Structures of Animal Cell & Nueron

• Structures of an animal cell

  • Plasma membrane
  • Nucleus
  • Mitochondrion
  • Ribosome
  • Proteins
  • Endoplasmic reticulum
• MOTOR NEURON: soma in the spinal cord, receives excitation through its dendrites and conducts impulses along its axon to a muscle
• MYELIN SHEATH: covered with an insulating material with interruptions known as Nodes of Ranvier
• Larger neurons contain four major components: dendrites, cell body, axon, and presynaptic terminal
• ASTROCYTES: star-shaped cells that wrap around the synapses of functionally related axons. They remove waste products, cause blood vessels to dilate to bring in more nutrients at times of increased brain activity
• INTERNEURON or INTRINSIC NEURON: cell’s dendrites and axon are entirely contained within a single structure
• Components of neurons

  • Dendrites
  • Synaptic receptors
  • Dendritic spines
  • Cell body or soma
  • Axon
  • Myelin sheath
  • Presynaptic terminal
  • Afferent axon
  • Efferent axon
  • Interneuron or intrinsic neuron
• AFFERENT AXON brings information into a structure (admit)
• Types of glia (neuroglia)

  • Astrocytes
• Structures of a neuron

  • Dendrites
  • Cell body
  • Axon
  • Presynaptic terminal
• SENSORY NEURON: specialized at one end to be highly sensitive to a particular type of stimulation, such as light, sound, or touch
• PRESYNAPTIC TERMINAL: the end of each branch has a swelling also known as end bulb or bouton. Axon releases chemicals that cross through the junction between that neuron and another cell
• EFFERENT AXON carries information away from a structure (exit)
• Types of neurons

  • Motor neuron
  • Sensory neuron
• AXON: the information-sending part of the neuron, sending an impulse toward other neurons, an organ, or a muscle
• Phospholipid molecules


  Containing chains of fatty acids and a phosphate group
• Depolarization


  Reduction in polarization towards zero, negative charge inside the axon decreases
• Oligodendrocytes


  • Build myelin sheaths around certain neurons in the brain and spinal cord
• Hyperpolarization

  Increased polarization, negative charge inside the axon increases
• Radial glia


  • Guide the migration of neurons and the growth of axons and dendrites during embryonic development
• Microglia


  • Tiny cells that act as part of the immune system, removing viruses and fungi from the brain
• Resting potential of a neuron: All parts of a neuron are covered by a membrane about 8 nanometers thick. The membrane maintains an electrical gradient, with a slightly more negative charge on the inside relative to the outside, known as the resting potential. Typical resting membrane potential is -70 millivolts
• Messages sent by axons are called action potentials
• Tripartite synapse


  The tip of an axon releases chemicals that cause the neighboring astrocyte to release chemicals of its own, magnifying or modifying the message to the next neuron
• Electrical gradient (polarization)


  A difference in electrical charge between the inside and outside of the cell
• Schwann cells


  • Build myelin sheaths around certain neurons in the periphery of the body
• Astrocytes


  • Star-shaped cells that wrap around the synapses of functionally related axons
  • Remove waste products, particularly those created after neurons die
  • Cause blood vessels to dilate to bring in more nutrients at times of increased brain activity
  • Act as a recycling system for glutamate released by neurons
• Subthreshold stimulation


  Produces a small response that quickly decays