PHYSIOLOGY 2.1 Somatosensory Physiology PDF

PHYSIOLOGY MODULE 2.1 LE Somatosensory Physiology...

PHYSIOLOGY MODULE 2.1 LE Somatosensory Physiology 2 Dr. Edroico Brillante, MD | October 8, 2024 | Trans #8 TABLE OF CONTENTS I. SOMATOSENSORY SYSTEM A. Somatosensory System IV. MECHANORECEPTORS V. PAIN PATHWAY A. Neospinothalamic Pathway 💬 I.SOMATOSENSORY SYSTEM Everyday, we are bombarded by a lot of stimuli. From the moment you open your eyes, light enters your eyes. Once these B. Nervous System B. Paleospinothalamic Pathway C. Somatosensory Pathway VI. ANALGESIA SYSTEM sensory information reach our consciousness, it now becomes a D. Adequate Stimulus VII. REFERRED PAIN sensation. E. Differential Sensitivity of VIII. THERMORECEPTORS A.SOMATOSENSORY SYSTEM Receptors IX. GENERAL CLASSIFICATION F. Labeled Line Principle OF NERVE FIBERS G.Receptive Fields X. DERMATOMES II. TRANSDUCTION PROCESS XI. SENSORY PATHWAYS III. SOMATIC SENSATIONS XII. PRE-TEST A. Classification of Somatic Senses XIII. POST-TEST XIV. REFERENCES [PPT] 💬 LEGEND Figure 1. Somatosensory System 💬 Must Lecturer Book Prev. YouTube PPT Everyday we receive thousands of stimulation. ❗️ Know 💬 📖 Trans 📋 🔺 Video 🖥️ These stimuli are transduced into our nervous system, and we LEARNING OUTCOMES 💬 receive them as sensation. Sensation vs. Perception → Sensation: ability to feel, hear, see, taste At the end of this module, the future BEDAN MD must be able to: 1. Define the following terms: 💬 → Perception: interpreting information that comes to the brain Transduction → The stimulus (ex. light, sound) is converted into an action Sensation potential or electrical signal Perception Remember, the brain can only process electrical signals. Receptor It can not process light, sound, etc. These should be Sensory Unit converted into something that can be interpreted by the Receptive Field Classify the sensory receptors 2. Explain how receptors function as transducers in the initiation of 💬 brain, which is an electrical signal. Sensation → Once it’s converted into an electrical signal, it is now nerve impulses conducted. Runs towards the central nervous system for us to 3. Name the parameters determined when there is effective stimulation of sensory receptors: Modality of Sensation 💬 be able to have sensation. Perception → Once the sensation has meanings, it is now called a Stimulus intensity perception. Localization ○ Lateral inhibition mechanism B. NERVOUS SYSTEM ○ Two-point discrimination threshold 4. Differentiate the sensory receptors based on their adaptation characteristics Fast adapting receptors Slow adapting receptors 5. Classify the different somatic senses Name the types of mechanoreceptive senses and its receptors Name the two thermoreceptive senses Name the types of nociceptive senses ○ Differentiate somatic from visceral pain ○ Differentiate between acute and chronic pain 6. Trace the 2 pain pathways Neospinothalamic tract Paleospinothalamic tract 7. Explain pain suppression Gate control theory Analgesia system 💬 8. Name the sensory pathways for transmitting somatic signals to the Figure 2. Nervous System [PPT] CNS The nervous system is divided into two portions, the Central Dorsal Column Pathway Spinothalamic Pathway 💬 Nervous System and Peripheral Nervous System. Central Nervous System 💬 → Brain and spinal cord Peripheral Nervous System LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 1 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 → anything outside the brain and spinal cord → “Afferent”: nerves that bring information from the periphery to the CNS. (Sensory division of PNS) PERIPHERAL NERVOUS SYSTEM → “Efferent”: nerves that bring information from the CNS to the 💬 periphery. (Motor division of the PNS) Special senses → The sensation is received by the receptors localized within special organs. 💬 → Ex. smell, taste, sight, hearing, balance Special Somatic Afferent 💬 → Sight, hearing, balance Special Visceral Afferent → Smell, taste → Receptors located within mucosal surfaces C. SOMATOSENSORY PATHWAY 💬 [PPT] Figure 3. Peripheral Nervous System The peripheral nervous system is anything outside the brain 💬 and spinal cord. Divided into two: → Sensory division 💬 → Motor division Imagine the peripheral nervous system as a highway. → There’s Northbound and Southbound. 💬 One goes upwards, and the other goes downwards. Sensory division → One that goes upwards. 💬 → Brings information from the periphery to the CNS. Motor division → One that goes downwards. → Brings information from the CNS towards the periphery. SENSES [PPT] Figure 4. Major Components of a Somatosensory Pathway Sensory receptors will receive the stimulus, and it will bring information to the spinal cord or brain stem depending on the pathway being followed, then it will proceed to the thalamus then 💬 the cortex. Imagine you are driving from Manila to Vigan. You will pass thru 3 expressways (NLEX, SCTEX, TPLEX) and just like the information being passed through, for you to be able to reach the brain, you have to go through 3 expressways: the blue line, red line and black line (from the given picture). You also have to pass through toll gates before entering the expressways. In summary, you will enter the toll gate – NLEX (sensory receptor) stopover at a gas station (dorsal root ganglion) enter SCTEX (spinal cord or