XXVII. Examination of reflexes in man XXVIII. Recording of Achilles’ tendon reflex practical (autumn 2018: 1. – 3. week) Department of Physiology, Faculty of Medicine, LF MU Reflexes • Reflex: is an involuntary response of organism triggered by stimulation of receptors. • Reflex arch: consists of 1.receptor, 2. afferent pathway, 3. centre, 4. efferent pathway and 5. effectors organ. • Particular reflexes have anatomically strictly defined reflex arches, e.g. pathway and centre. • According to the character of reflex response to certain stimulus we can topically diagnose and point out the place of nervous system disablement. • Function: correction of changes or protection against damage. Examination of Reflexes • When examining reflexes the following items are considered: • Electability of a reflex • Quantitative changes in the response • Qualitative changes • Proprioceptor reflexes (stretch reflexes) • Most reflexes are elicited by fast, springy tapping the corresponding receptor area with a percussion hammer. • The tapping of the hammer should be adequately strong, fast, and precise, but not painful. • Muscles involved in the muscle response must be sufficiently relaxed. • Facilitating manoeuver consisting in a voluntary contraction of antagonistic muscles, should be used if the reflex can not be elicited even in a correct procedure. • Sometimes it is necessary to distract the subject’s attention by asking him to perform a simple calculation (repeated subtraction of a number) or use Jendrassik’s manoeuvre. Proprioreceptors in the muscle efferent fibre of γ- motoneuron - innervates contractile part of muscle spindle afferent neural fibre Ia muscle spindle muscle length reception Golgi tendon organ tension in muscle intrafusal fibres extrafusal fibres (muscle fibres) efferent neural fibre of α-motoneuron afferent fibre Ib, II Stretch reflex extensor flexor muscle spindle synapse neural fibre of α-motoneuron neural fibre Ia body of neuron Ia percussion hammer spinal cord Stretch reflex: Unwanted extension causes contraction of muscle (containing muscle spindle). Reflex serves as a correction to unwanted prolongation of muscles (maintaining of posture). Correction of muscle spindle sensitivity α-motoneuron extensor flexor muscle spindle γ-motoneuron extrapyramidal pathwayspyramidal pathways spinal cord The desired change of muscle length activates simultaneously γ-motoneurons and αmotoneurons. Intrafusal and extrafusal fibres extend simultaneously and the sensitivity of muscle spindle does not change. Activity of γmotoneurons regulates muscle spindle sensitivity. Golgi tendom reflex, inverse stretch reflex extensor flexor Golgi tendon organ neural fibres Ib, II - inhibitory interneuron excitatory interneuron + α-motoneuron spinal cord Golgi tendon reflex (inverse stretch reflex): Increase of tension in a tendon causes relaxation of a muscle (containing a Golgi receptor) and contraction of an antagonist muscle. This reflex serves as a protection from muscle and tendon damage. • According to the number of synapses: a- monosynaptic reflexes b- polysynaptic reflexes 2- According to the receptor: a- exteroceptive reflexes b- interoceptive reflexes c- proprioceptive reflexes 3- According to the center: a- extracentral reflexes - axonal reflexes - ganglionic reflexes b- central reflexes - spinal reflexes - brain reflexes 4- According to the effector: a- somatic reflexes b- autonomic reflexes 5- According to the genesis: a- unconditioned reflex (congenital) b- conditioned reflexes (acquired) Reflexes in practicals • Proprioceptive (myotatic, stretch) reflexes: 1- masseter reflex, 2- Nasopalpebral reflex, 3- Biciptal reflex, 4-Styloradial reflex, 5- Triceps reflex, 6- Patellar reflex, 7- Achilles’ tendon reflex and 8Medioplantar reflex. • Exteroceptive reflexes (cutaneous and mucous): 1- Corneal and conjunctival reflexes, 2- Palatal reflex, 3- Epigastric, mesogastric, hypogastric reflexes and 4- Plantar reflex. • Sensory reflexes: 1- Pupillary responses: a- Response to light, b- Response to convergence, c- Response on pain 2- Twinkle reflex Reflexes in practicals Pupillary responses https://www.researchgate.net/figure/Schematic-drawing-of-the-pupillary-light-reflex-pathway- By-way-of-the-optic-tract-the_fig1_318593544 • The impulses generated in the sensory nerve are transmitted anti-directionally (upstream) to other branches of the sensoric fiber • When irritating the skin receptors, the pulse is converted to nearby arterioles innervated by the same fiber • Substance P from the nerve endings dilates the arteriol and increases the vascular permeability (red dermatographismus) • In addition histamine