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Australian and New Zealand Journal of... Aug 1994Reflexes are an essential part of protective and homeostatic function, both in general terms and with specific reference to ocular structures. A wide range of stimuli... (Review)
Review
Reflexes are an essential part of protective and homeostatic function, both in general terms and with specific reference to ocular structures. A wide range of stimuli and responses, with varying degrees of central processing, is involved in such reflexes. The simplest reflexes are monosynaptic, such as the stretch or myotatic reflex. More complex polysynaptic reflexes are involved in many regulatory and protective functions--these include autonomic as well as somatic reflexes. Ocular autonomic reflexes include the oculocardiac, pupillary, accommodative and lacrimatory reflexes. Ocular somatic reflexes include eyelid and extra-ocular muscle reflexes (such as Bell's phenomenon, vestibulo-ocular and optokinetic reflexes). An account of the above reflexes is given in the format of an essay, modified from the FRACO Part I Examination in Physiology. The topic was 'Discuss reflex activities with particular reference to the eye'. The content is based on several of the texts recommended for the Part I Examination, as listed under references.
Topics: Blinking; Humans; Ocular Physiological Phenomena; Oculomotor Muscles; Reflex; Reflex, Monosynaptic; Reflex, Oculocardiac; Reflex, Pupillary; Reflex, Vestibulo-Ocular
PubMed: 7818872
DOI: 10.1111/j.1442-9071.1994.tb01710.x -
Muscle & Nerve Jul 1989Authorities advocate different stimulus durations to produce an H reflex. In order to find the optimal stimulus duration for recording H reflexes, the recruitment curves...
Authorities advocate different stimulus durations to produce an H reflex. In order to find the optimal stimulus duration for recording H reflexes, the recruitment curves for H reflexes and M responses were studied in 10 healthy subjects. The H reflex was recorded in the upper and lower extremities, and the durations of the electrical stimulus used ranged from 0.1 to 3 msec. The amplitude of the H reflex and the relation between the H reflex and M response changed with stimulus duration. H reflexes are brought out to advantage using a stimulus duration between 0.5 and 1 msec.
Topics: Adult; Electric Stimulation; H-Reflex; Humans; Middle Aged; Reflex, Monosynaptic; Time Factors
PubMed: 2779606
DOI: 10.1002/mus.880120708 -
Journal of Neurophysiology Feb 1987The study of primate memory substrates, the CNS alterations which preserve conditioned responses, requires an experimental model that fulfills two criteria. First, the...
The study of primate memory substrates, the CNS alterations which preserve conditioned responses, requires an experimental model that fulfills two criteria. First, the essential alterations must be in a technically accessible location. Second, they must persist without input from other CNS regions. The spinal cord is the most technically accessible and readily isolated portion of the primate CNS. Recent work has demonstrated that the spinal stretch reflex (SSR), the initial, wholly segmental response to muscle stretch, can be operantly conditioned and suggests that this conditioning may produce persistent spinal alteration. The present study attempted similar operant conditioning of the H-reflex, the electrical analog of the SSR. The primary goals were to demonstrate that spinal reflex conditioning can occur even if the muscle spindle is removed from the reflex arc and to demonstrate conditioning in the lumbosacral cord, which is far preferable to the cervical cord for future studies of neuronal and synaptic mechanisms. Nine monkeys prepared with chronic fine-wire triceps surae (gastrocnemius and soleus) electromyographic (EMG) electrodes were taught by computer to maintain a given level of background EMG activity. At random times, a voltage pulse just above M response (direct muscle response) threshold was delivered to the posterior tibial nerve via a chronically implanted silicon nerve cuff and elicited the triceps surae H-reflex. Under the control mode, reward always followed. Under the HR increases or HR decreases mode, reward followed only if the absolute value of triceps surae EMG from 12 to 22 ms after the pulse (the H-reflex interval) was above (HR increases) or below (HR decreases) a set value. Monkeys completed 3,000-6,000 trials/day over study periods of 2-3 mo. Background EMG and M response amplitude remained stable throughout data collection. H-reflex amplitude remained stable under the control mode. Under the HR increases mode (5 animals) or HR decreases mode (4 animals), H-reflex amplitude (EMG amplitude in the H-reflex interval minus background EMG amplitude) changed appropriately over at least 6 wk. Change appeared to occur in two phases: an abrupt change within the first day, followed by slower change, which continued indefinitely. Change occurred in all three triceps surae muscles (medial and lateral gastrocnemii and soleus). Under the HR increases mode, H-reflex amplitude rose to an average of 213% of control, whereas under the HR decreases mode it fell to an average of 68% of control. The results demonstrate that the H-reflex can be operantly conditioned.(ABSTRACT TRUNCATED AT 400 WORDS)
Topics: Animals; Conditioning, Operant; H-Reflex; Macaca nemestrina; Male; Reflex; Reflex, Monosynaptic; Spinal Cord
PubMed: 3559687
DOI: 10.1152/jn.1987.57.2.443 -
Advances in Experimental Medicine and... 2002Over the past four decades, the understanding of proprioceptive spinal reflexes has advanced far more rapidly than generally considered. This problem could be largely... (Review)
Review
Over the past four decades, the understanding of proprioceptive spinal reflexes has advanced far more rapidly than generally considered. This problem could be largely obviated in undergraduate and graduate training programs if the topic of reflexes was introduced subsequent to the concept and mechanisms of pattern generation within the central nervous system. The key advantage would then be that the neuroscience community as a whole would gain appreciation of the fact that proprioceptive reflexes are not hard-wired but rather are context- and phase-dependent, with the central nervous system selecting input-output pathways appropriate for the task at hand.