brainstem or second order neuron) 💬 [PPT] proceed to the next toll gate – TPLEX (thalamus or third order Figure 3. Senses Senses are divided into: neuron) – then proceed to the last expressway (cortex preferably the primary somatosensory cortex). → General senses 💬 → Special senses General senses 💬 INFORMATION CONVEYED → Modality → The sensation is received by the receptors distributed over a sensation we’re trying to know (pain, temperature, large part of the body. pressure, touch) → The rest of the body has it. Each modality has a sub-modality → Divided into two: − Temperature (modality) – cold, warm (sub-modality) Somatic − “soma” means body − “bodily sensations” 💬 − Taste – sweet, sour, umami You want to know what sensation you received → Location − located in skin, muscle, and joints − Ex. touch, pressure, proprioception, temperature, pain General senses Visceral Where the sensation was felt − located in internal organs or “lamang loob” → Duration 💬 − Ex. pain, pressure How long have you been receiving this stimulus; is it still If the receptors are distributed over a large part of the body, there? Is it not there anymore? → Intensity and the receptors are located in skin, muscle, and joints, they are The amount or force of stimulus received (gaano kalakas called general somatic afferent. yung stimulus) Mild pain, moderate pain, intense pain LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 2 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 SENSORY RECEPTORS E. DIFFERENTIAL SENSITIVITY OF RECEPTORS Provide input to the nervous system by detecting sensory stimuli such as touch, sound, light, pain, cold and warmth. Activated by stimuli in the environment Highly specialized structures that are located between the nervous system and the “outside world”. Most basic function of the sensory receptors is converting the stimuli into action potentials. Respond to environmental changes by producing action potentials that are transmitted to the central nervous system → This process is called transduction. 💬 Exhibit differential sensitivities. “Gateways” to enter the nervous system. You cannot enter the nervous system if you will not go through the sensory receptors. Table 1. Types of Sensory Receptors and the Stimuli they detect Type of Sensory Stimulus Detected Receptors mechanical compression (stretching) MECHANORECEPTORS Stretching of the receptor or of tissues adjacent to the receptor Touch and pressure Located in muscle, tendons Figure 5. Types of Sensory Receptors and Their Structural and joints and relay information Variations about muscle length and PROPRIOCEPTORS 💬 tension Receive information in actions such as contraction of Each receptor is highly sensitive to one type of stimulus and is almost non-responsive to the other types of sensory stimulus → This is what we call adequate stimulus. muscles We have different sensory receptors and each modality has a THERMORECEPTORS Changes in temperature, with specific receptor: some receptors detecting cold → Pressure – only detected by the Pacinian corpuscle. and others detecting warmth → Pain – detected by the free nerve endings Physical or chemical damage → Light waves or electromagnetic waves – only receptors occurring in the tissues that is assigned are the rods and cones converted into electrical signals The rods and cones in our eyes are highly specialized to NOCICEPTORS (pain receptors) to detect pain Mediate potentially harmful stimuli such as pain, extreme 💬 detect the electromagnetic waves or the light. Why can’t skin detect light? – because we don’t have the receptors for light in our skin; we only have them for our 💬 heat and extreme cold pain When you hear it, think of eyes. Free Nerve Endings → can detect touch, pressure, pain, temperature, tickle and itch Light on the retina of the eye → can be rapidly adapting (tickle and itch) or slowly adapting ELECTROMAGNETIC (electromagnetic waves) (Pain and temperature) RECEPTORS ·Rods and cones in the retina Meissner’s Corpuscles → encapsulated receptors Taste in the month → dermis of non hairy skin, most prominently on the fingertips Smell in the nose and lips Oxygen level in the arterial → rapidly adapting blood → encode point discrimination, precise location, tapping and CHEMORECEPTORS Osmolality of the body fluids vibration (low frequency) (chemo = chemical) (concentration of blood) → used for two-point discrimination Carbon dioxide concentration Merkel’s Receptors Other factors that make up the → usually found together with Meissner’s corpuscles in non hairy chemistry of the body skin → Iggo dome/touch receptor - group of Merkel’s discs → slowly adapting with very small receptive fields D. ADEQUATE STIMULUS → localizing touch sensations and determining texture A stimulus to which a sensory receptor is highly sensitive. → Tactile discs *Information conveyed = MODALITY same function as Merke’s disc but found in hairy skin also slow adapting Table 2. Adequate Stimulus Hair Follicles Receptos → arrays of nerve fibers surrounding hair follicles Sensory Receptor Adequate Stimulus → excited by displacement of hair Free nerve endings Pain → rapidly adapting Rods and cones Light → encode velocity and direction of movement across the skin Hair cells in the ears Sound Ruffini’s Corpuscles Taste receptor Taste → dermis of non hairy and hairy