Jugularis 2

• Neurons


  The functional unit of the nervous system
• Neurons


  • They are excitable cells that transmit nerve impulses by transmitting electrical signals along their excitable membranes
• Neuron


  Composed of a cell body and its cytoplasmic projections (axons and dendrites)
• Synapses


  Specialized junctions where information is passed between neurons. We have chemical and electrical synapses.
• Types of neurons


  • Sensory neurons (afferent neurons)
  • Interneurons
  • Motor neurons (efferent neurons)
• Types of neurons


  • Unipolar neurons
  • Pseudounipolar neurons
  • Bipolar neurons
  • Multipolar neurons
• Perikaryon (cell body)


  Contains the nucleus, Nissl substance, Golgi apparatus, mitochondria, and axon hillock
• Cytoskeletal structures


  • Microtubules called neurotubules and neurofilaments form neurofibrils which are involved in transport
• Axons


  Function to propagate stimuli, with anterograde and retrograde axonal transport
• Synapses


  Chemical synapses convert electrical signals into chemical signals, with unidirectional transmission
• Morphological types of synapses

  • Grey's type I
  • Grey's type II
  • Ribbon synapse
• Types/sites of synapses


  • Axo-dendritic
  • Axo-axonic
  • Axo-somatic
  • Axo-spinous
• Synaptic transmission


  1. Neurotransmitter synthesis and storage

  2. Action potential invasion

  3. Ca2+ influx

  4. Vesicle fusion

  5. Neurotransmitter release

  6. Neurotransmitter binding

  7. Postsynaptic channel opening/closing

  8. Postsynaptic potential change

  9. Neurotransmitter removal

  10. Vesicle retrieval
• Electrical synapses


  Transmit signals bidirectionally through gap junctions
• Types of neuroglia


  • Astrocytes
  • Oligodendrocytes
  • Microglia
  • Ependymal cells
  • Schwann cells
  • Satellite cells
• Astrocytes


  • Largest neuroglia, form blood-brain barrier, uptake and degrade neurotransmitters, secrete, phagocytose
• Oligodendrocytes


  • Responsible for myelination in CNS
• Microglia


  • Smallest neuroglia, capable of phagocytosis, activated by injury, secrete inflammatory factors
• Ependymal cells


  • Line ventricles and central canal, produce cerebrospinal fluid
• Schwann cells


  • Responsible for myelination in PNS
• Satellite cells


  • Provide structural and metabolic support to perikarya in PNS
• Classification of neurotransmitters


  • Amino acids and derivatives
  • Monoamines
  • Neuropeptides
• Types of receptors


  • Exteroceptors
  • Proprioceptors
  • Interoceptors
• Types of effectors


  • Motor end plate
  • Autonomic nerve plexus
• Decreased myelin covering


  Decreased conduction velocity
• Regeneration takes place in the PNS but not in the CNS. Establishment of functions in the CNS can be explained by other mechanisms, such as plasticity.
• Exteroreceptors


  Sensory receptors that receive external stimuli
• Skin receptors


  • Merkel cells
  • Meissner corpuscles
  • Krause end bulbs
  • Ruffini corpuscles
  • Free nerve endings
• Merkel cells


  • For light touch sensation and light pressure, found in the stratum basale of the epidermis (Abundant on fingertips and on the lips)
• Meissner corpuscles


  • For light touch sensation, found in the stratum papillare of the dermis
• Krause end bulbs


  • For low frequency vibrations, found in the stratum reticulare of the dermis (In clitoris)
• Ruffini corpuscles


  • For distortion of skin
• Free nerve endings


  • For temperature, pain and superficial touch, found in the epidermis and in the stratum papillare of the dermis
• Deep receptors


  • Vater-Pacinian corpuscles
• Vater-Pacinian corpuscles


  • For deep pressure and vibration, found in the subcutis
• Proprioceptors


  Sensory receptors that respond to position and movement, "sense of self"
• Proprioceptors


  • Muscle spindle in muscle
  • Golgi tendon organ in tendon
• Muscle spindle


  • Stretch receptors within the body of a muscle, primarily detect changes in the length of the muscle
• Golgi tendon organ


  • Found in the origin and insertion of skeletal muscle fibers, sense changes in muscle tension
• Interoceptors


  Receptors that receive stimuli from within the body