Topics: Animals; Humans; Periodicity; Reflex; Spinal Cord
PubMed: 12171118
DOI: 10.1007/978-1-4615-0713-0_30 -
Psychophysiology Mar 2011The postauricular reflex is a relatively new psychophysiological measure of appetitive emotional processing during picture viewing. However, the degree to which other...
The postauricular reflex is a relatively new psychophysiological measure of appetitive emotional processing during picture viewing. However, the degree to which other auricular (i.e., superior and anterior auricular) muscles might exhibit reflexive activity congruent with that found in the postauricular muscle has not been investigated, nor has the robustness of postauricular reflex modulation across stimulus modality. In this study, postauricular reflexes were the only reflexes that showed consistent emotional modulation across ears and genders. Additionally, postauricular reflexes were significantly modulated for both emotional pictures and sounds; in both cases, postauricular reflexes were greatest during pleasant stimuli.
Topics: Acoustic Stimulation; Data Interpretation, Statistical; Ear Auricle; Emotions; Female; Humans; Male; Noise; Photic Stimulation; Reflex; Reflex, Startle; Sex Characteristics; Young Adult
PubMed: 20636290
DOI: 10.1111/j.1469-8986.2010.01071.x -
The European Respiratory Journal Jul 2006The cough reflex (CR) and the expiration reflex (ER) are two defensive reflexes from the respiratory tract, the latter mainly from the larynx. Both are elicited by... (Review)
Review
The cough reflex (CR) and the expiration reflex (ER) are two defensive reflexes from the respiratory tract, the latter mainly from the larynx. Both are elicited by mechanical and chemical irritation of the airway mucosa, and are a characteristic of airway diseases, but they have different functions. The CR first draws air into the lungs, to accentuate the subsequent expulsive phase; the ER consists of a strong expiration, to prevent aspiration of material into the lungs. They have different sensory pathways, central nervous circuits, and physiological and pharmacological modulations. In practice, coughing often consists of a combination of the two reflexes, a cough bout, epoch or attack. Articles on cough usually do not distinguish between the two reflexes, or whether the coughs are single events or epochs; they usually only measure frequency of expiratory efforts, and neglect other aspects. Current methods for measuring and assessing cough are described, with indications of when the use of these methods may be important.
Topics: Bronchi; Cough; Humans; Larynx; Pulmonary Stretch Receptors; Reflex; Respiration; Respiratory Physiological Phenomena; Respiratory System; Trachea
PubMed: 16816346
DOI: 10.1183/09031936.06.00096905 -
The Journal of Physiology May 2024
Topics: Cats; Animals; Reflex; History, 20th Century
PubMed: 38602708
DOI: 10.1113/JP286594 -
Movement Disorders : Official Journal... 2002
Topics: Animals; Blinking; Humans; Masseter Muscle; Reflex; Trigeminal Nerve
PubMed: 11836747
DOI: 10.1002/mds.10052 -
World Journal of Urology Jun 2002Recent research on the neural control of female sexual function is reviewed. The control of female genital responses has not been extensively studied and significant... (Review)
Review
Recent research on the neural control of female sexual function is reviewed. The control of female genital responses has not been extensively studied and significant gaps in our knowledge remain. Sexual arousal is largely the product of spinal level reflexes. A network of interneurons processes the sensory information and generate complex patterns of activities that are then distributed to the autonomic and somatic efferents. The spinal reflexive systems are under inhibitory and excitatory control from the brainstem and hypothalamic sites. Further research is necessary to identify the mechanisms underlying female sexual function, the pathogenesis of sexual dysfunctions and their possible treatment.
Topics: Afferent Pathways; Animals; Brain; Coitus; Female; Humans; Interneurons; Nervous System Physiological Phenomena; Pelvis; Reflex; Sensation; Spinal Cord
PubMed: 12107539
DOI: 10.1007/s00345-002-0270-7 -
Journal of Neurology, Neurosurgery, and... Jan 1978The facilitating effect of the Jendrassik manoeuvre on monosynaptic reflexes in man has been studied by comparing H and T reflexes of the soleus and by blocking the...
The facilitating effect of the Jendrassik manoeuvre on monosynaptic reflexes in man has been studied by comparing H and T reflexes of the soleus and by blocking the effects of spindle activation by ischaemia of the leg. The Jendrassik manoeuvre equally enhances H and T reflexes provided that the test reflexes are small. The H reflex remains facilitated when the spindle activation cannot affect the soleus alpha-motoneurones--that is, when the Ia afferent nerve fibres from the soleus are blocked by ischaemia. It is concluded that the facilitating effect of the Jendrassik manoeuvre on the alpha-motoneurones is not predominantly routed via the gamma-loop.
Topics: Achilles Tendon; Adult; H-Reflex; Humans; Ischemia; Leg; Methods; Motor Neurons; Nerve Block; Neurons, Afferent; Reflex, Monosynaptic; Reflex, Stretch
PubMed: 621529
DOI: 10.1136/jnnp.41.1.40