Adobe Systems 1 XXVII. Examination of reflexes in man Physiology - practices Department of Physiology, Faculty of Medicine, LF MU Adobe Systems Examination of reflexes in man 2 Reflexes ̶Reflex: is an involuntary response of an organism triggered by stimulation of receptors – the main functional unit of the nervous system based on negative feedback ̶Reflex arch: consists of 1. receptor, 2. afferent pathway, 3. centre (brain or spinal cord), 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 a reflex response to a certain stimulus, we can topically diagnose and point out the place of nervous system disablement. ̶Function: correction of changes or protection against damage. Adobe Systems 3 Examination of Reflexes ̶When examining reflexes the following items are considered: ̶Elicitability of a reflex – if we can elicit the reflex ̶Quantitative changes in the response – the strength or symmetry of the response ̶Qualitative changes – if the response is as expected or different ̶Proprioceptor reflexes (stretch reflexes) ̶Most reflexes are elicited by fast, springy tapping of 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 of a voluntary contraction of antagonistic muscles should be used if the reflex can not be elicited even in a correct procedure, e.g. Jendrassik’s manoeuvre (the patient flexes both sets of fingers into a hook-like form and tries to put them apart) Sometimes it is necessary to distract the subject’s attention by asking him to perform a simple calculation (repeated subtraction of a number). Adobe Systems 4 Classification of reflexes Receptor Afferent pathway Effector Efferent pathway interoreceptors exteroreceptors proprio- receptors somatic autonomic combined spinal brain axonal, ganglionic central extracentral e.g.: baroreflex, chemoreflex, emetic reflex, gastroileal reflex genesis unconditioned (congenital) conditioned (acquired) senses e.g.: stretch reflex (patellar, bicipital), inverse stretch reflex e.g.: vestibulo-ocular, pupillary e.g.: baroreflex, chemoreflex e.g.: flexor reflex e.g.: cough reflex e.g.: stretch, flexor reflex e.g.: red dermographism e.g.: vestibulo-ocular, pupillary reflex e.g.: stretch reflex (patellary, bicipital Centre number of synapses monosynaptic, polysynaptic viscero- receptors skin Adobe Systems Examination of reflexes in man 5 Reflexes in practicals ̶Proprioceptive reflexes (myotatic, stretch): ̶jaw thrust reflex (masseter), nasopalpebral ̶biceps, styloradial, triceps ̶patellar (knee jerk), ankle jerk (Achilles‘ tendon reflex), medioplantar ̶Exteroceptive reflexes (cutaneous and mucous): ̶corneal and conjuctival, palatal ̶epigastric, mesogastric, hypogastric ̶plantar ̶Sensory reflexes: ̶pupillary reponse to light (direct or indirect), to convergence, to pain ̶twinkle reflex Adobe Systems Examination of reflexes in man 6 Proprioreceptors in the muscle efferent fibre of γ-motoneuron - innervates contractile part of muscle spindle afferent neural fibre Ia intrafusal fibres muscle spindle muscle length reception extrafusal fibres (muscle fibres) Golgi tendon organ regulation of tension in muscle efferent neural fibre of α-motoneuron afferent fibre Ib, II Apart from muscle spindles and Golgi tendon organs, proprioceptors in joints registering the position of a joint also exist Adobe Systems Stretch reflex – reflex arch (myotatic reflex: monosynaptic, proprioceptive) extensor flexor muscle spindle synapse neural fibre of α-motoneuron neural fibre Ia body of neuron Ia percussion hammer spinal cord Receptor: Muscle spindle Main function: Unwanted extension causes contraction of the muscle (containing muscle spindle). Reflex serves as a correction to unwanted prolongation of muscles - maintaining of erect posture, defying gravity (closing of the mouth) Elicitation: By percussion of the tendon of a muscle with a reflex hammer, passive and involuntary prolongation of the muscle occurs. The muscle spindle is triggered and a reflexive muscle contraction is started. Adobe Systems Stretch reflex – correction of muscle spindle sensitivity α-motoneuron extensor flexor muscle spindle γ-motoneuron extrapyramidal pathways pyramidal pathways spinal cord The activity