Bio 252 Test 2 Review Questions and Correct Answers
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Course
BIO 252
Institution
BIO 252
Presynaptic neurons can form synapses with a post synaptic neuron
Axosomatic Interaction between axon and some (or cell body)
Axoaxonic synapses Interaction between axon of one neuron and the axon of another
Axodendritic interaction between axon and dendrite
Electrical syanpses via gap junction...
Bio 252 Test 2 Review Questions and
Correct Answers
Presynaptic neurons ✅can form synapses with a post synaptic neuron
Axosomatic ✅Interaction between axon and some (or cell body)
Axoaxonic synapses ✅Interaction between axon of one neuron and the axon of
another
Axodendritic ✅interaction between axon and dendrite
Electrical syanpses ✅via gap junctions between two adjacent neurons
Allows bidirectional transmission
Very quick
Synchronized action potentials
Associated with programmed, autonomic behaviors (breathing)
Chemical synapses ✅1. Action potential in presynaptic neuron opens Ca2+ channels
in axon terminal
2. Ca2+ with a Eca of +137 mv, enters the cell
3. Influx of Ca2+ causes synaptic vesicles to release neurotransmitters into the synaptic
cleft via exocytosis
4. Neurotransmitters bins to receptors on postsynaptic neuron
5. Ion channels on postsynaptic vesicle open, including local and or action potentials
Iontropic Neurotransmitter Receptors ✅ligand-gated ion channels
Rapid, but short-lived impact an membrane potential
Ex: acetylcholine
Metabotropic neurotransmitter receptors ✅indirectly connected to an ion channel
G-protein mediated activation of second messenger induced opening of ion channel
Slower, but longer-lasting impact on membrane potential
,Electrical vs. Chemical ✅Cell interaction: Gap-junction aligned ion channels, synaptic
cleft- larger interaction with ECF and enzymes.
Receptors: none- gap junctions, post-synapyic neuron (iontropic or metabotropic)
Speed: fast, slow
Direction: Bi-directional, single-directional
Size of signal: uniform, proportional to neuro-transmitter release
Exitatory postsynaptic potential (EPSP) ✅ion channels open and positive charges
enter the postsynaptic neuron, causing and EPSP
Depolarization of the membrane
To induce an action potential, summation must occur
Temporal summation ✅repeated release of neurotransmitters, inducing EPSP in rapid
succession. "stair case"
Spatial summation ✅Simultaneous release of neurotransmitters from multiple neurons.
"smooth rise"
AP generated axon hillock as a result of a stimulus reaching the threshold ✅The
stimulus: local potential coming from cell body and dendrites
Inhibitory Postsynaptic Potential (IPSP) ✅Ion channels open and the synaptic neuron
gains negative charges or loses positive charges, causing IPSP
Hyperpolarization of the membrane
Efflux of K+ or influx of Cl-
Found at the cell body or close to axon hillocks (synapses)
Don't stay bound on neuron
Neurotransmitters don't stay in the synapse long term
Ways to stop neurotransmitters ✅Diffusion and absorption: diffuse through ECM and
plasma membrane of the presynaptic neuron.
Degradation: enzymes in the synaptic cleft degrade neurotransmitters, taken up by
presynaptic neuron to resynthesize.
, Reuptake: transported back into presynaptic neuron via membrane bound proteins
Venom ✅female black widow: venom stimulates presynaptic neurons to cause
massive release of neuro-transmitters simultaneously.
Black scorpion: voltage-gated Na+ channels remain inactive in postsynaptic neuron:
prohibit activation. Continuous firing of action potentials.
Acetylcholin ✅small molecule-transmitter
Cholinergic synapses
Neuronmascular junctions, brin, and spinal cord and autonomic nervous system.
Mostly excitatory, but can have inhibitory effects
Degraded by acetylcholinesterase
Beware of organophosphates ✅common in insecticides, herbicides, an nerve agents
Inhibits acetylcholinesterase
Respiratory distress, convursions, and neuropathologies
Biogenic amines synthesized from amino ✅catecholamines (tyrosine)- epinephrined,
norepinephrine, dopamine (emotion, motivation, and targets of illegal drugs)
Serotonin (tryptophan)- mood regulation, emotion attention, motor funtions
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