Peripheral Nervous System 1
Sensory Receptors Sensory Receptors and Sensation Respond to changes (stimuli) in the environment Generate graded potentials that can trigger an action potential that is carried to the CNS Sensation awareness of the stimulus Perception interpretation of the stimulus Classification by Stimulus Type Mechanoreceptors Thermoreceptors Photoreceptors Chemoreceptors nociceptors 2
Classification by Location Exteroceptors Interoceptors Proprioceptors Sensory Receptors and Sensation Classification by Structural Complexity Simple Receptors Modified dendritic endings Found throughout the body Monitor general sensation Complex Receptors Sense organs (special senses) 3
Sensory Receptors and Sensation Simple Receptors of the General Senses 4
Sensory Receptors and Sensation 5
Sensory Receptors and Sensation Sensation to Perception General Organization of the Somatosensory System three major levels Receptor Level Processing sensory neurons For a sensation to occur a stimulus must excite a receptor Receptor specificity Stimulus must be applied to the receptor s receptive field (the smaller the field the better the brain can localize the stimulus) Energy of the stimulus must be converted to a graded potential (receptor potential); called transduction Generator potential of the first order neuron must reach threshold to be transmitted Strength of stimulus is encoded in frequency (the faster the stronger) Terminology» Tonic receptors usually firing at a particular rate constantly; stimulus changes the rate» Phasic receptors usually off; stimulus turns them on» Adaptation reduction in sensitivity to a stimulus 6
Sensory Receptors and Sensation Circuit Level Processing ascending (sensory) pathways (tracts) Job is to deliver impulses the correct area of the cerebral cortex Impulses first goes from the a nerve to the spinal cord, ultimately to either the cerebellum or thalamus (second order neuron) If the information is going to the cerebral cortex a third order neuron carries it from the thalamus to the appropriate area of the cerebral cortex Perceptual Level Processing cerebral cortex, but also along the way perception is defined by the region of the brain interpreting it not necessarily the stimulus the brain interprets and projects where in the body the stimulus is coming from 7
Sensory Receptors and Sensation Main Aspects of Perception Perceptual Detection Magnitude Estimation Spatial Discrimination two-point discrimination test Feature Abstraction interpreting several features of a perception to determine the actual make-up of the stimulus Quality Discrimination some modalities have different qualities, ex. taste; bitter, sour, sweet, salty Pattern Recognition misspelled sheet I handed out 8
Transmission Lines: Nerves and Their Structure and Repair Nerves and Associated Ganglia Structure 9
Transmission Lines: Nerves and Their Structure and Repair Classification Sensory (afferent) nerves Motor (efferent) nerves Mixed nerves Ganglia 10
Transmission Lines: Nerves and Their Structure and Repair Regeneration of Nerve Fibers 11
Cranial Nerves Naming Use of Roman numerals I XII Named according to structures served or function(s) On occasion our trust truck acts funny very good vehicle anyhow Some say marry money but my brothers say bad business marry money 12
Spinal Nerves General Features 31 pairs Naming 13
Spinal Nerves Anatomy 14
Spinal Nerves 15
Spinal Nerves Innervation of Specific Body Regions Dorsal Rami supply skin and muscles of posterior trunk Ventral Rami anterior trunk and limbs All but T 1 T 12 form plexuses 16
Cervical Plexus 17
Brachial Plexus 18
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Dermatomes 30
Motor Endings and Motor Activity Peripheral Motor Endings Innervation of Skeletal Muscle - neuromuscular junctions Innvervation of Visceral (Smooth) Muscle and Glands Possess varicosities that typically contain either acetylcholine or norepinephrine 31
Reflexes Reflex Arc 32
Spinal Reflexes Stretch and Golgi Tendon Reflexes Functional anatomy 33
Spinal Reflexes 34
Spinal Reflexes Stretch Reflex Demonstrates reciprocal inhibition Example is the knee-jerk or patellar reflex Monosynaptic Ipsilateral Gives us information concerning The status of both the sensory and motor pathway The status of the spinal cord 35
Spinal Reflexes 36
Spinal Reflexes Golgi Tendon Reflex Polysynaptic Results in reciprocal activation 37
Spinal Reflexes Flexor (Withdrawl) Reflex/Crossed Extensor Reflex 38
Spinal Reflexes Superficial Reflexes Plantar Reflex blunt object stroked along lateral side of the plantar surface Test spinal cord segment (L 4 S 2 ) Integrity of corticospinal tracts Normal response downward deflection of toes Abnormal Babinski s sign toes dorsiflex, smaller toes flare laterally this is normal in children Abdominal Reflexes - stroke skin on lateral side of abdomen to the side, above or below the umbilicus Normal umbilicus should move towards stroked side Test cord segments (T 8 T 12 ) Integrity of corticospinal tracts 39