1. Copyright 2010, John Wiley & Sons, Inc. Chapter 15 Sensory, Motor and Integrative Systems

2. Copyright 2010, John Wiley & Sons, Inc. Chapter 15: Sensory, Motor and Integrative Systems The work of the nervous system requires that information be collected, processed, and acted upon: Sensory systems respond to stimuli by sending signals to the CNS Integrative systems ( within the CNS) process and evaluate the sensory information in a process called integration Motor systems carry signals from the CNS to effectors, and makes sure that motor output is coordinated for efficient responses

3. Copyright 2010, John Wiley & Sons, Inc. Sensory Information: Basic Terminology Some terms used to describe sensory information Sensory modality refers to the type of sensation (touch, vision, etc.) The special senses include five key types of sensory input, all originating in the head (smell, taste, vision, hearing, and balance) The general senses include input from throughout the body  Somatic senses (input from skin and musculoskeletal system)  Visceral senses (input from internal organs) Sensation - conscious or subconscious awareness Perception - awareness plus interpretation of sensory information

4. Copyright 2010, John Wiley & Sons, Inc. The Process of Sensation ■ Four events typically involved when a sensation happens 1.A sensory receptor is stimulated 2.The sensory receptor transduces the sensory stimulus – creating a graded potential in response to a specific type of stimuli 3.The sensory neuron creates one or more nerve impulses which travel toward the CNS 4.Integration of the sensory input occurs in specific regions of the CNS

5. Copyright 2010, John Wiley & Sons, Inc. Three Structural Classes of Sensory Receptors ■Sensory receptors vary structurally in how the stimulus is received—by free nerve endings, by encapsulated nerve endings, or by specialized sensory receptor cells

6. Copyright 2010, John Wiley & Sons, Inc. Three Structural Classes of Sensory Receptors

7. Copyright 2010, John Wiley & Sons, Inc. Classification of Sensory Receptors Classification by location (at the body surface, inside the body, in muscles and joints) Classification by the type of stimulus (light, heat, etc)

8. Copyright 2010, John Wiley & Sons, Inc. Sensory Receptors: Adaptation Most sensory receptors adapt to a constant stimulus, by decreasing their response and sending fewer action potentials to the CNS  Rapidly adapting receptors decrease their responses quickly. These receptors help the nervous system monitor changes in the environment  Slowly adapting receptors decrease their responses slowly, and continue to send action potentials as long as the stimulus lasts. These receptors help monitor tension in postural muscles, pain, and blood chemistry

9. Copyright 2010, John Wiley & Sons, Inc. Somatic Sensations Somatic (“of the body”) sensations arise from body surfaces, muscles and joints  Tactile sensations  Thermal sensations  Pain  Proprioception Somatic sensations arising from the skin are known as cutaneous sensations

10. Copyright 2010, John Wiley & Sons, Inc. Somatic Sensations

11. Copyright 2010, John Wiley & Sons, Inc. Tactile Sensations Tactile receptors in the skin include  Corpuscles of touch (also called Meissner corpuscles)  Hair root plexuses  Mechanoreceptors Merkel discs Ruffini corpuscles  Lamellated corpuscles also called Pacinian corpuscles)  Free nerve endings

12. Copyright 2010, John Wiley & Sons, Inc. Tactile Sensations

13. Copyright 2010, John Wiley & Sons, Inc. Thermal Sensations We have two different classes of thermal receptors located in the dermis  Cold receptors respond to low temperatures (10–40  C)  Warm receptors respond to a higher temperature range (32–48  C)  Temperatures outside of the ranges above primarily stimulate nociceptors (pain)

14. Copyright 2010, John Wiley & Sons, Inc. Pain Pain sensations (or just “pain”) is how we learn about things that are harmful. Pain serves a protective function, since it motivates us to avoid harmful stimuli Nociceptors are free nerve endings found everywhere in the body (except the brain). Nociceptors have several unusual properties  Nociceptors are activated by multiple types on stimuli  Many chemicals can stimulate nociceptors, and/or sensitize them to other stimuli - in this way pain plays a major role in inflammation  Nociceptors adapt poorly, allowing pain to continue

15. Copyright 2010, John Wiley & Sons, Inc. Types of Pain Painful sensations can be described by how quickly they appear, and by where in the body they originate Fast pain is perceived rapidly (< 0.1 second). Fast pain includes acute, sharp, and prickly sensations. Slow pain is perceived more slowly (after 1 second or more), and gradually increases in intensity. Slow pain includes chronic, burning, aching, and throbbing sensations.

