BIOL-K 416 Exam 1

• What happens when CREB is phosphorylated by the RTK (receptor tyrosine kinase) pathway.

  RTK activates ras, which activates MAPK, which phosphorylates CREB and triggers transcription
• What 4 types of cellular responses result from intracellular signaling?

  Altered membrane potential, altered metabolism, altered gene expression, altered cell shape/movement
• What differentiates the 4 categories of cellular receptors?

  Channel linked: ionotropicEnzyme linkedG protein-coupled: ligand binding turns on the G protein (metabotropic)Intracellular receptors: ionotropic
• Name 3 characteristics of a receptor.

  Specificity: must be able to distinguish between closely-related signalsHigh affinity: how strongly ligand binds to the receptorSaturability: cell has finite number of receptorsReversibility: ligand-receptor linkage not covalentCoupling: receptor transfers a signal from outside to inside of cell
• How do the three types of chemical communication talked about in class work?

  Synaptic transmission: NTs are released from the synaptic vesicleParacrine signaling: similar, but doesn't always involve NTsEndocrine signaling: signals travel with the blood to effector organs
• What is meant by the term signal transduction?

  Process of converting an extracellular signal to a functional change in the cell
• How do neurotransmitters and neuropeptides differ in the transmission process?

  Neuropeptides are slow acting and have long duration, usually inhibitory, and they have a low concentration in the brain
• What transmitter system(s) do MAO inhibitors and SSRI's target?

  MAO inhibitors block MAO from removing serotonin, norepinephrine, and dopamine from the synapse; SSRIs inhibit the reuptake of serotonin
• What is myasthenia gravis? What leads to symptoms described by patients?

  A disease where patients make autoantibodies that inhibit the nicotinic and acetylcholine receptors; symptoms include partial paralysis of eye movements, droopy eyelids, and double vision (diplopia), and leads to more serious problems
• What properties of the NMDA receptor make it interesting?

  ligand-gated receptor that allows primarily Ca2+ into the cell, but also allows some Na+ in and some K+ out; underlies synaptic plasticity responsible for learning and memory; requires a change in membrane potential to dislodge Mg2+ gate, as well as binding of glutamate AND glycine
• Enkephalins


  Synthesis: made as pre-peptides and are processed into active peptides
• Serotonin

  Synthesis: tryptophan is converted to 5-HTP by tryptophan hydroxylase, which is then converted to 5-HT using 5-HT decarboxylase clearance from synapse: transport into nerve terminals through serotonin transporter (SERT)
• Dopamine

  Synthesis: derived from tyrosine, which is converted to DOPA by tyrosine hydroxylase. DOPA is converted to dopamine by DOPA decarboxylase.Vesicle loading: vesicular monamine transporters (VMATs)Clearance from synapse: dopamine transporters (DATs) on terminals and astrocytesDegraded by monoamine oxidase (MAO) and catechol O-methyltransferase (COMT)
• Acetylcholine

  Synthesis: Cholineacetyltransferase (ChAT) synthesizes it from acetyl CoA and Choline (taken up from environment through choline transporter, ChT) in the axon terminalsVesicle loading: vesicular ACh transporter (VAChT)Clearance from synapse: degraded in synapse by Acetylcholinesterase
• GABA


  Synthesis: glutamic acid decarboxylase (GAD) and pyridoxal phosphate convert glutamate to GABAVesicle loading: vesicular inhibitory amino acid transporter (VIAAT)Clearance from synapse: GABA transporters (GATs)Can be degraded into other chemicals like succinate
• Glutamate

  Synthesis: part of the citric acid cycle or from glutamine via glutaminaseVesicle loading: vesicular glutamate transporters (VGLUTs)Clearance from synapse: an excitatory amino acid transporter (EAAT1-5) or surrounding astrocytesReturned to terminal from astrocytes
• What are the 4 categories of neurotransmitters discussed in class?