skin and in joint capsules Pacinian corpuscle Touch/Pressure → slowly adapting Olfactory receptor Smell → stimulated when skin is stretched LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 3 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 → encode prolonged touch, pressure and stretch and degree of rotation TYPES OF RECEPTIVE FIELD Pacinian Corpuscles → encapsulated receptors Table 3. Types of Receptive field → subcutaneous layers of non hairy and hairy skin and in muscle TYPE 1 UNITS TYPES 2 UNITS → very rapidly adapting Small receptive fields with Wider receptive fields with → encode vibration (high frequency) and tapping well-defined borders poorly defined borders More precise perception Less precise perception F. LABELED LINE PRINCIPLE Circular or ovoid, within Only a single point of Adequate stimulus will only be accepted by their respective which there is relatively maximal sensitivity from sensory receptors. uniform and high sensitivity which there is a gradual 1 receptor :1 stimulus to stimuli that decreases reduction in sensitivity with → 💬 For example: If a sound wave reaches the CNS, it knows that the hair sharply at the border. distance. → 💬 cells received this stimulus. The stimulus received by the CNS is pressure, it knows 💬 Type 2 units don’t have a specific shape because they have poorly defined borders. that the sensory receptor that was stimulated will be the Pacinian corpuscles, because they are the one made to receive pressure. Figure 6. Labeled line principle [Video Lecture] G. RECEPTIVE FIELDS Receptive field is an area of the body/skin from which a sensory Figure 8. Receptive field types [Video Lecture] 💬 neuron receives its information. Simplified Concept: Let’s assume that the hand has 5 💬 Higher threshold – needs more pressure for the stimulus to 💬 Lower threshold – needs less pressure for the stimulus to be receptive fields, 1 for each finger. Each receptive field is be felt. connected to a neuron. Imagine that each neuron will have a 💬 To test whether type 1 or type 2: corresponding light bulb in the brain. When you touch receptive felt. field A, light bulb A in the brain will light up. If you touch receptive field B, light bulb B will light up. → Start with a stimulus outside the receptor field, then go Each receptive field will have one neuron associated with it. This closer towards the border – At this point you will not feel neuron will be responsible for bringing information to the CNS. anything. → The stimulus touches the border – you will need higher pressure/intensity to feel the stimulus. → The stimulus is inside the receptive field – you won’t need much pressure/intensity to feel the stimulus. It is now sensitive. → Refer to Figure X., high points in the graph for Type 1 RF represent the borders of the receptive field. Stimulus decreases sharply at the border so the threshold of the pressure must be increased. While Type 2 RF, there is just gradual decrease of stimulus at the borders. Figure 7. Receptive field [Video Lecture] LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 4 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 In Figure 10, We have 3 overlapping receptive fields. When a stimulus hits neuron B, 3 receptive fields are stimulated, the periphery of Receptive field A, the middle of Receptive field B, and the periphery of Receptive field C. Remember, since the center of receptive field B is more sensitive than the periphery or edge of Receptive field A and C, the stimulus will have a greater intensity of touch in B and lesser in receptive field A and C causing the difference in Action Potential frequency in figure 1.. The brain will process these signals by sending many receptive field signals from B and small signals from receptive field A and C. The brain will then identify that the stimulus originated in receptive field B and in the edges of Figure 9. Two-Point Discrimination Test receptive field A and C hence the Overlapping of Receptive 💬 fields. Two-Point Discrimination is a test that will be able to know how precise it is to locate a sensory stimulus. The figure X that is shown above is how the Two-Point Discrimination test is done. We put the points on our finger and LATERAL INHIBITION see if we could feel a two point pressure or a single point pressure, we repeat it until we could only feel a single point pressure. Repeat the process on our back and compare the results 💬 The result would be that the back would feel a single point even if the object applying pressure is still wide apart compared to the sensation felt in our hands where we have to move the object closer in order to feel a single pressure point. The reason behind it is that our backs have a larger receptive field while our hands have a smaller receptive field. 