Nervous System

• The nervous system works in conjunction with what?

  endocrine system
• Nervous System


  responds to both internal and external environment change and maintains homeostasis within the body
• Glial Cell


  structural and nutritional support
• Neurons


  conduct nerve impulses throughout the body. they are supported by the glial cells
• Dendrites


  branches which accept nerve impulses form other neurons and carry them towards the cell body
• Axon


  longer branches which carry nerve impulses away from the cell body
• Myelin Sheath


  around the axon, speeds up the rate of impulse transmission
• Schwann Cell


  produces the myelin
• Nodes of Ranvier


  gaps between the Schwann cells
• Axon Terminal


  end of the axon and passes the electrical signal to other neurons
• Myelinated Neurons


  "white matter" which conducts nerve impulses, can regenerate after injury
• Unmyelinated Neurons


  "grey matter" responsible for processing information, cannot regenerate after injury
• Sensory Neurons (afferent)


  gather information from sensory receptors, transmit the impulses to the brain
• Interneurons


  process and integrate sensory information from sensory neurons and relay information to motor neurons
• Motor Neurons (efferent)


  transmit information from the brain to muscles(effectors)
• Reflex Arc


  neural circuit that passes through interneurons in the spinal cord for immediate response
• Summation


  sum of multiple neurons leads to greater stimulation
• What are the four stages of a nerve impulse?

  polarized, depolarization, repolarization, and refractory period
• Resting State/Polarized


  inside of neuron has a slight positive charge at rest and the outside has a slight negative charge. has a potential at -70mV
• Does sodium ions go in or out?

  in
• Does potassium ions go in or out?

  out
• Depolarization


  an impulse causes the sodium gates to open and sodium rushes into the cell, causing a more positive charge and reverses the membrane potential to +40mV
• Threshold


  any stimulus that does not reach a potential of -55mV will have no effect
• Stimulus Strength


  if an increase of stimulus strength occurs, there will not be an increase of impulse strength. there will only be an increased frequency of nerve impulses
• Repolarization


  once action potential is reached sodium gates close and the potassium gates open, K+ rushes out of the axon and restores the positive charge on the outside and goes back to the initial resting potential of -70mV
• Hyperpolarization 


  will become too negative (-70mV to -90mV) until the resting potential has been restored by the sodium-potassium pump. a second action potential cannot be conducted along the axon
• Neurotransmitters


  help "carry" the electrical impulse from one neuron to another
• Pre-Synaptic Membrane


  axon terminal
• Post-Synaptic Membrane


  dendrites
• First step of Synapse

  action potential reaches the axon terminal and the calcium gates open causing calcium ions to flow into the cell triggering the vesicle to fuse into the membrane
• Second step of Synapse

  neurotransmitters diffuse across the synaptic cleft to the post-synaptic membrane then bind to the receptors and induces or inhibits an action potentail