Neural Communication

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Neural Communication
This is anything that deals with the synapse and
the neurons communication with each other

• By Ryan Gov
• Sera Choi
• Iris Gonzalez

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Movement of information

• Information in the nervous system moves to other
  locations through action potentials
• These electrical movements are nerve impulses
• Chemicals known as neurotransmitters transfer the
  information when released.
• In neuron communication, the synapse may be at
  the dendrite, cell body, or the axon.
• Neuroeffector junctions are synapses between a
  neuron and other types of cells
• Neuronglandular junctions are where a neuron
  controls the activity of a secretory cell.

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Structure of a synapse

• Communication between neurons occur in only one
  direction across a synapse.
• An impulse can travel from the synaptic knob of
  the presynaptic neuron to the postsynaptic
  neuron.
• The opposing cell membranes are separated by
  narrow spaces called a synaptic cleft.
• The synaptic terminals have mitochondria,
  synaptic vesicles, and endoplasmic reticulum.
• Synaptic vesicles have thousands of molecules of
  specific neurotransmitters.
• When the vesicles release these neurotransmitters
  they diffuse across the synaptic cleft, then they
  bind to the receptors

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Functions and neurontransmitters

• There are many different neurotransmitters, an
  example being acetylcholine or ACh.
• The cholinergic synapses is where the ACh is
  released, and these are numerous in and out of
  the Central Nervous system.
• Another common neurotransmitter is norepinephrine
  (NE), or nonadrenaline.
• NE is important to the brain and the autonomic
  nervous system.
• Dopamine is another important neurotransmitter in
  the central nervous system
• Serotonin is a neurotransmitter important to the
  mood of humans, it is known as the happy
  hormone even though its not a hormone.

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The sequence of events for a cholinergic synapse

• Step 1
• An action potential arrives and depolirizes the
  synaptic knob.
• The binding of ACh to sodium channels causes them
  to pen and allows sodium ions to enter.
• Step 2
• Calcium ions enter the cytoplasm of the synaptic
  knob
• ACh release occurs through exocytosis of
  nuerotransmitter.
• The release ends quickly because the calcium ions
  are removed from the cytoplasm by active
  transport

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• Step 3
• ACh binds to receptors and depolarizes the
  postsynaptic membrane
• The binding of ACh to sodium channels causes them
  to open and allows sodium ions to enter
• If the depolarization of the postsynaptic
  membrane reaches threshold, an action potential
  is produced.
• Step 4
• Then the removal of ACh by AChE occurs
• The effects on the postsynaptic membrane is
  temporary because of AChE
• The AChE removes ACh by breaking it into acetate
  and choline

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• In the central nervous system, there are 50 other
  neurotransmitters that are not well understood
• There are also gases that are important to
  neurotransmitters nitric oxide and carbon
  monoxide
• Neurotransmitters released from the synapse can
  have either excitatory or inhibitory effects
• Excitatory effects means the nerve cells have a
  higher probably of producing an action potential
• Inhibitory effects is when the intensity of the
  action potential is suppressed
• ACh and NE have an excitatory effect
• Dopamine and serotonin are usually inhibitory

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• The action potential depends on the balance of
  depolarization and hyperpolarizing stimuli
  arriving.
• The activity of a neuron depends on the balance
  between excitation and inhibition.
• These interactions between neurons are very
  complex and somewhat confusing
• The synapses at the cell body and dendrites may
  involve tens of thousands of other neurons.
• Some neurons will be releasing excitatory
  neurotransmitters while others inhibitory.

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Neuron pools

• A human has about 10 million sensory neurons, 20
  billion interneurons, and one-half million motor
  neurons
• This is the simplest form of organization in the
  CNS
• A neuronal pool is a group of interconnected
  interneurons with specific functions.
• Neuronal pools have limited numbers of input
  sources and output destinations
• Thus the output of one pool may stimulate or
  depress the activity of other pools
• The neuronal pool may also exert direct control
  over motor neurons or peripheral effectors.

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• Neurons and neuronal pools communicate in
  different patterns called neural circuits
• The two simple circuit patterns are divergence
  and convergence.
• This is how information spreads from one neuron
  or neuronal pool to other neurons or neuronal
  pools
• Divergence occurs when sensory neurons bring
  sensory information to the CNS
• This is due to the distribution of the sensory
  information through the brain and the spinal
  column
• Ex The information from your eyes reaches your
  conscious awareness at the same time its carried
  to the areas of the brain that control posture
  and balance at the subconscious level.

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• Divergence can also be involved with other
  responses
• Ex when you step on a sharp object
• The action stimulates sensory neurons that
  distribute information to neuronal pools
• There will be several possible reactions
  withdrawing your foot, shifting your weight,
  moving your arms, feeling the pain, or saying
  ouch
• This all may even happen at the same time
•  When the neuron fires, the signal is sent to
  many other neurons, resulting in a divergence of
  output.

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Convergence

• Convergence is when several neurons synapse on a
  single postsynaptic neuron.
• This makes both voluntary and involuntary control
  of some body processes
• Ex the movement of your diaphragm now.
• The movement is being involuntarily controlled by
  the brain
• These movements can be controlled voluntarily too
• When you take a deep breathe and hold it.
• Two neuron pools are involved, and both synapse
  on the same motor neuron.

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Quiz time!!!!

• 1. What are the electrical movements that help
  disperse information between neurons?
• 2. Name at least two neurotransmitters and what
  their functions are.
• 3. How is an action potential produced?
• 4. Describe the two effects a neuron can have.
• 5. Describe the two simple circuits of a neuron.

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• 1. Nerve impulses
• 2. Serotonin (mood regulator) and Dopamine
  (important in the CNS)
• 3. If the depolarization of the postsynaptic
  membrane reaches threshold, an action potential
  is produced.
• 4. excitatory and inhibitory
• 5. divergence or convergence