* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Somatosensory 2
Psychophysics wikipedia , lookup
Neuromuscular junction wikipedia , lookup
Synaptogenesis wikipedia , lookup
Caridoid escape reaction wikipedia , lookup
Neural coding wikipedia , lookup
Neuroanatomy wikipedia , lookup
Axon guidance wikipedia , lookup
Embodied cognitive science wikipedia , lookup
Endocannabinoid system wikipedia , lookup
Central pattern generator wikipedia , lookup
Signal transduction wikipedia , lookup
Sensory substitution wikipedia , lookup
Molecular neuroscience wikipedia , lookup
Neural engineering wikipedia , lookup
Neuroregeneration wikipedia , lookup
Development of the nervous system wikipedia , lookup
Proprioception wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
Evoked potential wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Spinal cord wikipedia , lookup
Quote of the Day "Make sure you have finished speaking before your audience has finished listening" Assignments -Read Chapters 10 and 11 in the Course Pack. Make a list of any terms that you don!t understand and/or any questions that you may have. -Start working on Study Guide 2 (Somatosensory system). -Dorothy Sarnoff - Exam 2 is coming up on Monday, November 9. This exam will cover the somatosensory system, and whatever part of the visual system has been covered by then. submitted by Deborah Clark Relationship between receptive field size and spatial acuity 2-point discrimination varies across different parts of the body The more closely spaced the receptors are and the smaller their receptive fields, the better the ability to resolve two pressure points on the skin. Stretch receptors Hair follicle receptors Hairy skin contains hair follicle mechanoreceptors that sense movement of the hair. Animals! whiskers are specialized variations of hair follicle receptors. Muscles and tendons have embedded within them receptors that respond to stretch 1 Free nerve endings Free nerve endings throughout the skin respond to heat, cold, and/or pain. “Paradoxical cold” Cold receptors are also activated by high temperatures Thermoreceptors The skin contains receptors that are activated by warmth, and others that are activated by cold. Pain (Nociception) The sensation of pain is caused by activation of very small diameter nerve endings. When tissue is damaged, chemical substances are released that stimulate these fibers. Some stimuli that activate nociceptors: Thermal: high heat or extreme cold Mechanical: Intense mechanical stimuli Chemical: Irritants or substances released by injured tissue Nerve fibers conveying different types of information have different diameters Key Concept: Neural latency In any sensory pathway, different neurons respond to a stimulus with different latencies. This means that information about the same stimulus reaches its destination(s) at different times. This principle will later become important in understanding how neural circuits in sensory systems analyze temporal patterns. Larger fibers conduct information faster than small ones. 2 Somatosensory pathways in the CNS Nerve fibers that innervate skin receptors of the body have their cell bodies in the dorsal root ganglion, a group of neuron cell bodies located near the spinal cord. Each spinal nerve has a dorsal root (sensory) and a ventral root (motor) • Motor neurons! cell bodies are in the ventral horn of the grey matter. Their axons exit via the ventral root of each spinal nerve. • Sensory neurons! cell bodies are located in the dorsal root ganglion. Their axons enter the spinal cord via the dorsal root of each spinal nerve. Cross-section through spinal cord Information processing in the spinal cord • Sensory information may be transmitted directly to motor neurons or indirectly via interneurons. The same information may be relayed to the brainstem. Each spinal nerve innervates a specific area of the body Spinal nerves innervate body segments • Nerves from/to different parts of the body enter the spinal cord at different places. The dorsal columns transmit information about touch and proprioception • The dorsal columns are fiber tracts that send information to the thalamus via nuclei in the brainstem and the medial lemniscus (a CNS fiber tract) 3 The spinothalamic tracts transmit information about temperature and pain Different pathways for different somatic“modalities” • The spinothalamic tracts are fiber tracts that send information to the thalamus and from there to the cortex via the anterolateral pathway (a CNS fiber tract) Key Concept: Parallel Pathways Different aspects of a sensory stimulus may be processed in different neural pathways. For a somatosensory stimulus, a single physical object could provide information about pressure, temperature, pain, etc., which could be thought of as different modalities. Parallel pathways can also selectively process specific aspects of a stimulus within a single modality. 4