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Nervous System - Coggle Diagram

- - - - Neurons are the structural units of the nervous system, whereas neuroglia support the functions of the neurons
      - Consist of a cell body, soma, with extensions called an axon and one or more (sometimes many) extensions called dendrites
        
        Dendrites receive electrical nerve impulses and conduct them toward the cell body and the axon
        
        Axons conduct nerve impulses away from the cell body
        
        Neuroglia support, nourish, and protect neurons
      - Types of neurons
        
        Sensory (afferent)
        
        Conduct action potentials toward the CNS. Sensory neurons detect the internal and external environments and facilitate motor coordination
        
        Motor (efferent)
        
        conduct action potentials away from the CNS toward muscles or glands
        
        Interneuron
        
        Conduct action potentials within the CNS from one neuron to another, primarily between sensory and motor neurons
    - - Certain neuroglia wrap themselves around the axons of neurons to create a structure known as the myelin sheath
        
        Myelin is a whitish protein-lipoid. An axon with a myelin sheath is called myelinated, whereas those without myelin sheaths are called unmyelinated
    - - Axodendritic synapses are those between the axon endings of a neuron and the dendrites of other neurons
      - Neuromuscular junction
        
        synapse between a neuron and a muscle cell is known as a neuromuscular junction
        
        Postsynaptic neuron
        
        The neuron receiving this impulse is called a postsynaptic neuron. The process of the impulse crossing the synaptic cleft is called synaptic transmission
        
        Pre-synaptic neuron
        
        A neuron carrying an impulse into a synapse is called a presynaptic neuron.
        
        Synaptic Cleft
        
        A synapse is a junction between any two communicating neurons. The actual gap between neurons is known as the synaptic cleft
- - - - Types of sensory receptors
        
        Chemoreceptors-respond to chemicals in solution, including smelled or tasted molecules, changes in blood chemistry, and changes in interstitial fluid chemistry.
        
        Mechanoreceptors- respond to mechanical forces such as pressure, touch, stretching, and vibrations.
        
        Nociceptors- respond to stimuli that may be damaging, such as extreme heat or cold, excessive pressure, and inflammatory chemicals, resulting in pain.
        
        Thermoreceptors- respond to temperature changes
  - - - Two types of General sensory receptors
        
        nonencapsulated (free) - mostly respond to temperature and painful stimuli in the skin and internal tissues, except for the brain.
        encapsulated
  - - - Inborn reflexes are rapid and predictable motor responses to stimuli that are formed between neurons during human development
      - involuntary and subconsciously maintain body posture, help to avoid pain, and control visceral activities
- - - - Synaptic transmission is commonly affected by either the enhancing or inhibiting effects of neurotransmitters, their destruction, or the blocking of receptor binding
- - - - sensory functions include the olfactory and optic nerves. Each of these has no parasympathetic fibers.
        31 pairs of spinal nerves, which bring information into the spinal cord and carry messages from the cord to the effectors
        
        Voluntary nervous system
  - - - In-voluntary nervous system
- - - - layered membranes known as meninges that protect the brain and spinal cord
      - Cerebrospinal fluid
        
        CSF surrounds the brain and spinal cord, maintaining a stable ionic concentration and protecting CNS structures
      - Blood- Brain Barrier
        
        electively allow certain molecules to pass and to keep others from reaching the brain