Touch and Pain

1. Touch and Pain Lindsey DeJean, Elizabeth Killmeyer, and Rebecca Richman

2. Do Now What do you think touch is? How does the brain get the message of pain?

3. Introduction to touch

4. Touch: the sense • Touch is the sense by which we determine the characteristics of objects such as: • Size • Shape • Texture • These characteristics are determined through touch receptors in the skin

5. Touch: the sense(with hair) • Receptors consist of webs of sensory nerve cell endings wrapped around the base of hairs • Can be triggered by the slightest movement

6. Quick Review • What are the three characteristics of an object touch can determine? • How are we able to determine this? • How are the sensory nerve cell endings placed in association with the hair? Size Shape Texture Touch receptors in the skin Wrapped around the base of hairs

7. Path of signals of touch Signals from touch receptors pass via sensory nerves ➡Spinal cord: here they synapse and contact other nerve cells➡ Send the information to the thalamus and sensory cortex

10. Senses of touch highly topographic (what does that mean?) • That the body is represented in an orderly fashion at different levels of the nervous system • Larger area of the cortex are devoted to sensation from the hands and lips • Smaller areas of the cortex are less sensitive parts of the body

11. Different parts of the body vary in their sensitivity to tackle and painful stimuli. • These varying responses are based largely on the number and distribution of receptors

12. Quick Review • What three characteristics of touch an object can determine? • Size • Shape • Texture • What is the path of signals of touch? • Signals from touch receptors pass via sensory nerves ➡Spinal cord: here they synapse and contact other nerve cells ➡ Send the information to the thalamus and sensory cortex

13. What are larger areas of the cortex devoted to? • hands and lips • Smaller? • less sensitive parts of the body • How do different points of the body very in their sensitivity? • number and distribution of receptors

14. How do neurologists measure sensitivity? • Two-point threshold, the distance between two points on the skin necessary in order for the individual to distinguish two distinct stimuli from just one • Threshold is lowest at fingers and lips

16. Quick Review • How do neurologists measure sensitivity? • Two-point threshold • How does this work? • distance between two points on the skin necessary in order for the individual to distinguish two distinct stimuli from just one • Where is it lowest? • lowest at fingers and lips

17. Nocireceptors • The sensory fibers that respond to stimuli that damage tissue and can cause pain are called nocireceptors • Different nociceptor subsets produce molecules that are responsible for the response to noxious thermal, mechanical, or chemical stimulation • Some nociceptors in the skin respond to chemical stimuli that cause itch

18. Quick Review • What are he sensory fibers that respond to stimuli that damage tissue and can cause pain? • Nocireceptors • What are the different nociceptor molecules responsible for? • noxious thermal, mechanical, or chemical stimulation • What can chemical stimuli cause in the skin? • itch

19. Tissue Damage • Tissue injury causes the release of numerous chemicals at the site of damage/inflammation • Prostaglandins enhance the sensitivity of the receptors • Pretty much makes the pain more intense….painful • Prostaglandins contributes to the clinical condition of allodynia, in which innocuous stimuli can produce pain • When sunburn is touched is an example of allodynia

20. Persistent Injury • Persistent injury can lead to changes in the nervous system that amplify and prolong the “pain” signal • The result is a state of hypersensitivity in which pain persists and can even be evoked by normally innocuous stimuli

21. Quick Review • What does tissue injury cause? • the release of numerous chemicals at the site of damage/inflammation • What enhance the sensitivity of the receptors? • Prostaglandins • What does prostaglandins contribute to? • allodynia

22. What can persistent injury lead to? • to changes in the nervous system that amplify and prolong the “pain” signal • What is hypersensitivity? • pain persists and can even be evoked by normally innocuous stimuli

23. What we know so far.. • What are the three characteristics of an object touch can determine? • Size • Shape • Texture • How are we able to determine this? • Touch receptors in skin • What is the path of signals of touch? • Signals from touch receptors pass via sensory nerves ➡Spinal cord: here they synapse and contact other nerve cells ➡ Send the information to the thalamus and sensory cortex

24. What are larger areas of the cortex devoted to? • hands and lips • Smaller? • less sensitive parts of the body • How do different points of the body very in their sensitivity? • number and distribution of receptors • How do neurologists measure sensitivity? • Two-point threshold

