five basic components of the pupillary light reflex pathway

trigeminal1 afferent (free nerve endings in the cornea, trigeminal 2 afferent in the spinal trigeminal nucleus, some of which send their axons to, reticular formation interneurons, which send their axons bilaterally to. During accommodation three motor responses occur: convergence (medial rectus contracts to direct the eye nasally), pupil constriction (iris sphincter contracts to decrease the iris aperture) and lens accommodation (ciliary muscles contract to decrease tension on the zonules). Blocks contraction of sphincter pupillae muscle. Figure 7.10 A cataract occurs when the lens becomes cloudy. If the pupillary dilation is due to the ciliospinal reflex, prolonged pupillary light stimulation should constrict the pupils[8] However, prolonged light stimulation cannot overcome pupillary dilation caused by bilateral third nerve palsies and midbrain dysfunction[8]. Part B - Pupillary Light Reflex Pathway Drag The Labels To Identify The Five Basic Components Of The Pupillary Light Reflex Pathway. The eye blink reflex is the simplest response and does not require the involvement of cortical structures. Reflexes are rapid, predictable, and involuntary motor responses to stimuli. This cookie is set by GDPR Cookie Consent plugin. The pupillary light reflex pathway involves the optic nerve and the oculomotor nerve and nuclei. 1. toxin into the lacrimal gland. sends these control signals bilaterally to the oculomotor complex. Figure 7.7 A consensual pupillary reflex is response of a pupil to light that enters the contralateral (opposite) eye. The accommodation reflex (or accommodation-convergence reflex) is a reflex action of the eye, in response to focusing on a near object, then looking at a distant object (and vice versa), comprising coordinated changes in vergence, lens shape (accommodation) and pupil size. While light stimulates the parasympathetic output, giving rise to the light reflex, it can both inhibit and stimulate the sympathetic output. Which of the following does NOT describe graded potentials? [8][9][10] Moreover, the magnitude of the pupillary light reflex following a distracting probe is strongly correlated with the extent to which the probe captures visual attention and interferes with task performance. Reflex arcs are neural pathways composed of five basic components. An RAPD is a defect in the direct pupillary response and usually suggests optic nerve disease or severe retinal disease. The horizontal gaze center coordinates signals to the abducens and oculomotor nuclei to reflexively induce slow movement of the eyes. Pupillary reflex is conceptually linked to the side (left or right) of the reacting pupil, and not to the side from which light stimulation originates. . function, pupil diameter Vagal outflow via the cardiac depressor nerve stimulates muscarinic cholinergic receptors, which results in sinus bradycardia that can progress to AV block, ventricular tachycardia, or asystole[17]. Experts are tested by Chegg as specialists in their subject area. Since the pupil constriction velocity is approximately 3 times faster than (re)dilation velocity,[15] different step sizes in the numerical solver simulation must be used: where Table I summarizes these structures and the function(s) of these ocular motor responses. The gustolacrimal reflex is also called crocodile tears or Bogorad syndrome[4]. The pupil dilates in the dark. When the right eye is stimulated by light, left pupil does not constrict consensually. Please consult your physician for advice about changes that may affect your health. Arch ophthalmol. This page was last edited on 7 January 2023, at 06:24. as well as parasympathetic preganglionic axons to the ciliary ganglion. Possible combinations and permutations are: (a) segment 1 only, (b) segment 3 only, (c) segment 5 only, (d) combination of segments 1 and 3, (e) combination of segments 1 and 5, (f) combination of segments 3 and 5, and (g) combination of segments 1, 3, and 5. This is called abnormal miosis, and it can happen in one or both of your eyes. When you login first time using a Social Login button, we collect your account public profile information shared by Social Login provider, based on your privacy settings. C. Edinger-Westphal nucleus This answer is INCORRECT. This syndrome is characterized by miosis (pupil constriction), anhidrosis (loss of sweating), pseudoptosis (mild eyelid droop), enopthalmosis (sunken eye) and flushing of the face. In contrast, voluntary eye movements (i.e., visual tracking of a moving object) involve multiple areas of the cerebral cortex as well as basal ganglion, brain stem and cerebellar structures. the best-known reflex is the pupillary light reflex. His speed remains constant as he goes counterclockwise around a level track with two straight sections and two nearly semicircular sections as shown in the helicopter. He