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Neuroanatomy/Pain Review. Anatomy Cell body (in ganglion) Cell body (in ganglion) nucleus nucleus Dendrites Dendrites axon Dendrite Body Synapse.

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Presentation on theme: "Neuroanatomy/Pain Review. Anatomy Cell body (in ganglion) Cell body (in ganglion) nucleus nucleus Dendrites Dendrites axon Dendrite Body Synapse."— Presentation transcript:

1 Neuroanatomy/Pain Review

2 Anatomy Cell body (in ganglion) Cell body (in ganglion) nucleus nucleus Dendrites Dendrites axon Dendrite Body Synapse

3 Anatomy Cont. Axons (actual nerve fibers) Axons (actual nerve fibers) peripheral nervous system: may be covered by myelin sheath (schwann cell) which allows for regrowth peripheral nervous system: may be covered by myelin sheath (schwann cell) which allows for regrowth CNS: oligodendrocytes are the myelin but it doesn't allow for regrowth CNS: oligodendrocytes are the myelin but it doesn't allow for regrowth

4 Anatomy Cont. Nodes of Ranier: breaks in myelin. Action potentials jump from node to node (salutatory condition) myelin acts as resistance and insulation and thus needs nodes for function. Nodes of Ranier: breaks in myelin. Action potentials jump from node to node (salutatory condition) myelin acts as resistance and insulation and thus needs nodes for function.

5 Nerve Types Afferent; sensory nerves (ascending tracts) Afferent; sensory nerves (ascending tracts) A A Beta): sensory, large diameter with myelin (Fastest) A A Beta): sensory, large diameter with myelin (Fastest) A delta: pain fibers, smaller with less myelin (4- 30m/s) A delta: pain fibers, smaller with less myelin (4- 30m/s) C: pain, smallest, non myelinated (.5-2m/s) dull slow pain C: pain, smallest, non myelinated (.5-2m/s) dull slow pain See Prentice Table 1-2 for Classes of Afferent Neurons See Prentice Table 1-2 for Classes of Afferent Neurons Note: First pain is from Adelts (faster), second pain is C Note: First pain is from Adelts (faster), second pain is C

6 Nerve Types Cont. Efferent Nerves: motor nerves (descending tracts) Efferent Nerves: motor nerves (descending tracts) Gamma: motor neuron Gamma: motor neuron Ascending and descending tracts: Ascending and descending tracts: myelination increases conduction velocity myelination increases conduction velocity Diameter increases conduction velocity (less resistance) Diameter increases conduction velocity (less resistance)

7 Nerve Types: Afferent Nerves Afferent Nerves CNS A Beta Adelta C

8 Physiology Excitable Tissue: only nerves and muscles are excitable tissue due to the fact only they have a resting membrane potential Excitable Tissue: only nerves and muscles are excitable tissue due to the fact only they have a resting membrane potential

9 Physiology Cont. Resting membrane Potential: a chemical and electrical balance with a pump to aid in return to homeostasis. Resting membrane Potential: a chemical and electrical balance with a pump to aid in return to homeostasis. at rest membrane in -70 mV to -90 mV at rest membrane in -70 mV to -90 mV semipermeable membrane which is impermeable to Sodium at rest semipermeable membrane which is impermeable to Sodium at rest

10 Physiology Cont. Sodium Potassium pump keeps the potential by pump in K+ in and Na+ out Sodium Potassium pump keeps the potential by pump in K+ in and Na+ out Na+ want in the cell but if it gets in an action potential is formed Na+ want in the cell but if it gets in an action potential is formed to +30 mV (a 100 mV difference) to +30 mV (a 100 mV difference) hormone, chemical, electrical, thermal or mechanical factors may create action potentials hormone, chemical, electrical, thermal or mechanical factors may create action potentials As athletic trainers we try and change this status and create an action potential As athletic trainers we try and change this status and create an action potential

11 Threshold The minimum amount of stimulus necessary to create an action potential The minimum amount of stimulus necessary to create an action potential Polar: refers to negative Polar: refers to negative depolarize: less negative depolarize: less negative repolarize: becoming negative repolarize: becoming negative hyperpolarize: more negative hyperpolarize: more negative

12 Physiology Cont. All or none theory: If stimulus meets the threshold, action potential will always go to +30mV, even if supra-threshold stimulus is given All or none theory: If stimulus meets the threshold, action potential will always go to +30mV, even if supra-threshold stimulus is given

13 Physiology Cont. Refractory period: membrane potential goes below the resting potential of -70mV and may not be stimulated for a given period of time. This limits how many action potentials may be produced Refractory period: membrane potential goes below the resting potential of -70mV and may not be stimulated for a given period of time. This limits how many action potentials may be produced Absolute refractory period: NO stimulus will create a response no matter how strong Absolute refractory period: NO stimulus will create a response no matter how strong Relative refractory period: resting potential is much lower, therefore a higher stimulus is needed Relative refractory period: resting potential is much lower, therefore a higher stimulus is needed