of γ- motoneurons regulates muscle spindle sensitivity via contraction of intrafusal fibres. Shortening of muscle spindle fibres leads to higher sensitivity to a stimulus. The desired change of muscle length activates simultaneously γ-motoneurons and α- motoneurons. Intrafusal and extrafusal fibres extend simultaneously and the sensitivity of the muscle spindle does not change. Adobe Systems Golgi tendom reflex, inverse stretch reflex (bisynaptic, proprioceptive) Function: An increase of tension in a tendon causes the 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. extensor flexor Golgi tendon organ neural fibres Ib, II - inhibitory interneuron excitatory interneuron + α-motoneuron spinal cord Receptor: Golgi tendon organ Adobe Systems 10 Axon reflex (extracentral) ̶The impulses generated in the sensory nerve are transmitted anti-directionally (upstream) to other branches of the sensory fibre ̶When irritating the skin receptors, the pulse is converted to nearby arterioles innervated by the same fibre body of sensoric neuron spinal cord skin nerve endings arteriolar nerve endings antidrome axon reflex arch orthodrome conduction ̶Substance P from the nerve endings dilates the arteriol and increases the vascular permeability (red dermographismus) ̶In addition, histamine released from mast cells also dilates the vessels and increases their permeability ̶ Adobe Systems Examination of reflexes in man 11 Pupillary responses ̶Constriction of pupils in reaction to light ̶symmetrical constriction of both pupils ̶miosis – constriction of pupils, parasympathetic activity ̶mydriasis – dilatation of pupils, sympathetic activity ̶centre of reflex: brainstem (diencephalon) ̶ https://www.researchgate.net/figure/Schematic-drawing-of-the-pupillary-light-reflex-pathway- By-way-of-the-optic-tract-the_fig1_318593544 Adobe Systems 12 XXVIII. Recording of Achilles’ tendon reflex Physiology - practices Department of Physiology, Faculty of Medicine, LF MU Adobe Systems Recording of Achilles’ tendon reflex 13 Recording of Achilles’ tendon reflex Aim: ̶To learn how to register electrical and mechanical responses of Achilles’ tendon reflex. ̶After measuring particular values get an idea about the time sequence of electrophysiological processes of reflex response, which start with stimulation of appropriate receptors and ends up in muscle relaxation. ̶Achilles' tendon reflex – monosynaptic, proprioceptive, somatic, stretch, unconditioned, spinal, monosegmental ̶ Adobe Systems Recording of Achilles’ tendon reflex 14 ̶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 (mainly in the S1 segment) which in turn activate the 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 using 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. Adobe Systems 15 Methods ̶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 fibres and eventually the amount of light converted to an electric signal. The first derivative of the signal yields the velocity of contraction and relaxation. ̶Electrodes are placed on the calf and an electromyographic curve is obtained. ̶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 of thyroid hypofunction, whereas it is shortened in hyperthyroidism Adobe Systems Recording of Achilles’ tendon reflex 16 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 on the right leg Adobe Systems Polygraphic record of the Achilles tendon reflex t 1 t2 t3 t4 t 5 EML time 0 movement velocity of muscle contraction and relaxation electromyography Physiological values: •t1 : 32 ± 3 ms •t3 : 140 ± 20 ms •t5 : 320 ± 50 ms 2 1 •CAMP (t - t ): 14,9 ± 2,5 ms end of contraction, start relaxation time of maximal contraction velocity time of maximal relaxation velocity = time duration of reflex Adobe Systems Define footer – presentation title / department 18 Example of how to process the protocol: ̶Write results from 5 records in the table ̶ ̶ ̶ ̶ ̶ ̶ In conclusion: ̶Compare acquired values to physiological values ̶High t5 values may point to reduced thyroid function and vice versa ̶ ̶ 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 Adobe Systems 19 Interesting links ̶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 ̶