has normal ocular mobility and his eyelids can be elevated and depressed at will. Were the solution steps not detailed enough? Clinical Significance. The main types of pupillary abnormalities include: Anisocoria: unequal pupil sizes. The afferent limb has nerve fibers running within the optic nerve (CN II). A single lesion anywhere along segment 1, the left afferent limb, which includes the left retina, left optic nerve, and left pretectal nucleus, can produce the light reflex abnormalities observed. A consensual pupillary reflex is response of a pupil to light that enters the contralateral (opposite) eye. Option (e) involves a combined lesion of segments 1 and 5. Left consensual light reflex involves neural segments 2, 4, and 7. Segments 1 and 2 each includes both the retina and the optic nerve (cranial Nerve #2). Ophthalmologic considerations: Bells reflex is present in about 90% of the population[11]. Each Edinger-Westphal nucleus gives rise to preganglionic parasympathetic fibers which exit with CN III and synapse with postganglionic parasympathetic neurons in the ciliary ganglion. The oculomotor nerve is responsible for the efferent limb of the pupillary reflex it drives the muscles that constrict the pupil. The patient presents with a left eye characterized by ptosis, lateral strabismus, and dilated pupil. The lines ending with an arrow indicate axons terminating in the structure at the tip of the arrow. Neurosyphilis occurs due to an invasion of the cerebrospinal fluid (CSF) by the spirochete which likely occurs soon after the initial acquisition of the disease. The decreased tension allows the lens to increase its curvature and refractive (focusing) power. In this article, we will cover a variety of reflexes involving the eye and their ophthalmologic considerations. Thus, the Pupillary Light Reflex Pathwayregulates the intensity of light entering the eye by constricting or dilating the pupils. Afferent signals from the left eye cannot pass through the transected left optic nerve to reach the intact efferent limb on the left. Few reflexes are monosynaptic (one synapse) and involve only two neuronsone sensory and one motor. Figure 7.8 Complete the Concept Map to trace the pathway of light through the eye to the retina and explain how light is focused for distant or close vision. The vestibulo-ocular reflex (VOR) allows for eye movements in the opposite direction of head movement to maintain steady gaze and prevent retinal image slip[4]. Thus, the pupillary light reflex regulates the intensity of light entering the eye. When left eye is stimulated by light, afferent signals from the left eye cannot pass through the transected left optic nerve to reach the intact efferent limb on the right. VOR can be assessed in several ways. Direct light reflex of right pupil involves the right optic nerve and right oculomotor nerve, which are both intact. Observe the reaction of the patient's pupils to light directed in the left or right eye. Touching the right or left cornea with a wisp of cotton elicits the eye blink reflex in the right eye, but not the left eye (Figure 7.7). The pupil is constricted, reducing the amount of light entering the eye. {\displaystyle \Phi =IA} Finally, a picture that is subjectively perceived as bright (e.g. Physical examination determines that touch, vibration, position and pain sensations are normal over the entire the body and over the lower left and right side of his face. The patient complains of a badly infected left eye. [6] Sympathetic fibers from the upper thoracic and lower cervical spinal cord make up the efferent portion of the ciliospinal reflex. Autonomic reflexes: activate cardiac muscles, activate smooth muscles, activate glands. When asked to rise his eyelids, he can only raise the lid of the right eye. It is the response of the eye that is being stimulated by light. Repeat this procedure on the opposite eye. Touch, vibration, position and pain sensations are normal over the entire the body and face. The receptor is the site of stimulus action. Havelius U, Heuck M, Milos P, Hindfelt B. Ciliospinal reflex response in cluster headache. [6] Central sympathetic fibers, which are the first order neurons, begin in the hypothalamus and follow a path down the brainstem into the cervical spinal cord through the upper thoracic segments. Anaesthesia for paediatric eye surgery. The superior salivatory nucleus in the pons gives off parasympathetic fibers that join other parasympathetic efferents from the salivatory nucleus[1]. Which of the following responded to a chemical stimulus? We also get your email address to automatically create an account for you in our website. is a constant that affects the constriction/dilation velocity and varies among individuals. Accommodation insufficiency is also less commonly associated with primary ocular disorders (e.g. Microscopically precise strokes in the midbrain, involving