRENGTH is great enough
Adequate Stimulus LABthe instructor will darken the laboratory; with closed eyes, turn eyes as far left as possible; use right index finger to gently press out right eyeball
Adequate Stimulus RESULTSA dark circle surrounded by a bright white RING near the bridge of the nose will soon be "seen".
Adequate Stimulus WHYThis visual sensation of light occurs because mechanical pressure is stimulating the retina.
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Section 3

Question Answer
Tactile sensitivityany area of the body can be measured as the absolute threshold for touch
Absolute threshold for touchthe MINIMUM amount of pressure on the skin that can be felt; it varies depending on the part of the body being examined
Threshold locationsThe highest SENSITIVITY touch thresholds are located on the lips and face; the highest ABSOLUTE threshold (lowest sensitivity) is found on the soles of the feet.
Tactile discriminationcan be measured by the two-point threshold
Two-Point Thresholdthe minimum physical separation between two pressure points required for both of them to be perceived
Two-Point Threshold LABUse the tips of the two-point discriminator to gently touch various parts of lab partners skin with their eyes closed; decrease and increase the distance between the points
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Section 4

Question Answer
AdaptationIf a stimulus strength remains constant and is not removed from the receptor, the receptor may become progressively less sensitive to the presence of the stimulus
Adaptation typesSome receptor types adapt rapidly to the presence of stimuli, others adapt very slowly, and some not at all. With the exception of nociceptors (pain receptors), most cutaneous receptors adapt rapidly.
Adaptation LABWarm a coin with hands for 30 secs; place the coin on motionless forearm for 3 minutes; determine the length of time the SENSATION of the coin on your forearm will persist
Afterimagethe sensation perceived after the removal of the stimulus
Tactile Afterimage LABplace a large rubber band on forehead for 2 minutes and then remove; Compare the SENSATION perceived once rubber band is removed to the sensation perceived when first placed on forehead
Visual Afterimage3 types of color receptors called cones in the eye's retina; individual cones are sensitive to red, blue, green and starring at these colors for an extended time makes the cones for that color oversaturtaed or "fatigued"; because the cones have lost sensitively to starred at color, but remain strong to the other colors, this imbalance causes the mind to perceive the 'afterimage' in color opposite the original color
Visual Afterimage LABUse large black and white sheets of paper and smaller colored cards; place the colored card in middle of black sheet of paper and stare for 30 secs; now look at the white sheet of paper
Visual Afterimage RESULTSIf you are staring at a green image, the afterimage should be red. Staring at a yellow image, the afterimage should be blue
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Section 5 (Shifting of Physiological Zero)

Question Answer
Thermoreceptorsrespond to changes in temperature rather than a fixed value of temperature
Physiological Zerothe baseline skin temperature; approximately 33*C (91*F) under normal conditions
Temperature Adaptationno longer occurs when the temperature is below 29*C (84*F) or above 37*C (111*F)
Paradoxical coldwhere a very hot stimulus applied to a cold spot on the skin feels cold because it activates cold fibers
Temperature Adaptation LABplace 2 fingers into 45*C water bath and 2 fingers of other hand in 0*C water bath for 30 secs; then place all fingers at the same time into the room temperature water bath
Temperature Adaptation RESULTSthe fingers placed in the 45*C will feel colder and the fingers paced in the 0*C will feel hotter than the actual temperature of the room temperature water bath
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Section 6 (Sensory Interpretation of Wetness)

Question Answer
Sensory Interpretation of Wetnesssometimes perception is based on the combined influence of separate sensations
Feeling of Wetnessresults from the combined influence of COLD and PRESSURE
Sensory Interpretation LABput on a nitrile glove & dip hand into 0*C water bath
Sensory Interpretation RESULTSAlthough the hand remained dry, the sensation of wetness is usually felt because its two components (cool temperature and pressure) are sensed. We have no single type of receptor that detects wetness.
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Section 7 (Weber-Fechner Principle)

Question Answer
Weber-Fechner Principledescribed relationships in the intensity of visual , auditory, or cutaneous sensory information.
Weber-Fechner Principle relationshipswhen the total load is increased, the ability to discriminate is poorer; the greater the sensory intensity, any additional change in stimulus must be proportionately greater to detect the change
Weber-Fechner Principle LABmeasure the ability to detect differences between weights; using 10-grams, 20-grams, 90-grams, 100-grams weights
Weber-Fechner Principle RESULTSit should be more difficult to distinguish between the heavier containers than the lighter containers
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Section 8 (Somatic Reflex Arcs)

Question Answer
Somatic reflexesinvolve involuntary control of skeletal muscles
Biceps Tendon Reflexstriking the biceps tendon stretches the muscle and activates the deep muscle receptors for a reflex response of forearm flexion
Biceps Tendon Reflex testfor functional integrity of the musculocutaneous nerve and the C5 and C6 segments of the spinal cord
Babinski (Planter) Reflexis elicited by stimulating the cutaneous receptors in the sole of the foot
Babinski (Planter) Reflex testused to test the integrity of the spinal cord form L4 to S2 corticospinal tracts and cerebral function involved in motor movement
Babinski (Planter) Reflex normal responsethe older children and healthy adult response is for the toes to curl; also called negative Babinski sign
Babinski (Planter) Reflex abnormal responsethe big toe will dorsiflex and the smaller toes will fan laterally; also called positive Babinski sign
Babinski (Planter) Reflex incompletecharacterized by dorsiflexion of the big toe and plantar flexion of the other toes.
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Section 9 (Somatic Reflex Arcs continued)

Question Answer
Triceps Tendon Reflexcauses forearm extension
Triceps Tendon Reflex testthe functional integrity of the radial nerve and the C7 and C8 segments of the spinal cord
Achilles Tendon (Ankle-Jerk) Reflexexists without the involvement of higher brain centers
Achilles Tendon (Ankle-Jerk) Reflex testintegrity of the S1 and S2 tracts
Achilles Tendon (Ankle-Jerk) Reflex LABwhen you strike the Achilles tendon, it stretches the gastrocnemius and soleus muscles. This initiates reflex contraction of the muscles and slight plantar flexion of the foot. This is a positive result.
Patellar (Knee-Jerk) Reflex testintegrity of the L2, L3, L4 spinal nerves
Patellar (Knee-Jerk) Reflex LABwhen the patellar tendon is tapped with a reflex hammer, receptors in the quadriceps femoris muscle are stretched. This leads to reflexive contraction of the quadriceps muscles with extension of the knee in a brief kick.
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Section 10 (Autonomic Reflexes)

Question Answer
Autonomic (visceral) Reflexesadjustment of heart rate, respiratory rate, blood flow, and digestion are examples; also coughing, sneezing, swallowing, and vomiting
Ciliospinal Reflexa reflexive response to pain mediated by the sympathetic nervous system
Ciliospinal Reflex testevaluating disruption of sympathetic pathways to the eye and face
Ciliospinal Reflex LABpinch or scratch the skin on back of neck; this activates sympathetic outflow, causing ipsilateral pupillary dilation followed by rapid constriction. since the sympathetic nervous system has poor crossover, the contralateral eye should show no response.
Oculocardiac Reflex testhelps evaluate parasympathetic tracts between the eye and medulla, vagal outflow to the heart, and the cardiac response to parasympathetic stimulation.
Oculocardiac Reflexnociceptive free nerve endings of the extraocular musculature are stimulated when eyes are rubbed. These fibers convey information to the vagal motor nucleus in the spinal cord. A widespread vagal response is elicited to cause a decrease in heart
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