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Nervous System (Central Nervous System (CNS) (Four major regions of the…

- - - - Frontal lobe - Executive functions such as thinking, planning, organising, problem solving, emotions and behavioural control, and personality
      - Motor cortex - Movement
      - Sensory cortex - Sensations
      - Parietal lobe - Perception, making sense of the world, arithmetic, and spelling
      - Occipital lobe - Vision
      - Temporal lobe - Memory, understanding, and language
    - - Endothelial cells sit tight with one another with tight junctions and are assisted by astrocytes. Many solutes are unable to pass this barrier
    - - Dura mater - This is the outer most layer of the meninges and is made up of dense connective tissue that includes the periosteum of the skull
      - Pia mater - This is a thin membrane that lies directly on the surface of the brain or spinal cord and accompanies larger blood vessels to the brain or spinal cord
      - The bony skull (cranium) and the vertebrae are the outer most protective layers of the nervous system
      - Arachnoid mater - Separated from the pia mater by connective tissue trabeculae (partitions formed by bands or columns of connective tissue). It encloses the subarachnoid space which contains the cerebrospinal fluid
- - - - Sensor > Afferent pathway > Control centre > Efferent pathway > Effector
  - - - Integration is the process of combining information from many sources. The nervous system combines information from many other parts of the brain. This process is essential for the smooth operation of the body.
    - - Dorsal root ganglion - These contain the cell bodies of sensory neurons and of efferent neurons from the autonomic nervous system. These neurons are pseudounipolar and myelinated
      - Sympathetic (autonomic) ganglion - Contain multipolar neurons, most of which are unmyelinated. These ganglia receive messages from axons from presynaptic cells of the CNS
      - Trigeminal ganglion - A sensory ganglion found in the dura mater
- - - - For example, somatosensory neurons begin with a peripheral receptor and travel towards the cell body in the dorsal root ganglion and trigeminal ganglion. They synapse with the spinal cord and brains stem
    - - Dendrites - Dendrites are the extensions from the soma of the neuron and are 'listening extensions'. They are able to take in nerve impulses (neurotransmitters) from a pre-synaptic neuron and allow it to be transferred further
      - Schwann cell - Cells that protect the axon, as well as facilitating saltatory transmission of nerve impulses. These cells are what allow for myelination as they are 90% lipid
      - Axon - The axon is the main transmitting body of the neuron. It takes the nerve impulse and broadcast it with the assistance of Schwann cells and Nodes of Ranvier. It is usually defined as the 'longest dendrite'
      - Nucleolus - In neurons, it is the centre for ribosomal genesis, for the growth and maintaining maturity of the neuron.
      - Axon terminal - The axon terminal is the end of the axon and is the point where neurotransmitters are released from the axon terminal (pre-synaptic neuron) to the dendrites of the post-synaptic neuron
      - Nucleus - The nucleus stores the genetic information for the neuron and also is the site where mRNA is made
      - Cell body (soma) - The cell body is the main control centre of the neuron and is where all of the inputs from the dendrites reach. The soma also contains the organelles of the neuron and allows for nerve impulses to travel to the axon hillock for transmission
      - Axon hillock - The axon hillock is the base of the soma (cell body) and is the location where the axon joins with the soma. Electrical impulses from the dendrites are summed here and they are then sent down the axon
      - Myelin sheath - The myelin sheath is made up of Schwann cells and these cells allow fort he protection of the axon as well as facilitation of saltatory transmission. It also allows for electrical insulation of the axon
      - Nissl bodies - These are granules within the neuron which are rosetted with ribosomes
      - Terminal branches - These are the ends of the axon body and are what allow for a pre- and post-synaptic neuron to connect to one another
      - Terminal boutons - Terminal boutons are the button-like enlarged ends of the axon that release neurotransmitters and allow for connection between pre- and post-synaptic neurons
      - Node of Ranvier - Nodes of Ranvier are present between the endings of Schwann cells and facilitate saltatory transmission of nerve impulses by allowing the impulses to 'jump' over the nodes to allow for faster transmission
      - Neurotransmitter - A chemical that modifies or results in the transmission of nerve impulses between synapses. A vesicle travelling from the post- to pre-synaptic neuron can carry up to 10,000 neurotransmitters
      - Satellite cells - They have the role of supplying nutrients to surrounding neurons and can also protect and cushion them. They cover the surface of neurons in the sensory sympathetic and parasympathetic nervous ganglia
      - Endoneurium - The endoneurium is a reticulin fibre connective tissue that covers the individual nerve fibres
      - Perineurium - The perineurium is a connective tissue covering that encases individual nerve fascicles. This protective lining also has the blood-nerve barrier which is selectively permeable
      - Epineurium - A connective tissue covering that encases the nerve
      - Neurofilaments - These filaments are present throughout the axon and are responsible for support and maintaining diameter
    - - Oligodendrocytes - These cells allow for many neurons (up to 50) to be myelinated at once. They play a similar role to Schwann cells in the PNS but can cover many cells at once. Oligodendrocytes are unable to regenerate
      - Astrocytes - Located in the CNS, they connect blood vessels and neurons and allow for the passage of nutrients to neurons
      - Ependymal cells - These cells are located in the ventricles of the brain and are glial cells responsible for the synthesis of cerebrospinal fluid
      - Microglia - These glial cells are equivalent to macrophages in the immune system but are much smaller and are associated in the cleaning and management of the neurons and brain
      - Purkinje cell - Purkinje cells are large neurons with many branches found in the cortex of the cerebellum of the brain. They play a fundamental role in controlling motor movement
      - Pyramidal cell - These cells have a dendrite on the apical end as well as a dendrite tree on the basal and are primary excitation units
    - - The process of myelination in the PNS involves Schwann cells wrapping repeatedly around the axon. As they wrap around, they create multiple layers around. The inner mesaxon is the point at which the inner part of the Schwann cell meets the myelin sheath. The outer mesaxon is the connection of the outer cell membrane to the compact myelin sheath