Ch 7 Part 2: The Nervous System

• Synapses: connections between neurons and a 2nd cell.
• Presyanaptic Cell: neuron before the synapse.

  Postsynaptic Cell: the cell after the synapse.
• How are Synapses Stimulated?

  • Axodendritic: axon to dendrite.
  • Axosomatic: axon to cell body.
  • Axoaxonic: axon to axon.
• Electrical Synapses:

  • occurs via gap junctions
  • found in cardiac and smooth muscle, brain neurons, and neuroglial cell.
• Botulism: a bacterial toxin that leads to paralysis. Alters SNARE and synaptic vesicles cannot undergo exocytosis, NTs are not released, which prevents the diaphragm from contracting.
• Terminal Boutons: enlargements at the tips of axons.

  • inside are synaptic vesicles with NTs
  • docked to the plasma membrane by SNARE
• Synaptic Cleft: space between two cells. Very stable due to cell adhesion molecules.
• The number of synaptic vesicles that release NTs is a result of the frequency of the AP.
• Grade Potentials: vary in size. Can cause a depolarization or hyperpolarization.

  • conducted through the cytoplasm with cable properties
  • decrement: lose amplitude as they move
• Depolarization: excitatory postsynaptic potential

  Hyperpolarization: inhibitory postsynaptic potential
• 1. Neurotransmitter released
  2. diffuse across the cleft
  3. bind with receptors either in/on the membrane or inside the postsynaptic cell
  4. junction causes the opening and closing of chemically gated channels.
  5. changes the permeability of the plasma membrane. leads to a chnage in the membrane potential.
• Neuromuscular Junction: skeletal muscle with somatic neuron
• Acetylcholine:

  • main neurotransmitter
  • opens an ion channel
• Exogenous Chemicals: chems from outside of the body.

  • Agonist: same effect on the receptor as intended ligand.
  • Antagonist: blocks the effect of the intended ligand.
• Ionotropic Receptor: directly opens an ion channel.
• Metabotropic Receptor: requires a secondary messenger
• The 2 Receptors for Acetylcholine:

  • Nicotinic
  • Muscarinic
• Nicotinic Receptor:

  • ionotropic receptor
  • skeletal muscle junctions
  • causes a contraction
• Muscarinic Receptor:

  • metabotropic receptor
  • smooth and cardiac muscle
  • can generate an EPSP or an IPSP
• LSD and Serotonin are derived from Tryptophan.
• Catecholamines:

  • catechol group
  • derived from Tyrosine
  • Ex: Norepinephrine
• Monoamine Oxidase (MAO):

  • breaks down monoamines
  • inside terminal buttons
• Catechol-o-methyl Transferase (COMT):

  • in post synaptic cell
  • doesn't work on serotonin
• Atropine: Ach antagonist, counteracts nerve gas.

  Botox: Ach antagonist, causes muscle paralysis.
• EPSP: positive charges go in, negative charges go out.

  IPSP: positive charges go out, negative charges go in.
• Graded Potentials:

  • Dendrites and Cell Body
  • No Threshold
  • Graded in Magnitude
  • Ligand-gated channels
  • Decreases in Amplitude
• Action Potentials:

  • Axon Hillock and Axon
  • Threshold = -55mV
  • Not graded in magnitude
  • Voltage-gated channels
  • Does not decrease in amplitude
• Vertebrate Brain:

  1. Telencephalon
  2. Diencephalon
  3. Mesencephalon
  4. Metencephalon
  5. Myelencephalon
• Telencephalon:

  • cerebral hemispheres, cerebrum
  • limbic system
  • self, conciousness, sensory info.
• Diencephalon:

  • fluid-filled ventricle
  • roof: epithalamus, pineal gland
  • side walls: thalamus
  • bottom: hypothalamus, pituitary gland
• Mesencephalon:

  • roof: tectum
  • floor: tegmentum
  • relays info for vision and hearing
• Metencephalon:

  • cerebellum
  • pons -> raphe nucleus -> serotonin
• Myelnecephalon:

  • brain stem
  • autonomic nervous system
  • heart rate and respiratory rate
• Serotonin:

  • affects mood and emotions
  • involved in depression and bipolar
  • cause of migraines
• SSRIs: Serotonin Specific Reuptake Inhibitors

  • prevent reuptake of serotonin into terminal button
  • Zoloft, Prozac
• SNRI: Serotonin Norepinephrine Reuptake Inhibitors

  • Cymbalta, Effexor
• A byproduct of Dopamine synthesis is Melanin.
• Mesolimbic System:

  • controls emotions, reward system for behavior to increase fitness
• Norepinphrine:

  • innervate cardiac, smooth muscles, and glands
  • makes heart beat faster and more forcefully
  • stimulates general behavioral arousal
• ADD/ADHD:

  • Ritalin: dopamine reuptake inhibitor, abuse potential.
  • Adderall/ Vyvanse: mix of amphetamines, "legal meth", abuse potential.