14 Pain How is this class affecting your pain receptors?

15 Pain The purpose of pain is as a protective mechanism. Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage: The purpose of pain is as a protective mechanism. Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage: The types of pain are The types of pain are Acute Acute Chronic Chronic Referred Referred

16 Acute Pain First pain: carried in A-delta fires: larger diameter fibers contain myelin, reflex to get off source, goes to cognitive level (more discrete - very localized) First pain: carried in A-delta fires: larger diameter fibers contain myelin, reflex to get off source, goes to cognitive level (more discrete - very localized) Second Pain: carried in C fibers. Smaller diameter, non myelinated, slower. (less discrete - more diffuse) Second Pain: carried in C fibers. Smaller diameter, non myelinated, slower. (less discrete - more diffuse)

17 Acute Pain Treatment Goal Goal block the pain through: block the pain through: inhibition inhibition blocking A fibers (Gate Control) blocking A fibers (Gate Control)

18 Chronic Pain: Any pain which lasts for six months or more (in athletes we may consider chronic pain to be pain which is continue from months but is not in proportion to tissue injury or activity... i.e... chronic tendinitis may be long lasting but have organic root) Any pain which lasts for six months or more (in athletes we may consider chronic pain to be pain which is continue from months but is not in proportion to tissue injury or activity... i.e... chronic tendinitis may be long lasting but have organic root) No real purpose (?) No real purpose (?) numerous by-passes. Also goes to limbic system (emotional control)- learned response numerous by-passes. Also goes to limbic system (emotional control)- learned response

19 Chronic Pain Goals in treating Goals in treating unlearn the Pain unlearn the Pain Acute pain control techniques are usually ineffective Acute pain control techniques are usually ineffective Exercise my affect pain by distraction Exercise my affect pain by distraction Important to have guidance under a physician Important to have guidance under a physician

20 Referred Pain (projected pain) Felt at other site than injured area Felt at other site than injured area Dermatome (skin represented by nerve root) Dermatome (skin represented by nerve root) Myotome (muscle innovated by nerve root) Myotome (muscle innovated by nerve root) Sclerotome (bones innovated by nerve root) Sclerotome (bones innovated by nerve root)

21 Pain Transmission Acute Pain Noxious Stimulus travel Via A-Delta and C- delta Fibers to Dorsal Horn (spinal Cord) Doral Horn A-Beta C-Delta Pain Transmitted to Higher Brain Centers Acute Pain STT (Spinal thalamic Tract) Thalamus and Cortex location and discrimination Retinacular Formation & Periaquductal Gray (PAG) Motor, sensory and autonomic Response Discrimination and Location of pain occurs during this sequence Limbic System & Cortex Descending Control Mech. Activated here once noxious stimuli reaches higher centers of brain. Incoming stimuli can be inhibited at various levels and endoginous opiates released

22 Pain theories Specificity Theory Specificity Theory Pattern Theory Pattern Theory Gate Control Theory Gate Control Theory

23 Specificity theory: specific stimulus has a specific receptor which goes to a location in the brain The specific location identifies the pains quality. Thus any noxious stimulus applied to the surface of the skin results in a pain sensation. The evaluation of the type of pain occurs in the brain.

24 Pattern Theory: a pattern or coding of sensory information is created by different sensations. This theory is faulty due to the number of different types of receptors proven to exist.

25 Gate Control Theory (1965) Melzack and Wall originally described a neurophsiologic mechanism which involved the concept of peripheral and central gating. The gate theory utilizes the specificity theory and the pattern theory and added the interaction of peripheral afferents with a modulation system in the spinal cord gray matter. Additionally Melzack and Wall believed there also exists a descending modulation system. Melzack and Wall originally described a neurophsiologic mechanism which involved the concept of peripheral and central gating. The gate theory utilizes the specificity theory and the pattern theory and added the interaction of peripheral afferents with a modulation system in the spinal cord gray matter. Additionally Melzack and Wall believed there also exists a descending modulation system.

26 Gate Control Theory First Order neurons: the theory focuses on the first order neurons (primary afferents): the A-beta (large diameter sensory neurons) and A-delta and C neurons (both small diameter sensory neurons). First Order neurons: the theory focuses on the first order neurons (primary afferents): the A-beta (large diameter sensory neurons) and A-delta and C neurons (both small diameter sensory neurons). A non-painful stimulus can block the transmission of a noxious stimulus A non-painful stimulus can block the transmission of a noxious stimulus Brain/Pain centers C delta noxious stimulus A-beta non-painful stimulus Blocking entry of c-delta Fibers

