Peripheral Nervous System

Peripheral Nervous System

Peripheral Nervous System 1 Sensory Receptors and Sensation • Sensory Receptors – 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 Sensory Receptors and Sensation • Classification by Location – Exteroceptors – Interoceptors – Proprioceptors • 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 T1 – T12 form plexuses 16 Cervical Plexus 17 Brachial Plexus 18 Skin of the inferior, lateral portion of the shoulder – m uscles of the lateral arm for rotation and abduction 19 Skin of posterior surface of the arm and forearm , lateral 2/3 of back of hand – m uscles for extension of elbow , extends w rist, fingers, thum b, supinates 20 forearm Skin of lateral surface of forearm – m uscles for elbow (flexion) 21 Skin of m edial 1/3 of hand, little finger, and m edial ½ of ring finger– m uscles for w rist (flexion), m ost intrinsic finger m uscles 22 Lateral 2/3 of palm of hand, thum b, index and m iddle finger, and the lateral ½ of ring finger, and dorsal tips of the sam e fingers – m uscles for forearm (pronation), w rist (flexion/abduction), finger (flexion) 23 24 Superior m edial side of thigh – m uscles for: thigh (lateral rotation/adduction), hip (flexion) 25 Anterior and lateral branches supply the anterior and lateral thigh; saphenous branch supplies the m edial leg and foot – m uscles for: thigh (flexion), leg (flexion, extension) Carry inform ation concerning pain and tem perature 26 27 Branches from tibial nerve serve the sole of the foot and lateral and posterior 1/3 of leg and lateral side of foot – m uscles for: thigh (extension/adduction), leg (flexion), foot (plantar flexes), toes 28 (flexes) CaLrrayt etwraol- psouinrfta dcisec orifm kinnaeteio, ng, rperaotp raioncde psteiocno,n pdr etsoseu,r ed,o arnsda lv aibnrta.t itohni rd seonsf aletigon asnd top of foot – m uscles for: thigh (extension), leg 29 (flexion), foot (flexion/eversion), toes (extension) 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 (L4 – S2) • 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 (T8 – T12) • Integrity of corticospinal tracts 39.

View Full Text

Details

  • File Type
    pdf
  • Upload Time
    -
  • Content Languages
    English
  • Upload User
    Anonymous/Not logged-in
  • File Pages
    39 Page
  • File Size
    -

Download

Channel Download Status
Express Download Enable

Copyright

We respect the copyrights and intellectual property rights of all users. All uploaded documents are either original works of the uploader or authorized works of the rightful owners.

  • Not to be reproduced or distributed without explicit permission.
  • Not used for commercial purposes outside of approved use cases.
  • Not used to infringe on the rights of the original creators.
  • If you believe any content infringes your copyright, please contact us immediately.

Support

For help with questions, suggestions, or problems, please contact us