Laboratory 5: Cranial
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  • 1. Cranial and Peripheral Nerves Principles of anatomy-ANSC 2202 Fall 2006
  • 2. Somatic motor neurons (efferent) Somatic sensory neurons (afferent) Central Nervous System = brain + spinal cord Peripheral Nervous System = cranial + spinal nerves Nervous System Skeletal muscles Parasympathetic NS (rest& digestion): Pelvic nerves+Cranial III, VII,IX,X Sympathetic NS (fight or flight): all spinal and most cranial nerves Skin, muscles, tendons, bones Smooth muscles, heart, glands Autonomic motor neurons (efferent) Autonomic sensory neurons (afferent) Smooth muscles, heart, glands voluntary involuntary Special sensory fibers Cn I,II,VII, VIII, IX Taste, smell, vision, hearing
  • 3. Types of neurons in the PNS
    • Cranial - connects the brain with the periphery
    • Sensory (afferent) - carry information INTO the CNS from sense organs
    • Motor (efferent) - carry information away from the CNS (for muscle control).
    • Spinal - connects the spinal cord with the periphery:
    • Somatic - connects the skin or muscle with the CNS; afferent and efferent
    • Autonomic - connects the internal organs with the CNS; afferent and efferent
  • 4. Central nervous system
  • 5. The Brain: sagittal section of a sheep’s brain: A review Links the 2 hemispheres
    • Cerebral cortex:
    • Thought
    • Voluntary movement
    • Language
    • Reasoning
    • Perception
    • Movement
    • Balance
    • Posture
    • Brain stem=area of the brain between the thalamus and spinal cord:
    • Breathing . Heart rate, Blood Press
    • Vision
    • Audition
    • Eye Movement
    • Body Movement
    Circadian rythm
  • 6. The spinal cord
    • Extension of brain stem starting at the foramen magnum and ending at:
      • L1 in humans (extension of pia matter attaches to coccyx)
      • S2 in animals
    • 2 roles:
      • Transmission of nerve impulses (white matter-axons; grey matter-nuclei)
      • Spinal reflexes
  • 7. The spinal cord
  • 8. The spinal cord
  • 9. The spinal cord
  • 10. Spinal reflexes
  • 11. Damages to the Central Nervous System
    • Brain does not regenerate
    • Spinal cord:
      • If severed: function below the lesion will not be restored
        • Babinski (extensor toe) reflex: withdrawal = chronic spinal cord lesion
        • Patellar (knee-jerk) reflex: no kick = femoral nerve and/or segment of spinal cord L4-6
      • Partial damage: may recover but stagnates after a certain period
  • 12. Peripheral nervous system
  • 13. PNS: Cranial nerves (12 pairs) “ On Old Oklahoma’s Towering Tops a Fine Vet Gastroenterologist Viewed Some Horses” “ Six Sailors Made Merry But My Brother Said Bad Business My Man” M Hypoglossal XII M Spinal Accessory XI B Vagus X B Glossopharyngeal IX S Vestibulocochlear VIII B Facial VII M Abducens VI B Trigeminal V M Trochlear IV M Oculomotor III S Optic II S Olfactory I Nerve type (Sensory, Motor, Both) Cranial nerve
  • 14. Function of cranial nerves Hypoglossal Nerve: movements of tongue XII Accessory Nerve: shoulder and neck muscles XI Vagus Nerve: autonomic functions of gut, sensation from pharynx, muscles of vocal cords, swallowing X Glossopharyngeal Nerve: sensation from pharynx, taste from posterior tongue, carotid baroceptors IX Auditory/Vestibular Nerve: hearing, sense of balance VIII Facial Nerve: controls the muscles of facial expression, taste from anterior tongue, lacrimal (tears) and salivary glands VII Abducens Nerve: eye movements VI Trigeminal Nerve: somatic sensations from face, mouth, cornea; muscles of mastication (chewing) V Trochlear Nerve: eye movements IV Oculomotor Nerve: eye movements, pupillary constriction and  accommodation, eyelid muscles III Optic Nerve: vision II Olfactory Nerve: sense of smell I 
  • 15. Cranial nerves: origin
  • 16. Damage to the cranial nerves
    • Pupillary light reflex: oculomotor nerve : flash light in right pupil: right pupil should constrict more
    • Corneal and palpebral (eyelid) reflexes (state of anesthesia): trigeminal nerve : blink before touching eyelids (ophtalmic branch); retraction of ocular globe when touch cornea (maxillary branch)
    • Reaction to smell (link with appetite): olfactory nerve (see experiment with Boar Mate)
    • Torticollis: spinal accessory nerve : neck muscles innervation
    • Pharynx paralysis: glossopharyngeal and vagus nerves : rabies!!
  • 17. PNS: Spinal nerves (31 pairs; don’t need to identify them all)
    • Anatomy:
      • Emerges from dorsal and ventral roots
      • Emerges through intervertebral foramen (except 1 st spinal nerve)
    • Somatic and autonomic systems
  • 18. Somatic nervous system (skeletal muscles)
  • 19. Autonomic nervous system: organization
  • 20. Autonomic nervous system: organization
  • 21. Differences between sympathetic and parasympathetic (autonomic nervous system)
  • 22. Autonomic nervous system: targets
  • 23. Autonomic nervous system: targets Erection Ejaculation Penis none Stim.secretion Adrenal medulla None Increases blood sugar Liver Increases Decreases GI activity Constricts Dilates Lungs (bronchi) Decreases Increases Heart rate Lots of dilute saliva Dry mouth (thick saliva) Salivary glands Constricts pupil Dilates pupil Eye Parasympathetic Sympathetic
  • 24. Some important spinal nerves (pig)
  • 25. Some important spinal nerves (human)
  • 26. Damages to peripheral nerves
    • Sciatic nerve pinched: lower back pain
    • Foot nerves: 90% of all lameness in horses. Heel, pastern/foot and fetlock blocks should identify damage; if not, work way up he limb.
    • Knee-jerk reflex
  • 27. Conclusion
    • CNS: brain + spinal cord
    • PNS: cranial+ peripheral nerves:
      • Somatic nervous system: skeletal muscle control
      • Autonomic nervous system: smooth and cardiac muscle. Sympathetic/parasympathetic and fight/flight reactions
    • Neurological exams: non invasive, symptoms often specific to one type of lesion
    • To suspect if pain does not originate in muscles, tendons,…
  • 28. The end
    • Stations
    • Knee-jerk reflex
    • Pupillary light reflex
    • Palpebral reflex
    • Spinal cord model
    • Fetal pig, dissect:
      • Vagus and sciatic nerves
      • Brain
    • Handout
    • - Table of cranial nerves (with function and type-sensory or motor or both)
    • Answer the vignettes
    • Sympathetic/parasympathetic actions