27 Gate Control Theory Cont. The second order neuron, the T-cell and the substantia gelatinosa (Rexeds laminae II and II of the dorsal horn of the spinal gray matter) can exert affects on the primary afferent The second order neuron, the T-cell and the substantia gelatinosa (Rexeds laminae II and II of the dorsal horn of the spinal gray matter) can exert affects on the primary afferent Works on the premise that the SG (located in dorsal horn) modulates afferent nerve impulses and influence transmission of T cells. This activates a central controlling mechanism Works on the premise that the SG (located in dorsal horn) modulates afferent nerve impulses and influence transmission of T cells. This activates a central controlling mechanism

28 Gate Control In Dorsal Horn of Spinal Cord In Dorsal Horn of Spinal Cord T Brain. A-Beta Sensory, Proprioception, Etc A-Delta, C Fibers Pain Transmission SG Facilitator Synapse Inhibitory Synapse

29 The second order neuron When the substantia gelatinosa is active the gate is closed and there is a decrease in the amount of sensory input to the T-cell When the substantia gelatinosa is active the gate is closed and there is a decrease in the amount of sensory input to the T-cell If the S.G. is relatively inactive the gate is open If the S.G. is relatively inactive the gate is open the balance of activity in the large and small diameter sensory neurons determines the position of the gate the balance of activity in the large and small diameter sensory neurons determines the position of the gate

30 Gate Control Theory Large diameter afferents cause an initial increase in the T-cells followed by a reduction of activity. The initial increase is due to direct activation of the second- order neuron by primary afferents. The reduction is an indirect result due to large-diameter afferents also activating the s.g. cells which causes the gate to close Large diameter afferents cause an initial increase in the T-cells followed by a reduction of activity. The initial increase is due to direct activation of the second- order neuron by primary afferents. The reduction is an indirect result due to large-diameter afferents also activating the s.g. cells which causes the gate to close

31 Gate Control Theory Cont. Small diameter afferents increase T-cell activity by these primary afferents also activate inhibitory interneurons that reduce activity in the s.g which open the gate Small diameter afferents increase T-cell activity by these primary afferents also activate inhibitory interneurons that reduce activity in the s.g which open the gate

32 Gate Control Theory When the balance of small to large diameter sensory neuronal input is no longer maintained and reaches a critical value the second-order neurons are activated. This activation is of the ascending system and leads to the perception of pain and the subsequent behavioral responses. When the balance of small to large diameter sensory neuronal input is no longer maintained and reaches a critical value the second-order neurons are activated. This activation is of the ascending system and leads to the perception of pain and the subsequent behavioral responses.

33 Gate Control Theory The Descending control system in which emotion and past experience evoke descending input, impinging upon the gating mechanism to block pain sensation at the spinal level. The Descending control system in which emotion and past experience evoke descending input, impinging upon the gating mechanism to block pain sensation at the spinal level. PAIN is an excellent bible for those working clinically with pain control PAIN is an excellent bible for those working clinically with pain control

34 Pain modulation: Levels Theory of Pain Control Spinal Levels of Pain Control Spinal Levels of Pain Control Gate Control Theory Gate Control Theory Central Biasing (hyperstimulation analgesia) Central Biasing (hyperstimulation analgesia) Endogenous Opiate (Pituitary level) Endogenous Opiate (Pituitary level)

35 Level I: Presynaptic inhibition Gate Control Theory The concept that when several sensory stimuli reach the spinal cord at the same location and time. one of them becomes dominant. The concept that when several sensory stimuli reach the spinal cord at the same location and time. one of them becomes dominant. As long as the stimulation is causing firing of the sensory nerve, the gate to pain should be closed As long as the stimulation is causing firing of the sensory nerve, the gate to pain should be closed If accommodation occurs (electrical stimulus) the gate is then open and pain returns If accommodation occurs (electrical stimulus) the gate is then open and pain returns

36 Level 2: Descending inhibition Central Biasing A theory of pain modulation where higher centers such as the cerebral cortex influence the perception of and response to pain A theory of pain modulation where higher centers such as the cerebral cortex influence the perception of and response to pain Impulses from higher centers act to close the gate and block transmission of the pain message at the dorsal horn synapse Impulses from higher centers act to close the gate and block transmission of the pain message at the dorsal horn synapse Transmission of sensory input ot higher brain centers Transmission Cell Substantia gelitinosa A-beta fiber Afferents A-Delta & C fiber afferents Central Control +-+- +- +-+-

37 Level 3: -Endorphin modulation Endogenous Opiate Opiate like substance made by the body Opiate like substance made by the body Norepinephrine Norepinephrine Seratonin Seratonin These opiates inhibit the depolarization of second order nociceptive nerve fibers (thus no pain) These opiates inhibit the depolarization of second order nociceptive nerve fibers (thus no pain) Found in substantia gelatinosa - activated in tract Found in substantia gelatinosa - activated in tract Causes degeneration of prostaglandin and dorsal horn inhibition Causes degeneration of prostaglandin and dorsal horn inhibition

38 The purpose of knowing all the pain control theories is to use modalities to assess these pain theories and decrease the athlete/patients pain The purpose of knowing all the pain control theories is to use modalities to assess these pain theories and decrease the athlete/patients pain


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