RESULTS AND DISCUSSION
The basic unit for behavior is the reflex. Reflexes generally occur quickly and are the result of excita excitati tion on of sensor sensory y recept receptors ors,, nerve nerve fibers fibers,, integr integrati ation on by the Centra Centrall Nervou Nervouss System System,, transmission of motor impulses and excitation of an effector organ or tissue. . !otor ctivity Through the course of the experiment, reflex action is verified via the use of normal, spinal and decerebrate and double"pithed toads. #n normal toad, the brain and spinal cord are still inta intact ct.. #n sing single le"p "pit ithe hed d toads toads,, all all conne connect ctio ions ns bet$ bet$ee een n the the brai brain n and and the the spin spinal al cord cord all all connections are broken, therefore it eliminates any influence the brain could have on reflex activities. %hile, the decerebrated toad refers to the removal of the brain $hich affects functions or reflexes controlled by it. &astly, in a double"pithed toad all control by the central nervous system are eliminated including the brain and spinal cord. Several actions are tested to compare the differences in the reflex of toad in the four states such as the posture reflex, locomotion, righting reflex, s$imming reflex, pain response and scratch reaction. %ith %ith the normal toad, as seen belo$ in Table Table ', it blinks as the eyelids $ere touched and croaks as response to posture reflex $ith a respiration rate of (')*minute, at this state the nostrils $ere observed to be used during respiration+ it reacts $ith dilute acetic acid as response to scra scratc tch h refl reflex ex $ith $ithin in five five secon seconds ds++ othe otherr leg leg flex flexed ed as the the rema remain inin ing g leg leg is pinc pinche hed d for for $ithdra$al reflex+ it also umped more frequently $ith a continuous and coordinated umping movements. s it $as placed on its dorsal side, it makes a righting movement immediately for t$o seconds -fast righting reflex and s$ims immediately $ith a $ell"coordinated s$imming
movements. s the normal toad $as hanged, both legs flexed and extended as they reacted to pain immediately after pinching.
#n the spinal state, $here single pith $as done, the toad remained motionless and lost muscle tone+ ho$ever the respiration rate lo$ered to / )*min. This can be explained as the toad $as kept moist $hen tested in s$imming reflex for they breathe primarily through the skin, not the lungs. %ithout the brain, perception of any sensory phenomena is impossible. This explained the reason $hy $hen the eyelid $as touched, the toad did not blink. #t also umped four times but $as not continuous. #t did not respond to the righting reflex but the s$imming reflex $as observed but slo$er compared to the normal state. spinal toad cannot perceive pain. fter a recovery period ho$ever it $ill be able to resume its ability to carry on spinal reflex activity. The toad may crouch, ump, scratch or even make noise, but it is not in pain. These actions are neural reflexes controlled via motor senses in the spinal cord, not brain functions.
%hile at the decerebrated state, $here the brain is removed, the toad does not blink but does have a slight croak+ does not react upon exposure to acetic acid+ does still flex other leg as the remaining leg is pinched+ does make a slo$ righting movement and does still s$im. Thus, it still have the ability to respond to external stimuli. #n decerebrated toad, brain stem is transected at the middle to lo$er mesencephalic level, $hich blocks normal inhibitory signals from the higher control centers of the brain to the pontile and vestibular muscle control nuclei resulting to involuntary extension of extremities in response to external stimuli. The result is that the spinal cord motor reflexes become very excitable and, therefore, easy to activate by even the slightest sensory input signals to the cord. 0%ilson, '121.
#n double"pithed toads, the spinal cord is severed including the brain. Still, it managed to have a respiration rate of (3*min but the breathing may be through the skin or called cutaneous respiration. t this state the legs of the toad become completely limp due to flaccid paralysis of skeletal muscle. The frog $ill never assume a crouching position again, and if pinch the frog $ill not respond after the spinal cord is severed, the frog $ill not feel anything and there $ill not be a reflex $ithdra$al along $ith the other reflexes. #n other $ords, spinal severing makes $ork easier because the muscle no longer reflexes. Scratch reflex
nother is the scratch reflex of the toad in $hich dilute acetic acid is introduced. s itchiness occurs, it proceeds $ith scratch reflex as to relieve cutaneous irritation. This is a form of defense mechanism $hen parasites or irritants are present. 4ain receptors are activated as acid is applied onto the skin. #n addition to this, acid is permeable to the toad skin that allo$s easy access of the acid to the toad5s internal system resulting to a greater e ffect of the acid on the toad.
aerentbers of the seudounipolar spinal ganglion cells
Nerve endings on the surface of the skin
somatic motor neurons
Cerebellu m
Muscle s
6ig.'. !otor path$ay of Scrath reflex. Withdrawal reflex
7pon induction of stimuli either painful or harmful, there $ill be a counteracting flex movement of a specific part of a body called $ithdra$al reflex 0%ilson, '121. 4inching is a type of cutaneous stimulation and its natural response is to $ithdra$ that part of the body that is stimulated. 7pon pinching, the pain receptors made up of nerve endings in the skin transmit signal to the cerebellum $hich controls motor function thus, causing a flex to the muscle affected by the stimulus. So, $ithdra$al reflex is executed by pinching off the legs or toes of either side of the toad. #n normal toad, $hen left leg is pinched, right leg $ill flex follo$ed by the left leg. Theoretically, as expected, decerebrated toad responses as $hat normal toad does+ but not in the case of pithed toads. 8esides, $hat is responsible for the pain is the spinal cord.
pontine nuclei and the inferior olive temperatur e and pain receptor in the skin
dentate nucleus to the red nucleus and the ventrolateral nucleus
Cerebellu m
Muscle (usually the exors)
6ig.(. !otor path$ay of %ithdra$al reflex. Righting reflex
Recovery to its normal position after orienting from different position of the body is called righting reflex. #n normal toad, there is righting movement due to functional brain and spinal cord observed $hile in decerebrated toad+ a slo$ righting movement is observed. 9o$ever, on the pithed toads, righting movements $ere not observed. Righting reflex is a mobili:ing response $hich requires a coordinated sensory input and motor output to be able to materiali:e. #f the somatic motor neurons are no longer transmitted to the sensory receptor organs, no action potential $ill travel to the medulla oblongata and, hence, $ill not reach the effector organ $hich is the muscles in the limbs.
CN !!! (Cochlear branch of the estibulocochle ar nerve)
somatic motor neurons
sensory Medulla receptors oblong on the organs ata that perceive body 6ig.3. !otor path$ay of righting reflex. orientation
Muscles (specic ally of the limbs)
Swimming reflex
S$imming reflex is the coordinated movement of the limbs to sustain its body afloat the $ater and to gain movement. The normal toad $as observed to immediately s$im $hen it $as placed in the $ater because its brain and spinal cord are intact, and, thus, function the $ay they should be in order to maintain equilibrium. #n the case of single"pithed toad it still s$ims but accompanied $ith the movement $as not $ell"coordinated. %hile decerebrated and double" pithed toads still s$im, but it should not s$im since complete removal of the brain $hich contained the nuclei necessary for the processing of any sensory information from the receptors is taken.
CN !!! (vestibulocochl ear nerve)
somatic motor neurons
;
"ar # labyrint h
Cerebellu m
muscles (specical ly of the hind limbs)
%ilson, <. . 0'121. 4rinciples of nimal 4hysiology. (nd ed. Collier !acmillan #nternational =ditions> Ne$ ?ork.