💬 What are the areas that are type 1 and the areas that are type 2? Type 1 areas would be the areas that we need precise localization such as our fingers and face, while those areas that we don't need very specific localization such as the back and legs are type 2. OVERLAPPING OF RECEPTIVE FIELDS Another way of localizing sensation or stimulus is by the overlapping of the receptive fields. if you touch the point of stimulation, your stimulus lands 💬 on the periphery of A, middle of B, and periphery of C. As i mentioned earlier, you need to apply more pressure on the edge or the peripheral in order to feel the sensation while you only Figure 11. Lateral Inhibition phenomenon need a little touch in order to detect the pressure. In Figure 11, ❖ When receptive field B is stimulated due to stronger signals, Afferent Neuron B will send inhibitory signals to Neuron A and Neuron C. ❖ Original signal of neuron a and c is lessened (due to inhibition) while ascending to the brain. ❖ RED LINE in Figure 2 is an Interneuron because it is a connection between neurons. Interneurons have the capacity to either stimulate or inhibit a neuron. For example, since neuron B is stimulated, it will send inhibitory signals to Neuron A and Neuron C causing fewer signals to be received by the brain from Neuron A and Neuron C thus lower Action-potential frequency as shown in Figure 1. Vise versa, if Neuron A is stimulated, it will send inhibitory signals Neuron B. Lateral Inhibition- “iniinhibit mo yung katabi mo para Figure 10. 3 afferent neurons with overlapping receptive fields. ikaw ang masgshine” Namely, Overlapping field A, Overlapping field B, and Overlapping field C. LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 5 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 RECEPTOR ADAPTATION pressure on a specific part of Sensory receptors adapt either partially or completely to your body, for instance, your any constant stimulus after a period of time. finger. Immediately touching it, ❖ For example, the sensation we feel when putting it can be detected readily by on clothes will not be felt after a period of time. the pacinian. If you This is because of the receptor that was continuously press that finger, triggered when we put on our clothes “adapts”. it will adapt and you will not When a continuous sensory stimulus is applied, the feel it eventually. receptor responds at a high impulse rate at first and then But, if you remove the at a progressively slower rate until, finally, the rate of pressure, the pacinian action potentials decreases to very few or to none at all. corpuscle will feel or detect it The pattern of adaptation differs among different types of again. receptors. That is what it means by the onset and offset of a stimulus or if a changing stimulus is present. Pacinian corpuscles Merkel’s receptors Meissner’s Ruffini endings corpuscles Pain receptors Hair receptors Chemoreceptors Baroreceptors Joint capsule receptors Muscle spindle 💬 Another example stimulus is temperature. The minute you dive in a pool, unang dive mo, lamig na lamig ka but when you stay for long periods, you will feel less cold (adapted) eventhough, technically, the 💬 temperature of the water did not change. ADAPTATION - is the reaction of the receptors to the prolonged stimulus. II.SENSORY TRANSDUCTION TABLE 5. Types of Sensory Transduction Mechanisms and Their Figure 12. Adaptation Rates of Various Sensory Receptors to Effects on Ion Channels Sustained Stimuli Mechanical Mechanical deformation of the receptor, which stretches the receptor membrane and In figure 12, we have four receptors: Hair receptor, Pacinian opens ion channels corpuscle, muscle spindle and joint capsule receptors. Chemical Application of a chemical to the membrane, The stimulus is continuous. In PACINIAN CORPUSCLE, after a which also opens ions channels very few seconds, it cannot detect the stimulus already because it has already adapted. On the other hand, in HAIR RECEPTORS in which it detects the movement of hair, if the hair Thermal Change of the temperature of the is continuously moving, after 1 second, it cannot detect the membrane, which alters the permeability of movement of that single hair because it’s already adapting. the membrane The MUSCLE SPINDLE detects the stretching of the muscle. For Electromagnetic Effects of electromagnetic radiation , which instance, if your triceps is stretched, with continuous stimulus Radiation either directly or indirectly changes the (stretching), even after long periods of time na nakastretch, it will receptor membrane characteristics and always be detected by the muscle spindle. This is because it allows ions to flow through membrane needs to inform the brain about the location of the extremities. It channels is important when it comes to balance and movement. ❗️ ** The main point is, to fire a potential, YOU HAVE TO OPEN ION CHANNEL So, the Pacinian corpuscle and hair receptors are rapidly adapting and the joint capsule and muscle spindle are slow-adapting receptors. they may take hours, days before they fully adapt. 