25. How does this work? • distance between two points on the skin necessary in order for the individual to distinguish two distinct stimuli from just one • Where is it lowest? • lowest at fingers and lips • What are the sensory fibers that respond to stimuli that damage tissue and can cause pain? • Nocireceptors

26. What are the different nociceptor molecules responsible for? • noxious thermal, mechanical, or chemical stimulation • What can chemical stimuli cause in the skin? • Itch • What does tissue injury cause? • the release of numerous chemicals at the site of damage/inflammation • What enhances the sensitivity of the receptors? • Prostaglandins

27. What does prostaglandins contribute to? • allodynia • What can persistent injury lead to? • to changes in the nervous system that amplify and prolong the “pain” signal • What is hypersensitivity? • pain persists and can even be evoked by normally innocuous stimuli

28. Sending and Relieving Pain and Itch Messages How do you think pain and itch messages are transmitted to the spinal cord? Ideas?

29. Messages through Spinal Cord • Pain and itch messages are transmitted through the spinal cord through • Small myelinated fibers • C fibers (unmyelinated fibers)

30. Fibers • Myelinated nerve fibers • Very pain sensitive • Produce fast, sharp pains • C fibers (unmyelinated) • Induce pain • Slower in onset, dull

31. Quick Review • How are pain and itch signals sent to the spinal cord? • Via mylinated fibers and C fibers • Describe the signals sent by mylinated nerve fibers. • Pain sensitive and sends fast, sharp pains • Describe the signals sent by C fibers. • Sends slow onset pains, dull, pain induced • What makes mylinated nerve fibers different from C fibers? • Mylinated nerve fibers send fast sharp pains and C fibers send slow dull pains.

32. Sending and Relieving Pain and Itch Messages • When signals are sent from the spinal cord to the brain it is called the ascending system. • There are several brain structures that pain impulses are sent to.. • Thalamus • Cerebral cortex

33. Pain and Itch Messages • The thalamus and cerebral cortex are involved in the process where pain and itch messages become a conscious experience. • For example • Setting when injury occurs (ex.childbirth, car accident) • Emotional impact • These factors contribute to determine our overall response to the experience.

34. Quick Review • What is the system where impulses are relayed from the spinal cord to the brain? • Ascending system • What structures of the brain are involved in the process by which pain or itch messages become a conscious experience? • Thalamus and cerebral cortex • What are other factors that contribute to a humans pain or itch response? • Setting and emotional impact

35. Pain Messages • Neurons in the gray matter in the brainstem can stop pain messages from the dorsal end of the spinal cord to the brain centers. • Endorphins, which serve as opioid receptors, are used by the systems.

36. Modern Imaging Tools • Modern imaging tools areused to determine what happens in the brain when pain is in motion. • Emotional and sensory together create the activity of pain. • In the future, scientists hope to monitor changes in an individual’s brain who experiences a lot of pain so that they can test different painkilling drugs.

37. Quick Review • How can pain messages be suppressed? • Neurons in the gray matter of the brainstem • What acts as opioid receptors in the brain and spinal cord and are used for pain therapy? • Endorphins • What are used to help scientists see what occurs in the brain when pain is felt? • Modern Imaging Tools • True/False: only one area in the brain generates pain • False emotional and sensory together create the activity of pain.

38. What we know about sending and receiving pain and itch messages… • How are pain and itch signals sent to the spinal cord? • Via mylinated fibers and C fibers • Describe the signals sent by mylinated nerve fibers. • Pain sensitive and sends fast, sharp pains • Describe the signals sent by C fibers. • Sends slow onset pains, dull, pain induced • What makes mylinated nerve fibers different from C fibers? • Mylinated nerve fibers send fast sharp pains and C fibers send slow dull pains.

39. What is the system where impulses are relayed from the spinal cord to the brain? • Ascending system • What structures of the brain are involved in the process by which pain or itch messages become a conscious experience? • Thalamus and cerebral cortex • What are other factors that contribute to a humans pain or itch response? • Setting and emotional impact • How can pain messages be suppressed? • Neurons in the gray matter of the brainstem

40. What acts as opioid receptors in the brain and spinal cord and are used for pain therapy? • Endorphins • What are used to help scientists see what occurs in the brain when pain is felt? • Modern Imaging Tools • True/False: only one area in the brain generates pain • False emotional and sensory together create the activity of pain.