the left pretectal nucleus, bilateral Edinger-Westphal nuclei, and their interconnecting fibers, could theoretically produce this result. Direct reflex of the right pupil is unaffected, The right afferent limb, right CN II, and the right efferent limb, right CN III, are both intact. Thus there are four types of pupillary light reflexes, based on this terminology of absolute laterality (left versus right) and relative laterality (same side versus opposite side, ipsilateral versus contralateral, direct versus consensual): The pupillary light reflex neural pathway on each side has an afferent limb and two efferent limbs. https://www.aao.org/bcscsnippetdetail.aspx?id=767021d9-21a5-4b76-af43-49468a5bbd0c, https://www.aao.org/bcscsnippetdetail.aspx?id=3d31809c-9673-453c-a6c7-018c4540e6f9, https://eyewiki.org/w/index.php?title=Reflexes_and_the_Eye&oldid=83681. Integration center #3. monosynaptic reflex. where Examination of the VOR via head rotation or caloric stimulation can be useful in the evaluation of unconscious patients, as tonic eye deviation indicates preserved pontine function[4]. 2.) Atropine does not have an effect on the reflex. The palpebral oculogyric reflex, or Bells reflex, refers to an upward and lateral deviation of the eyes during eyelid closure against resistance, and it is particularly prominent in patients with lower motor neuron facial paralysis and lagopthalmos (i.e. When assessing the pupillary light reflex, the nurse should use which technique? {\displaystyle \mathrm {d} t_{c}} Intrinsic reflexes are inborn and serve to protect the body. The reflex can also occur in patients with entrapment after orbital floor fracture. The patient complains of pain in her left eye. Part B - Pupillary Light Reflex Pathway Drag the labels to identify the five basic components of the pupillary light reflex pathway. This cookie is set by GDPR Cookie Consent plugin. The reflex describes unilateral lacrimation when a person eats or drinks[14]. 4 days ago. This response involves the relaxation of the iris sphincter and contraction of the iris dilator. Drag and drop the correct terms on the left to complete the sentences. {\displaystyle M} Right consensual light reflex involves neural segments 1, 3, and 8. The left consensual reflex is intact. The nerves may redirect themselves through the greater superficial petrosal nerve to reach the lacrimal gland, causing ipsilateral tearing when the patient eats. The Basilica-Cathedral of Our Lady of the Pillar (Spanish: Catedral-Baslica de Nuestra Seora del Pilar) is a Roman Catholic church in Zaragoza, Aragon, Spain.The Basilica worships Blessed Virgin Mary, under her title Our Lady of the Pillar.According to its website, this church is the first church dedicated to Mary. There are no other motor symptoms. The action of the muscle will be weakened or lost depending on the extent of the damage. (adsbygoogle=window.adsbygoogle||[]).push({}); The optic nerve, or more precisely, the photosensitive ganglion cells through the retinohypothalamic tract, is responsible for the afferent limb of the Pupillary Light Reflex Pathway it senses the incoming light. one year ago, Posted The neural pathway of the pupillary light reflex as first described by Wernicke [1, 2] in 1880s consists of four neurons (Fig. View Available Hint (s) Reset Help Optic nerve Retinal photoreceptors Sphincter pupillae Midbrain Ciliary ganglion Oculomotor nervo Stimulus Receptor Sensory Integration Efectos neuron Submit The Oculomotor Nerve. The effect of sectioning the trigeminal nerve is to remove the afferent input for the eye blink reflex. 447). This website uses cookies to improve your experience while you navigate through the website. Francis, IC, Loughhead, JA. Figure 7.11 Symptoms. Which of the following structures of the eye is most responsible for absorbing light? Pathway: Short ciliary nerves come together at the ciliary ganglion and converge with the long ciliary nerve to form the ophthalmic division of the trigeminal nerve, which continues to the Gasserian ganglion and then the main sensory nucleus of the trigeminal nerve[17][18]. Side & Level of damage: As the ocular loss involves. Observe for blinking and tearing in that eye (direct corneal reflex). Even one lesion in the pathway can severely deteriorate the quality of vision. When the left eye is stimulated by light, left pupil does not constrict, because the efferent signals cannot pass from midbrain, through left CN III, to the left pupillary sphincter. The consensual response is the change in pupil size in the eye opposite to the eye to which the light is directed (e.g., if the light is shone in the right eye, the left pupil also constricts consensually). London, R. Optokinetic nystagmus: a review of pathways, techniques and selected diagnostic applications. ) Reflex pathway with only one synapse between the sensory and motor neurons (ex: knee-jerk). The OKN