PostLabEx 16, 18, 23

REFLEXES IN HUMANSExercise 16

A. EYE REFLEX1. CORNEAL/CONJUNCTIVAL REFLEX- contraction of the orbicularis oculi muscle

causes closure of the eyelid (blinking)

2. BLINK REFLEX- blinking upon rapid passing of hand in front of

subjects face

3. PUPILLARY REFLEXES a. Light or Photopupillary Reflex

bright light – pupil is constricteddim light – pupil is dilated

b. Accomodation Reflex Accommodation is the ability of the eyes to focus on

objects at different distances so as to produce a clear vision

far – dilated pupilsnear – normal sized or constricted pupils

c. Pupillary Skin Reflex Dilation of the pupil upon pinching the cheeks

4. CONVERGENCE REFLEXReflexive movement of the eyes medially

when we view close objects

distant objects – eyeballs parallel with each other : no convergence of eyeballs

near objects – eyeballs come close to each other at a point: there is convergence

B. STRETCH REFLEXES1. Patellar reflex – the appropriate response is contraction

of the quadriceps femoris which results to a knee jerk or patellar reflex

2. Biceps reflex – contraction of biceps and flexion of the forearm

3. Triceps reflex - extension of the elbow4. Ankle jerk – flexion of the foot5. Wrist reflex – flexion of the wrist6. Sneezing reflex - sneezing7. Palmar reflex – closing of the hand or flexion of the

fingers8. Abdominal reflex – drawing in of the abdominal wall

9. Pharyngeal reflex – induces vomiting10. Plantar reflex - plantar flexion of the toes11. Axon reflex – reddening of the skin; production of a red flare12. Babinski’s reflex – fanning out of toes with dorsal extension

of the big toe13. Palatal reflex – contraction of the palatal muscle14. Epigastric reflex – drawing in of the skin of the epigastrium15. Cremasteric reflex – elevation of the testes during stroking16. Gluteal reflex – contraction of the gluteal muscle which is

observed by the movement of the skin overlying the muscles

Answers to Questions

1. State and explain the phenomenon of reciprocal inhibition- stimulation of one muscle causes the inhibition of antagonistic muscleex. When flexor reflex excites the biceps muscle, it simultaneously inhibits the triceps muscle

2. Explain why the axon reflex is considered as the simplest type of reflex- axon reflex is considered the simplest type of reflex because it involves only a part of a single sensory neuron

3. Describe the components of a reflex arc- reflex arc: pathway taken by the impulse to produce the reflex action

Modalities of Somatic SensationsExercise 18

Sensation - conscious or subconscious awareness of

external or internal stimuli. - Each type of sensation felt whether touch,

pressure, pain, temperature, body position, etc. is sensory modality.

Sensory Receptor:1. Exteroceptors – stimulated by forces outside the

bodyex. somatic sensations – temp, touch, pain

2. Proprioceptors – stimulated by activities of the muscles and articulations.

a. rate of contraction of musclesb. locationc. rate of motion of legs, arms, fingers, and other body partsd. forces or pressure being exerted on the body

3. Enteroceptors – stimulated by substances or conditions within the viscera

Receptors for the following senses:

a. Touch – Meissner’s corpuscles, Merkel’s disks, free nerve endings around a hair follicleb. Pressure – VaterPacini corpusclesc. Cold – end-bulb of Kraused. Heat – corpuscles of Ruffinie. Pain – free nerve ending

Results and Observations:A. Sensation of Pain

The individual can distinguish all 3 types of pain. Adaptation is the lost of sensation due to frequent stimulation.

B. Stereognosis

- Appreciation of the form of three dimensional objects by palpation without the aid of vision. - Determined by the somatosensory area in the cerebrum of the brain

C.Pressure SensationLocated on the deeper tissue; longer lasting; with less intensity; has rapid adaptation

Physiology of Special SensesExercise 23

I. VISUAL TESTSA. Visual Acuity Test

- test that measures the ability of the lens to focus light reflected from an object to the retina

farsightedness – hyperopianearsightedness – myopiapresbyopia – difficulty to focus close objects

B. Demonstration of Blind SpotResult: Blind spot test figure (x or dot) disappears when it is focussed on the blind spot which lack photoreceptors

C. After ImageIt is a sensation that tends to persists in the consciousness after the cessation of stimulation.

There are 2 types:1. positive after image – appears in the same color as the original

stimulus2. negative after image – appears in color complementary to the

original stimulus

Results:a. after image of bulb appears in same color as stimulus – positive after imageb. after image of colored objects appears in complementary color – negative after image

C. Test for Astigmatism- caused by abnormal lens or corneal curvature which causes part of the image to appear blurred

result:a. there is no astigmatism if all the radiating lines

appear equally dark and distinctb. there is some degree of astigmatism if some of the

lines are blurred and appear less dark than the others.

II. HEARING The ear transmits sound vibrations and their patterns, intensities,

and directions of origin to the temporal lobe of the brain.

Sound waves have 2 major characteristics1. frequency or wavelength which determines pitch measured in cps2. amplitude or intensity which determines loudness measured in db

Types of hearing impairment:1. conduction deafness2. sensorineural deafness3. central deafness4. perceptive deafness

III. TasteThe tongue which is covered with papillae is the principal organ of taste. Taste buds which are located in the trenches of the papillae are sensitive to

substances dissolved in water. Taste, like smell, is a result of the stimulation of sensory neurons by

chemical substance.

The 4 tastes are: Salty – stimulated by metallic ionsSour - by hydrogen ionsSweet - by a hydroxyl ionBitter - by alkaloids

Each type of taste bud is concentrated on different areas of the tongue, with :

sweet – at the tipsalty – at the tip and anterior partsour – on the sidesbitter – at the back Results:A. 1. NaCl – salty at tip and anterior part of tongue2. Acetic acid – sour at the lateral side3. sucrose – sweet at the tip4. quinine sulphate – bitter at the posterior part or base of tongue

B. Solutions are perceived very rapidly, crystals are perceived afterseveral minutes due to longer dissolution time

IV. SmellThe sense of smell has 2 outstanding characteristics1. has a high degree of adaptation2. certain odors mask others

Masking is the ability of a high intensity odor to dominate and exclude any other odors

The taste receptors are excited by chemical substances like food while smell receptors by chemical substances in the air

Results:oil of cloves masked the odor of the other 2 oils, namely, wintergreen and

peppermint