  Amino acids, biogenic amines, neuropeptides, others (nucleosides, lipids, gases)
• What are the 3 ways neurotransmitters are removed from the synapse?

  Diffusion away from synapseReuptake into terminals or nearby glial cellsDegradation by enzymes
• What do the abbreviations EPSP and an IPSP refer?

  Excitatory and Inhibitory Postsynaptic Potentials
• What are the two general types of receptors found at the synapse?

  Ligand gated (ionotropic) and G protein-coupled receptors (metabotropic)
• How do tetanus and botulinum toxins poison the synapse?

  They affect the SNARE proteins involved in vesicle fusion
• What 3 criteria are used to define a neurotransmitter?

  1. Must be present within presynaptic neuron

  2. Must be released in response to presynaptic depolarization

  3. Must find receptors for NTs on postsynaptic cell
• Know the steps by which neuronal chemical synapses transmit and breakdown neurotransmitter, and how synaptic vesicles are re-filled.

  Neurotransmitters are released at the active zoneNeuropeptides are released away from the active zone
• What distinguishes Gray's Type I synapse from Gray's Type II synapse?

  Type I has asymmetrical membrane differentiations between pre and postsynaptic cells and is excitatory vs. Type II which has symmetrical membrane differentiation and is inhibitory
• How do vesicles and granules become filled?

  Neurotransmitters are synthesized in the presynaptic terminal, then loaded into vesicles via a transporter in the vesicular membraneNeuropeptides are synthesized in the cell body and loaded into granules
• What characteristics describe neurotransmitters?

  1. Must be present within presynaptic neuron 2. Must be released in response to presynaptic depolarization 3. Must find receptors for NTs on postsynaptic cell
• What 2 general kinds of molecules can pass between cells at a chemical synapse?

  ions and small hydrophilic molecules
• What is the synaptic cleft?

  the space between two neurons
• What proteins make electrical synapses possible?

  connexons
• How do electrical and chemical synapses differ?

  Electrical: uses gap junctions to transfer ions from one neuron to another (bidirectional) vs. Chemical: uses synaptic vesicles to release NTs across cleft and bind to receptors on the postsynaptic neuron
• Who is responsible for naming synapses?

  Charles Sherrington
• How do anesthetics/sedatives affect the action potential?

  Anesthetics prolong inactivation of voltage-sensitive Na+ channel, so the neuron cannot reactivate
• Movement of what ions drive the fast depolarization and the hyperpolarization of the action potential?

  Sodium drives depolarization and potassium drives repolarization (and eventually hyperpolarization due to the slow-closing gates)
• How do a receptor potential and an action potential differ from one another?

  Receptor potential: energy transduced by a receptor cell (a type of graded potential)Action potential: when a neuron reaches threshold and triggers active transport of ions
• Where are each of the gated channels talked about in class found in the neuron?

  Ligand gated: found in cell bodies and dendritesVoltage gated: found in initial segment, axon hillock, and axonMechanically gated: found in somatosensory neurons
• How do gated channels work? Specify three stimuli that can gate channels.

  They open/close based on their environment

  1. Ligand2. Voltage3. Mechanical (she used stretch as an example)
• What are the two major classes of channels?

  Leakage and gated
• Why is the inside of the neuron slightly more negative than the outside of the cell?

  More K+ insideMore Na+ outsideNet ion flux is K+ out of cell by K+ leakage channelsSodium potassium pump pumps 3 Na+ OUT and 2 K+ IN to maintain gradient
• What are the general steps a neuron moves through starting at resting membrane potential to communication with another neuron?

  Presynaptic cell has an action potentialChemical messenger releasedChemical messenger binds to special ligand-gated ion channelsActivation of the ion channelsChange in RMP of postsynaptic cell
• If you damage the cortex on one side of the head, sensory and motor deficits appear on the opposite side of the lesion. Why?

  Decussation and contralateral organization