response can also be used to evaluate for suspected subclinical internuclear ophthalmoplegia, which will show a slower response by the medial rectus on the side of the lesion, and for suspected Parinauds syndrome, in which the use of a downward OKN target will accentuate convergent retraction movements on attempted upgaze. the conversion of a stimulus to a change in membrane potential, amplitude can vary with the stimulus intensity, requires the appropriate stimulus and can be graded with a stimulus intensity. Optic nerve is incorrect as section of one nerve would not obliterate the consensual response to stimulation of the contralesional eye. t Pathway for slow pursuit phase: Afferent signals from the retina are conveyed through the visual pathways to the occipital lobe, which sends impulses to the pontine horizontal gaze center[15]. There will be an inability to close the denervated eyelid voluntarily and reflexively. Furthermore, segment 4 shares the same anatomical space in the midbrain as segment 3, therefore segment 4 will likely be affected if segment 3 is damaged. Blackwood W, Dix MR, Rudge P. The cerebral pathways of optokinetic nystagmus: A neuro-anatomical study. t Symptoms. Montoya FJ, Riddell CE, Caesar R, Hague S. Treatment of gustatory hyperlacrimation (crocodile tears) with injection of botulinum Analytical cookies are used to understand how visitors interact with the website. 7.2 Ocular Reflex Responses A circular muscle called the sphincter pupillae accomplishes this task. Damage to segment 5 may accompany a segment 1 lesion, but is unnecessary for producing the abnormal light reflex results in this case. Right afferent limb is intact, but left efferent limb, left CN III, is damaged. Eyelid closure reaction. the lower motor neurons innervating the superficial muscles of the face, the 1 gustatory afferents to the anterior tongue. the sensory neuron transmits afferent impulses to the CNS. d By analogy with a camera, the pupil is equivalent to aperture, whereas the iris is equivalent to the diaphragm. Segments 3, 4, 5, and 6 are all located within a compact region within the midbrain. Sphincter Pupillae- constrictor muscle that is innervated by the Parasympathetic nervous system innvervated by Oculomotor Nerve (CN3) Dilator Pupillae- dilator muscle that is innervated by the sympathetic nervous system Pathway of Pupillary Light Constriction Get it solved from our top experts within 48hrs! Even-numbered segments 2, 4, 6, and 8 are on the right. When the intensity of the appropriate stimulus was increased, the amplitude of the response _______. When the patient is asked to look straight ahead, you note his left eye remains directed to the left and depressed. Decreases pupil size (constriction) reduces the amount of light that enters the eye. Neuro-imaging, such as MRI scan, would be useful for confirmation of clinical findings. The oculo-emetic reflex causes increased nausea and vomiting due to extensive manipulation of extraocular muscles[21]. The patient cannot detect pinpricks to his left forehead. Pupillary Light Reflex Pathway,is a reflex that controls the diameter of the pupil, in response to the intensity (luminance) of light that falls on the retina of the eye, thereby assisting in adaptation to various levels of darkness and light, in addition to retinal sensitivity. In all probability, option (a) is the answer. Does the question reference wrong data/reportor numbers? retina, optic nerve, optic chiasm, and the optic tract fibers that join the ; brachium of the superior colliculus, which terminate in the ; pretectal area of the midbrain, which sends most of its axons bilaterally in the posterior commissure to terminate in the -The subject shields their right eye with a hand between the eye and the right side of the nose. D Complete the Concept Map to describe the sound conduction pathway to the fluids of the inner ear. What is the major role of the basilar membrane? Diplopia, ptosis, and impaired extraocular movements on the . The corneal eye blink reflex is initiated by the free nerve endings in the cornea and involves the trigeminal nerve and ganglion, the spinal trigeminal tract and nucleus, interneurons in the reticular formation, motor neurons in the facial nucleus and nerve, and the orbicularis oculi. Receptor, sensory neuron, integration center, motor neuron and effector. a picture of an indoor scene), even when the objective brightness of both images is equal. Drag the labels to identify the five basic components of the pupillary light reflex pathway. Vestibular reflexes and Reflexes are involuntary responses, usually asso- ciated with protective or regulatory functions in the organism in which they occur. . : luminance reaching the eye in lumens/mm2 times the pupil area in mm2. Observation: You observe that the patient has normal vision but that his pupils, You conclude that his eye's functional loss