Neuroanatomy

Neuroanatomy

1. sensorimotor

   • adj., (of nerves or their actions) having or involving both sensory and motor functions or pathways Mammalian sensorimotor systems (and, generally, brains) share basic structures. The human brain is just one evolutionary variation amongst many. It’s complex, but not the most complex (e.g dolphins).

2. For voluntary movement, the most important parts of the nervous system are the: motor cortex, the basal ganglia, the cerebellum, the thalamus, and the spinal cord.

   • Motor cortex
   • Basal Ganglia
   • The Cerebellum
   • Thalamus
   • Spinal Cord
     • is the caudal part of the CNS. It receives and processes sensory information from skin, joints, and muscles, and controls limb movement. It has 4 regions: cervical, thoracic, lumbar, and sacral
       • If we follow the spinal cord in the rostral direction we encounter the brain stem
         • Perched atop the brain stem is the diencephalon, part of which is the thalamus. The thalamus plays an important role not only in voluntary behaviour, but also sensory processing.
         • The cerebellum, rostral to the spinal cord, is connected to the brain stem by several major fiber tracts called peduncles. The cerebellum modulates the force and range of movement, and is involved in the learning of motor skills.

3. Luke uses Ventral (anterior) and Dorsal (posterior for heading towards front and back of the head for humans)

4. Grey matter: (darker shade) - find cell bodies of neurons and dendrites.

5. Lighter shade, show white matter - find the axons of neurons (fibre carrying singals from one site to the other site of nervous system.

6. Medial - refers to sites in the nervous system close to the midline . Midline - lines in the place that divides the body into two equal parts. Lateral - heading away from the midline.

7. "H-shape" (bottom picture) in humans - organizational of grey matter in spinal cord, can see compiimentary white matter around the edge.

8. Parallel to the floor when human subject is standing upright

9. Perpendicular to the floor - if human upright. Sagittal - find the midline (divides the body into two symmetric halves.

10. Peripheral Nervous System (PNS)

    • nervous system
      • the network of nerve cells and fibers that transmits nerve impulses between parts of the body
    • those parts of the nervous system not encased in bone, ie., not the brain, and not the spinal cord
      • PNS is comprised of the somatic and visceral nervous systems, afferent and efferent axons.
        • afferent,
          • conducting [impulses] inward or toward [the central nervous system]
          • Muscles of the hand
        • efferent,
          • conducting [impulses] outward or away [from the CNS]
            • Fingertip
        • Somatic PNS:
          • Efferent motor axons innervating the muscles, skin, and joints. Afferent sensory axons, from muscles, skin, and joints, which meet their cell bodies at the dorsal root ganglia.
        • Visceral PNS (a.k.a. Autonomic NS):
          • Supports involuntary function, innervating organs, blood vessels, and glands.
    • gray matter
      • the darker tissue of the CNS, consisting mainly of nerve cell bodies and branching dendrites
    • white matter,
      • the paler tissue of the brain and spinal cord, consisting mainly of nerve fibers

11. Central Nervous System

    • those parts of the nervous system encased in bone, ie., the brain, and the spinal cord.
      • The CNS has these main parts: spinal cord, brain stem, diencephalon, cerebellum, and cerebrum. The most important parts for motor control are these (from the top down): motor cortex, basal ganglia, cerebellum, the thalamus, and the spinal cord.
    • The cerebrum, derived from the prosencephalon and composed of two cerebral hemispheres, is the largest part of the human brain. The outer layer of the cerebrum is the cerebral cortex and is characterized by elevated ridges (gyri) parted by depressions (sulci).
      • cerebrum
      • The cerebrum comprises two hemispheres, each comprising a convoluted outer layer (“cortex”) and three deep structures (the basal ganglia, the hippocampus, and the amygdaloid nuclei).
        • Central Sulcus, divides the brain into half (the two hemispheres0>
          • Sulci is the plural form of sulcus. Gyri plural form of gryus.
            • Gyri - ridges
            • Sulci - grooves
        • Occipital lobe - associated with visual behaviours. Important in object identification.
        • Temporal lobe is associated with hearing and speech production.
        • Parietal lobe helps in processing sensory signals.
        • Frontal lobe - planning and execution of movements.
    • Basal Ganglia
      • Much of the information the basal ganglia receives comes from the cerebral cortex and travels first to the caudate or putamen, the main input nuclei of the basal ganglia. The globus pallidus and substantia nigra are the main output nuclei, and they send projections out of the BG to the cerebral cortex, mostly by the way of the thalamus as well as to nuclei in the brainstem.
    • In all vertebrates, cortical grey matter is organized as layers (the “characteristic cytoarchitecture”). In humans and other mammals, there are 6 layers running parallel to cortical surface
      • Distinct layers under microscope, formed by different neurons and densities.
        • Different types between areas of the cerebral cortex.
          • Notice on the right, 6 layers, often denowed roman numerals. Different neurons become active, and can be measured by EEG. Paramteral neuron, has a relatively large neuronal body/soma, and dendrites that extends from level 5 to surface.

12. Note: German neuroanatomist Korbinian Brodmann, on the basis of anatomy alone, identified dozens of different cortical areas (early 1900s). He hypothesized (but didn’t have the tools to prove) that different areas served different functions

Images and files in the map