synaptic transmission

Question 1

synaptic transmission

Answer 1

the process involved in transferring an electrical signal across a specialized synapse, there are two types in the mammalian nervous system: electrical and chemical

Question 2

Comparison of electrical and chemical synapses

Answer 2

Electrical: Agonist (none), membrane protein (connexon), speed of transmission (instant)

Chemical:
Ionotropic chemical: Agonist (Ach), membrane protein (ion channels), speed of transmission (short msec)

Metabotrobic chemical: Agonist (Ach), membrane protein (G protein), speed of transmission (long sec minutes)

Question 3

structure of the electrical synapse

Answer 3

In the electrical synapse, the presynaptic cell terminal membrane is sealed to the postsynaptic cell by gap jusntions called connexons (integral proteins made up of 6 monomers) electronic current goes thru a low resistance pathway

extremely fast transmission thru CNS (us very little energy) make the syncsial muscles

Question 4

nicotinic receptor example

Answer 4

Muscle ach accepting post synaptic receptor its an ionotropic channel because it leads to the increased permeability of NA and K (but Na is increased more than K so that causes a n non propagated local depolarization-> AP

Question 5

Metabotropic example

Answer 5

G protein receptor, muscarinic receptor
binding o f muscarine leads to the dissociation of the B and the y subunits of the G protein that go and activate a K channel and causes a hyperpolarization (relaxation of heart via vagus nerve release of Ach on the muscarinic receptors

Question 6

Synaptic transmission at the skeletal neuromuscular junction

Answer 6

APs are generated in the myelinated motor nerve axons and are propagated to the peripheral terminal of the axon. At the terminal, the axon is split into multiple terminal branches with each ending forming a bouton that synapses on a single muscle fiber, the branched axon with all the innervated muscle fibers/cells is called the motor unit

When Ap depolarization causes coltage gated Ca channels to open (influx of Ca) and Ca has three functions: release of the vesicles bound to reticular sites, fusion of the synaptic vesivle to the presynaptic membrane, and the opening of the and release of vesicular materials in the synapse

in the presynaptic neuron there is choline acetyltransferase to make Ach and theres an Ach-H+ transporter on the vesicle to uptake Ach

Ach esterase is in the cleft to stop Ach from working too much

When Ach binds it produces an EPP (much higher than threshold) to ensure a muscle action potential starts

Curare is a competitive inhibitor of Ach- paralyzes

Question 7

Synaptic transmission in the CNS

Answer 7

Have a diverse field of synaptic connections,
number of spines varies greatly and can increase nerve cell activity EPSP

Spatially focused (one neuron targets a few, talking walking etc)
Widely divergent (one neuron targets many)- memory emotions

Question 8

EPSPs vs IPSPs

Answer 8

at low firing rates EPSPS bring the neuron closer to threshold, when many EPSP-> threshold (triggered by many NT)

IPSPs-> hyperpolarizations (activated Cl or K channels) GABA or glycine