is, Pathway(s) affected: You conclude that structure(s) in the, Side & Level of damage: As the pupillary response deficit. Why CO2 is used in supercritical fluid extraction? As with all experiments, it is important to establish a standard of comparison (control group). stimulus(light)(simulus):retinal The nurse is assessing a patients eyes for the accommodation response and would expect to see which normal finding? Caloric stimulation can also be used to examine the VOR[4]. Gamlin, D.H. McDougal, in Encyclopedia of the Eye, 2010 Description Anatomically located in front of the lens, the pupil's size is controlled by the surrounding iris. The Academy uses cookies to analyze performance and provide relevant personalized content to users of our website. Recall that presbyopia most commonly results from structural changes in the lens which impedes the lens accommodation response. Segment 1 is the afferent limb. The iris dilator is controlled by the sympathetic nervous system. The pupillary light reflex is an example of a(n) ________. As the afferent information from each cornea is distributed bilaterally to facial motor neurons by the reticular formation interneurons, the eye blink response is consensual, that is, both eye lids will close to stimulation of the cornea of either eye. Pupillary Light Reflex Pathway, is a reflex that controls the diameter of the pupil, in response to the intensity (luminance) of light that falls on the retina of the eye, thereby assisting in adaptation to various levels of darkness and light, in addition to retinal sensitivity. Remaining segments where lesion may be located are segments 1, 3, and 5. CONTINUE SCROLLING OR CLICK HERE. The pupil of the right eye constricts while shining a flashlight into the left eye. When asked to close both eyes, both eyelids close fully. {\displaystyle S} It is hypothesized that it is due to oculomotor disinhibition. We use our eyes to monitor our external environment and depend on our ocular motor systems to protect and guide our eyes. Pathway: The ophthalmic division of the trigeminal nerve carries impulses to the main sensory nucleus of the trigeminal nerve. -Measure the diameter of the left pupil in normal lighting. Abnormal pupillary reflex can be found in optic nerve injury, oculomotor nerve damage, brain stem lesion (including brain stem death), and depressant drugs, such as barbiturates. Bharati SJ, Chowdhury T. Chapter 7: The Oculocardiac Reflex. There are two key muscles involved in pupillary constriction. The effect of sectioning one optic nerve is to remove the afferent input for the direct reflex of the blinded eye and the afferent input for the consensual reflex of the normal eye. d I am currently continuing at SunAgri as an R&D engineer. Pupil dilation is mediated by a sympathetic output acting in opposition to parasympathetically mediated pupil constriction. VOR can also be assessed via dynamic visual acuity, during which multiple visual acuity measurements are taken as the examiner oscillates the patients head. Pathway(s) affected: You conclude that structures in the following reflex pathway have been affected. The lacrimatory reflex causes tear secretion in response to various stimuli: 1. physical and chemical stimuli to the cornea, conjunctiva and nasal mucosa, 2. bright light, 3. emotional upset, 4. vomiting, 5. coughing, 6. yawning[1]. A combined lesion in segments 3 and 5 as cause of defect is very unlikely. The right consensual reflex is lost. Section of the oculomotor nerve produces a non-reactive pupil in the ipsilesional side as well as other symptoms related to oculomotor nerve damage (e.g., ptosis and lateral strabismus). Afferent pathway for pupillary constriction, lens accommodation, and convergence: Afferent input from the retina is sent to the lateral geniculate nucleus via the optic tract. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. incomplete eyelid closure)[10]. The diagram may assist in localizing lesion within the pupillary reflex system by process of elimination, using light reflex testing results obtained by clinical examination. The pupillary light reflex two main parts: an afferent limb and an efferent limb. 11 months ago, Posted It consists of a pupillary accommodation reflex, lens accommodation reflex, and convergence reflex. When lower motor neurons are damaged, there is a flaccid paralysis of the muscle normally innervated. The motor losses may be severe (i.e., a lower motor neuron loss that produces total paralysis) if the cranial nerve contains all of the motor axons controlling the muscles of the normally innervated area. Eye reflex which alters the pupil's size in response to light intensity, "Eyeing up the Future of the Pupillary Light Reflex in Neurodiagnostics", "Understanding the effects of mild traumatic brain injury on the pupillary light reflex", "Perceptual rivalry: Reflexes reveal the gradual nature of visual awareness", "Attention