📋 Process by which an external or environmental stimulus would be activated and converted into electrical energy. Conversion typically involves the opening or closing of ion channels in the receptor membrane, which leads to a flow of ions TABLE 4. Patterns of Adaptation (current flow) across the membrane. Phasic Receptors Tonic Receptors Current flow then leads to a change in membrane potential, called Rapidly adapting receptors Slowly adapting receptors receptor potential, which increases or decreases the likelihood that action potentials will occur. Primarily detect onset and Detect steady pressure, and “From stimulus, it becomes an electrical signal.” offset of a stimulus and a encode duration and intensity changing stimulus. of stimulus. ❗️ For example, si Pacinian corpuscle, it detects pressure. So if you apply LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 6 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 Figure 13: Transduction Process In figure 13, zooming in on the branches of our neurons. Yong pinakadulong part, ‘yong RECEPTOR MEMBRANE. ‘yong may Node of Ranvier na part, that is the NEURON itself. We have two types of potentials → Action potential- happens on the neurons itself → Receptor potential- form the name itself, potential on the receptor membrane This how intensity is detected → On ACTION POTENTIAL, it is all-or-none while with RECEPTOR potential, it is graded. Looking at the picture, when the stimulus is weak, the potential in the receptor membrane is also weak but THERE IS NO ACTION POTENTIAL because the threshold is not reached. When the stimulus is stronger that it reaches the THRESHOLD, the potential on the receptor membrane will be stronger also and the there is firing of action potential (only limited and with same identity with each potential) As the stimulus becomes stronger and EXCEEDS the Figure 14: Pacinian Corpuscle Transduction Process threshold greatly, the receptor potential becomes stronger also and the action potential FIRES MANY POTENTIALS BUT ❗️ WITH SIMILAR INTENSITIES. Height is the AMPLITUDE and the number is the In the Pacinian Corpuscle, the tip of a neuron has a capsule. The picture above will help to visualize the pacinian corpuscle. ❗️ FREQUENCY of the potential. In receptor potential, the AMPLITUDE becomes taller and In figure X, we zoomed in on a pacinian corpuscle which ❗️ taller as the stimulus becomes stronger, detects PRESSURE. In action potential, the FREQUENCY increases but the When pressure is applied, mechanical compression will show amplitude stays the same even stimulus continuously a DEFORMED AREA (D) that opens ion channels intensifies. (RECEPTOR MEMBRANE POTENTIAL HAPPENS), making the inner cell membrane LESS NEGATIVE/MORE POSITIVE because of the sodium ions entering the cell. If the stimulus is intense enough reaching the threshold, the sodium ions on the NERVE ITSELF will open up and ACTION POTENTIAL begins. If the pressure does not reach the threshold, the potential is until THE RECEPTOR MEMBRANE ONLY, hindi na aabot sa nerve to fire action potential. LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 7 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 → Slowly adapting but with very small receptive fields → Localizing touch sensations and determining texture → Group of Merke’s discs = Iggo Dome/Touch receptor → 💬 → Merke’s discs in hair skin = Tactile discs Usually found in junction with dermis and epidermis Ruffini Endings → Located in dermis of non-hairy and hairy skin and in joint capsules → Slowly adapting → Stimulated when skin is stretched → Prolonged touch, pressure, stretch, degree of join rotation Hair Follicle Receptors → Nerve fibers surrounding hair follicles → Excited by displacement of hair → Rapidly adapting → Encode velocity and direction of movement across the skin Free Nerve Endings → Can detect touch, pressure, pain, temperature, tick and itch Figure 15: Action Potential VS Receptor Potential → Rapidly adapting (tickle, itch) As we increase the intensity of the stimulus, the receptor potential becomes stronger also. And as soon as it reaches the threshold, → 💬 → Slowly adapting (pain and temperature) Unencapsulated, given that they are free nerve endings Pain Receptors it will fire an action potential. LOOK, the height of the action → Also called nociceptors potentials are all the SAME but it increases in number. → Free nerve endings → Found in the: Superficial layers of the skin III. SOMATIC SENSATIONS Periosteum A. CLASSIFICATIONS SOMATIC SENSES Arterial walls Joint surfaces Falx and tentorium Mechanoreceptive Somatic Sense (Touch, Pressure, and Pain stimuli Proprioception Sense) → Pain can be elicited by three types of stimuli Thermoreceptive Somatic Senses (Temperature Sense) Mechanical - both fast and slow Nociceptive Somatic Senses (Pain Sense) Thermal - both fast and slow Chemical - slow only TABLE 6. Receptors − Bradykinin Receptor Tonic Receptors Examples − Serotonin Exteroceptive Contact of the skin Mechanoreceptive, − Histamine with objects in the Nociceptive, − Potassium ion external world thermal receptors − Acids in the skin − Acetylcholine Proprioceptive Body and limb Receptors in the − Proteolytic enzymes position joints, muscles, and tendons Enteroreceptive Internal state of Receptors that TYPES OF PAIN the body detect gut Fast Pain distension or → Felt within.1 seconds after a pain stimulus bladder fullness → Described as sharp, pricking, acute pain, electric pain → Not felt in most deep tissues of the body → Conducted by A-delta fibers IV. MECHANORECEPTORS Slow Pain Meissner's Corpuscles → Begins only after 1 second or more and then increases slowly → Encapsulated receptors over many seconds → Found in dermis of NON-HAIRY/GLABROUS skin → Described as slow, burning pain, aching, throbbing, → Most prominent on fingertips and lips nauseous and chronic pain → Point-discrimination, precise location, tapping and vibration → Usually associated with tissue destruction 💬 (low-frequency) Small, Type I Receptive Fields → Can occur in both skin and deep tissue or organ → Conducted by C fiber 💬 → Rapidly adapting