16. Copyright 2010, John Wiley & Sons, Inc. Types of Pain Superficial somatic pain arises from nociceptors in the skin Deep somatic pain arises from nociceptors in muscles, joints, tendons, ligaments, and fascia Visceral pain arises from stimulation of nociceptors in visceral organs

17. Copyright 2010, John Wiley & Sons, Inc. Localization of Pain Fast pain is precisely localized - we know exacty where the stimulus is Slow pain has a more general localization - we can only localize the stimulus to a broader region of the body In referred pain, the pain is perceived to arise from surface tissues that share neural pathways with the visceral source of the pain

18. Copyright 2010, John Wiley & Sons, Inc. Localization of Pain

19. Copyright 2010, John Wiley & Sons, Inc. Proprioception Proprioceptive sensations allow us an awareness of where our head and limbs are, and where they are going; these sensations are critical for the precise control of body movements Proprioceptors inform us about several categories of mechanical stimuli  The degree to which muscles are stretched  The tension in tendons, and the position of our joints  The position and movements of our head Proprioceptors adapt only slightly, and feedback from propriceptors allows us to adjust our movements to match changing physical challenges

20. Copyright 2010, John Wiley & Sons, Inc. Muscle Spindles Muscle spindles are proprioceptors located within skeletal muscles  The length of the muscl is monitored  Muscle spindles are involved in the stretch reflex, and help maintain muscle tone  Muscle spindles contain a mechanism for maintaining their own level of tension - this ensures sensitivity at all muscle lengths

21. Copyright 2010, John Wiley & Sons, Inc. Muscle Spindles

22. Copyright 2010, John Wiley & Sons, Inc. Other Proprioceptors Tendon organs are located where tendons meet muscle  The level of tension in the tendon is monitored  Excessive tension results in reflexive muscle relaxation, protecting the muscle from damage Joint kinesthetic receptors (not shown) are located within and around synovial joint capsules  These receptors provide feedback on joint position

23. Copyright 2010, John Wiley & Sons, Inc. Other Proprioceptors

24. Copyright 2010, John Wiley & Sons, Inc. Somatic Sensory “Map” in the Cerebral Cortex The primary somatosensory area is in the postcentral gyrus of the parietal lobe Body regions are “mapped” to specific regions Extensive sensory input from some regions (e.g., lips, hands) results in larger cortical regions representing them The left side of the body maps to the right cerebral cortex, and vice versa

25. Copyright 2010, John Wiley & Sons, Inc. Somatic Sensory “Map” in the Cerebral Cortex

26. Copyright 2010, John Wiley & Sons, Inc. Somatic Motor “Map” in the Cerebral Cortex The primary motor area is in the precentral gyrus of the frontal lobe Major region for control of voluntary movements Larger cortical areas exist for detailed motor control Just anterior to the primary motor area is the premotor area of the frontal lobe

27. Copyright 2010, John Wiley & Sons, Inc. Somatic Motor “Map” in the Cerebral Cortex

28. Copyright 2010, John Wiley & Sons, Inc. Somatic Sensory Pathways Somatic sensory pathways carry information from the body to the somatosensory cortex, and to the cerebellum Sets of three neurons carry information along the pathways  First-order neurons carry signals as far as the spinal cord or brainstem  Second-order neurons carry signals on to the thalamus  Third-order neurons travel from the thalamus to the cerebral cortex CNS regions where the three neurons synapse with each other are know as relay stations - these include the spinal cord, regions of the brainstem, and the thalamus

29. Copyright 2010, John Wiley & Sons, Inc. Copyright 2009, John Wiley & Sons, Inc. Sensory Pathways: The Posterior Column Pathway This pathway carries information from touch, vibration, and proprioceptors  First-order neurons travel via the posterior column of the spinal cord to the medulla oblongata  Second-order neurons cross to the opposite side of the medulla, then ascend via the medial lemniscus to the thalamus  Third-order neurons project from the thalamus to the cerebral cortex

30. Copyright 2010, John Wiley & Sons, Inc. Sensory Pathways: The Posterior Column Pathway

31. Copyright 2010, John Wiley & Sons, Inc. Sensory Pathways: The Anterolateral Pathway This pathway carries information for pain, temperature, itch, and tickle sensations  First-order neurons travel to the spinal cord and synapse in the posterior gray horn  Second-order neurons cross to the opposite side of the spinal cord, then ascend in the spinothalamic tract to the thalamus  Third-order neurons project from the thalamus to the cerebral cortex

32. Copyright 2010, John Wiley & Sons, Inc. Sensory Pathways: The Anterolateral Pathway

33. Copyright 2010, John Wiley & Sons, Inc. Somatic Sensory Pathways Interactions Animation Somatic Sensory Pathways You must be connected to the internet to run this animation.