to bright surfaces enhances the pupillary light reflex", "The pupillary response to light reflects the focus of covert visual attention", "The pupillary light response reflects exogenous attention and inhibition of return", "Pupil size and social vigilance in rhesus macaques", "Pupil constrictions to photographs of the sun", "Bright illusions reduce the eye's pupil", "Photorealistic models for pupil light reflex and iridal pattern deformation", "The pupillary light reflex in normal subjects", https://en.wikipedia.org/w/index.php?title=Pupillary_light_reflex&oldid=1132093314, Short description is different from Wikidata, Creative Commons Attribution-ShareAlike License 3.0, Retina: The pupillary reflex pathway begins with the photosensitive. View Available Hint(s) Reset Help Optic nerve Retinal photoreceptors Sphincter pupillae Midbrain Ciliary ganglion Oculomotor nervo Stimulus Receptor Sensory Integration Efectos neuron Submit. 3.) Irrigation of the external auditory meatus with ice water causes convection currents of the vestibular endolymph that displace the cupula in the semicircular canal, which induces tonic deviation of the eyes toward the stimulated ear[4]. Which is Clapeyron and Clausius equation. Signals from the pneumotaxic respiratory center in the ventrolateral tegmentum of the pons reach the medullary respiratory area and travel through the phrenic and other respiratory nerves, which lead to bradypnea, irregular respiratory movements, and respiratory arrest[20]. protecting the retina from damage by bright light. View chapter Purchase book Pupil P.D.R. d 4.) Which of the following statements is an example of the consensual light reflex? Drag the labels to identify the five basic components of the pupillary light reflex pathway. The parasympathetic preganglionic axons of the Edinger-Westphal nucleus, which normally travel in the oculomotor nerve, will be cut off from the ciliary ganglion, disrupting the circuit normally used to control the iris sphincter response to light. Light is the stimulus; impulses reach the brain via the optic nerve; and the response is conveyed to the pupillary musculature by autonomic nerves that supply the eye. When he is asked to close both eyes, both eyelids close. What is consensual Pupillary Light Reflex? Which of the following cranial nerve mediates the corneal reflex? Pupillary reflex is synonymous with pupillary response, which may be pupillary constriction or dilation. Part B - Pupillary Light Reflex Pathway Drag The Retinal photoreceptors, the optic nerve, the midbrain's integration centre, the occulomotor nerve, the motor neuron, and the sphincter pupilae all Posted Lesions of the deep parietal tract, a region close to where efferent pursuit fibers pass close to afferent optic radiations, will show directional asymmetry of the OKN response. The iris sphincter is innervated by the postganglionic parasympathetic axons (short ciliary nerve fibers) of the ciliary ganglion (Figure 7.3). It will be present in newborns, semi-obtunded patients, and patients who are attempting to malinger. Her left pupil appears dilated and is not reactive to light directed at either the left or right eye (Figure 7.10). Cranial nerve damage: Damage to cranial nerves may result in sensory and motor symptoms. J Neurosurg. In general, ocular reflexes are consensual (i.e., the response is bilateral involving both eyes). An abnormal blink reflex may be present in patients with various posterior fossa disorders, including acoustic neuroma, multiple sclerosis, Parkinson disease, trigeminal nerve lesions, and brainstem strokes, tumors, or syrinxes[4]. However, the patient reports he can feel the cotton when it touches either eye. Incidence varies between 50-90%[19], and children 2-5 years old are thought to be more affected due to high resting vagal tone[17]. Symptoms. Due to innervation of the bilateral E-W nuclei, a direct and consensual pupillary response is produced[2]. Sharma D, Sharma N, Kumar Mishra A, Sharma P, Sharma N, Sharma P. POSTOPERATIVE NAUSEA AND VOMITING: A REVIEW. The ocular reflexes are the simplest ocular motor responses. Words may be used once, more than once, or not at all. Afferent pathway for pupillary constriction, lens accommodation, and convergence: Afferent input from the retina is sent to the lateral geniculate nucleus via the optic tract[2]. Which eye structure is primarily responsible for making the adjustments required to focus on objects both near and far? The eye blink reflex is the simplest response and does not require the involvement of cortical structures. If his acceleration is the same size at two points, display that fact in your ranking. Figure 7.13 Parasympathetic Innervation of the Eye. Probably the best-known reflex is the pupillary light reflex.If a light is flashed near one eye, the pupils of both eyes contract.

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