Kahit may continuous stimulus, ang madedetect lang is on and off V. PAIN PATHWAY Pacinian Corpuscles A. NEOSPINOTHALAMIC PATHWAY → Encapsulated receptors Not seen in lower forms of animals → Found in subcutaneous layers of non-hairy and hairy skin FAST PAIN and muscle Glutamate - Usual neurotransmitter → Very Rapidly adapting Pathway: → 💬 → Vibration (high-frequency) and tapping are for deep pressure Merkel’s Disk Pain Stimulus → Free Nerve Endings (Create Receptor Potential) → A Delta Fiber → lamina I (Dorsal horns of Spinal Cord) → decussates to opposite side → Neospinothalamic tract → → Usually found with Meissner’s corpuscles in non-hairy/glabrous anterolateral columns → reticular areas or thalamus → ventrobasal skin complex (Cerebrum) LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 8 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 VII. REFERRED PAIN Phenomenon where a person feels pain in a part of the body that is partly remote from the tissue causing the pain → Ex. Pain in one of visceral organs (Heart) is referred to an area on the body surface (Left Upper Arm) Figure 16. Pain Pathway Reticular Formation Part of the Brain that keeps us awake → Some of the A Delta Fibers go here Figure 18. Areas of the Body Affected by Referred Pain from Reason why we can’t sleep with pain Visceral Organs Cause: Neuron 1 receives information from both Visceral and Skin nerve B. PALEOSPINOTHALAMIC PATHWAY fiber because it synapses there Seen in lower form of animals → Pain stimulation from Visceral NF → Neuron 1 (Brain will SLOW PAIN interpret as from Skin NF) → Cause Pain in Skin NF(Referred Neurotransmitter Involved: Glutamate and Substance P Pain) Pathway: C Fiber → laminae II and III (Substantia gelatinosa of spinal cord) → lamina V → Decussates to the opposite → Anterolateral columns → Brainstem (Reticular Formation, tectal area of midbrain, periaqueductal gray region) VI. ANALGESIA SYSTEM Pain Suppression Involves: → Periaqueductal Gray and Periventricular Areas “Peri” - beside − Periaqueductal Gray Area - Beside Aqueduct of Sylvius − Periventricular Area - Beside 3rd Ventricle → Raphe Magnus of the Nucleus (In Pons) → Pain Inhibitory Complex (Dorsal Horns of Spinal Cord) Neurotransmitter: Figure 19. Mechanism of Referred Pain: Convergence of Visceral Enkephalin - Inhibits type C and A Delta fibers and Skin Nerve Fibers Serotonin - Stimulates neurons in Spinal Cord to release APPENDICITIS Enkephalin (End goal) Nerve Fiber in Appendix and Umbilicus (Belly Button) synapses in → Brain Stem and Spinal Cord - Enkephalin and Dynorphin T10 (Opiate and Lower Quantity) → Sometimes, pain stimulus in Appendix will have a referred pain → Hypothalamus and Pituitary Gland - Beta Endorphin in the Belly Button PAIN FOR RIGHT LOWER QUADRANT → Inflamed appendix touches the Peritoneum (covering of abdomen) → Stimulate NF in L1 → Pain in RLQ Figure 20. Pain Pathways in Appendicitis: Referred Pain and Right Figure 17. Analgesia System Lower Quadrant Pain LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 9 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 VIII. THERMORECEPTORS 4 TYPES: → Cold Pain Less than 8C → Heat Pain Greater than 45C → Cold Receptors 8C to 36C → Warmth Receptors 📋 37C to 45C Slowly adapting receptors that detect changes in the skin 📋 temperature 📖Stimulated by changes in metabolic rates within the receptors Pain Receptors are only stimulated by extreme heat or cold, and along with warm and cold receptors they are responsible for “Freezing Cold” and “Burning Hot” sensations. Figure 22. Physiological Classifications and Functions of Nerve Fibers IX. GENERAL CLASSIFICATION OF NERVE FIBERS Type A fibers are the typical large and medium sized myelinated fibers of spinal nerves. Figure 21. Thermal Receptor Activity: Responses of Cold and Warm Type C fibers are the small unmyelinated nerve fibers that Receptors to Temperature conduct impulses at low velocities. → C fibers constitute more than half of the sensory fibers in most Table 7. Comparison of Cold and Warm Receptors peripheral nerves, as well as all the post ganglionic autonomic COLD RECEPTORS WARM RECEPTORS fibers. → Note: few large myelinated fibers can transmit impulses at velocities as great as 120m/sec, covering a distance that is Inactive above 36C Inactive above 45C longer than a football field in 1 second. Conversely, the smallest fibers transmit impulses as slowly as 0.5/sec, Involves TRPM8 channel Involves TRP channels in the requiring about 2 seconds to go from the big toe to the spinal receptor family of vanilloid cord. receptors Stimulus: Menthol Stimulus: Capsaicin 📖 Group Ia - Fibers from the annulospiral endings of muscle spindles. Group Ib - Fibers from the Golgi tendon organs. Transmitted by both C and A Transmitted by C Fiber Group II - Fibers from most discrete cutaneous tactile receptors and Delta Fiber from the flower-spray endings of the muscle spindles. Group III - Fibers carrying temperature, crude touch, and pricking 💬 Beyond 45C or below 8C, warm and cold receptors will overlap with pain receptors thus you feel heat or cold but it’s already pain sensations. Group IV - Unmyelinated fibers carrying pain, itch, temperature, and painful crude touch sensations. X. DERMATOMES Specific part of a body is transmitted by a specific neuron Each spinal nerve