34. Copyright 2010, John Wiley & Sons, Inc. Sensory Pathways to the Cerebellum The cerebellum helps us maintain our balance and posture, and execute skilled movements - all requiring extensive input from proprioceptors Input to the cerebellum is not consciously perceived Input to the cerebellum travels via two pathways  Posterior spinocerebellar tract  Anterior spinocerebellar tract

35. Copyright 2010, John Wiley & Sons, Inc. Sensory Pathways to the Cerebellum

36. Copyright 2010, John Wiley & Sons, Inc. Somatic Motor Pathways Skeletal muscles are innervated by lower motor neurons, located in either the spinal cord or the brainstem Axons of lower motor neurons travel via either spinal nerves or cranial nerves to reach the muscles they innervate

37. Copyright 2010, John Wiley & Sons, Inc. Copyright 2009, John Wiley & Sons, Inc. Somatic Motor Pathways Many other neurons help determine the activity of lower motor neurons  Local circuit neurons help control rhythmic activities  Upper motor neurons help maintain muscle tone, posture and balance  Basal nuclei neurons help begin and end movements  Cerebellar neurons helps coordinate the actions of different muscles

38. Copyright 2010, John Wiley & Sons, Inc. Upper Motor Neuron Pathways Direct motor pathways descend from the cerebral cortex to lower motor neurons  Lateral corticospinal tract  Anterior corticospinal tract  Corticobulbar tract Indirect motor pathways (not shown) descend from the brainstem

39. Copyright 2010, John Wiley & Sons, Inc. Upper Motor Neuron Pathways

40. Copyright 2010, John Wiley & Sons, Inc. Modulation of Movement by the Basal Nuclei The basal nuclei play a key role in the initiation and termination of movements:  They receive input from various cortical areas  They provide feedback to the motor cortex (by way of the thalamus)  They also help suppress unwanted movements, and influence muscle tone

41. Sagittal plane Motor areas of cerebral cortex Thalamus Corrective feedback Motor centers in brainstem Pons Pontine nuclei Direct pathways Indirect pathways Signals to lower motor neurons Sagittal section through brain and spinal cord Sensory signals from proprioceptors in muscles and joints, vestibular apparatus, and eyes Cortex of cerebellum 1 Sagittal plane Motor areas of cerebral cortex Corrective feedback Pons Direct pathways Indirect pathways Signals to lower motor neurons Sagittal section through brain and spinal cord Sensory signals from proprioceptors in muscles and joints, vestibular apparatus, and eyes Cortex of cerebellum 1 2 Thalamus Motor centers in brainstem Pontine nuclei Sagittal plane Motor areas of cerebral cortex Corrective feedback Pons Direct pathways Indirect pathways Signals to lower motor neurons Sagittal section through brain and spinal cord Sensory signals from proprioceptors in muscles and joints, vestibular apparatus, and eyes Cortex of cerebellum 1 2 3 Thalamus Motor centers in brainstem Pontine nuclei Sagittal plane Motor areas of cerebral cortex Corrective feedback Pons Direct pathways Indirect pathways Signals to lower motor neurons Sagittal section through brain and spinal cord Sensory signals from proprioceptors in muscles and joints, vestibular apparatus, and eyes Cortex of cerebellum 1 2 4 3 Thalamus Motor centers in brainstem Pontine nuclei

42. Copyright 2010, John Wiley & Sons, Inc. Modulation of Movement by the Cerebellum The cerebellum helps us maintain posture and balance, as well as learn complex motor skills Four steps in cerebellar activity 1.Monitors intentions for movement 2.Monitors actual movement 3.Compares command signals with sensory information 4.Sends out corrective feedback

43. Copyright 2010, John Wiley & Sons, Inc. Modulation of Movement by the Cerebellum

44. Copyright 2010, John Wiley & Sons, Inc. Integrative Functions: Wakefulness and Sleep Our sleep-wake cycles are connected to a 24-hour circadian rhythm which originates in the hypothalamus The reticular activating system (RAS) is a diffuse series of brainstem nuclei that help us transition between sleep and being awake  The state of wakefulness is also referred to as consciousness  Sleep is a state of partial unconsciousness from which we can be aroused

45. Copyright 2010, John Wiley & Sons, Inc. Integrative Functions: Wakefulness and Sleep

46. Copyright 2010, John Wiley & Sons, Inc. Integrative Functions: Learning and Memory Learning is the acquisition of new information or skills - we learn by instruction or experience Memory is the process of storing and retrieving the information we learn  Memory must involve structural and functional changes in brain neurons  Areas of the brain involved in memory include association areas, the thalamus and hypothalamus, and parts of the limbic system

47. Copyright 2010, John Wiley & Sons, Inc. Integrative Functions: Memory Occurs in Stages Memory occurs in several stages, over distinct time periods  Immediate memory gives us knowledge of our current surroundings (duration: one to a few seconds)  Short-term memory allows immediate recall of information (duration: seconds to minutes)  Long-term memory allow retrieval of much older information (duration: days to years)

48. Copyright 2010, John Wiley & Sons, Inc. Integrative Functions: Memory Occurs in Stages Memories for complex motor skills are a special category of long-term memory, and seem to be stored in the basal nuclei and cerebellum in addition to the cerebral cortex A number of clinical conditions disrupt retention of recent memory, and in the worst cases can result in amnesia

49. Copyright 2010, John Wiley & Sons, Inc. End of Chapter 15 Copyright 2010 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information herein.