Anatomy: Nervous system

Anatomy: Nervous system

1. Functions

   • Sensory nerves
     • Sense things
     • Pain, touch, temperature
   • Motor functions
     • Movement
     • Voluntary
       • locomotion - skeletal muscle movement
     • Involuntary
       • Smooth muscle
         • Glands and cardiac muscle
   • reflex functions
     • react quickly
   • Thinking, emotion, memories
     • higher functions
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2. Anatomical Subdivisions

   • CNS
     • Brain
     • Spinal cord
     • "Central controller"
   • PNS
     • All other nerve tissue not within the CNS
     • Spinal nerves
       • Connect with spinal cord
     • Cranial nerves
       • connect with brain
     • Autonomic nerves
       • organs, smooth muscle, glands
       • Visceral afferents
       • Sympathetic nerves
       • parasympathetic nerves
     • "Wiring"

3. Synapses

   • One neuron communicates with another neurone in a ganglion in the PNS
   • electrical signal (AP) becomes a chemical signal (neurotransmitter) then an electrical signal again
   • Drugs can block specific neurotransmitters at specific synpases

4. Peripheral Nerves

   • Bundles of axons (nerve fibres) wrapped in connective
   • Travelling to/from the same region or structure
   • Bundles of axons can leave as branches
   • Named nerves
     • Larger nerves supplying body wall, body cavities and organs
     • Traditionally been given names e.g - phrenic, musculocutaneous

5. Brain

   • Outermost layer of the cerebral hemispheres
     • Cortex
     • consists of gyri and sulci
   • 4 lobes of each cerebral hemisphere
     • named according to the cranial bone they lie deep to

6. Cranial nerves

   • Oll, Of, Olly's, Troughs, Trigger, Abby's, Fear of, Very, Great, Vaginas, Spouting, Hate
     • Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducent, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, Spinal accessory, Hypoglossal
       • Modalities = Sensory, Sensory, Motor, Motor, Both, Motor, Both, Sensory, Both, Both, Motor, Motor
         • Some, Say, Marry, Money, But, My, Brother, Says, Big, Brains, Matter, More
   • Where nerves connect to brain
     • Forebrain, Forebrain, Midbrain, Midbrain, Pons, Junction, Junction, Junction, Medulla, Medulla, spinal Cord, Medulla
       • For, Four, Million, Millenia, Pepe, Just, Jumped, Jollily, Making, Memes, Special, Material
   • Where nerves enter/exit cranial cavity
     • 1 = anterior fossa, 2-6 = middle fossa, 7-12 = posterior fossa

7. Cranial formaniae

   • Anterior cranial fossa
     • cribriform plate of the ethmoid bone
       • CN I
   • Middle cranial fossa
     • Optic canal
       • CN II
     • Superior orbital fissure
       • CN III, IV, V1 & VI
     • Foramen rotundum
       • CN V2
     • Foramen ovale
       • CN V3
   • Posterior cranial fossa
     • internal acoustic meatus
       • CN VII & VIII
     • jugular foramen
       • CN IX, X & XI
     • Hypoglossal canal
       • CN XII
     • Foramen magnum

8. Course of a cranial nerve

   • CNS part of course
   • Intracranial part of course (within cranial cavity
   • extracranial part of course (outwith cranial cavity)

9. Spinal Nerves and Vertebral Column

   • Spinal nerves
     • Named according to the vertebrae above it (expect in cervical region where they are named according to vertebra below)
     • Extend from spinal cord to periphery
     • Only called spinal nerves while within IV foramina
     • From IV foramina, they become rami or connect with the spinal cord via roots and rootlets
       • Rami leave the Iv foramina
         • Anterior rami = larger, supplies anterolateral body wall, all of the limbs via plexus
         • Posterior rami = smaller, supplies posterior body wall
       • Roots turn back further into IV foramina, become rootlets and connect with grey matter
     • Enlargements = where nerves for limbs come from
     • Lower spinal nerves become cauda equina
     • Rami connect to structures of the soma
     • Grey matter = axons (on inside)
     • White matter = myelin (on outside)
     • Each pair of spinal nerves supplies one strip of the soma
       • T10 supplies umbillicus
       • T4 supplies male nipple
   • Nerve plexuses
     • Made of anterior rami
     • Cervical plexus = C1-C4, supplies posterior scalp, neck wall and diaphragm
     • Brachial plexus = C5-T1, supplies upper limb
     • Lumbar plexus = L1-L4, supplies lower limb
     • Saccral plexus = L5-S4, supplies lower limb, gluteal region and perineum

10. Sympathetics

    • Originates from control centres in brain
    • Passes down spinal cord
    • Exits spinal cord with T1-L2 spinal nerves
    • Travel to sympathetic chains running the length of the vertebral column
    • Pass into all spinal nerves (anterior and posterior rami)
      • Supply sweat glands, arrector muscles, arterioles
    • Pass into splanchnic nerves to eventually supply organs
    • Visceral afferent fibres

11. Sympathetic outflow

    • Only T1 to L2 segments of the spinal cord have lateral horns
      • For cell bodies of the next sympathetic neurones in the chain
    • Rami communicans between sympathetic axons in anterior rami and paravertebral ganglion of the right sympathetic trunk (runs parallel to the vertebral column)

12. Parasympathetic outflow

    • All parasympathetic axons leave the CNS via canial nerves III, VII, IX & X and via sacral spinal nerves
    • Craniosacral outflow
    • Internal organs, not body wall
      • Parasympathetic ganglia in the head - to lacrimal gland and salivary glands
      • Vagus nerve supplies organs of the neck, chest and abdomen as far as the mid-gut