released from mast cells also dilates the vessels and increases their permeability Axon reflex (extracentral) body of sensoric neuron spinal cord skin nerve endings arteriolar nerve endings antidrome conduction axon reflex arch orthodrome conduction . XXVIII. Recording of Achilles’ tendon reflex Recording of Achilles’ tendon reflex Aim: To learn how to register electrical and mechanical response of Achilles’ tendon reflex. After measuring of particular values get an idea about time sequence of electrophysiological processes of reflex response, which start with stimulation of appropriate receptors and ends up in muscle relaxation. . • Achilles tendon reflex (or ankle jerk) as a proprioceptive reflex is elicited by tapping the tendon of the soleus muscle with a reflex hammer. The rapid stretch of muscle activates the muscle spindles and evokes an increased discharge of action potentials from the spindles. • The volley of action potentials in the primary sensors Ia fibres monosynaptically excites the alpha motoneurons which in turn activate soleus muscle, where the reflex begins. • Contraction of muscle is preceded by membrane depolarisation of activated muscle fibres which generate the so called compound muscle action potential (CMAP). This potential may be recorded by means of surface electrodes (electromyographically). Two parameters of electromyogram (EMG) are of interest: the duration of the signal and the interval of its delay, the latency period. . • According to different sites of stimulation two kinds of reflexes may be obtained. • T-reflex is triggered by simple tapping the tendon with the reflex hammer and thus, is subject to various irregularities. As a result the amplitudes of responses are not identical. • H-reflex is triggered by an electric pulse of submaximal intensity. The latter method employs surface electrodes placed on fossa poplitea close to tibial nerve. The amplitudes of responses are almost identical. H-reflex is routinely employed as a diagnostic tool in neurology. • The mechanical response of the muscle, contraction and relaxation, may be recorded with a joint goniometer fixed on the calf and the foot. The muscle contraction changes the angle formed by the attached boxes, thereby the deflexion of the fibers and eventually the amount of light converted to electric signal. The first derivative of the signal yields the velocity of contraction and relaxation. • The measurement of Achilles tendon reflex was formerly used to assess indirectly the thyroid function. Prolongation of the mechanical response (specifically the time when the velocity of muscle relaxation reaches its maximal value) is symptomatic for thyroid hypofunction, where as it is abbreviated in hyperthyroidism. Methods Description of the recording: • Time of the stimulation is common for all channels and is displayed on channel 3 (EMG) by a vertical line as time 0. • The electrical component of the reflex (EMG, channel 3) begins at the isoelectric line. • Small, incidental deviations are caused by instabilities in mutual position of the electrode and the the skin during tapping the tendon. • A positive deflection (downward directed) appears with a latency t1. • A negative deflection (upward directed) and the second positive deflection follow (see the Fig.) • The triphasic curve represents CMAP. Its shape depends on position of the electrodes. • Duration of CMAP is given by the interval t2-t1. • Physiological values: t1 = 32 +/- 3ms, CMAP duration = 14 +/- 2.5ms. Polygraphic record of the Achilles tendon reflex t1 t2 t3 t4 t5 EML čas0 movement velocity of muscle contraction and relaxation electromyography CAMP Physiological values: • t1 : 32 ± 3 ms • t3 : 120 ± 20 ms • t5 : 320 ± 50 ms • CAMP (t2 - t1): 14,9 ± 2,5 ms time of maxima contraction time of maximal contraction velocity time of maximal relaxation velocity ground electrode (green) active electrode (yellow) reference electrode (black) goniometer (a box with a cable located on the medial side of the calf) PC Position of goniometer and electrodes • Write results from 5 records in the table record 1 2 3 4 5 mean phys. values (ms) t1 32 ± 3 t2 t3 120 ± 20 t4 t5 320 ± 50 CAMP 14,9 ± 2,5 Stretch reflexes https://www.youtube.com/watch?v=0sqCIzuotWo Babinski and plantar reflex: https://www.youtube.com/watch?v=HnX4bH1WRHQ https://www.youtube.com/watch?v=iV_a2WSbdM8 Reflexes used in brain dead examination: https://www.youtube.com/watch?v=Nty6bICZlyA From 8:40 min https://www.youtube.com/watch?v=qiZBGFWvv4E&t=524s Vestibuloocular reflex https://www.youtube.com/watch?v=j_R0LcPnZ_w Pupillary reflex https://www.youtube.com/watch?v=aM0ipmW3ikc Interesting links