innervated a “segmental field” on the skin called a dermatome. Determine the level in the spinal cord at which a cord injury has occurred when the peripheral sensations are disturbed by the injury → ex. if you touch C5, C5 neuron will care information from that area LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 10 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 → Thermal sensations, including both warm and cold sensations → Crude touch and pressure sensations capable only of crude localizing ability on the surface of the body → Tickle and itch sensation → Sexual sensations → consists mainly of group III and IV nerve fibers (small myelinated and unmyelinated nerve fibers) 1st order neurons: Dorsal root ganglion 2nd order neurons: Dorsal horn laminae → Send out fibers that cross immediately in the anterior commissure to the opposite anterior and lateral white columns and ascend as the spinal lemniscus 3rd order neurons: VPL of the thalamus → Sends impulses that pass through the posterior limb of the internal capsule to reach the cortex 4th order neurons: Post central gyrus/Primary Somatosensory complex 💬 THALAMUS – “major relay center” Dorsal column and anterolateral pathway passes the thalamus except OLFACTION. Figure 23. Dermatome Map: Segmental Fields of Spinal Nerve Innervation XI. SENSORY PATHWAYS 📋 DORSAL COLUMN – MEDIAL LEMNISCAL PATHWAY Transmits information about: → Touch sensations require a high degree of localization of the nucleus. → Touch sensations requiring transmission of fine gradations of intensity → Phasic sensations, such as vibratory sensations → Sensations that signal movement against the skin → Position sensations from the joints → Pressure sensations related to fine degrees of judgment of pressure intensity → consists mainly of group I and II nerve fibers (large myelinated nerve fibers) 1st order neurons: Dorsal root ganglion → signal pass directly to the posterior white columns on the same side and ascends as either the fasiculus gracilis (lower body) or fasciculus cuneatus(upper body) 2nd order neurons: Nucleus gracilis & Nucleus cuneatus of the medulla → axons then decussate to the opposite side and ascend as the medial lemniscus → Nucleus gracilis (lower body) → Nucleus cuneatus (upper body) 3rd order neurons: VPL of thalamus → Sends impulses that pass through the posterior limb of the internal capsule to reach the cortex 4th order neurons: Post central gyrus/ Primary somatosensory Cortex 📋ANTEROLATERAL SPINOTHALAMIC TRACT Transmits information about: → Pain LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 11 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 XII. PRE TEST Questions & Choices Answer and Rationale 1. Tactile acuity is least exhibited by The trapezius muscle is located at the back of _____ our body and has a large receptive field a. Vermillion border meaning tactile acuity is least exhibited here. b. Lingual tip E c. Palmar area d. Papillary ridge e. Area of the trapezius muscle 2. True about thalamus in the 1st order neurons somatosensory pathway? Dorsal root/ cranial nerve ganglia a. 1st order somatosensory 2nd order neurons neuron Spinal cord/ brainstem b. 5th order somatosensory 3rd order neurons neuron Relay nucleus of the thalamus D c. 2nd order somatosensory 4th order neurons neuron Sensory cortex: results in the conscious d. 3rd order somatosensory perception of stimulus neuron e. 4th order somatosensory neuron 3. Sensory nerve fiber responsible for transmission of fast pain? a. Type II b. Type Ib E c. Type IV d. Type Ia e. Type III LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 12 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 4. Type of sensory receptor responsible for detection of light? a. Electromagnetic receptor b. Thermoreceptor c. Proprioceptor d. Chemoreceptor e. Nociceptor A Mechanoreceptors: mechanical 5. Somatosensory receptor responsible compression: touch and pressure for body and limb position? Proprioceptors: relay information about a. Nociceptor muscle length and tension b. Enteroceptor E Nociceptors: pain receptors c. Mechanoreceptor Chemoreceptors: taste in the mouth, d. Exteroceptor smell in the nose, other factors that make e. Proprioceptor up the chemistry of the body 6. A generator potential Local potential pertains to the change in the a. Is a local potential electrical membrane potential of a certain cell. b. Always lead to an action It only increases the positivity of the cell reach potential A in threshold. c. Decreases threshold d. Exhibit all or none principle e. Increases threshold 7. Sensory system responsible for two Location is responsible for 2 point discrimination. point discrimination? Stimulation of sensory receptors that have a a. Location wide location will result in a less precise b. Duration A sensation. Stimulation of sensory receptors with c. Modality closer localization will result in a more precise d. Adaptation sensation. e. Intensity Anterolateral spinothalamic pathway transmits 8. True about anterolateral information about pain and thermal sensation. spinothalamic pathway? a. Second order neuron for E upper limb consists of nucleus gracilis b. Consist mainly of afferent A-gamma and C fiber type LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 13 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 c. Transmit information about discriminative touch and proprioception d. Information from lower limb synapses in the nucleus cuneatus e. Transmit information from nociceptors and thermoreceptors information 9. Sensory alteration with loss of Vibratory perception? a. Pallanesthesia b. Hypovibresia c. Hypoalgesia d. Analgesia e. Causalgia A 1st order neurons 10. In which part of the CNA does the Dorsal root/ cranial nerve ganglia first order somatosensory neuron 2nd order neurons belong? Spinal cord/ brainstem a. Spinal ganglion A 3rd order neurons b. Cranial nerves Relay nucleus of the thalamus c. Ventral horn 4th order neurons d. Posterior column Sensory cortex: results in the conscious e. Dorsal horn perception of stimulus LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 14 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 XIII. POST TEST Questions & Choices Answer and Rationale 1. Which of the following is an example Merkel’s receptors - slowly adapting of a rapidly adapting receptor? Baroreceptors - slowly adapting a. Merkel’s receptors Hair receptors - rapidly adapting b. Baroreceptors C Muscle spindle - slowly adapting c. Hair receptors d. Muscle spindle Proprioceptors - information about muscle length and tension Mechanoreceptors - mechanical compression or stretching of receptors Nociceptors - physical or chemical damage occurring in tissues Elastoreceptors - ??? 2. What general type of receptor detects muscle length and tension? a. Proprioceptors A b. Mechanoreceptors c. Nociceptors d. Elastoceptors 3. Which sensory pathway conducts Corticospinal tract - motor information from proprioceptive information? primary motor cortex to body a. Corticospinal tract Corticobulbar tract - motor information from b. Corticobulbar tract primary motor cortex to face c. Anterolateral spinothalamic D Anterolateral spinothalamic tract - pain and tract temperature d. Dorsal column - medial DCML - vibration and proprioception lemniscal system (DCML) 4. Which part of the brain is considered Hypothalamus - not involved in somatic B sensory pathway the primary sensory relay station? LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 15 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 a. Hypothalamus Thalamus - primary sensory relay station b. Thalamus EXCEPT olfaction c. Epithalamus Epithalamus - pineal gland d. Diencephalon Diencephalon - region that contains thalamus, hypothalamus, epithalamus T4 - nipple line T10 - umiblicus 5. The umbilicus lies at which dermatomal level? a. T4 b. T6 D c. T8 d. T10 6. Which of the following differentiates A-delta fibers contain a large diameter and fast pain from slow pain? myelinated. Therefore, it can conduct fast action a. It is conducted by A-delta potentials across the nervous system. It is used fibers to the spinal cord for fast pain. b. It travels through the paleospinothalamic tract c. It is usually described as A burning, aching pain d. It is usually felt after 1 second and increases over many seconds Pain can be elicited by three types of stimuli Mechanical - both fast and slow Thermal - both fast and slow Chemical - slow ○ Bradykinin 7. Which substance is considered the ○ Serotonin (5HT) most responsible for causing pain B ○ Histamine after tissue damage? ○ Potassium ion ○ Acids ○ Acetylcholine (ACh) ○ Proteolytic enzymes LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 16 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 Analgesia System Pain suppression Involves: a. Periaqueductal gray and 8. Which opiate-like substance is found periventricular areas in the brainstem and spinal cord b. Raphe magnus nucleus areas involved in the analgesia C c. Pain inhibitory complex system? Enkephalin and Serotonin d. Brainstem and spinal cord - enkephalin and dynorphin (lower quantities) e. Hypothalamus and pituitary gland - Beta- endorphin 9. This phenomenon is when a person feels pain in a part of the body that is fairly remote from the tissue causing B the pain. Referred pain: a phenomenon where a person feels pain in a part of the body that is fairly remote from the tissue causing pain. Example: pain in one of the visceral organs (heart) is referred to an area on the body surface ( left upper arm) 10. Which of the following receptors is B stimulated at 20 degrees Celsius? LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 17 of 18 TRANS 1 Ocoma PHYSIOLOGY 2.1 Somatosensory Physiology | Dr. Brillante LE 1 XIV. REFERENCES Guyton & Hall Textbook of Medical Physiology 14th Edition by Hall, John & Guyton, Arthur C.,, Published in Philadelphia, Pennsylvania: Saunders/Elsevier, 2021 Ganong Review of Medical Physiology, 25th Edition, by Barrett, Kim, Barrett, Kim E., Barman, Susan, Boitano, Scott, Brooks, Heddwen, Published: New York: MCGraw-Hill Medical, 2016 Berne & Levy Physiology 6th Edition by Berne, Robert M., 1918-2001., Koeppen, Bruce M., Published: Philadelphia: Mosby/Elsevier, 2008 Costanzo Physiology 6th Edition by Linda Costanzo Published in Philadelphia, Pennsylvania: Saunders/Elsevier, 2018 BRS Physiology 7th Edition by Linda Constanzo, 2019, Published: Lippincott and Williams & Wilkins, 2019, Canva [online]. https://www.canva.com/ (Accessed: October 2024) LE 1 Montemayor, Montero, Nakazawa, Naval, Navarro, Naynes, R. Ocampo, P. Ocampo, Trans Head | Motin PAGE 18 of 18 TRANS 1 Ocoma